MCU encodes the pore conducting mitochondrial calcium currents

Mitochondrial calcium (Ca2+) import is a well-described phenomenon regulating cell survival and ATP production. Of multiple pathways allowing such entry, the mitochondrial Ca2+ uniporter is a highly Ca2+-selective channel complex encoded by several recently-discovered genes. However, the identity of the pore-forming subunit remains to be established, since knockdown of all the candidate uniporter genes inhibit Ca2+ uptake in imaging assays, and reconstitution experiments have been equivocal. To definitively identify the channel, we use whole-mitoplast voltage-clamping, the technique that originally established the uniporter as a Ca2+ channel. We show that RNAi-mediated knockdown of the mitochondrial calcium uniporter (MCU) gene reduces mitochondrial Ca2+ current (IMiCa), whereas overexpression increases it. Additionally, a classic feature of IMiCa, its sensitivity to ruthenium red inhibition, can be abolished by a point mutation in the putative pore domain without altering current magnitude. These analyses establish that MCU encodes the pore-forming subunit of the uniporter channel. DOI: http://dx.doi.org/10.7554/eLife.00704.00

Elementary Mechanisms Producing Facilitation of Cav2.1 (P/Q-type) Channels

The regulation of CaV2.1 (P/Q-type) channels by calmodulin (CaM) showcases the powerful Ca2+ decoding capabilities of CaM in complex with the family of CaV1-2 Ca2+ channels. Throughout this family, CaM does not simply exert a binary on/off regulatory effect; rather, Ca2+ binding to either the C- or N-terminal lobe of CaM alone can selectively trigger a distinct form of channel modulation. Additionally, Ca2+ binding to the C-terminal lobe triggers regulation that appears preferentially responsive to local Ca2+ influx through the channel to which CaM is attached (local Ca2+ preference), whereas Ca2+ binding to the N-terminal lobe triggers modulation that favors activation via Ca2+ entry through channels at a distance (global Ca2+ preference). CaV2.1 channels fully exemplify these features; Ca2+ binding to the C-terminal lobe induces Ca2+-dependent facilitation of opening (CDF), whereas the N-terminal lobe yields Ca2+-dependent inactivation of opening (CDI). In mitigation of these interesting indications, support for this local/global Ca2+ selectivity has been based upon indirect inferences from macroscopic recordings of numerous channels. Nagging uncertainty has also remained as to whether CDF represents a relief of basal inhibition of channel open probability (Po) in the presence of external Ca2+, or an actual enhancement of Po over a normal baseline seen with Ba2+ as the charge carrier. To address these issues, we undertake the first extensive single-channel analysis of CaV2.1 channels with Ca2+ as charge carrier. A key outcome is that CDF persists at this level, while CDI is entirely lacking. This result directly upholds the local/global Ca2+ preference of the lobes of CaM, because only a local (but not global) Ca2+ signal is here present. Furthermore, direct single-channel determinations of Po and kinetic simulations demonstrate that CDF represents a genuine enhancement of open probability, without appreciable change of activation kinetics. This enhanced-opening mechanism suggests that the CDF evoked during action-potential trains would produce not only larger, but longer-lasting Ca2+ responses, an outcome with potential ramifications for short-term synaptic plasticity

Transient Receptor Potential channels (TRP) in GtoPdb v.2022.1

The TRP superfamily of channels (nomenclature as agreed by NC-IUPHAR [159, 999]), whose founder member is the Drosophila Trp channel, exists in mammals as six families; TRPC, TRPM, TRPV, TRPA, TRPP and TRPML based on amino acid homologies. TRP subunits contain six putative TM domains and assemble as homo- or hetero-tetramers to form cation selective channels with diverse modes of activation and varied permeation properties (reviewed by [679]). Established, or potential, physiological functions of the individual members of the TRP families are discussed in detail in the recommended reviews and in a number of books [371, 635, 1066, 236]. The established, or potential, involvement of TRP channels in disease is reviewed in [412, 634] and [637], together with a special edition of Biochemica et Biophysica Acta on the subject [634]. Additional disease related reviews, for pain [585], stroke [1052], sensation and inflammation [921], itch [117], and airway disease [284, 979], are available. The pharmacology of most TRP channels has been advanced in recent years. Broad spectrum agents are listed in the tables along with more selective, or recently recognised, ligands that are flagged by the inclusion of a primary reference. See Rubaiy (2019) for a review of pharmacological tools for TRPC1/C4/C5 channels [751]. Most TRP channels are regulated by phosphoinostides such as PtIns(4,5)P2 although the effects reported are often complex, occasionally contradictory, and likely to be dependent upon experimental conditions, such as intracellular ATP levels (reviewed by [941, 638, 747]). Such regulation is generally not included in the tables.When thermosensitivity is mentioned, it refers specifically to a high Q10 of gating, often in the range of 10-30, but does not necessarily imply that the channel's function is to act as a 'hot' or 'cold' sensor. In general, the search for TRP activators has led to many claims for temperature sensing, mechanosensation, and lipid sensing. All proteins are of course sensitive to energies of binding, mechanical force, and temperature, but the issue is whether the proposed input is within a physiologically relevant range resulting in a response. TRPA (ankyrin) familyTRPA1 is the sole mammalian member of this group (reviewed by [268]). TRPA1 activation of sensory neurons contribute to nociception [382, 831, 555]. Pungent chemicals such as mustard oil (AITC), allicin, and cinnamaldehyde activate TRPA1 by modification of free thiol groups of cysteine side chains, especially those located in its amino terminus [529, 51, 336, 531]. Alkenals with α, β-unsaturated bonds, such as propenal (acrolein), butenal (crotylaldehyde), and 2-pentenal can react with free thiols via Michael addition and can activate TRPA1. However, potency appears to weaken as carbon chain length increases [23, 51]. Covalent modification leads to sustained activation of TRPA1. Chemicals including carvacrol, menthol, and local anesthetics reversibly activate TRPA1 by non-covalent binding [391, 470, 1007, 1006]. TRPA1 is not mechanosensitive under physiological conditions, but can be activated by cold temperatures [392, 193]. The electron cryo-EM structure of TRPA1 [688] indicates that it is a 6-TM homotetramer. Each subunit of the channel contains two short ‘pore helices’ pointing into the ion selectivity filter, which is big enough to allow permeation of partially hydrated Ca2+ ions. TRPC (canonical) familyMembers of the TRPC subfamily (reviewed by [261, 726, 15, 4, 84, 410, 687, 60]) fall into the subgroups outlined below. TRPC2 is a pseudogene in humans. It is generally accepted that all TRPC channels are activated downstream of Gq/11-coupled receptors, or receptor tyrosine kinases (reviewed by [713, 889, 999]). A comprehensive listing of G-protein coupled receptors that activate TRPC channels is given in [4]. Hetero-oligomeric complexes of TRPC channels and their association with proteins to form signalling complexes are detailed in [15] and [411]. TRPC channels have frequently been proposed to act as store-operated channels (SOCs) (or compenents of mulimeric complexes that form SOCs), activated by depletion of intracellular calcium stores (reviewed by [689, 15, 718, 765, 1039, 141, 675, 55, 142]). However, the weight of the evidence is that they are not directly gated by conventional store-operated mechanisms, as established for Stim-gated Orai channels. TRPC channels are not mechanically gated in physiologically relevant ranges of force. All members of the TRPC family are blocked by 2-APB and SKF96365 [319, 318]. Activation of TRPC channels by lipids is discussed by [60]. Important progress has been recently made in TRPC pharmacology [751, 571, 400, 92]. TRPC channels regulate a variety of physiological functions and are implicated in many human diseases [270, 61, 827, 960]. TRPC1/C4/C5 subgroup TRPC1 alone may not form a functional ion channel [210]. TRPC4/C5 may be distinguished from other TRP channels by their potentiation by micromolar concentrations of La3+. TRPC2 is a pseudogene in humans, but in other mammals appears to be an ion channel localized to microvilli of the vomeronasal organ. It is required for normal sexual behavior in response to pheromones in mice. It may also function in the main olfactory epithelia in mice [1036, 672, 673, 1037, 496, 1077, 1032].TRPC3/C6/C7 subgroup All members are activated by diacylglycerol independent of protein kinase C stimulation [319].TRPM (melastatin) familyMembers of the TRPM subfamily (reviewed by [252, 318, 689, 1064]) fall into the five subgroups outlined below. TRPM1/M3 subgroupIn darkness, glutamate released by the photoreceptors and ON-bipolar cells binds to the metabotropic glutamate receptor 6 , leading to activation of Go . This results in the closure of TRPM1. When the photoreceptors are stimulated by light, glutamate release is reduced, and TRPM1 channels are more active, resulting in cell membrane depolarization. Human TRPM1 mutations are associated with congenital stationary night blindness (CSNB), whose patients lack rod function. TRPM1 is also found melanocytes. Isoforms of TRPM1 may present in melanocytes, melanoma, brain, and retina. In melanoma cells, TRPM1 is prevalent in highly dynamic intracellular vesicular structures [368, 657]. TRPM3 (reviewed by [663]) exists as multiple splice variants which differ significantly in their biophysical properties. TRPM3 is expressed in somatosensory neurons and may be important in development of heat hyperalgesia during inflammation (see review [878]). TRPM3 is frequently coexpressed with TRPA1 and TRPV1 in these neurons. TRPM3 is expressed in pancreatic beta cells as well as brain, pituitary gland, eye, kidney, and adipose tissue [662, 877]. TRPM3 may contribute to the detection of noxious heat [949].TRPM2TRPM2 is activated under conditions of oxidative stress (respiratory burst of phagocytic cells) and ischemic conditions. However, the direct activators are ADPR(P) and calcium. As for many ion channels, PIP2 must also be present (reviewed by [1020]). Numerous splice variants of TRPM2 exist which differ in their activation mechanisms [219]. The C-terminal domain contains a TRP motif, a coiled-coil region, and an enzymatic NUDT9 homologous domain. TRPM2 appears not to be activated by NAD, NAAD, or NAADP, but is directly activated by ADPRP (adenosine-5'-O-disphosphoribose phosphate) [902]. TRPM2 is involved in warmth sensation [789], and contributes to neurological diseases [66]. Recent study shows that 2'-deoxy-ADPR is an endogenous TRPM2 superagonist [253]. TRPM4/5 subgroupTRPM4 and TRPM5 have the distinction within all TRP channels of being impermeable to Ca2+ [999]. A splice variant of TRPM4 (i.e.TRPM4b) and TRPM5 are molecular candidates for endogenous calcium-activated cation (CAN) channels [301]. TRPM4 is active in the late phase of repolarization of the cardiac ventricular action potential. TRPM4 deletion or knockout enhances beta adrenergic-mediated inotropy [546]. Mutations are associated with conduction defects [374, 546, 821]. TRPM4 has been shown to be an important regulator of Ca2+ entry in to mast cells [926] and dendritic cell migration [43]. TRPM5 in taste receptor cells of the tongue appears essential for the transduction of sweet, amino acid and bitter stimuli [494] TRPM5 contributes to the slow afterdepolarization of layer 5 neurons in mouse prefrontal cortex [471]. Both TRPM4 and TRPM5 are required transduction of taste stimuli [226].TRPM6/7 subgroupTRPM6 and 7 combine channel and enzymatic activities (‘chanzymes’). These channels have the unusual property of permeation by divalent (Ca2+, Mg2+, Zn2+) and monovalent cations, high single channel conductances, but overall extremely small inward conductance when expressed to the plasma membrane. They are inhibited by internal Mg2+ at ~0.6 mM, around the free level of Mg2+ in cells. Whether they contribute to Mg2+ homeostasis is a contentious issue. When either gene is deleted in mice, the result is embryonic lethality. The C-terminal kinase region is cleaved under unknown stimuli, and the kinase phosphorylates nuclear histones. TRPM7 is responsible for oxidant- induced Zn2+ release from intracellular vesicles [3] and contributes to intestinal mineral absorption essential for postnatal survival [574]. TRPM8Is a channel activated by cooling and pharmacological agents evoking a ‘cool’ sensation and participates in the thermosensation of cold temperatures [54, 161, 205] reviewed by [943, 516, 420, 599]. TRPML (mucolipin) familyThe TRPML family [729, 1049, 723, 1010, 173] consists of three mammalian members (TRPML1-3). TRPML channels are probably restricted to intracellular vesicles and mutations in the gene (MCOLN1) encoding TRPML1 (mucolipin-1) cause the neurodegenerative disorder mucolipidosis type IV (MLIV) in man. TRPML1 is a cation selective ion channel that is important for sorting/transport of endosomes in the late endocytotic pathway and specifically, fission from late endosome-lysosome hybrid vesicles and lysosomal exocytosis [766]. TRPML2 and TRPML3 show increased channel activity in low extracellular sodium and are activated by similar small molecules [293]. A naturally occurring gain of function mutation in TRPML3 (i.e. A419P) results in the varitint waddler (Va) mouse phenotype (reviewed by [729, 639]). TRPP (polycystin) familyThe TRPP family (reviewed by [197, 195, 275, 988, 345]) or PKD2 family is comprised of PKD2 (PC2), PKD2L1 (PC2L1), PKD2L2 (PC2L2), which have been renamed TRPP1, TRPP2 and TRPP3, respectively [999]. It should also be noted that the nomenclature of PC2 was TRPP2 in old literature. However, PC2 has been uniformed to be called TRPP2 [317]. PKD2 family channels are clearly distinct from the PKD1 family, whose function is unknown. PKD1 and PKD2 form a hetero-oligomeric complex with a 1:3 ratio. [845]. Although still being sorted out, TRPP family members appear to be 6TM spanning nonselective cation channels. TRPV (vanilloid) familyMembers of the TRPV family (reviewed by [928]) can broadly be divided into the non-selective cation channels, TRPV1-4 and the more calcium selective channels TRPV5 and TRPV6.TRPV1-V4 subfamilyTRPV1 is involved in the development of thermal hyperalgesia following inflammation and may contribute to the detection of noxius heat (reviewed by [710, 824, 860]). Numerous splice variants of TRPV1 have been described, some of which modulate the activity of TRPV1, or act in a dominant negative manner when co-expressed with TRPV1 [787]. The pharmacology of TRPV1 channels is discussed in detail in [303] and [947]. TRPV2 is probably not a thermosensor in man [684], but has recently been implicated in innate immunity [503]. TRPV3 and TRPV4 are both thermosensitive. There are claims that TRPV4 is also mechanosensitive, but this has not been established to be within a physiological range in a native environment [114, 488].TRPV5/V6 subfamily TRPV5 and TRPV6 are highly expressed in placenta, bone, and kidney. Under physiological conditions, TRPV5 and TRPV6 are calcium selective channels involved in the absorption and reabsorption of calcium across intestinal and kidney tubule epithelia (reviewed by [984, 185, 601, 248])

Transient Receptor Potential channels (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The TRP superfamily of channels (nomenclature as agreed by NC-IUPHAR [145, 915]), whose founder member is the Drosophila Trp channel, exists in mammals as six families; TRPC, TRPM, TRPV, TRPA, TRPP and TRPML based on amino acid homologies. TRP subunits contain six putative transmembrane domains and assemble as homo- or hetero-tetramers to form cation selective channels with diverse modes of activation and varied permeation properties (reviewed by [630]). Established, or potential, physiological functions of the individual members of the TRP families are discussed in detail in the recommended reviews and in a number of books [344, 589, 979, 216]. The established, or potential, involvement of TRP channels in disease is reviewed in [384, 588] and [591], together with a special edition of Biochemica et Biophysica Acta on the subject [588]. Additional disease related reviews, for pain [542], stroke [967], sensation and inflammation [843], itch [109], and airway disease [261, 896], are available. The pharmacology of most TRP channels has been advanced in recent years. Broad spectrum agents are listed in the tables along with more selective, or recently recognised, ligands that are flagged by the inclusion of a primary reference. See Rubaiy (2019) for a review of pharmacological tools for TRPC1/C4/C5 channels [692]. Most TRP channels are regulated by phosphoinostides such as PtIns(4,5)P2 although the effects reported are often complex, occasionally contradictory, and likely to be dependent upon experimental conditions, such as intracellular ATP levels (reviewed by [862, 592, 689]). Such regulation is generally not included in the tables.When thermosensitivity is mentioned, it refers specifically to a high Q10 of gating, often in the range of 10-30, but does not necessarily imply that the channel's function is to act as a 'hot' or 'cold' sensor. In general, the search for TRP activators has led to many claims for temperature sensing, mechanosensation, and lipid sensing. All proteins are of course sensitive to energies of binding, mechanical force, and temperature, but the issue is whether the proposed input is within a physiologically relevant range resulting in a response. TRPA (ankyrin) familyTRPA1 is the sole mammalian member of this group (reviewed by [246]). TRPA1 activation of sensory neurons contribute to nociception [356, 763, 516]. Pungent chemicals such as mustard oil (AITC), allicin, and cinnamaldehyde activate TRPA1 by modification of free thiol groups of cysteine side chains, especially those located in its amino terminus [491, 47, 311, 493]. Alkenals with α, β-unsaturated bonds, such as propenal (acrolein), butenal (crotylaldehyde), and 2-pentenal can react with free thiols via Michael addition and can activate TRPA1. However, potency appears to weaken as carbon chain length increases [21, 47]. Covalent modification leads to sustained activation of TRPA1. Chemicals including carvacrol, menthol, and local anesthetics reversibly activate TRPA1 by non-covalent binding [364, 438, 923, 922]. TRPA1 is not mechanosensitive under physiological conditions, but can be activated by cold temperatures [365, 175]. The electron cryo-EM structure of TRPA1 [639] indicates that it is a 6-TM homotetramer. Each subunit of the channel contains two short ‘pore helices’ pointing into the ion selectivity filter, which is big enough to allow permeation of partially hydrated Ca2+ ions. TRPC (canonical) familyMembers of the TRPC subfamily (reviewed by [239, 673, 14, 4, 79, 382, 638, 55]) fall into the subgroups outlined below. TRPC2 is a pseudogene in humans. It is generally accepted that all TRPC channels are activated downstream of Gq/11-coupled receptors, or receptor tyrosine kinases (reviewed by [661, 814, 915]). A comprehensive listing of G-protein coupled receptors that activate TRPC channels is given in [4]. Hetero-oligomeric complexes of TRPC channels and their association with proteins to form signalling complexes are detailed in [14] and [383]. TRPC channels have frequently been proposed to act as store-operated channels (SOCs) (or compenents of mulimeric complexes that form SOCs), activated by depletion of intracellular calcium stores (reviewed by [640, 14, 665, 703, 954, 132, 626, 51, 133]). However, the weight of the evidence is that they are not directly gated by conventional store-operated mechanisms, as established for Stim-gated Orai channels. TRPC channels are not mechanically gated in physiologically relevant ranges of force. All members of the TRPC family are blocked by 2-APB and SKF96365 [295, 294]. Activation of TRPC channels by lipids is discussed by [55]. Important progress has been recently made in TRPC pharmacology [692, 529, 372, 87]. TRPC channels regulate a variety of physiological functions and are implicated in many human diseases [248, 56, 759, 879]. TRPC1/C4/C5 subgroup TRPC1 alone may not form a functional ion channel [191]. TRPC4/C5 may be distinguished from other TRP channels by their potentiation by micromolar concentrations of La3+. TRPC2 is a pseudogene in humans, but in other mammals appears to be an ion channel localized to microvilli of the vomeronasal organ. It is required for normal sexual behavior in response to pheromones in mice. It may also function in the main olfactory epithelia in mice [951, 625, 624, 952, 462, 988, 947].TRPC3/C6/C7 subgroup All members are activated by diacylglycerol independent of protein kinase C stimulation [295].TRPM (melastatin) familyMembers of the TRPM subfamily (reviewed by [230, 294, 640, 978]) fall into the five subgroups outlined below. TRPM1/M3 subgroupIn darkness, glutamate released by the photoreceptors and ON-bipolar cells binds to the metabotropic glutamate receptor 6 , leading to activation of Go . This results in the closure of TRPM1. When the photoreceptors are stimulated by light, glutamate release is reduced, and TRPM1 channels are more active, resulting in cell membrane depolarization. Human TRPM1 mutations are associated with congenital stationary night blindness (CSNB), whose patients lack rod function. TRPM1 is also found melanocytes. Isoforms of TRPM1 may present in melanocytes, melanoma, brain, and retina. In melanoma cells, TRPM1 is prevalent in highly dynamic intracellular vesicular structures [341, 609]. TRPM3 (reviewed by [615]) exists as multiple splice variants which differ significantly in their biophysical properties. TRPM3 is expressed in somatosensory neurons and may be important in development of heat hyperalgesia during inflammation (see review [803]). TRPM3 is frequently coexpressed with TRPA1 and TRPV1 in these neurons. TRPM3 is expressed in pancreatic beta cells as well as brain, pituitary gland, eye, kidney, and adipose tissue [614, 802]. TRPM3 may contribute to the detection of noxious heat [870].TRPM2TRPM2 is activated under conditions of oxidative stress (respiratory burst of phagocytic cells) and ischemic conditions. However, the direct activators are ADPR(P) and calcium. As for many ion channels, PIP2 must also be present (reviewed by [935]). Numerous splice variants of TRPM2 exist which differ in their activation mechanisms [200]. The C-terminal domain contains a TRP motif, a coiled-coil region, and an enzymatic NUDT9 homologous domain. TRPM2 appears not to be activated by NAD, NAAD, or NAADP, but is directly activated by ADPRP (adenosine-5'-O-disphosphoribose phosphate) [827]. TRPM2 is involved in warmth sensation [724], and contributes to neurological diseases [61]. Recent study shows that 2'-deoxy-ADPR is an endogenous TRPM2 superagonist [231]. TRPM4/5 subgroupTRPM4 and TRPM5 have the distinction within all TRP channels of being impermeable to Ca2+ [915]. A splice variant of TRPM4 (i.e.TRPM4b) and TRPM5 are molecular candidates for endogenous calcium-activated cation (CAN) channels [278]. TRPM4 is active in the late phase of repolarization of the cardiac ventricular action potential. TRPM4 deletion or knockout enhances beta adrenergic-mediated inotropy [507]. Mutations are associated with conduction defects [347, 507, 753]. TRPM4 has been shown to be an important regulator of Ca2+ entry in to mast cells [847] and dendritic cell migration [39]. TRPM5 in taste receptor cells of the tongue appears essential for the transduction of sweet, amino acid and bitter stimuli [460] TRPM5 contributes to the slow afterdepolarization of layer 5 neurons in mouse prefrontal cortex [439]. Both TRPM4 and TRPM5 are required transduction of taste stimuli [206].TRPM6/7 subgroupTRPM6 and 7 combine channel and enzymatic activities (‘chanzymes’). These channels have the unusual property of permeation by divalent (Ca2+, Mg2+, Zn2+) and monovalent cations, high single channel conductances, but overall extremely small inward conductance when expressed to the plasma membrane. They are inhibited by internal Mg2+ at ~0.6 mM, around the free level of Mg2+ in cells. Whether they contribute to Mg2+ homeostasis is a contentious issue. When either gene is deleted in mice, the result is embryonic lethality. The C-terminal kinase region is cleaved under unknown stimuli, and the kinase phosphorylates nuclear histones. TRPM7 is responsible for oxidant- induced Zn2+ release from intracellular vesicles [3] and contributes to intestinal mineral absorption essential for postnatal survival [532]. TRPM8Is a channel activated by cooling and pharmacological agents evoking a ‘cool’ sensation and participates in the thermosensation of cold temperatures [50, 147, 186] reviewed by [864, 481, 391, 556]. TRPML (mucolipin) familyThe TRPML family [676, 964, 670, 926, 156] consists of three mammalian members (TRPML1-3). TRPML channels are probably restricted to intracellular vesicles and mutations in the gene (MCOLN1) encoding TRPML1 (mucolipin-1) cause the neurodegenerative disorder mucolipidosis type IV (MLIV) in man. TRPML1 is a cation selective ion channel that is important for sorting/transport of endosomes in the late endocytotic pathway and specifically, fission from late endosome-lysosome hybrid vesicles and lysosomal exocytosis [704]. TRPML2 and TRPML3 show increased channel activity in low extracellular sodium and are activated by similar small molecules [270]. A naturally occurring gain of function mutation in TRPML3 (i.e. A419P) results in the varitint waddler (Va) mouse phenotype (reviewed by [676, 593]). TRPP (polycystin) familyThe TRPP family (reviewed by [179, 177, 252, 905, 320]) or PKD2 family is comprised of PKD2 (PC2), PKD2L1 (PC2L1), PKD2L2 (PC2L2), which have been renamed TRPP1, TRPP2 and TRPP3, respectively [915]. It should also be noted that the nomenclature of PC2 was TRPP2 in old literature. However, PC2 has been uniformed to be called TRPP2 [293]. PKD2 family channels are clearly distinct from the PKD1 family, whose function is unknown. PKD1 and PKD2 form a hetero-oligomeric complex with a 1:3 ratio. [775]. Although still being sorted out, TRPP family members appear to be 6TM spanning nonselective cation channels. TRPV (vanilloid) familyMembers of the TRPV family (reviewed by [849]) can broadly be divided into the non-selective cation channels, TRPV1-4 and the more calcium selective channels TRPV5 and TRPV6.TRPV1-V4 subfamilyTRPV1 is involved in the development of thermal hyperalgesia following inflammation and may contribute to the detection of noxius heat (reviewed by [660, 756, 786]). Numerous splice variants of TRPV1 have been described, some of which modulate the activity of TRPV1, or act in a dominant negative manner when co-expressed with TRPV1 [722]. The pharmacology of TRPV1 channels is discussed in detail in [280] and [868]. TRPV2 is probably not a thermosensor in man [635], but has recently been implicated in innate immunity [469]. TRPV3 and TRPV4 are both thermosensitive. There are claims that TRPV4 is also mechanosensitive, but this has not been established to be within a physiological range in a native environment [106, 454].TRPV5/V6 subfamily TRPV5 and TRPV6 are highly expressed in placenta, bone, and kidney. Under physiological conditions, TRPV5 and TRPV6 are calcium selective channels involved in the absorption and reabsorption of calcium across intestinal and kidney tubule epithelia (reviewed by [901, 168, 558, 227])

Transient Receptor Potential channels (TRP) in GtoPdb v.2023.1

The TRP superfamily of channels (nomenclature as agreed by NC-IUPHAR [176, 1072]), whose founder member is the Drosophila Trp channel, exists in mammals as six families; TRPC, TRPM, TRPV, TRPA, TRPP and TRPML based on amino acid homologies. TRP subunits contain six putative TM domains and assemble as homo- or hetero-tetramers to form cation selective channels with diverse modes of activation and varied permeation properties (reviewed by [730]). Established, or potential, physiological functions of the individual members of the TRP families are discussed in detail in the recommended reviews and in a number of books [401, 686, 1155, 256]. The established, or potential, involvement of TRP channels in disease [1126] is reviewed in [448, 685], [688] and [464], together with a special edition of Biochemica et Biophysica Acta on the subject [685]. Additional disease related reviews, for pain [633], stroke [1135], sensation and inflammation [988], itch [130], and airway disease [310, 1051], are available. The pharmacology of most TRP channels has been advanced in recent years. Broad spectrum agents are listed in the tables along with more selective, or recently recognised, ligands that are flagged by the inclusion of a primary reference. See Rubaiy (2019) for a review of pharmacological tools for TRPC1/C4/C5 channels [805]. Most TRP channels are regulated by phosphoinostides such as PtIns(4,5)P2 although the effects reported are often complex, occasionally contradictory, and likely to be dependent upon experimental conditions, such as intracellular ATP levels (reviewed by [1009, 689, 801]). Such regulation is generally not included in the tables.When thermosensitivity is mentioned, it refers specifically to a high Q10 of gating, often in the range of 10-30, but does not necessarily imply that the channel's function is to act as a 'hot' or 'cold' sensor. In general, the search for TRP activators has led to many claims for temperature sensing, mechanosensation, and lipid sensing. All proteins are of course sensitive to energies of binding, mechanical force, and temperature, but the issue is whether the proposed input is within a physiologically relevant range resulting in a response. TRPA (ankyrin) familyTRPA1 is the sole mammalian member of this group (reviewed by [293]). TRPA1 activation of sensory neurons contribute to nociception [414, 890, 602]. Pungent chemicals such as mustard oil (AITC), allicin, and cinnamaldehyde activate TRPA1 by modification of free thiol groups of cysteine side chains, especially those located in its amino terminus [575, 60, 365, 577]. Alkenals with α, β-unsaturated bonds, such as propenal (acrolein), butenal (crotylaldehyde), and 2-pentenal can react with free thiols via Michael addition and can activate TRPA1. However, potency appears to weaken as carbon chain length increases [26, 60]. Covalent modification leads to sustained activation of TRPA1. Chemicals including carvacrol, menthol, and local anesthetics reversibly activate TRPA1 by non-covalent binding [424, 511, 1081, 1080]. TRPA1 is not mechanosensitive under physiological conditions, but can be activated by cold temperatures [425, 212]. The electron cryo-EM structure of TRPA1 [740] indicates that it is a 6-TM homotetramer. Each subunit of the channel contains two short ‘pore helices’ pointing into the ion selectivity filter, which is big enough to allow permeation of partially hydrated Ca2+ ions. TRPC (canonical) familyMembers of the TRPC subfamily (reviewed by [284, 778, 18, 4, 94, 446, 739, 70]) fall into the subgroups outlined below. TRPC2 is a pseudogene in humans. It is generally accepted that all TRPC channels are activated downstream of Gq/11-coupled receptors, or receptor tyrosine kinases (reviewed by [765, 953, 1072]). A comprehensive listing of G-protein coupled receptors that activate TRPC channels is given in [4]. Hetero-oligomeric complexes of TRPC channels and their association with proteins to form signalling complexes are detailed in [18] and [447]. TRPC channels have frequently been proposed to act as store-operated channels (SOCs) (or compenents of mulimeric complexes that form SOCs), activated by depletion of intracellular calcium stores (reviewed by [741, 18, 770, 820, 1121, 157, 726, 64, 158]). However, the weight of the evidence is that they are not directly gated by conventional store-operated mechanisms, as established for Stim-gated Orai channels. TRPC channels are not mechanically gated in physiologically relevant ranges of force. All members of the TRPC family are blocked by 2-APB and SKF96365 [347, 346]. Activation of TRPC channels by lipids is discussed by [70]. Important progress has been recently made in TRPC pharmacology [805, 619, 436, 102, 851, 191, 291]. TRPC channels regulate a variety of physiological functions and are implicated in many human diseases [295, 71, 885, 1031, 1025, 154, 103, 561, 913, 409]. TRPC1/C4/C5 subgroup TRPC1 alone may not form a functional ion channel [229]. TRPC4/C5 may be distinguished from other TRP channels by their potentiation by micromolar concentrations of La3+. TRPC2 is a pseudogene in humans, but in other mammals appears to be an ion channel localized to microvilli of the vomeronasal organ. It is required for normal sexual behavior in response to pheromones in mice. It may also function in the main olfactory epithelia in mice [1114, 723, 724, 1115, 539, 1168, 1109].TRPC3/C6/C7 subgroup All members are activated by diacylglycerol independent of protein kinase C stimulation [347].TRPM (melastatin) familyMembers of the TRPM subfamily (reviewed by [275, 346, 741, 1151]) fall into the five subgroups outlined below. TRPM1/M3 subgroupIn darkness, glutamate released by the photoreceptors and ON-bipolar cells binds to the metabotropic glutamate receptor 6 , leading to activation of Go . This results in the closure of TRPM1. When the photoreceptors are stimulated by light, glutamate release is reduced, and TRPM1 channels are more active, resulting in cell membrane depolarization. Human TRPM1 mutations are associated with congenital stationary night blindness (CSNB), whose patients lack rod function. TRPM1 is also found melanocytes. Isoforms of TRPM1 may present in melanocytes, melanoma, brain, and retina. In melanoma cells, TRPM1 is prevalent in highly dynamic intracellular vesicular structures [398, 708]. TRPM3 (reviewed by [714]) exists as multiple splice variants which differ significantly in their biophysical properties. TRPM3 is expressed in somatosensory neurons and may be important in development of heat hyperalgesia during inflammation (see review [941]). TRPM3 is frequently coexpressed with TRPA1 and TRPV1 in these neurons. TRPM3 is expressed in pancreatic beta cells as well as brain, pituitary gland, eye, kidney, and adipose tissue [713, 940]. TRPM3 may contribute to the detection of noxious heat [1017]. TRPM2TRPM2 is activated under conditions of oxidative stress (respiratory burst of phagocytic cells). The direct activators are calcium, adenosine diphosphate ribose (ADPR) [970] and cyclic ADPR (cADPR) [1118]. As for many ion channels, PI(4,5)P2 must also be present [1109]. Numerous splice variants of TRPM2 exist which differ in their activation mechanisms [239]. Recent studies have reported structures of human (hs) TRPM2, which demonstrate two ADPR binding sites in hsTRPM2, one in the N-terminal MHR1/2 domain and the other in the C-terminal NUDT9-H domain. In addition, one Ca2+ binding site in the intracellular S2-S3 loop is revealed and proposed to mediate Ca2+ binding that induces conformational changes leading the ADPR-bound closed channel to open [387, 1027]. Meanwhile, a quadruple-residue motif (979FGQI982) was identified as the ion selectivity filter and a gate to control ion permeation in hsTRPM2 [1120]. TRPM2 is involved in warmth sensation [848], and contributes to several diseases [76]. TRPM2 interacts with extra synaptic NMDA receptors (NMDAR) and enhances NMDAR activity in ischemic stroke [1164]. Activation of TRPM2 in macrophages promotes atherosclerosis [1165, 1147]. Moreover, silica nanoparticles induce lung inflammation in mice via ROS/PARP/TRPM2 signaling-mediated lysosome impairment and autophagy dysfunction [1028]. Recent studies have designed various compounds for their potential to selectively inhibit the TRPM2 channel, including ACA derivatives A23, and 2,3-dihydroquinazolin-4(1H)-one derivatives [1137, 1139]. TRPM4/5 subgroupTRPM4 and TRPM5 have the distinction within all TRP channels of being impermeable to Ca2+ [1072]. A splice variant of TRPM4 (i.e.TRPM4b) and TRPM5 are molecular candidates for endogenous calcium-activated cation (CAN) channels [327]. TRPM4 is active in the late phase of repolarization of the cardiac ventricular action potential. TRPM4 deletion or knockout enhances beta adrenergic-mediated inotropy [593]. Mutations are associated with conduction defects [404, 593, 879]. TRPM4 has been shown to be an important regulator of Ca2+ entry in to mast cells [993] and dendritic cell migration [52]. TRPM5 in taste receptor cells of the tongue appears essential for the transduction of sweet, amino acid and bitter stimuli [537] TRPM5 contributes to the slow afterdepolarization of layer 5 neurons in mouse prefrontal cortex [513]. Both TRPM4 and TRPM5 are required transduction of taste stimuli [246]. TRPM6/7 subgroupTRPM6 and 7 combine channel and enzymatic activities (‘chanzymes’) [172]. These channels have the unusual property of permeation by divalent (Ca2+, Mg2+, Zn2+) and monovalent cations, high single channel conductances, but overall extremely small inward conductance when expressed to the plasma membrane. They are inhibited by internal Mg2+ at ~0.6 mM, around the free level of Mg2+ in cells. Whether they contribute to Mg2+ homeostasis is a contentious issue. PIP2 is required for TRPM6 and TRPM7 activation [810, 1077]. When either gene is deleted in mice, the result is embryonic lethality [413, 1065]. The C-terminal kinase region of TRPM6 and TRPM7 is cleaved under unknown stimuli, and the kinase phosphorylates nuclear histones [479, 480]. TRPM7 is responsible for oxidant- induced Zn2+ release from intracellular vesicles [3] and contributes to intestinal mineral absorption essential for postnatal survival [622]. The putative metal transporter proteins CNNM1-4 interact with TRPM7 and regulate TRPM7 channel activity [40, 467]. TRPM8Is a channel activated by cooling and pharmacological agents evoking a ‘cool’ sensation and participates in the thermosensation of cold temperatures [63, 178, 224] reviewed by [1011, 562, 457, 649]. Direct chemical agonists include menthol and icilin[1086]. Besides, linalool can promote ERK phosphorylation in human dermal microvascular endothelial cells, down-regulate intracellular ATP levels, and activate TRPM8 [68]. Recent studies have found that TRPM8 has typical S4-S5 connectomes with clear selective filters and exowell rings [512], and have identified cryo-electron microscopy structures of mouse TRPM8 in closed, intermediate, and open states along the ligand- and PIP2-dependent gated pathways [1111]. Moreover, the last 36 amino acids at the carboxyl terminal of TRPM8 are key protein sequences for TRPM8's temperature-sensitive function [194]. TRPM8 deficiency reduced the expression of S100A9 and increased the expression of HNF4α in the liver of mice, which reduced inflammation and fibrosis progression in mice with liver fibrosis, and helped to alleviate the symptoms of bile duct disease [556]. Channel deficiency also shortens the time of hypersensitivity reactions in migraine mouse models by promoting the recovery of normal sensitivity [12]. A cyclic peptide DeC‐1.2 was designed to inhibit ligand activation of TRPM8 but not cold activation, which can eliminate the side effects of cold dysalgesia in oxaliplatin-treated mice without changing body temperature [9]. Analysis of clinical data shows that TRPM8-specific blockers WS12 can reduce tumor growth in colorectal cancer xenografted mice by reducing transcription and activation of Wnt signaling regulators and β-catenin and its target oncogenes, such as C-Myc and Cyclin D1 [732]. TRPML (mucolipin) familyThe TRPML family [782, 1132, 775, 1084, 190] consists of three mammalian members (TRPML1-3). TRPML channels are probably restricted to intracellular vesicles and mutations in the gene (MCOLN1) encoding TRPML1 (mucolipin-1) cause the neurodegenerative disorder mucolipidosis type IV (MLIV) in man. TRPML1 is a cation selective ion channel that is important for sorting/transport of endosomes in the late endocytotic pathway and specifically, fission from late endosome-lysosome hybrid vesicles and lysosomal exocytosis [822]. TRPML2 and TRPML3 show increased channel activity in low luminal sodium and/or increased luminal pH, and are activated by similar small molecules [319, 147, 877]. A naturally occurring gain of function mutation in TRPML3 (i.e. A419P) results in the varitint waddler (Va) mouse phenotype (reviewed by [782, 690]). TRPP (polycystin) familyThe TRPP family (reviewed by [216, 214, 300, 1061, 374]) or PKD2 family is comprised of PKD2 (PC2), PKD2L1 (PC2L1), PKD2L2 (PC2L2), which have been renamed TRPP1, TRPP2 and TRPP3, respectively [1072]. It should also be noted that the nomenclature of PC2 was TRPP2 in old literature. However, PC2 has been uniformed to be called TRPP2 [345]. PKD2 family channels are clearly distinct from the PKD1 family, whose function is unknown. PKD1 and PKD2 form a hetero-oligomeric complex with a 1:3 ratio. [905]. Although still being sorted out, TRPP family members appear to be 6TM spanning nonselective cation channels. TRPV (vanilloid) familyMembers of the TRPV family (reviewed by [995]) can broadly be divided into the non-selective cation channels, TRPV1-4 and the more calcium selective channels TRPV5 and TRPV6. TRPV1-V4 subfamilyTRPV1 is involved in the development of thermal hyperalgesia following inflammation and may contribute to the detection of noxius heat (reviewed by [762, 882, 922]). Numerous splice variants of TRPV1 have been described, some of which modulate the activity of TRPV1, or act in a dominant negative manner when co-expressed with TRPV1 [844]. The pharmacology of TRPV1 channels is discussed in detail in [329] and [1015]. TRPV2 is probably not a thermosensor in man [736], but has recently been implicated in innate immunity [547]. Functional TRPV2 expression is described in placental trophoblast cells of mouse [204]. TRPV3 and TRPV4 are both thermosensitive. There are claims that TRPV4 is also mechanosensitive, but this has not been established to be within a physiological range in a native environment [127, 530]. TRPV5/V6 subfamily TRPV5 and TRPV6 are highly expressed in placenta, bone, and kidney. Under physiological conditions, TRPV5 and TRPV6 are calcium selective channels involved in the absorption and reabsorption of calcium across intestinal and kidney tubule epithelia (reviewed by [1057, 205, 651, 270]).TRPV6 is reported to play a key role in calcium transport in the mouse placenta [1056]

Transient Receptor Potential channels (TRP) in GtoPdb v.2023.2

The TRP superfamily of channels (nomenclature as agreed by NC-IUPHAR [176, 1072]), whose founder member is the Drosophila Trp channel, exists in mammals as six families; TRPC, TRPM, TRPV, TRPA, TRPP and TRPML based on amino acid homologies. TRP subunits contain six putative TM domains and assemble as homo- or hetero-tetramers to form cation selective channels with diverse modes of activation and varied permeation properties (reviewed by [730]). Established, or potential, physiological functions of the individual members of the TRP families are discussed in detail in the recommended reviews and in a number of books [401, 686, 1155, 256]. The established, or potential, involvement of TRP channels in disease [1126] is reviewed in [448, 685], [688] and [464], together with a special edition of Biochemica et Biophysica Acta on the subject [685]. Additional disease related reviews, for pain [633], stroke [1135], sensation and inflammation [988], itch [130], and airway disease [310, 1051], are available. The pharmacology of most TRP channels has been advanced in recent years. Broad spectrum agents are listed in the tables along with more selective, or recently recognised, ligands that are flagged by the inclusion of a primary reference. See Rubaiy (2019) for a review of pharmacological tools for TRPC1/C4/C5 channels [805]. Most TRP channels are regulated by phosphoinostides such as PtIns(4,5)P2 although the effects reported are often complex, occasionally contradictory, and likely to be dependent upon experimental conditions, such as intracellular ATP levels (reviewed by [1009, 689, 801]). Such regulation is generally not included in the tables.When thermosensitivity is mentioned, it refers specifically to a high Q10 of gating, often in the range of 10-30, but does not necessarily imply that the channel's function is to act as a 'hot' or 'cold' sensor. In general, the search for TRP activators has led to many claims for temperature sensing, mechanosensation, and lipid sensing. All proteins are of course sensitive to energies of binding, mechanical force, and temperature, but the issue is whether the proposed input is within a physiologically relevant range resulting in a response. TRPA (ankyrin) familyTRPA1 is the sole mammalian member of this group (reviewed by [293]). TRPA1 activation of sensory neurons contribute to nociception [414, 890, 602]. Pungent chemicals such as mustard oil (AITC), allicin, and cinnamaldehyde activate TRPA1 by modification of free thiol groups of cysteine side chains, especially those located in its amino terminus [575, 60, 365, 577]. Alkenals with α, β-unsaturated bonds, such as propenal (acrolein), butenal (crotylaldehyde), and 2-pentenal can react with free thiols via Michael addition and can activate TRPA1. However, potency appears to weaken as carbon chain length increases [26, 60]. Covalent modification leads to sustained activation of TRPA1. Chemicals including carvacrol, menthol, and local anesthetics reversibly activate TRPA1 by non-covalent binding [424, 511, 1081, 1080]. TRPA1 is not mechanosensitive under physiological conditions, but can be activated by cold temperatures [425, 212]. The electron cryo-EM structure of TRPA1 [740] indicates that it is a 6-TM homotetramer. Each subunit of the channel contains two short ‘pore helices’ pointing into the ion selectivity filter, which is big enough to allow permeation of partially hydrated Ca2+ ions. TRPC (canonical) familyMembers of the TRPC subfamily (reviewed by [284, 778, 18, 4, 94, 446, 739, 70]) fall into the subgroups outlined below. TRPC2 is a pseudogene in humans. It is generally accepted that all TRPC channels are activated downstream of Gq/11-coupled receptors, or receptor tyrosine kinases (reviewed by [765, 953, 1072]). A comprehensive listing of G-protein coupled receptors that activate TRPC channels is given in [4]. Hetero-oligomeric complexes of TRPC channels and their association with proteins to form signalling complexes are detailed in [18] and [447]. TRPC channels have frequently been proposed to act as store-operated channels (SOCs) (or compenents of mulimeric complexes that form SOCs), activated by depletion of intracellular calcium stores (reviewed by [741, 18, 770, 820, 1121, 157, 726, 64, 158]). However, the weight of the evidence is that they are not directly gated by conventional store-operated mechanisms, as established for Stim-gated Orai channels. TRPC channels are not mechanically gated in physiologically relevant ranges of force. All members of the TRPC family are blocked by 2-APB and SKF96365 [347, 346]. Activation of TRPC channels by lipids is discussed by [70]. Important progress has been recently made in TRPC pharmacology [805, 619, 436, 102, 851, 191, 291]. TRPC channels regulate a variety of physiological functions and are implicated in many human diseases [295, 71, 885, 1031, 1025, 154, 103, 561, 913, 409]. TRPC1/C4/C5 subgroup TRPC1 alone may not form a functional ion channel [229]. TRPC4/C5 may be distinguished from other TRP channels by their potentiation by micromolar concentrations of La3+. TRPC2 is a pseudogene in humans, but in other mammals appears to be an ion channel localized to microvilli of the vomeronasal organ. It is required for normal sexual behavior in response to pheromones in mice. It may also function in the main olfactory epithelia in mice [1114, 723, 724, 1115, 539, 1168, 1109].TRPC3/C6/C7 subgroup All members are activated by diacylglycerol independent of protein kinase C stimulation [347].TRPM (melastatin) familyMembers of the TRPM subfamily (reviewed by [275, 346, 741, 1151]) fall into the five subgroups outlined below. TRPM1/M3 subgroupIn darkness, glutamate released by the photoreceptors and ON-bipolar cells binds to the metabotropic glutamate receptor 6 , leading to activation of Go . This results in the closure of TRPM1. When the photoreceptors are stimulated by light, glutamate release is reduced, and TRPM1 channels are more active, resulting in cell membrane depolarization. Human TRPM1 mutations are associated with congenital stationary night blindness (CSNB), whose patients lack rod function. TRPM1 is also found melanocytes. Isoforms of TRPM1 may present in melanocytes, melanoma, brain, and retina. In melanoma cells, TRPM1 is prevalent in highly dynamic intracellular vesicular structures [398, 708]. TRPM3 (reviewed by [714]) exists as multiple splice variants which differ significantly in their biophysical properties. TRPM3 is expressed in somatosensory neurons and may be important in development of heat hyperalgesia during inflammation (see review [941]). TRPM3 is frequently coexpressed with TRPA1 and TRPV1 in these neurons. TRPM3 is expressed in pancreatic beta cells as well as brain, pituitary gland, eye, kidney, and adipose tissue [713, 940]. TRPM3 may contribute to the detection of noxious heat [1017]. TRPM2TRPM2 is activated under conditions of oxidative stress (respiratory burst of phagocytic cells). The direct activators are calcium, adenosine diphosphate ribose (ADPR) [970] and cyclic ADPR (cADPR) [1118]. As for many ion channels, PI(4,5)P2 must also be present [1109]. Numerous splice variants of TRPM2 exist which differ in their activation mechanisms [239]. Recent studies have reported structures of human (hs) TRPM2, which demonstrate two ADPR binding sites in hsTRPM2, one in the N-terminal MHR1/2 domain and the other in the C-terminal NUDT9-H domain. In addition, one Ca2+ binding site in the intracellular S2-S3 loop is revealed and proposed to mediate Ca2+ binding that induces conformational changes leading the ADPR-bound closed channel to open [387, 1027]. Meanwhile, a quadruple-residue motif (979FGQI982) was identified as the ion selectivity filter and a gate to control ion permeation in hsTRPM2 [1120]. TRPM2 is involved in warmth sensation [848], and contributes to several diseases [76]. TRPM2 interacts with extra synaptic NMDA receptors (NMDAR) and enhances NMDAR activity in ischemic stroke [1164]. Activation of TRPM2 in macrophages promotes atherosclerosis [1165, 1147]. Moreover, silica nanoparticles induce lung inflammation in mice via ROS/PARP/TRPM2 signaling-mediated lysosome impairment and autophagy dysfunction [1028]. Recent studies have designed various compounds for their potential to selectively inhibit the TRPM2 channel, including ACA derivatives A23, and 2,3-dihydroquinazolin-4(1H)-one derivatives [1137, 1139]. TRPM4/5 subgroupTRPM4 and TRPM5 have the distinction within all TRP channels of being impermeable to Ca2+ [1072]. A splice variant of TRPM4 (i.e.TRPM4b) and TRPM5 are molecular candidates for endogenous calcium-activated cation (CAN) channels [327]. TRPM4 is active in the late phase of repolarization of the cardiac ventricular action potential. TRPM4 deletion or knockout enhances beta adrenergic-mediated inotropy [593]. Mutations are associated with conduction defects [404, 593, 879]. TRPM4 has been shown to be an important regulator of Ca2+ entry in to mast cells [993] and dendritic cell migration [52]. TRPM5 in taste receptor cells of the tongue appears essential for the transduction of sweet, amino acid and bitter stimuli [537] TRPM5 contributes to the slow afterdepolarization of layer 5 neurons in mouse prefrontal cortex [513]. Both TRPM4 and TRPM5 are required transduction of taste stimuli [246]. TRPM6/7 subgroupTRPM6 and 7 combine channel and enzymatic activities (‘chanzymes’) [172]. These channels have the unusual property of permeation by divalent (Ca2+, Mg2+, Zn2+) and monovalent cations, high single channel conductances, but overall extremely small inward conductance when expressed to the plasma membrane. They are inhibited by internal Mg2+ at ~0.6 mM, around the free level of Mg2+ in cells. Whether they contribute to Mg2+ homeostasis is a contentious issue. PIP2 is required for TRPM6 and TRPM7 activation [810, 1077]. When either gene is deleted in mice, the result is embryonic lethality [413, 1065]. The C-terminal kinase region of TRPM6 and TRPM7 is cleaved under unknown stimuli, and the kinase phosphorylates nuclear histones [479, 480]. TRPM7 is responsible for oxidant- induced Zn2+ release from intracellular vesicles [3] and contributes to intestinal mineral absorption essential for postnatal survival [622]. The putative metal transporter proteins CNNM1-4 interact with TRPM7 and regulate TRPM7 channel activity [40, 467]. TRPM8Is a channel activated by cooling and pharmacological agents evoking a ‘cool’ sensation and participates in the thermosensation of cold temperatures [63, 178, 224] reviewed by [1011, 562, 457, 649]. Direct chemical agonists include menthol and icilin[1086]. Besides, linalool can promote ERK phosphorylation in human dermal microvascular endothelial cells, down-regulate intracellular ATP levels, and activate TRPM8 [68]. Recent studies have found that TRPM8 has typical S4-S5 connectomes with clear selective filters and exowell rings [512], and have identified cryo-electron microscopy structures of mouse TRPM8 in closed, intermediate, and open states along the ligand- and PIP2-dependent gated pathways [1111]. Moreover, the last 36 amino acids at the carboxyl terminal of TRPM8 are key protein sequences for TRPM8's temperature-sensitive function [194]. TRPM8 deficiency reduced the expression of S100A9 and increased the expression of HNF4α in the liver of mice, which reduced inflammation and fibrosis progression in mice with liver fibrosis, and helped to alleviate the symptoms of bile duct disease [556]. Channel deficiency also shortens the time of hypersensitivity reactions in migraine mouse models by promoting the recovery of normal sensitivity [12]. A cyclic peptide DeC‐1.2 was designed to inhibit ligand activation of TRPM8 but not cold activation, which can eliminate the side effects of cold dysalgesia in oxaliplatin-treated mice without changing body temperature [9]. Analysis of clinical data shows that TRPM8-specific blockers WS12 can reduce tumor growth in colorectal cancer xenografted mice by reducing transcription and activation of Wnt signaling regulators and β-catenin and its target oncogenes, such as C-Myc and Cyclin D1 [732]. TRPML (mucolipin) familyThe TRPML family [782, 1132, 775, 1084, 190] consists of three mammalian members (TRPML1-3). TRPML channels are probably restricted to intracellular vesicles and mutations in the gene (MCOLN1) encoding TRPML1 (mucolipin-1) cause the neurodegenerative disorder mucolipidosis type IV (MLIV) in man. TRPML1 is a cation selective ion channel that is important for sorting/transport of endosomes in the late endocytotic pathway and specifically, fission from late endosome-lysosome hybrid vesicles and lysosomal exocytosis [822]. TRPML2 and TRPML3 show increased channel activity in low luminal sodium and/or increased luminal pH, and are activated by similar small molecules [319, 147, 877]. A naturally occurring gain of function mutation in TRPML3 (i.e. A419P) results in the varitint waddler (Va) mouse phenotype (reviewed by [782, 690]). TRPP (polycystin) familyThe TRPP family (reviewed by [216, 214, 300, 1061, 374]) or PKD2 family is comprised of PKD2 (PC2), PKD2L1 (PC2L1), PKD2L2 (PC2L2), which have been renamed TRPP1, TRPP2 and TRPP3, respectively [1072]. It should also be noted that the nomenclature of PC2 was TRPP2 in old literature. However, PC2 has been uniformed to be called TRPP2 [345]. PKD2 family channels are clearly distinct from the PKD1 family, whose function is unknown. PKD1 and PKD2 form a hetero-oligomeric complex with a 1:3 ratio. [905]. Although still being sorted out, TRPP family members appear to be 6TM spanning nonselective cation channels. TRPV (vanilloid) familyMembers of the TRPV family (reviewed by [995]) can broadly be divided into the non-selective cation channels, TRPV1-4 and the more calcium selective channels TRPV5 and TRPV6. TRPV1-V4 subfamilyTRPV1 is involved in the development of thermal hyperalgesia following inflammation and may contribute to the detection of noxius heat (reviewed by [762, 882, 922]). Numerous splice variants of TRPV1 have been described, some of which modulate the activity of TRPV1, or act in a dominant negative manner when co-expressed with TRPV1 [844]. The pharmacology of TRPV1 channels is discussed in detail in [329] and [1015]. TRPV2 is probably not a thermosensor in man [736], but has recently been implicated in innate immunity [547]. Functional TRPV2 expression is described in placental trophoblast cells of mouse [204]. TRPV3 and TRPV4 are both thermosensitive. There are claims that TRPV4 is also mechanosensitive, but this has not been established to be within a physiological range in a native environment [127, 530]. TRPV5/V6 subfamily TRPV5 and TRPV6 are highly expressed in placenta, bone, and kidney. Under physiological conditions, TRPV5 and TRPV6 are calcium selective channels involved in the absorption and reabsorption of calcium across intestinal and kidney tubule epithelia (reviewed by [1057, 205, 651, 270]).TRPV6 is reported to play a key role in calcium transport in the mouse placenta [1056]

Coronavirus disease 2019 (COVID-19) excess mortality outcomes associated with pandemic effects study (COPES): A systematic review and meta-analysis

Background and aimWith the Coronavirus Disease 2019 (COVID-19) pandemic continuing to impact healthcare systems around the world, healthcare providers are attempting to balance resources devoted to COVID-19 patients while minimizing excess mortality overall (both COVID-19 and non-COVID-19 patients). To this end, we conducted a systematic review (SR) to describe the effect of the COVID-19 pandemic on all-cause excess mortality (COVID-19 and non-COVID-19) during the pandemic timeframe compared to non-pandemic times.MethodsWe searched EMBASE, Cochrane Database of SRs, MEDLINE, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Cochrane Controlled Trials Register (CENTRAL), from inception (1948) to December 31, 2020. We used a two-stage review process to screen/extract data. We assessed risk of bias using Newcastle-Ottawa Scale (NOS). We used Critical Appraisal and Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology.ResultsOf 11,581 citations, 194 studies met eligibility. Of these studies, 31 had mortality comparisons (n = 433,196,345 participants). Compared to pre-pandemic times, during the COVID-19 pandemic, our meta-analysis demonstrated that COVID-19 mortality had an increased risk difference (RD) of 0.06% (95% CI: 0.06–0.06% p < 0.00001). All-cause mortality also increased [relative risk (RR): 1.53, 95% confidence interval (CI): 1.38–1.70, p < 0.00001] alongside non-COVID-19 mortality (RR: 1.18, 1.07–1.30, p < 0.00001). There was “very low” certainty of evidence through GRADE assessment for all outcomes studied, demonstrating the evidence as uncertain.InterpretationThe COVID-19 pandemic may have caused significant increases in all-cause excess mortality, greater than those accounted for by increases due to COVID-19 mortality alone, although the evidence is uncertain.Systematic review registration[https://www.crd.york.ac.uk/prospero/#recordDetails], identifier [CRD42020201256]

AI is a viable alternative to high throughput screening: a 318-target study

: High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery