Electronic sculpting of ligand-GPCR subtype selectivity:the case of angiotensin II

GPCR subtypes possess distinct functional and pharmacological profiles, and thus development of subtype-selective ligands has immense therapeutic potential. This is especially the case for the angiotensin receptor subtypes AT1R and AT2R, where a functional negative control has been described and AT2R activation highlighted as an important cancer drug target. We describe a strategy to fine-tune ligand selectivity for the AT2R/AT1R subtypes through electronic control of ligand aromatic-prolyl interactions. Through this strategy an AT2R high affinity (<i>K</i>_i = 3 nM) agonist analogue that exerted 18,000-fold higher selectivity for AT2R versus AT1R was obtained. We show that this compound is a negative regulator of AT1R signaling since it is able to inhibit MCF-7 breast carcinoma cellular proliferation in the low nanomolar range

Examining the effects of sodium ions on the binding of antagonists to dopamine D2 and D3 receptors

Many G protein-coupled receptors have been shown to be sensitive to the presence of sodium ions (Na+). Using radioligand competition binding assays, we have examined and compared the effects of sodium ions on the binding affinities of a number of structurally diverse ligands at human dopamine D2 and dopamine D3 receptor subtypes, which are important therapeutic targets for the treatment of psychotic disorders. At both receptors, the binding affinities of the antagonists/inverse agonists SB-277011-A, L,741,626, GR 103691 and U 99194 were higher in the presence of sodium ions compared to those measured in the presence of the organic cation, N-methyl-D-glucamine, used to control for ionic strength. Conversely, the affinities of spiperone and (+)-butaclamol were unaffected by the presence of sodium ions. Interestingly, the binding of the antagonist/inverse agonist clozapine was affected by changes in ionic strength of the buffer used rather than the presence of specific cations. Similar sensitivities to sodium ions were seen at both receptors, suggesting parallel effects of sodium ion interactions on receptor conformation. However, no clear correlation between ligand characteristics, such as subtype selectivity, and sodium ion sensitivity were observed. Therefore, the properties which determine this sensitivity remain unclear. However these findings do highlight the importance of careful consideration of assay buffer composition for in vitro assays and when comparing data from different studies, and may indicate a further level of control for ligand binding in vivo

Community guidelines for GPCR ligand bias: IUPHAR review 32

GPCRs modulate a plethora of physiological processes and mediate the effects of one-third of FDA-approved drugs. Depending on which ligand activates a receptor, it can engage different intracellular transducers. This ‘biased signalling’ paradigm requires that we now characterize physiological signalling not just by receptors but by ligand–receptor pairs. Ligands eliciting biased signalling may constitute better drugs with higher efficacy and fewer adverse effects. However, ligand bias is very complex, making reproducibility and description challenging. Here, we provide guidelines and terminology for any scientists to design and report ligand bias experiments. The guidelines will aid consistency and clarity, as the basic receptor research and drug discovery communities continue to advance our understanding and exploitation of ligand bias. Scientific insight, biosensors, and analytical methods are still evolving and should benefit from and contribute to the implementation of the guidelines, together improving translation from in vitro to disease-relevant in vivo models

¹²⁹Xe NMR analysis of pore structures and adsorption phenomena in rare-earth element phosphates

Abstract Rare-earth elements (REEs) are indispensable in various applications ranging from catalysis to batteries and they are commonly found from phosphate minerals. Xenon is an excellent exogenous NMR probe for materials because it is inert and its ¹²⁹Xe chemical shift is very sensitive to its local physical or chemical environment. Here, we exploit, for the first time, ¹²⁹Xe NMR for the characterization of porous structures and adsorption properties of REE phosphates (REEPO₄). We study four different REEPO₄ samples (REE = La, Lu, Sm and Yb), including both light (La and Sm) and heavy (Lu and Yb) as well as diamagnetic (La and Lu) and paramagnetic (Sm and Yb) REEs. ¹²⁹Xe resonances are very sensitive to the porous structures and moisture content of the REEPO₄ samples. In the samples treated at a lower temperature (80 °C), free water hinders the access of hydrophobic xenon into small mesopores, but the treatment at a higher temperature (200 °C) removes the free water and allows xenon to explore the mesopores. Based on a standard two-site exchange model analysis of the variable-temperature ¹²⁹Xe chemical shifts, as well as its proposed, novel modification for paramagnetic materials, the average mesopore sizes were determined. The size was the largest (79 nm) for the La sample with mixed monazite (70%) and rhabdophane (30%) phases and the smallest (6 nm) for the Yb sample with pure xenotime phase. The mesopore sizes of the Lu and Yb samples (12 and 6 nm) differed by a factor of two regardless of their similar xenotime phase. The ¹²⁹Xe NMR analysis revealed that the heats of adsorption of the samples are similar, varying between 8.7 and 10.1 kJ/mol. For diamagnetic samples, computational modelling confirmed the order of magnitude of the chemical shifts of Xe adsorbed on surfaces and therefore the validity of the two-site exchange model analysis. Overall, ¹²⁹Xe NMR provides exceptionally versatile information about the pore structures and adsorption properties of REEPO₄ materials, which may be very useful for developing the extraction processes and applications of REEs

Correlation of aluminum doping and lithiation temperature with electrochemical performance of LiNi₁-ₓAlₓO₂ cathode material

Abstract This article presents a process for producing LiNi₁-ₓAlₓO₂ (0 &lt; × &lt; 0.05) cathode material with high capacity and enhanced cycle properties of 145 mAh/g after 600 cycles. The LiNi₁-ₓAlₓO₂ (0 &lt; × &lt; 0.05) cathode material is prepared by mixing coprecipitated Ni(OH)₂ with LiOH and Al(OH)₃, followed by lithiation at temperature range of 650–710 °C, after which any residual lithium from lithiation is washed from the particle surfaces. Electrochemical performance was studied within full-cell and half-cell application; in addition, different material characterization methods were carried out to explain structure changes when certain amount of aluminum is introduced in the LiNi₁-ₓAlₓO₂ structure. Surface analyses were carried out to demonstrate how washing process changes the chemical environment of the LiNi₁-ₓAlₓO₂ secondary particle surface. The results demonstrate how Al doping, lithiation temperature, and the washing process affect the performance of the LiNi₁-ₓAlₓO₂ cathode material

Tungstate activates BK channels in a β subunit-and Mg 2+-dependent manner: Relevance for arterial vasodilatation

Aims: Tungstate reduces blood pressure in experimental animal models of both hypertension and metabolic syndrome, although the underlying mechanisms are not fully understood. Given that the large-conductance voltage-and Ca 2+-dependent K + (BK) channel is a key element in the control of arterial tone, our aim was to evaluate whether BK channel modulation by tungstate can contribute to its antihypertensive effect.Methods and results: Patch-clamp studies of heterologously expressed human BK channels (α β 1-4 subunits) revealed that cytosolic tungstate (1 mM) induced a significant left shift (∼20 mV) in the voltage-dependent activation curve only in BK channels containing αβ 1 or αβ 4 subunits, but reduced the amplitude of K + currents through all BK channels tested. The β 1-dependent activation of BK channels by tungstate was enhanced at cytosolic Ca 2+ levels reached during myocyte contraction, and prevented either by removal of cytosolic Mg 2+ or by mutations rendering the channel insensitive to Mg 2+. A lower concentration of tungstate (0.1 mM) induced voltage-dependent activation of the vascular BKαβ 1 channel without reducing current amplitude, and consistently exerted a vasodilatory action on wild-type but not on β1-knockout mouse arteries pre-contracted with endothelin-1.Conclusion: Tungstate activates BK channels in a β subunit-and Mg 2+-dependent manner and induces vasodilatation only in mouse arteries that express the BK β 1 subunit. Published on behalf of the European Society of Cardiology. All rights reserved. © 2012 The Author.This work was supported by Spanish Ministry of Science and Innovation, Fondos Europeos de Desarrollo Regional (FEDER) Funds, and Plan E (grants SAF2009-13182-C03-02 and SAF2009-09848), Fondo de Investigación Sanitaria (Redes HERACLES RD06/0009 and RECAVA RD06/0020), Marató de TV3 (grant 080430), and Generalitat de Catalunya (grant 2009SGR1369). M.A.V. is the recipient of an ICREA Academia Award (Generalitat de Catalunya).Peer Reviewe