The trafficking and targeting of P2X receptors

The functional expression of P2X receptors at the plasma membrane is dependent on their trafficking along secretory and endocytic pathways. There are seven P2X receptor subunits, and these differ in their subcellular distributions because they have very different trafficking properties. Some are retained within the endoplasmic reticulum (ER), while others are predominantly at the cell surface or within endosomes and lysosomes. Changes in recruitment of receptors to and from the plasma membrane provides a way of rapidly up- or down-regulating the cellular response to adenosine triphosphate (ATP). An additional layer of regulation is the targeting of these receptors within the membranes of each compartment, which affects their stability, function and the nature of the effector proteins with which they form signaling complexes. The trafficking and targeting of P2X receptors is regulated by their interactions with other proteins and with lipids and we can expect this to vary in a cell-type specific manner and in response to changes in the environment giving rise to differences in receptor activity and function

Ca2+ transients are not required as signals for long-term neurite outgrowth from cultured sympathetic neurons

A method for clamping cytosolic free Ca2+ ([Ca2+]i) in cultures of rat sympathetic neurons at or below resting levels for several days was devised to determine whether Ca2+ signals are required for neurite outgrowth from neurons that depend on Nerve Growth Factor (NGF) for their growth and survival. To control [Ca2+]i, normal Ca2+ influx was eliminated by titration of extracellular Ca2+ with EGTA and reinstated through voltage-sensitive Ca2+ channels. The rate of neurite outgrowth and the number of neurites thus became dependent on the extent of depolarization by KCl, and withdrawal of KCl caused an immediate cessation of growth. Neurite outgrowth was completely blocked by the L type Ca2+ channel antagonists nifedipine, nitrendipine, D600, or diltiazem at sub- or micromolar concentrations. Measurement of [Ca2+]i in cell bodies using the fluorescent Ca2+ indicator fura-2 established that optimal growth, similar to that seen in normal medium, was obtained when [Ca2+]i was clamped at resting levels. These levels of [Ca2+]i were set by serum, which elevated [Ca2+]i by integral of 30 nM, whereas the addition of NGF had no effect on [Ca2+]i. The reduction of [Ca2+]o prevented neurite fasciculation but this had no effect on the rate of neurite elongation or on the number of extending neurites. These results show that neurite outgrowth from NGF-dependent neurons occurs over long periods in the complete absence of Ca2+ signals, suggesting that Ca2+ signals are not necessary for operating the basic machinery of neurite outgrowth

Stribild: A Review of Component Characteristics and Combination Drug Efficacy

BACKGROUND: Numerous methods have been devised to combat human immunodeficiency virus (HIV) replication and disease progression. Composed of an integrase strand transfer inhibitor, a pharmacoenhancer, and two reverse transcriptase inhibitors, Stribild is a relatively new combination HIV drug formulated for once-a-day dosing. METHODS: Relevant information, original research articles and reviews, were gathered primarily through the use of the PubMed database. The search was conducted without date restrictions in order to collect both historical and recent information concerning HIV, individual drugs, and combinations for a thorough overview. RESULTS: Stribild, when taken with food, provides therapeutic drug concentrations as seen through comparison with the respective individual or boosted individual drugs. Stribild non-inferiority has been shown when compared to other HIV drug combinations, ritonavir-boosted atazanavir or efavirenz each with a tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) backbone. The co-formulation also retained high viral suppression in patients switching from other regimens, such as efavirenz/TDF/FTC, raltegravir/TDF/FTC, or various ritonavir-boosted protease inhibitors with TDF/FTC. The elvitegravir and cobicistat combination was unaffected by moderate hepatic impairment; however, hepatic and renal function along with changes in bone mineral density should be monitored closely. Stribild presented with relatively few side effect occurrences, but drug interactions may pose a larger problem for continuous therapy. CONCLUSIONS: Stribild provides viral suppression, comparable to other combination HIV drugs through review of non-inferiority and regimen simplification studies, with minimal adverse effects. Although the breadth of Stribild effectiveness has begun to unfold, studies are lacking in older patients as well as adolescents

Coexisting Chalcophile and Lithophile Uranium in Qingzhen (EH3) Chondrite

Mineralogical and textural studies of Qingzhen have shown that it is highly unequilibrated and that it contains a population of chondrules and isolated enstatite grains which preserve the record of more oxidizing nebular conditions (Rambaldi et al., 1983, 1984). Even though in the majority of cases these objects have been affected by various degrees of reduction, some still contain silicates with high (up to 10%) FeO contents

Celecoxib or Diclofenac Hepatic Status in the Presence or Absence of Rebamipide

OBJECTIVE: Utilization of nonsteroidal anti-inflammatory drugs (NSAIDs), such as diclofenac, can produce gastrointestinal ulceration. Thus, cyclooxygenase-2-selective inhibitors, such as celecoxib, and protective agents (e.g. rebamipide) have been employed to alleviate harmful NSAID effects. This study sought to explore the influence of rebamipide on the hepatic outcomes following administration of two commonly prescribed NSAIDs. MATERIALS AND METHODS: Rats were given either vehicle or rebamipide (30 mg/kg) orally twice daily for two days, then on the third day respective groups were dosed with either vehicle, celecoxib (40 mg/kg), or diclofenac (10 mg/kg) in addition to a respective dose of vehicle or rebamipide. Livers were collected on day 4 following euthanasia. Hepatic tissue was examined via histopathology and assayed for oxidative stress and specific NSAID concentration. RESULTS: The liver sections were found to be free from structural changes. Oxidative stress biomarkers, reduced glutathione and malondialdehyde, were discovered to be unaltered among the groups tested. The hepatic NSAID concentrations were not significantly affected by the presence of rebamipide. CONCLUSIONS: The concomitant administration of rebamipide does not influence the hepatic condition of rats administered either celecoxib or diclofenac at the dosages and over the time course examined

Regulation of the apoptotic genes in breast cancer cells by the transcription factor CTCF

CTCF is a highly conserved and ubiquitous transcription factor with versatile functions. We previously demonstrated that elevated protein levels of CTCF in breast cancer cells were associated with the specific anti-apoptotic function of CTCF. We used proteomics and microarray approaches to identify regulatory targets of CTCF specific for breast cancer cells. Among the CTCF identified targets were proteins involved in the control of apoptosis. A proapoptotic protein, Bax, negatively regulated by CTCF, was chosen for further investigation. Repression of the human Bax gene at the transcriptional level by CTCF in breast cancer cells was confirmed by real-time PCR. Two CTCF binding sites within the Bax promoter were identified by electrophoretic mobility shift assay and footprinting. In reporter assays, the Bax-luciferase reporter construct, containing CTCF-binding sites, was negatively regulated by CTCF. In vivo, CTCF occupied its binding sites in breast cancer cells and tissues, as confirmed by chromatin immunoprecipitation assay. Our findings suggest a possible mechanism of the specific CTCF anti-apoptotic function in breast cancer cells whereby CTCF is bound to the Bax promoter, resulting in repression of Bax and inhibition of apoptosis; depletion of CTCF leads to activation of Bax and apoptotic death. CTCF binding sites in the Bax promoter are unmethylated in all cells and tissues inspected. Therefore, specific CTCF interaction with the Bax promoter in breast cancer cells, and the functional outcome, may depend on a combination of epigenetic factors characteristic for these cells. Interestingly, CTCF appears to be a negative regulator of other proapoptotic genes (for example, Fas, Apaf-1, TP531NP1). Conversely, stimulating effects of CTCF on the anti-apoptotic genes (Bcl-2, Bag-3) have been observed. Taken together, these findings suggest that specific mechanisms have evolved in breast cancer cells to protect them from apoptosis; regulation of apoptotic genes by CTCF appears to be one of the resistance strategies

A unique bacteriohopanetetrol stereoisomer of marine anammox

Anaerobic ammonium oxidation (anammox) is a major process of bioavailable nitrogen removal from marine systems. Previously, a bacteriohopanetetrol (BHT) isomer, with unknown stereochemistry, eluting later than BHT using high performance liquid chromatography (HPLC), was detected in ‘Ca. Scalindua profunda’ and proposed as a biomarker for anammox in marine paleo-environments. However, the utility of this BHT isomer as an anammox biomarker is hindered by the fact that four other, non-anammox bacteria are also known to produce a late-eluting BHT stereoisomer. The stereochemistry in Acetobacter pasteurianus, Komagataeibacter xylinus and Frankia sp. was known to be 17β, 21β(H), 22R, 32R, 33R, 34R (BHT-34R). The stereochemistry of the late-eluting BHT in Methylocella palustris was unknown. To determine if marine anammox bacteria produce a unique BHT isomer, we studied the BHT distributions and stereochemistry of known BHT isomer producers and of previously unscreened marine (‘Ca. Scalindua brodeae’) and freshwater (‘Ca. Brocadia sp.’) anammox bacteria using HPLC and gas chromatographic (GC) analysis of acetylated BHTs and ultra high performance liquid chromatography (UHPLC)-high resolution mass spectrometry (HRMS) analysis of non-acetylated BHTs. The 34R stereochemistry was confirmed for the BHT isomers in Ca. Brocadia sp. and Methylocella palustris. However, ‘Ca. Scalindua sp.’ synthesise a stereochemically distinct BHT isomer, with still unconfirmed stereochemistry (BHT-x). Only GC analysis of acetylated BHT and UHPLC analysis of non-acetylated BHT distinguished between late-eluting BHT isomers. Acetylated BHT-x and BHT-34R co-elute by HPLC. As BHT-x is currently only known to be produced by ‘Ca. Scalindua spp.’, it may be a biomarker for marine anammox

Geometric magic numbers of sodium clusters: Interpretation of the melting behaviour

Putative global minima of sodium clusters with up to 380 atoms have been located for two model interatomic potentials. Structures based upon the Mackay icosahedra predominate for both potentials, and the magic numbers for the Murrell-Mottram model show excellent agreement with the sizes at which maxima in the latent heat and entropy change at melting have been found in experiment.Comment: 4 pages, 2 figure