16 research outputs found
Molecular and functional properties of P2X receptorsârecent progress and persisting challenges
Cell-Deposited Matrix Improves Retinal Pigment Epithelium Survival on Aged Submacular Human Bruch's Membrane
Resurfacing submacular human Bruch's membrane with a cell-deposited extracellular matrix increases long-term survival of retinal pigment epithelial cells. This effect is most marked in submacular Bruch's membrane of aged Caucasians
Comparison of FRPE and Human Embryonic Stem CellâDerived RPE Behavior on Aged Human Bruch's Membrane
RPE derived from human embryonic stem cells (hES-RPE) survive to a limited degree on aged Bruch's membrane. While fetal RPE can initially resurface aged Bruch's membrane, hES-RPE attachment and survival is limited at early times in culture
Lymphocytes from P2X7-deficient mice exhibit enhanced P2X7 responses
The purinergic receptor P2X7 is expressed on immune cells, and its stimulation results in the release of IL-1ÎČ from macrophages. Its absence, as evidenced from the analysis of two independent strains of P2X7-deficient mice, results in reduced susceptibility to inflammatory disease, and the molecule is an important, potential therapeutic target in autoimmunity. However, P2X7 has also been detected in several neuronal cell types, although its function and even its presence in these cells are highly contested, with anti-P2X7 antibodies staining brain tissue from both strains of P2X7â/â mice identically to wild-type mice. It has therefore been suggested that neurons express a distinct âP2X7-likeâ protein that has similar antibody recognition epitopes to P2X7 and some properties of the genuine receptor. In this study, we show that whereas P2X7 activity is absent from macrophages and dendritic cells in P2X7â/â animals, T cells from one gene-deficient strain unexpectedly exhibit higher levels of P2X7 activity than that found in cells from control, unmanipulated C57BL/6 mice. A potential mechanism for this tissue-specific P2X7 expression in P2X7â/â animals is discussed, as is the implication that the immune and indeed neuronal functions of P2X7 may have been underestimated
Different properties of P2X7 receptor in hippocampal and cortical astrocytes
P2X7 receptor is a ligand-gated ion channel, which can induce the opening of large membrane pores. Here, we provide evidence that the receptor induces pore formation in astrocytes cultured from cortex, but not from the hippocampus. Furthermore, P2X7 receptor activation promptly induces p38 mitogen-activated protein kinase (MAPK) phosphorylation in cortical but not in hippocampal astrocytes. Given the role of p38 MAPK activation in pore opening, these data suggest that defective coupling of the receptor to the enzyme could occur in hippocampal cultures. The different capabilities of the receptor to open membrane pores cause relevant functional consequences. Upon pore formation, caspase-1 is activated and pro-IL1-ÎČ is cleaved and released extracellularly. The receptor stimulation does not result in interleukin-1beta secretion from hippocampal astrocytes, although the pro-cytokine is present in the cytosol of lipopolysaccharide-primed cultures. These results open the possibility that activation of P2X7 receptors differently influences the neuroinflammatory processes in distinct brain regions
Design and Synthesis of Novel, Selective GPR40 AgoPAMs
GPR40 is a G-protein-coupled receptor
expressed primarily in pancreatic islets and intestinal L-cells that
has been a target of significant recent therapeutic interest for type
II diabetes. Activation of GPR40 by partial agonists elicits insulin
secretion only in the presence of elevated blood glucose levels, minimizing
the risk of hypoglycemia. GPR40 agoPAMs have shown superior efficacy
to partial agonists as assessed in a glucose tolerability test (GTT).
Herein, we report the discovery and optimization of a series of potent,
selective GPR40 agoPAMs. Compound <b>24</b> demonstrated sustained
glucose lowering in a chronic study of Goto Kakizaki rats, showing
no signs of tachyphylaxis for this mechanism
Mouse Leydig cells express multiple P2X receptor subunits
ATP acts on cellular membranes by interacting with P2X (ionotropic) and P2Y (metabotropic) receptors. Seven homomeric P2X receptors (P2X1âP2X7) and seven heteromeric receptors (P2X1/2, P2X1/4, P2X1/5, P2X2/3, P2X2/6, P2X4/6, P2X4/7) have been described. ATP treatment of Leydig cells leads to an increase in [Ca2+]i and testosterone secretion, supporting the hypothesis that Ca2+ signaling through purinergic receptors contributes to the process of testosterone secretion in these cells. Mouse Leydig cells have P2X receptors with a pharmacological and biophysical profile resembling P2X2. In this work, we describe the presence of several P2X receptor subunits in mouse Leydig cells. Western blot experiments showed the presence of P2X2, P2X4, P2X6, and P2X7 subunits. These results were confirmed by immunofluorescence. Functional results support the hypothesis that heteromeric receptors are present in these cells since 0.5 ΌM ivermectin induced an increase (131.2â±â5.9%) and 3 ΌM ivermectin a decrease (64.2â±â4.8%) in the whole-cell currents evoked by ATP. These results indicate the presence of functional P2X4 subunits. P2X7 receptors were also present, but they were non-functional under the present conditions because dye uptake experiments with Lucifer yellow and ethidium bromide were negative. We conclude that a heteromeric channel, possibly P2X2/4/6, is present in Leydig cells, but with an electrophysiological and pharmacological phenotype characteristic of the P2X2 subunit