title: Nitric oxide lacks direct effect on TRPC5 channels but suppresses endogenous TRPC5-containing channels in endothelial cells.
abstract: TRPC5 is a member of the canonical transient receptor potential (TRPC) family of proteins that forms cationic channels either through homomultimeric assembly or heteromultimeric coordination with other TRPC proteins. It is expressed in a variety of cells including central neurones and endothelial cells and has susceptibility to stimulation by multiple factors. Here we investigated if TRPC5 is sensitive to nitric oxide. Mouse TRPC5 or human TRPC5 was over-expressed in HEK293 cells, and TRPC5 activity was determined by measuring the cytosolic Ca(2+) concentration with an indicator dye or by recording membrane current under voltage clamp. TRPC5 activity could be evoked by carbachol acting at muscarinic receptors, lanthanum, or a reducing agent. However, S-nitroso-N-acetylpenicillamine (SNAP) and diethylamine NONOate (DEA-NONOate) failed to stimulate or inhibit TRPC5 at concentrations that generated nitric oxide, caused vasorelaxation, or suppressed activity of TRPC6 via protein kinase G. At high concentrations, SNAP (but not DEA-NONOate) occasionally stimulated TRPC5 but the effect was confounded by background TRPC5-independent Ca(2+) signals. Endogenous Ca(2+)-entry in bovine aortic endothelial cells (BAECs) was suppressed by SNAP; TRPC5 blocking antibody or dominant-negative mutant TRPC5 suppressed this Ca(2+) entry and occluded the effect of SNAP. The data suggest that nitric oxide is not a direct modulator of homomeric TRPC5 channels but may inhibit endogenous BAEC channels that contain TRPC5.
authors.affiliation: Li Ka Shing Insitute of Health Sciences and School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, People's Republic of China.
authors.forename: Ching-On
authors.initials: CO
authors.lastname: Wong
authors.forename: Piruthivi
authors.initials: P
authors.lastname: Sukumar
authors.forename: David J
authors.initials: DJ
authors.lastname: Beech
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Yao
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D002417:Cattle; D002460:Cell Line; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D005470:Fluorometry; D006801:Humans; D007811:Lanthanum / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice; D018721:Muscarinic Agonists / Q000494:pharmacology; D009154:Mutation; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D019163:Reducing Agents / Q000494:pharmacology; D050052:TRPC Cation Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D000074287:TRPC6 Cation Channel; D013997:Time Factors; D014162:Transfection
chemical_list: D018721:Muscarinic Agonists; D020030:Nitric Oxide Donors; D019163:Reducing Agents; D050052:TRPC Cation Channels; C491780:TRPC5 protein, human; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C112021:Trpc5 protein, mouse; D009569:Nitric Oxide; D007811:Lanthanum; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; C569718:PRKG1 protein, human; C569720:Prkg1 protein, mouse
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