title: ATP acting through P2Y receptors causes activation of podocyte TRPC6 channels: role of podocin and reactive oxygen species.
abstract: Extracellular ATP may contribute to Ca(2+) signaling in podocytes during tubuloglomerular feedback (TGF) and possibly as a result of local tissue damage. TRPC6 channels are Ca(2+)-permeable cationic channels that have been implicated in the pathophysiology of podocyte diseases. Here we show using whole cell recordings that ATP evokes robust activation of TRPC6 channels in mouse podocyte cell lines and in rat podocytes attached to glomerular capillaries in ex vivo glomerular explants. The EC50 for ATP is ~10 μM and is maximal at 100 μM, and currents were blocked by the P2 antagonist suramin. In terms of maximal currents that can be evoked, ATP is the strongest activator of podocyte TRPC6 that we have characterized to date. Smaller currents were observed in response to ADP, UTP, and UDP. ATP-evoked currents in podocytes were abolished by TRPC6 knockdown and by pretreatment with 10 μM SKF-96365 or 50 μM La(3+). ATP effects were also abolished by inhibiting G protein signaling and by the PLC/PLA2 inhibitor D-609. ATP effects on TRPC6 were also suppressed by knockdown of the slit diaphragm scaffolding protein podocin, and also by tempol, a membrane-permeable quencher of reactive oxygen species. Modulation of podocyte TRPC6 channels, especially in foot processes, could provide a mechanism for regulation of glomerular function by extracellular nucleotides, possibly leading to changes in permeation through slit diaphragms. These results raise the possibility that sustained ATP signaling could contribute to foot process effacement, Ca(2+)-dependent changes in gene expression, and/or detachment of podocytes.
authors.affiliation: Dept. of Biology and Biochemistry, Univ. of Houston, Houston, TX 77204-5001. sdryer@uh.edu.
authors.forename: Hila
authors.initials: H
authors.lastname: Roshanravan
authors.forename: Stuart E
authors.initials: SE
authors.lastname: Dryer
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D020013:Calcium Signaling; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D055785:Gene Knockdown Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D008297:Male; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D064801:Phospholipase A2 Inhibitors / Q000494:pharmacology; D054467:Phospholipases A2 / Q000378:metabolism; D050199:Podocytes / Q000187:drug effects / Q000378:metabolism*; D058921:Purinergic P2Y Receptor Antagonists / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D058470:Receptors, Purinergic P2Y / Q000187:drug effects / Q000378:metabolism*; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D000074287:TRPC6 Cation Channel; D014162:Transfection; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000975:Antioxidants; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C407223:NPHS2 protein; D064801:Phospholipase A2 Inhibitors; D058921:Purinergic P2Y Receptor Antagonists; D017382:Reactive Oxygen Species; D058470:Receptors, Purinergic P2Y; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C492146:Trpc6 protein, mouse; C492145:Trpc6 protein, rat; D000255:Adenosine Triphosphate; D054467:Phospholipases A2; D010738:Type C Phospholipases
keywords: NADPH oxidase; TRPC6; glomerular filtration; podocin; podocyte; purinergic