title: Protein kinase G activates inwardly rectifying K(+) channel in cultured human proximal tubule cells.
abstract: An ATP-regulated inwardly rectifying K(+) channel, whose activity is enhanced by PKA, is present in the plasma membrane of cultured human proximal tubule cells. In this study, we investigated the effects of PKG on this K(+) channel, using the patch-clamp technique. In cell-attached patches, bath application of a membrane-permeant cGMP analog, 8-bromoguanosine 3',5'-monophosphate (8-BrcGMP; 100 microM), stimulated channel activity, whereas application of a PKG-specific inhibitor, KT-5823 (1 microM), reduced the activity. Channel activation induced by 8-BrcGMP was observed even in the presence of a PKA-specific inhibitor, KT-5720 (500 nM), which was abolished by KT-5823. Direct effects of cGMP and PKG were examined with inside-out patches in the presence of 1 mM MgATP. Although cytoplasmic cGMP (100 microM) alone had little effect on channel activity, subsequent addition of PKG (500 U/ml) enhanced it. Furthermore, bath application of atrial natriuretic peptide (ANP; 20 nM) in cell-attached patches stimulated channel activity, which was blocked by KT-5823. In conclusion, cGMP/PKG-dependent processes participate in activating the ATP-regulated K(+) channel and producing the stimulatory effect of ANP on channel activity.
authors.affiliation: Department of Physiology II, Iwate Medical University School of Medicine, Morioka 020-8505, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Junko
authors.initials: J
authors.lastname: Hirano
authors.forename: Shun-Ichi
authors.initials: S
authors.lastname: Itazawa
authors.forename: Manabu
authors.initials: M
authors.lastname: Kubokawa
mesh_terms: D000328:Adult; D000465:Algorithms; D000470:Alkaloids / Q000494:pharmacology; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D002227:Carbazoles; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D005260:Female; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D011758:Pyrroles / Q000494:pharmacology; D013268:Stimulation, Chemical
chemical_list: D000470:Alkaloids; D002227:Carbazoles; D007211:Indoles; D024661:Potassium Channels, Inwardly Rectifying; D011758:Pyrroles; C073601:KT 5823; C057416:KT 5720; D009320:Atrial Natriuretic Factor; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D006152:Cyclic GMP