Na+-alanine uptake activates a Cl- conductance in frog renal proximal tubule cells via nonconventional PKC.
Hyposmotically induced swelling of frog renal proximal tubule cells activates a DIDS-sensitive, outwardly rectifying Cl- conductance via a conventional protein kinase C (PKC). This study examines whether Na+-alanine cotransport similarly activates a DIDS-sensitive Cl- conductance in frog renal proximal tubule cells. On stimulation of Na+-alanine cotransport, the DIDS-sensitive current (I(DIDS-Ala)) increased markedly over time. I(DIDS-Ala) exhibited outward rectification, a Na+/Cl- selectivity ratio of 0.19 +/- 0.03, and an anion selectivity sequence Br- = Cl- > I- > gluconate-. Activation of I(DIDS-Ala) was dependent on ATP hydrolysis and PKC-mediated phosphorylation and was inhibited by hyperosmotic conditions. Activation could be not ascribed to a conventional PKC isoform, as I(DIDS-Ala) was not affected by removing Ca2+ or by phorbol ester treatment, suggesting a role for a nonconventional PKC isoform, either novel or atypical. We conclude that Na+-alanine cotransport activates a DIDS-sensitive Cl- conductance via a nonconventional PKC isoform. This contrasts with the hyposmotically activated Cl- conductance, which requires conventional PKC activation.
Millar
I D
ID
Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom.
Robson
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L
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000502:physiology; D000409:Alanine / Q000378:metabolism* / Q000494:pharmacology; D000465:Algorithms; D000818:Animals; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism*; D011896:Rana temporaria; D012964:Sodium / Q000378:metabolism*; D013237:Stereoisomerism
D018118:Chloride Channels; D000255:Adenosine Triphosphate; D012964:Sodium; D011493:Protein Kinase C; D000409:Alanine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid