title: Effects of protein tyrosine kinase and protein tyrosine phosphatase on apical K(+) channels in the TAL.
abstract: We have previously demonstrated that the protein level of c-Src, a nonreceptor type of protein tyrosine kinase (PTK), was higher in the renal medulla from rats on a K-deficient (KD) diet than that in rats on a high-K (HK) diet (Wang WH, Lerea KM, Chan M, and Giebisch G. Am J Physiol Renal Physiol 278: F165-F171, 2000). We have now used the patch-clamp technique to investigate the role of PTK in regulating the apical K channels in the medullary thick ascending limb (mTAL) of the rat kidney. Inhibition of PTK with herbimycin A increased NP(o), a product of channel number (N) and open probability (P(o)), of the 70-pS K channel from 0.12 to 0.42 in the mTAL only from rats on a KD diet but had no significant effect in tubules from animals on a HK diet. In contrast, herbimycin A did not affect the activity of the 30-pS K channel in the mTAL from rats on a KD diet. Moreover, addition of N-methylsulfonyl-12,12-dibromododec-11-enamide, an agent that inhibits the cytochrome P-450-dependent production of 20-hydroxyeicosatetraenoic acid, further increased NP(o) of the 70-pS K channel in the presence of herbimycin A. Furthermore, Western blot detected the presence of PTP-1D, a membrane-associated protein tyrosine phosphatase (PTP), in the renal outer medulla. Inhibition of PTP with phenylarsine oxide (PAO) decreased NP(o) of the 70-pS K channel in the mTAL from rats on a HK diet. However, PAO did not inhibit the activity of the 30-pS K channel in the mTAL. The effect of PAO on the 70-pS K channel was due to indirectly stimulating PTK because pretreatment of the mTAL with herbimycin A abolished the inhibitory effect of PAO. Finally, addition of exogenous c-Src reversibly blocked the activity of the 70-pS K channel in inside-out patches. We conclude that PTK and PTP have no effect on the low-conductance K channels in the mTAL and that PTK-induced tyrosine phosphorylation inhibits, whereas PTP-induced tyrosine dephosphorylation stimulates, the apical 70-pS K channel in the mTAL.
authors.affiliation: Department of Pharmacology, New York Medical College, Valhalla, New York 10595, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Gu
authors.forename: Y
authors.initials: Y
authors.lastname: Wei
authors.forename: J R
authors.initials: JR
authors.lastname: Falck
authors.forename: U M
authors.initials: UM
authors.lastname: Krishna
authors.forename: W H
authors.initials: WH
authors.lastname: Wang
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D001152:Arsenicals / Q000494:pharmacology; D016227:Benzoquinones; D000081247:CSK Tyrosine-Protein Kinase; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism; D006947:Hyperkalemia / Q000378:metabolism; D007008:Hypokalemia / Q000378:metabolism; D047029:Lactams, Macrocyclic; D008138:Loop of Henle / Q000201:enzymology*; D008297:Male; D010766:Phosphorylation; D011188:Potassium / Q000097:blood; D015221:Potassium Channels / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017828:Rifabutin / Q000031:analogs & derivatives; D012964:Sodium / Q000097:blood; D013047:Specific Pathogen-Free Organisms; D013450:Sulfones / Q000494:pharmacology; D019061:src-Family Kinases
chemical_list: D000577:Amides; D001152:Arsenicals; D016227:Benzoquinones; D004791:Enzyme Inhibitors; D006893:Hydroxyeicosatetraenoic Acids; C510692:Kcnj1 protein, rat; D047029:Lactams, Macrocyclic; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011809:Quinones; D013450:Sulfones; C029341:oxophenylarsine; D017828:Rifabutin; C020754:herbimycin; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D012964:Sodium; C117975:DDMS; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D017027:Protein Tyrosine Phosphatases; D011188:Potassium