Overexpression of csk inhibits acid-induced activation of NHE-3.
Opossum kidney OKP cells express an apical membrane Na+/H+ antiporter that is encoded by NHE-3 (for Na+/H+ exchanger 3) and is similar in many respects to the renal proximal tubule apical membrane Na+/H+ antiporter. Chronic incubation of OKP cells in acid medium for 24 hr increases Na+/H(+)-antiporter activity and NHE-3 mRNA abundance. The increase in Na+/H(+)-antiporter activity was not prevented by H7, a protein kinase C/protein kinase A inhibitor, but was prevented by herbimycin A, a tyrosine kinase inhibitor. Incubation of cells in acid medium increased c-src activity, and this was inhibited by herbimycin A. To determine the role of the src family of nonreceptor protein-tyrosine kinases, Csk (for carboxyl-terminal src kinase), a physiologic inhibitor of these kinases, was overexpressed in OKP cells. In three clones overexpressing csk, acid-induced increases in Na+/H(+)-antiporter activity and NHE-3 mRNA abundance were inhibited. In these clones, inhibition of acid activation of Na+/H(+)-antiporter activity paralleled inhibition of acid activation of c-src. Neither herbimycin A nor overexpression of csk inhibited dexamethasone-induced increases in Na+/H(+)-antiporter activity. These studies show that decreases in pH activate c-src and that the src family nonreceptor protein-tyrosine kinases play a key role in acid activation of NHE-3.
Yamaji
Y
Y
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-8856, USA.
Amemiya
M
M
Cano
A
A
Preisig
P A
PA
Miller
R T
RT
Moe
O W
OW
Alpern
R J
RJ
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D016227:Benzoquinones; D000081247:CSK Tyrosine-Protein Kinase; D002460:Cell Line; D002645:Chickens; D015870:Gene Expression; D005786:Gene Expression Regulation; D006863:Hydrogen-Ion Concentration; D007546:Isoquinolines / Q000494:pharmacology; D007668:Kidney; D007700:Kinetics; D047029:Lactams, Macrocyclic; D009893:Opossums; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000096:biosynthesis / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D011994:Recombinant Proteins / Q000096:biosynthesis; D017828:Rifabutin / Q000031:analogs & derivatives; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D019061:src-Family Kinases
D016227:Benzoquinones; D007546:Isoquinolines; D047029:Lactams, Macrocyclic; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011809:Quinones; D011994:Recombinant Proteins; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D017828:Rifabutin; C020754:herbimycin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D016392:Proto-Oncogene Proteins pp60(c-src); D019061:src-Family Kinases; D013755:Tetradecanoylphorbol Acetate