Role of tyrosine kinase pathways in ETB receptor activation of NHE3.
Endothelin-1 (ET-1) binding to ETB receptors increases the activity of the apical membrane Na+/H+ antiporter (NHE3) of renal proximal tubule and cultured OKP cells. In OKPETB6 cells, a clonal cell line of OKP cells that overexpresses ETB receptors, ET-1-induced increases in Na+/H+ antiporter activity are mediated 50% by Ca2(+)-dependent pathways and 50% by tyrosine kinase pathways. ET-1 induces tyrosine phosphorylation of proteins of 68, 110, 125, 130, and 210 kDa. ET-1-induced tyrosine phosphorylation is mediated by the ETB receptor and is not dependent on increases in cell Ca2+ or protein kinase C. The 68-, 110-, 125-, and 130-kDa phosphoproteins are cytosolic, whereas the 210-kDa phosphoprotein is an integral membrane protein. Immunoprecipitation studies showed that the 68-kDa protein is paxillin and the 125-kDa protein is p125FAK (focal adhesion kinase). Cytochalasin D, which disrupts focal adhesions, prevented ET-1-induced tyrosine phosphorylation of paxillin, p110, p125FAK, and p130 but did not prevent tyrosine phosphorylation of p210 and did not prevent ET-1-induced increases in Na+/H+ antiporter activity. Thus 50% of ETB receptor-induced Na+/H+ antiporter activation is mediated by tyrosine kinase pathways, possibly involving p210. ETB receptor activation also induces tyrosine phosphorylation of focal adhesion proteins, but this is not required for antiporter activation.
Chu
T S
TS
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235, USA.
Tsuganezawa
H
H
Peng
Y
Y
Cano
A
A
Yanagisawa
M
M
Alpern
R J
RJ
D000818:Animals; D002460:Cell Line; D019332:Endothelin-1 / Q000378:metabolism*; D019333:Endothelin-2 / Q000378:metabolism*; D004789:Enzyme Activation; D018014:Gene Transfer Techniques; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D019332:Endothelin-1; D019333:Endothelin-2; D017466:Receptors, Endothelin; D017923:Sodium-Hydrogen Exchangers; D011505:Protein-Tyrosine Kinases