Role of tyrosine kinase pathways in etb receptor activation of nhe
-3.
Chu, Tzong-Shinn, Hirohiko Tsuganezawa, Yan Peng, Adriana Cano,
Masashi Yanagisawa, and Robert J. Alpern.
Departments of Internal Medicine and Molecular Genetics and Howard
Hughes Medical Institute, University of Texas Southwestern Medical
Center, Dallas, Texas 75235
APStracts 3:0087C, 1996.
Endothelin-1 (ET-1) binding to ETB receptors increases the activity of
the apical membrane Na/H antiporter (NHE-3) 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, while 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.
Received 23 February 1996; accepted in final form 23 February
1996.
APS Manuscript Number C767-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96