ETB receptor activation leads to activation and phosphorylation of NHE3.
In OKP cells expressing ETB endothelin receptors, activation of Na+/H+ antiporter activity by endothelin-1 (ET-1) was resistant to low concentrations of ethylisopropyl amiloride, indicating regulation of Na+/H+ exchanger isoform 3 (NHE3). ET-1 increased NHE3 phosphorylation in cells expressing ETB receptors but not in cells expressing ETA receptors. Receptor specificity was not due to demonstrable differences in receptor-specific activation of tyrosine phosphorylation pathways or inhibition of adenylyl cyclase. Phosphorylation was associated with a decrease in mobility on SDS-PAGE, which was reversed by treating immunoprecipitated NHE3 with alkaline phosphatase. Phosphorylation was first seen at 5 min and was maximal at 15-30 min. Phosphorylation was maximal with 10(-9) M ET-1. Phosphorylation occurred on threonine and serine residues at multiple sites. In summary, ET-1 induces NHE3 phosphorylation in OKP cells on multiple threonine and serine residues. ETB receptor specificity, time course, and concentration dependence are all similar between ET-1-induced increases in NHE3 activity and phosphorylation, suggesting that phosphorylation plays a key role in activation.
Peng
Y
Y
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, 75235, Texas.
Moe
O W
OW
Chu
T
T
Preisig
P A
PA
Yanagisawa
M
M
Alpern
R J
RJ
D000818:Animals; D002460:Cell Line; D019332:Endothelin-1 / Q000378:metabolism / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D014162:Transfection
D019332:Endothelin-1; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D011994:Recombinant Proteins; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D019000:Phosphotyrosine; D012964:Sodium