A consensus sequence in the endothelin-B receptor second intracellular loop is required for NHE3 activation by endothelin-1.
Endothelin-1 (ET-1) increases the activity of Na(+)/H(+) exchanger 3 (NHE3), the major proximal tubule apical membrane Na(+)/H(+) antiporter. This effect is seen in opossum kidney (OKP) cells expressing the endothelin-B (ET(B)) and not in cells expressing the endothelin-A (ET(A)) receptor. However, ET-1 causes similar patterns of protein tyrosine phosphorylation, adenylyl cyclase inhibition, and increases in cell [Ca(2+)] in ET(A)- and ET(B)-expressing OKP cells, implying that an additional mechanism is required for NHE3 stimulation by the ET(B) receptor. The present studies used ET(A) and ET(B) receptor chimeras and site-directed mutagenesis to identify the ET receptor domains that mediate ET-1 regulation of NHE3 activity. We found that binding of ET-1 to the ET(A) receptor inhibits NHE3 activity, an effect for which the COOH-terminal tail is necessary and sufficient. ET-1 stimulation of NHE3 activity requires the COOH-terminal tail and the second intracellular loop of the ET(B) receptor. Within the second intracellular loop, a consensus sequence was identified, KXXXVPKXXXV, that is required for ET-1 stimulation of NHE3 activity. This sequence suggests binding of a homodimeric protein that mediates NHE3 stimulation.
Laghmani
Kamel
K
Univ. of Texas Southwestern Medical Center, Rm. H5.122, 5323 Harry Hines Blvd., Dallas, TX 75390-8856, USA.
Sakamoto
Aiji
A
Yanagisawa
Masashi
M
Preisig
Patricia A
PA
Alpern
Robert J
RJ
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D016384:Consensus Sequence; D019332:Endothelin-1 / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007668:Kidney / Q000166:cytology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009893:Opossums; D017434:Protein Structure, Tertiary; D044023:Receptor, Endothelin B / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D014162:Transfection
D019332:Endothelin-1; D044023:Receptor, Endothelin B; C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers