The NHERF1 PDZ1 domain and IRBIT interact and mediate the activation of Na+/H+ exchanger 3 by ANG II.
Na(+)/H(+) exchanger (NHE)3, a major Na(+) transporter in the luminal membrane of the proximal tubule, is subject to ANG II regulation in renal Na(+)/fluid absorption and blood pressure control. We have previously shown that inositol 1,4,5-trisphosphate receptor-binding protein released with inositol 1,4,5-trisphosphate (IRBIT) mediates ANG II-induced exocytosis of NHE3 in cultured proximal tubule epithelial cells. In searching for scaffold protein(s) that coordinates with IRBIT in NHE3 trafficking, we found that NHE regulatory factor (NHERF)1, NHE3, and IRBIT proteins were coexpressed in the same macrocomplexes and that loss of ANG II type 1 receptors decreased their expression in the renal brush-border membrane. We found that NHERF1 was required for ANG II-mediated forward trafficking and activation of NHE3 in cultured cells. ANG II induced a concomitant increase of NHERF1 interactions with NHE3 and IRBIT, which were abolished when the NHERF1 PDZ1 domain was removed. Overexpression of a yellow fluorescent protein-NHERF1 construct that lacks PDZ1, but not PDZ2, failed to exaggerate the ANG II-dependent increase of NHE3 expression in the apical membrane. Moreover, exogenous expression of PDZ1 exerted a dominant negative effect on NHE3 activation by ANG II. We further demonstrated that IRBIT was indispensable for the ANG II-provoked increase in NHERF1-NHE3 interactions and that phosphorylation of IRBIT at Ser(68) was necessary for the assembly of the NHEF1-IRBIT-NHE3 complex. Taken together, our findings suggest that NHERF1 mediates ANG II-induced activation of renal NHE3, which requires coordination between IRBIT and the NHERF1 PDZ1 domain in binding and transporting NHE3.
Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; phe3@emory.edu.
Peijian
P
He
Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Department of Gastroenterology, Beijing Hospital of Traditional Chinese Medicine affiliated with Capital Medical University, Beijing, China;
Luqing
L
Zhao
Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia;
Yi Ran
YR
No
Division of Gastroenterology and Hepatology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina;
Serhan
S
Karvar
Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Atlanta Veterans Affairs Medical Center, Decatur, Georgia; and Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia.
C Chris
CC
Yun
D043383:Adenosylhomocysteinase / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D019921:Biotinylation; D002460:Cell Line; D006863:Hydrogen-Ion Concentration; D051379:Mice; D018345:Mice, Knockout; D008871:Microvilli / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D044140:Receptor, Angiotensin, Type 1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000819:agonists* / Q000378:metabolism*
D010750:Phosphoproteins; D044140:Receptor, Angiotensin, Type 1; C000613386:Slc9a3 protein, mouse; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D000804:Angiotensin II; D012964:Sodium; D043383:Adenosylhomocysteinase; C510392:IRBIT protein, mouse
Na+/H+ exchanger 3; Na+/H+ exchanger regulatory factor 1; angiotensin II; inositol 1,4,5-trisphosphate; inositol 1,4,5-trisphosphate receptor-binding protein released with inositol 1,4,5-trisphosphate