Activation of renal NHE3 by angiotensin II requires NHERF1 (893.33)

Abstract

Na+/H+ exchanger (NHE3) plays a pivotal role in the reabsorption of Na+ and HCO3‐ in the kidney. The NHE3 activity is tightly regulated by hormones and growth factors to maintain fluid and blood pressure homeostasis. We have previously shown that NHE3 activity and trafficking is stimulated by low dose angiotensin II (Ang II) dependent on IRBIT and CaMKII. However, it remains unclear how IRBIT mediates the exocytosis of NHE3 protein. In this study, we found that IRBIT binds to NHERF1 in OKP cells, which was enhanced by Ang II. Overexpression of IRBIT or Ang II treatment increased NHERF1 and NHE3 binding, whereas knockdown of IRBIT attenuated the interaction. Knockdown of NHERF1 expression by lentiviral shRNA completely blocked the stimulatory effect of Ang II on NHE3 exocytosis and transport activity. Moreover, inhibition of CaMKII by KN‐93 abolished the Ang II‐induced NHERF1‐NHE3 interaction and membrane expression of NHE3, IRBIT and NHERF1. In conclusion, activation of NHE3 exocytosis by Ang II is dependent on the formation of a macromolecular complex containing IRBIT, NHERF1 and NHE3.Grant Funding Source: American Heart Association‐Scientist Development Grant