Concerted roles of SGK1 and the Na+/H+ exchanger regulatory factor 2 (NHERF2) in regulation of NHE3.

Na+/H+ exchanger regulatory factors, NHERF1 and NHERF2, are structurally related proteins and highly expressed in epithelial cells. These proteins are initially identified as accessory proteins in the regulation of Na+/H+ exchanger isoform 3, NHE3. In addition to regulation of NHE3, recent studies demonstrate the importance of NHERF1 and NHERF2 in recycling and localization of membrane receptors, ion channels and transporters. Recent studies show that serum- and glucocorticoid-induced kinase 1 (SGK1) specifically interacts with NHERF2 but not with NHERF1, adding to the growing number of differences between the two proteins. The association of SGK1 with NHERF2 is necessary for stimulation of NHE3 activity by glucocorticoids. In addition, SGK1 together with NHERF2 stimulates the K+ channel ROMK1, suggesting a broader role of SGK1 in regulation of ion transport.