NHERF family and NHE3 regulation

The intestinal and renal proximal tubule brush border (BB) Na⁺-H⁺ exchanger NHE3 binds to members of the NHERF (Na⁺-H⁺ exchanger regulatory factor) family. These are four proteins (current most used names include NHERF1, NHERF2, PDZK1 and IKEPP) which are related to each other, are present in locations in or close to the BB, and scaffold a variable series of proteins in NHE3-containing complexes in a dynamic manner that is altered by changes in signal transduction which affects NHE3 activity. The specific roles of these proteins in terms of NHE3 regulation as well as interactions with each other and with their many other substrates are only now being defined. Specificity for only one member of the NHERF family in one example of NHE3 regulation, inhibition by elevation in cGMP, is used to describe how NHERF family proteins are involved in NHE3 complex formation and its regulation. In this case, NHERF2 directly binds cGKII in the brush border to form an NHE3 complex, with cGKII also associating with the BB via its myristoylation.