Na+/hydrogen exchanger 4 (Na+/H+ exchanger 4, NHE-4, solute carrier family 9 member 4, SLC9A4, NHE4)

^[1]

Function

role in pH regulation to eliminate acids generated by active metabolism or to counter adverse environmental conditions
major H+ extruding system driven by the inward Na+ chemical gradient
plays an important role in signal transduction
may play a specialized role in the kidney in rectifying cell volume in response to extreme fluctuations of hyperosmolar-stimulated cell shrinkage
relatively amiloride & ethylisopropylamiloride (EIPA) insensitive
can be activated under conditions of hyperosmolar-induced cell shrinkage in a sustained intracellular acidification- dependence manner
activated by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) in a sustained intracellular acidification-dependence manner
affects K+/proton exchange as well as Na+/proton & Li+/proton exchange
in basolateral cell membrane, participates in homeostatic control of intracellular pH, & may play a role in proton extrusion in order to achieve transepithelial HCO3- secretion
an apical cell membrane may be involved in mediating Na+ absorption
requires for normal levels of gastric acid secretion, secretory membrane development, parietal cell maturation &/or differentiation & at least secondarily for chief cell differentiation (putative)
may be phosphorylated (putative)

belongs to the Na+/H+ exchanger (TC 2.A.36.5.1) family
number, localization & denomination of hydrophobic domains in the Na+/H+ exchangers vary among authors