Na(+)/H(+) antiporter that extrudes Na(+) or Li(+) in exchange for external protons across the membrane (PubMed:18000046, PubMed:28154142, PubMed:22948142, PubMed:18508966). Contributes to the regulation of intracellular pH, sodium homeostasis, and cell volume. Plays an important role for insulin secretion and clathrin-mediated endocytosis in beta-cells (By similarity). Involved in sperm motility and fertility (By similarity). It is controversial whether SLC9B2 plays a role in osteoclast differentiation or not (By similarity). Optimum pH is 8.5. Homodimer (PubMed:28071645). Strong colocalization with LAMP1 and TCIRG1 in osteoclasts. In beta-cells colocalizes with RAB4A and SYP. Localizes to the basolateral membrane of polarized osteoclasts. Widely expressed (PubMed:18508966). High levels detected in the distal tubules of the kidney nephron (PubMed:18508966). Detected in red blood cells (at protein level) (PubMed:18000046, PubMed:18508966). Inhibited by phloretin but not by the classical SLC9A-inhibitor amiloride (PubMed:18000046). Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family.