Sodium/bicarbonate cotransporter which plays an important role in regulating intracellular pH (PubMed:10993873, PubMed:20566632, PubMed:23409100). Has been shown to act as a sodium/bicarbonate cotransporter in exchange for intracellular chloride (PubMed:10993873, PubMed:20566632). Has also been shown to act as a sodium/biocarbonate cotransporter which does not couple net influx of bicarbonate to net efflux of chloride, with the observed chloride efflux being due to chloride self-exchange (By similarity). Controls neuronal pH and may contribute to the secretion of cerebrospinal fluid (By similarity). Reduces the excitability of CA1 pyramidal neurons and modulates short-term synaptic plasticity (By similarity). Required in retinal cells to maintain normal pH which is necessary for normal vision (By similarity). In the kidney, likely to mediate bicarbonate reclamation in the apical membrane of the proximal tubules (PubMed:28280139). Detected in dendrites and axon terminals of retinal OFF bipolar cells and in axon terminals of ON bipolar cells. In amacrine cells, located in the perikaryon. Also detected in basal and apical dendrites of hippocampal pyramidal cells (By similarity). In the kidney, isoforms starting with Met-Glu-Ile-Lys localize predominantly to the basolateral membrane of renal thick ascending limbs and inner medullary collecting ducts while isoforms starting with Met-Cys-Asp-Leu localize to the apical membrane of proximal tubules (PubMed:28280139). The use of 2 alternative promoters gives rise to isoforms which differ at the N-terminus. In addition, alternative splicing gives rise to further isoform diversity. In the brain, detected in cerebral cortex, subcortex, cerebellum, hippocampus and medulla (at protein level) (PubMed:18061361). Expressed in neurons but not in astrocytes (at protein level) (PubMed:18061361). Isoforms starting with Met-Glu-Ile-Lys are found predominantly in the brain with lower levels in the eye while isoforms starting with Met-Cys-Asp-Leu are most abundant in the kidney with lower levels in the duodenum, jejunum and ileum (at protein level) (PubMed:23409100). In the kidney, isoforms starting with Met-Cys-Asp-Leu are primarily expressed in the cortex, the outer stripe of the outer medulla and the inner stripe of the outer medulla (ISOM) but are not detectable in the inner medulla (IM) while isoforms starting with Met-Glu-Ile-Lys are predominantly expressed in the ISOM and IM (PubMed:28280139). Expressed in the brain, in the hippocampus as well as in dentate gyrus, cortical layers, cerebellum, olfactory bulb and in the epithelial cells of the choroid plexus. Detected in pituitary, testis, kidney and ileum. Detected also in spleen and lung. Expressed in spinal cord and brain at E19 through adulthood. The N-terminal cytoplasmic domain is likely to have a high level of intrinsic disorder. N-glycosylated. Belongs to the anion exchanger (TC 2.A.31) family. Has been shown to act as a sodium/bicarbonate cotransporter in exchange for intracellular chloride (PubMed:10993873, PubMed:20566632). Has also been shown to act as a sodium/biocarbonate cotransporter which is not responsible for net efflux of chloride, with the observed chloride efflux being due to chloride self-exchange (By similarity).