Expression and localization of Na-driven Cl-HCO3− exchanger (SLC4A8) in rodent CNS

The Na+-driven Cl-HCO3 exchanger (NDCBE or SLC4A8) is a member of the solute carrier 4 (SLC4) family of HCO3− transporters, which includes products of 10 genes with similar sequences. Most SLC4 members play important roles in regulating intracellular pH (pHi). Physiological studies suggest that NDCBE is a major pHi regulator in at least hippocampal (HC) pyramidal neurons. We generated a polyclonal rabbit antibody directed against the first 18 residues of the cytoplasmic N terminus (Nt) of human NDCBE. By Western blotting, the antibody distinguishes NDCBE—as a purified Nt peptide or a full-length transporter (expressed in Xenopus oocytes)—from other Na+-coupled HCO3− transporters. By Western blotting, the antiserum recognizes an ∼135-kDa band in several brain regions of adult mice: the cerebral cortex (CX), subcortex (SCX), cerebellum (CB), and HC. In CX, PNGase F treatment reduces the molecular weight to ∼116 kDa. By immunocytochemistry, affinity-purified (AP) NDCBE antibody stains the plasma membrane of neuron cell bodies and processes of rat HC neurons in primary culture as well as freshly dissociated mouse HC neurons. The AP antibody does not detect substantial NDCBE levels in freshly dissociated HC astrocytes, or astrocytes in HC or CB sections. By immunohistochemistry, the AP antibody recognizes high levels of NDCBE in neurons of CX, HC (including pyramidal neurons in Cornu Ammonis (CA)1-3 and dentate gyrus), substantial nigra, medulla, cerebellum (especially Purkinje and granular cells), and the basolateral membrane of fetal choroid plexus. Thus, NDCBE is in a position to contribute substantially to pHi regulation in multiple CNS neurons.