electrogenic Na+ bicarbonate cotransporter 4 (solute carrier family 4 member 5, NBCe2, SLC4A5, NBC4)
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Function
- mediates Na+ & bicarbonate-dependent electrogenic Na2CO3 cotransport, with a Na+:HCO3- stoichiometry of 2:1
- may have a housekeeping function in regulating the pH of tissues in which it is expressed
- may play a role in mediating Na+:HCO3- cotransport in hepatocytes & intrahepatic cholangiocytes
- may be important in protecting the renal parenchyma from alterations in urine pH
Inhibition:
- activity is inhibited by 4,4'-di-isothiocyanatostilbene-2,2'-disulfonic acid (DIDS) an inhibitor of several anionic channels & transporters
Structure
belongs to the anion exchanger (TC 2.A.31) family
Compartment
- membrane
- expressed in the apical plasma membrane domain of a subset of collecting ducts in the renal medulla
Alternative splicing
named isoforms=8
Expression
- expressed in liver, spleen & testis > choroid plexus, hippocampus, cerebrum & cerebellum of brain, renal cortex, renal medulla > heart, pancreas, muscle, lung, placenta, stomach & small intestine
- weakest expression in peripheral blood lymphocytes, colon, duodenum, jejunum, ileum & skeletal muscle