[Research progress on structure, function and disease correlation of solute carrier family 4].

The solute carrier family 4 (SLC4) includes 10 members (SLC4A1-5, SLC4A7-11), which are expressed in multiple tissues in the human body. The SLC4 family members differ in their substrate dependence, charge transport stoichiometry and tissue expression. Their common function is responsible for the transmembrane exchange of multiple ions, which is involved in many important physiological processes, such as erythrocyte CO2 transport and the regulation of cell volume and intracellular pH. In recent years, many studies have focused on the role of SLC4 family members in the occurrence of human diseases. When SLC4 family members have gene mutations, a series of functional disorders will occur in the body, leading to the occurrence of some diseases. This review summarizes the recent progress about the structures, functions and disease correlation of SLC4 members, in order to provide clues for the prevention and treatment of related human diseases.

NBCe1 as a model carrier for understanding the structure-function properties of Na⁺ -coupled SLC4 transporters in health and disease.

SLC4 transporters are membrane proteins that in general mediate the coupled transport of bicarbonate (carbonate) and share amino acid sequence homology. These proteins differ as to whether they also transport Na(+) and/or Cl(-), in addition to their charge transport stoichiometry, membrane targeting, substrate affinities, developmental expression, regulatory motifs, and protein-protein interactions. These differences account in part for the fact that functionally, SLC4 transporters have various physiological roles in mammals including transepithelial bicarbonate transport, intracellular pH regulation, transport of Na(+) and/or Cl(-), and possibly water. Bicarbonate transport is not unique to the SLC4 family since the structurally unrelated SLC26 family has at least three proteins that mediate anion exchange. The present review focuses on the first of the sodium-dependent SLC4 transporters that was identified whose structure has been most extensively studied: the electrogenic Na(+)-base cotransporter NBCe1. Mutations in NBCe1 cause proximal renal tubular acidosis (pRTA) with neurologic and ophthalmologic extrarenal manifestations. Recent studies have characterized the important structure-function properties of the transporter and how they are perturbed as a result of mutations that cause pRTA. It has become increasingly apparent that the structure of NBCe1 differs in several key features from the SLC4 Cl(-)-HCO3 (-) exchanger AE1 whose structural properties have been well-studied. In this review, the structure-function properties and regulation of NBCe1 will be highlighted, and its role in health and disease will be reviewed in detail.