Amino acids are necessary for all living cells and organisms. Specialized transporters mediate the transfer of amino acids across plasma membranes. A couple of these amino acid transporters belong to the SLC7 family, which is divided into two subgroups, the cationic amino acid transporters (the CAT family, SLC7A1-4) and the L-type amino acid transporters (the LAT family, SLC7A5-11). The latter are the light or catalytic subunits of the heteromeric amino acid transporters (HATs), which are associated by a disulfide bridge with the heavy subunits 4F2hc or rBAT. These two subunits are glycoproteins and form the SLC3 family. The CATs transport essentially cationic amino acids by facilitated diffusion with differential trans-stimulation by intracellular substrates. In certain cells, they play an important role in regulating the rate of NO synthesis by controlling the uptake of l-arginine as the substrate for nitric oxide synthase (NOS). In contrast, the HATs are quite diverse in terms of substrate selectivity and function (mostly) as obligatory exchangers. They can transport a broad spectrum of substrates, including neutral, negatively charged, cationic amino acids. Moreover, HATs are crucial in renal and intestinal reabsorption and cellular redox balance. Mutations in these transporters may give rise to diseases like inherited aminoacidurias, cystinuria, and lysinuric protein intolerance. Inhibitors have been developed for disease improvement and future therapeutic applications.
Here, we give an introduction of some certain members of the human solute carrier family 7, focusing on the substrate specificity, transport type, tissue distribution, cellular expression, link to disease, and recent findings.
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