REGULATION OF CAT - CATIONIC AMINO-ACID TRANSPORTER GENE-EXPRESSION

The majority of mammalian cationic amino acid transport is mediated by the transport system y(+) which facilitates Na+ independent cationic amino acid (arginine, lysine, & ornithine) transport and Nah dependent zwitterionic amino acid (glutamine & homoserine) transport. Other tra nsport systems y(+)L, b(0,+) and B-0,B-+ also mediate cationic amino a cid transport. Their broad substrate specificities and overlapping exp ression patterns confound biochemical analysis. The isolation of cDNA clones has permitted an analysis of their regulation and opens the opp ortunity to define the role of each protein in specific cell types. Tw o genes, Cat1 and Cat2 encode transporters with properties similar to the y(+) transport system. The cat2 gene from the mouse encodes two di stinct proteins. mCAT2, and mCAT2A via alternate splicing; each protei n has distinctly different transport properties. The regulation of mCA T1, mCAT2 and mCAT2A proteins are reviewed here. The implications of t his gene specific regulation on cationic amino acid transport is discu ssed.