Amino acid cotransporter SLC3A2 is selectively expressed in the early proximal segment of Xenopus pronephric kidney nephrons

The transport of amino acids across membranes is critical to all cells. As amino acids freely pass through the glomerular filtration barrier of the kidney, they must be efficiently resorbed to avoid depletion of circulating amino acid reserves. Not only do defects in amino acid resorption lead to costly wastage, they also cause congenital aminoacidurias. A clone encoding Xenopus SLC3A2 was identified and shown to be expressed at high levels in the early segment of the pronephric proximal tubules in developing tadpoles. The type II membrane glycoprotein encoded by this gene can associate with a wide variety of protein partners and participates in a broad spectrum of biological processes. In this report, the first whole-mount analysis of SLC3A2 during early embryonic development is presented. The expression pattern of SLC3A2 in the early proximal segment of the Xenopus pronephros is analogous to that of a previously described SLC7A8/XAA2 amino acid transporter. In mammals, SLC3A2 and SLC7A8/XAA2 associate to form a functional neutral amino acid transporter complex and coexpression of these two genes in a small domain within the pronephric tubules indicates that this is also the situation in the developing Xenopus kidney.