LAT3 (SLC43A1) and LAT4 (SLC43A2) are transporters with system L amino acid transporter activity, along with the structurally and functionally distinct transporters LAT1 and LAT2 that are members of the SLC7 family. LAT3 and LAT4 contain 12 putative TM domains with both N and C termini located intracellularly. They transport neutral amino acids in a manner independent of Na⁺ and Cl^- and with two kinetic components [1-2]. LAT3/SLC43A1 is expressed in human tissues at high levels in the pancreas, liver, skeletal muscle and fetal liver [1] whereas LAT4/SLC43A2 is primarily expressed in the placenta, kidney and peripheral blood leukocytes [2]. SLC43A3 is expressed in vascular endothelial cells [3] but remains to be characterised.

Covalent modification of LAT3 by N-ethylmaleimide inhibits its function [1] and at LAT4 inhibits the low-, but not high-affinity component of transport [2].

1. Babu, E; Kanai, Y; Chairoungdua, A; Kim, DK; Iribe, Y; Tangtrongsup, S; Jutabha, P; Li, Y; Ahmed, N; Sakamoto, S; et al.. (2003) Identification of a novel system L amino acid transporter structurally distinct from heterodimeric amino acid transporters. J. Biol. Chem., 278 (44): 43838-45. [PMID:12930836]

2. Bodoy, S; Martín, L; Zorzano, A; Palacín, M; Estévez, R; Bertran, J. (2005) Identification of LAT4, a novel amino acid transporter with system L activity. J. Biol. Chem., 280 (12): 12002-11. [PMID:15659399]

3. Wallgard, E; Larsson, E; He, L; Hellström, M; Armulik, A; Nisancioglu, MH; Genove, G; Lindahl, P; Betsholtz, C. (2008) Identification of a core set of 58 gene transcripts with broad and specific expression in the microvasculature. Arterioscler. Thromb. Vasc. Biol., 28 (8): 1469-76. [PMID:18483404]