The heterodimer with SLC3A2 functions as sodium-independent, high-affinity transporter that mediates uptake of large neutral amino acids such as phenylalanine, tyrosine, L-DOPA, leucine, histidine, methionine and tryptophan (PubMed:9915839, PubMed:11011012). Functions as an amino acid exchanger (By similarity). May play a role in the transport of L-DOPA across the blood-brain barrier (Probable). May act as the major transporter of tyrosine in fibroblasts (By similarity). May mediate blood-to-retina L-leucine transport across the inner blood-retinal barrier (By similarity). Can mediate the transport of thyroid hormones triiodothyronine (T3) and thyroxine (T4) across the cell membrane. When associated with LAPTM4B, the heterodimer formed by SLC3A2 and SLC7A5 is recruited to lysosomes to promote leucine uptake into these organelles, and thereby mediates mTORC1 activation. Involved in the uptake of toxic methylmercury (MeHg) when administered as the L-cysteine or D,L-homocysteine complexes. Involved in the cellular activity of small molecular weight nitrosothiols, via the stereoselective transport of L-nitrosocysteine (L-CNSO) across the membrane (By similarity). Disulfide-linked heterodimer with the amino acid transport protein SLC3A2/4F2hc (PubMed:9915839, PubMed:11011012). Interacts with LAPTM4B; this recruits the heterodimer formed by SLC3A2 and SLC7A5 to lysosomes to promote leucine uptake into these organelles and is required for mTORC1 activation (By similarity). Located to the plasma membrane by SLC3A2/4F2hc (PubMed:9915839). Localized to the apical membrane of placental syncytiotrophoblastic cells. Recruited to lysosomes by LAPTM4B (By similarity). Expressed in both luminal and abluminal membranes of brain capillary endothelial cells (By similarity). Detected in brain, spleen, liver and testis (at protein level) (PubMed:9915839). Predominantly expressed in the microvessels in the brain parenchyma of the central nervous system. Also detected in the subfornical organ, the subcommissural organ, ventromedial nucleus of the hypothalamus, subgranular zone of the dentate gyrus in hippocampus, ependymal layer of the lateral ventricles, and the olfactory bulb. Very strong expression also seen in testis, ovary, and placenta with weaker expression in spleen, skin, brain, thymus, stomach, lung, heart, kidney, small intestine, uterus and skeletal muscle. Strong expression in the liver of 14 dpc embryo. In embryo of 18 dpc expressed strongly in brain, moderate expression in spleen and brain and weak expression in liver. Expression induced by concanavalin-A stimulation. Leucine uptake was inhibited by ileum, valine histidine and phenylalanine as well as by 2-amino-bicyclo-(2,2,1)-heptane-2-carboxylate (BCH) (a specific inhibitor of system L transport). Belongs to the amino acid-polyamine-organocation (APC) superfamily. L-type amino acid transporter (LAT) (TC 2.A.3.8) family.