Component of several heterodimeric complexes involved in amino acid transport. The precise substrate specificity depends on the other subunit in the heterodimer. The complexes function as amino acid exchangers. The heterodimer functions as sodium-independent, high-affinity transporter that mediates uptake of large neutral amino acids such as phenylalanine, tyrosine, leucine, histidine, methionine, tryptophan, valine and isoleucine. The heterodimer with SLC7A5/LAT1 mediates the uptake of L-DOPA. The heterodimer formed by SLC3A2 and SLC7A6 or SLC3A2 and SLC7A7 mediates the uptake of dibasic amino acids. The heterodimer with SLC7A5/LAT1 mediates the transport of thyroid hormones diiodothyronine (T2), triiodothyronine (T3) and thyroxine (T4) across the cell membrane. The heterodimer with SLC7A5/LAT1 is involved in the uptake of toxic methylmercury (MeHg) when administered as the L-cysteine or D,L-homocysteine complexes. When associated with LAPTM4B, the heterodimer with SLC7A5/LAT1 is recruited to lysosomes to promote leucine uptake into these organelles, and thereby mediates mTORC1 activation. The heterodimer with SLC7A5/LAT1 may play a role in the transport of L-DOPA across the blood-brain barrier. The heterodimer formed by SLC3A2 and SLC7A5/LAT1 or SLC3A2 and SLC7A8/LAT2 is involved in the cellular activity of small molecular weight nitrosothiols, via the stereoselective transport of L- nitrosocysteine (L-CNSO) across the transmembrane. The heterodimer with SLC7A10 translocates small neutral L- and D-amino acids across the plasma membrane. SLC3A2-SLC7A10 preferentially mediates exchange transport, but can also operate via facilitated diffusion. Together with ICAM1, regulates the transport activity of SLC7A8/LAT2 in polarized intestinal cells by generating and delivering intracellular signals. Required for .geting of SLC7A5/LAT1 and SLC7A8/LAT2 to the plasma membrane and for channel activity. Plays a role in nitric oxide synthesis in human umbilical vein endothelial cells (HUVECs) via transport of L-arginine. May mediate blood-to-retina L-leucine transport across the inner blood-retinal barrier.