SLC7A5 also known as CD98, LAT1 is a multipass-membrane protein responsible for sodium-independent, high-affinity transport of large neutral amino acids. SLC7A5 functions as a disulfide-linked heterodimer with the amino acid transport protein CD98. SLC7A5 is expressed predominantly in adult lung and liver but is also expressed in brain, thymus, retina, testis, placenta, bone marrow and fetal liver. In the retina, SLC7A5 localizes to the blood-retinal-barrier (BRB) and mediates L-leucine transport from the blood to the retina. The devastating effects on the brain caused by phenylketonuria are due to the increased levels of SLC7A5 on the blood-brain-barrier in response to high concentrations of phenylalanine in the blood. SLC7A5 accepts the amino-acid related anticancer agent melphalan and plays a significant role in cell proliferation, differentiation, and invasion in esophageal squamous cell carcinoma.