Role of T-Type Amino Acid Transporter TAT1 (S1C 16a 10) in Aromatic Amino Acid Homeostasis

TAT1 (T-type amino acid transporter 1), also known as SLC16A10 (solute carrier family 16, member 10), aromatic amino acid transporter 1, MCT10 (mono carboxylate transporter 10) or PRO0813, is a 515 amino acid protein that belongs to the monocarboxylate porter family. It is a uniporter, which is a Na+-independent transporter of aromatic amino acids (AAA) such as tryptophan, tyrosine, and phenylalanine across plasma membranes .It is highly expressed in skeletal muscle and kidney, found in low levels in heart, placenta, spleen , thymus , small intestine and liver epithelial cells. The gene encoding TAT1 maps to human chromosome 6, which contains170 million base pairs and comprises nearly 6% of the human genome. Its role in aminoacid homeostasis has been investigated using TAT1 defective mice (tat1(-/-). These mice show no gross phenotype or neurological defect however there is increased plasma, muscle and kidney AAA concentration under both normal and high protein diet, although this concentration remains normal in the liver. A major aromatic aminoaciduria and a smaller urinary loss of all substrates were revealed under a high protein diet suggesting an epithelial transport defect. Thus this indicates that uniporter TAT1 is required to equilibrate the concentration of AAAs across specific membranes by enabling the hepatocyte to function as a sink and also facilitates the release of AAAs across the basolateral membrane of small intestine and proximal kidney tubule epithelial cells thereby controlling the extracellular AAAs concentration.