Neutral amino acid transporter A is a protein that in humans is encoded by the SLC1A4 gene. In melanocytic cells SLC1A4 gene expression may be regulated by MITF. ASCT1 does not transport glutamate or aspartate but alanine, serine, cysteine, and threonine instead. ASCT1 transporter functions primarily as an amino acid exchanger. Transport is associated with a chloride channel activity that is thermodynamically uncoupled from amino acid transport.