Cystine/H(+) symporter that mediates export of cystine, the oxidized dimer of cysteine, from lysosomes (   ). Plays an important role in melanin synthesis by catalyzing cystine export from melanosomes, possibly by inhibiting pheomelanin synthesis . In addition to cystine export, also acts as a positive regulator of mTORC1 signaling in kidney proximal tubular cells, via interactions with components of the v-ATPase and Ragulator complexes . Also involved in small GTPase-regulated vesicle trafficking and lysosomal localization of LAMP2A, independently of cystine transporter activity (By similarity).
Subcellular locations: Lysosome membrane, Melanosome membrane
AP-3 complex is required for localization to the lysosome.
Subcellular locations: Lysosome membrane, Cell membrane
Strongly expressed in pancreas, kidney (adult and fetal), skeletal muscle, melanocytes and keratinocytes . Expressed at lower levels in placenta and heart. Weakly expressed in lung, liver and brain (adult and fetal) .
Represents 5-20 % of CTNS transcripts, with the exception of the testis that expresses both isoforms in equal proportions.