Sodium-coupled neutral amino acid transporter 9 (SLC38A9)

Lysosomal amino acid transporter involved in the activation of mTORC1 in response to amino acids. Probably acts as an amino acid sensor of the Rag GTPases and Ragulator complexes, 2 complexes involved in amino acid sensing and activation of mTORC1, a signaling complex promoting cell growth in response to growth factors, energy levels, and amino acids (PubMed:25561175, PubMed:25567906).

After activation by amino acids, the Ragulator and Rag GTPases function as a scaffold recruitment mTORC1 to lysosomes where it is in turn activated. SLC38A9 mediates transport of amino acids with low capacity and specificity using a small taste for polar amino acids, indicating that it acts as an amino acid sensor instead (PubMed:25561175, PubMed:25567906).