Sodium-coupled neutral amino acid transporter 9 is a protein in humans that is encoded by SLC38A9 gene. 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.