Lysosomal integral membrane protein that regulates the localization and activity of mTORC1, a signaling complex promoting cell growth in response to growth factors, energy levels, and amino acids. Interacts with Rag GTPases and increases the lysosomial localization and activity of Rag GTPases and thereby regulates mTORC1 translocation and activity in lysosome. Involved in the regulation of lysosomal morphology and autophagy (By similarity). Acts also as a negative regulator of osteoclast activity (PubMed:31173907). Involved in interleukin-4-induced M2 macrophage polarization (PubMed:30595385). Acts also as a negative regulator of osteoclast activity (PubMed:31173907). Involved in interleukin-4-induced M2 macrophage polarization (PubMed:30595385). Interaction with RRAGA; increases RRAGA recruitment to lysosomes. Interacts with MTOR; this interaction is amino acid sensitive. Colocalized with MTOR in lysosome after amino acid stimulation. Widely expressed with high expression in bone marrow and kidney (PubMed:30595385). Highly expressed in osteoclasts (at protein level) (PubMed:31173907). Up-regulated during osteoclastogenesis (in vitro). Belongs to the GPR137 family.