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 (PubMed:31036939). Interacts with Rag GTPases and increases the lysosomal localization and activity of Rag GTPases and thereby regulates mTORC1 translocation and activity in lysosome (PubMed:31036939). Involved in the regulation of lysosomal morphology and autophagy (PubMed:31036939). . Also acts as a negative regulator of osteoclast activity (By similarity). Involved in interleukin-4-induced M2 macrophage polarization (By similarity). . This is the function of GPR137B (G protein-coupled receptor 137B, ENSG00000077585).