Lysosomal membrane chaperone required to export cobalamin (vitamin B12) from the lysosome to the cytosol, allowing its conversion to cofactors. Targets ABCD4 transporter from the endoplasmic reticulum to the lysosome. Then forms a complex with lysosomal ABCD4 and cytoplasmic MMACHC to transport cobalamin across the lysosomal membrane (By similarity). Acts as an adapter protein which plays an important role in mediating and regulating the internalization of the insulin receptor (INSR) (By similarity). Involved in clathrin-mediated endocytosis of INSR via its interaction with adapter protein complex 2 (By similarity). Essential for the initiation of gastrulation and early formation of mesoderm structures during embryogenesis (By similarity). Interacts with ABCD4; this interaction induces the translocation of ABCD4 from the endoplasmic reticulum to the lysosome. Interacts with ABCD4 and MMACHC; this interaction ensures the transport of cobalamin from the lysosome to the cytoplasm (By similarity). Interacts with INSR, adapter protein complex 2 and clathrin heavy chain (By similarity). N-glycosylated. Belongs to the LIMR family. LMBRD1 subfamily.