The function of SLC46A3 (solute carrier family 46 member 3, ENSG00000139508) is as follows. Lysosomal proton-coupled steroid conjugate and bile acid transporter. Preferentially recognizes lipophilic steroid conjugates or bile acis as endogenous substrates and seems to mediate escape from lysosomes to the cytoplasm (PubMed:36741448). Modulates hepatic cytosolic copper homeostasis, maybe acting as a lysosomal copper transporter and sequestering copper ions in the lysosome (By similarity). Transports catabolites of non-cleavable antibody-drug conjugates from the lysosome to the cytoplasm (PubMed:26631267, PubMed:30131388, PubMed:36741448). Delivers pathogen-associated molecular patterns to cytosolic pattern recognition receptors as part of the innate immune response to microbes. Selectively transports bacterial muramyl dipeptide (MDP) into the cytosol for recognition by NOD2, triggering inflammatory responses (By similarity). Likely acts as a redundant importer of cyclic GMP-AMP dinucleotides (cGAMPs) in monocyte and macrophage cell lineages (PubMed:34235268). The transport mechanism, its electrogenicity and stoichiometry remain to be elucidated (Probable). {ECO:0000250|UniProtKB:Q9DC26, ECO:0000269|PubMed:26631267, ECO:0000269|PubMed:30131388, ECO:0000269|PubMed:34235268, ECO:0000269|PubMed:36741448, ECO:0000305}.