SLC15A4 Protein, Human (HEK293, His)

SLC15A4 is a proton-coupled amino acid transporter that facilitates the transmembrane transport of L-histidine and select di- and tripeptides from lysosomes to the cytosol, playing a pivotal role in innate immunity. It transports diverse peptides, including carnosine and certain peptidoglycans, with pH-dependent activity maximized in acidic lysosomal environments (By similarity). The protein contributes to microbial pathogen detection via Toll-like receptors (TLRs) and NOD-like receptors (NLRs), likely by shuttling bacterial peptidoglycans (e.g., NOD2 ligand muramyl dipeptide [MDP] and NOD1 ligand tri-DAP) across endolysosomal membranes. In plasmacytoid dendritic cells (pDCs), it is essential for TLR7/8/9-mediated type I interferon (IFN-I) production. Independently of transport function, SLC15A4 recruits the innate immune adapter TASL to endolysosomes downstream of TLR7/8/9, enabling IRF5 activation. It also supports TLR9-stimulated class switch recombination to IgG2c (By similarity) and regulates mast cell secretory-granule homeostasis by restraining inflammatory responses (By similarity).