Proton-coupled transporter that delivers pathogen-associated or danger-associated molecular patterns to cytosolic pattern recognition receptors as part of the innate immune response to microbes or tissue injury (, ). Has selectivity toward muropeptides that contain the amino acid diaminopimelic acid (DAP-type peptidoglycan muropeptides) including Tri-DAP and tracheal toxin (TCT), common in Gram-negative bacteria and Gram-positive bacilli. In the context of immune recognition of skin microbiota, shuttles bacterial muropeptides across the endolysosomal membranes into the cytosol for recognition by NOD1, triggering MYD88-dependent secretion of IL1A and neutrophil recruitment in a pyroptosis-type inflammatory process . To a lesser extent and redundantly, transports muramyl dipeptides derived from most bacterial proteoglycans, eliciting NOD2 receptor activation and downstream inflammatory responses . Postulated to function as a dominant importer of cyclic GMP-AMP dinucleotides (cGAMPs) in monocyte and macrophage cell lineages. Selectively imports cGAMPs derived from pathogenic bacteria such as 3'3'-cGAMP thus providing for differential immune recognition of pathogenic versus commensal bacteria. During tumorigenesis may transport extracellular tumor-derived 2'3'-cGAMP across the plasma membrane of M1-polarized macrophages to activate the anti-tumoral stimulator of interferon genes (STING) pathway . The transport mechanism, its electrogenicity and stoichiometry remain to be elucidated (Probable).
Subcellular locations: Endosome membrane, Cell membrane
Localizes in acidic vesicles likely late endosomes and/or endolysosomes.
Strongly expressed in the adult thymus. Expressed in spleen, lymph nodes, thymus, PBL, bone marrow and fetal liver. Expressed in monocytes and pre-dendridic cells.