Lysosomal membrane glycoprotein which plays an important role in lysosome biogenesis, autophagy, and cholesterol homeostasis (PubMed:15121881). Also plays an important role in NK-cells cytotoxicity (PubMed:23847195). Mechanistically, participates in cytotoxic granule movement to the cell surface and perforin trafficking to the lytic granule (By similarity). In addition, protects NK-cells from degranulation-associated damage induced by their own cytotoxic granule content (By similarity) (PubMed:23847195). Presents carbohydrate ligands to selectins. Also implicated in tumor cell metastasis (By similarity). Interacts with ABCB9; this interaction strongly stabilizes ABCB9 and protects ABCB9 against lysosomal degradation (PubMed:22641697). Interacts with FURIN (By similarity). This protein shuttles between lysosomes, endosomes, and the plasma membrane (By similarity). Colocalizes with OSBPL1A at the late endosome (By similarity). O- and N-glycosylated; some of the N-glycans attached to LAMP-1 are polylactosaminoglycans. Deficient mice are viable and fertile (PubMed:10212251). However, mice deficient in both LAMP1 and LAMP2 are embryonic lethal, with the accumulation of autophagic vacuoles in many tissues (PubMed:15121881). In addition, LAMP1 deletion results in increased NK-cell apoptosis upon target cell-induced degranulation (PubMed:23847195). Belongs to the LAMP family.