The function of LAMP1 (lysosome associated membrane protein 1, ENSG00000185896) is as follows. Lysosomal membrane glycoprotein which plays an important role in lysosome biogenesis, lysosomal pH regulation, autophagy and cholesterol homeostasis (PubMed:37390818). Acts as an important regulator of lysosomal lumen pH regulation by acting as a direct inhibitor of the proton channel TMEM175, facilitating lysosomal acidification for optimal hydrolase activity (PubMed:37390818). Also plays an important role in NK-cells cytotoxicity (PubMed:2022921, PubMed:23632890). Mechanistically, participates in cytotoxic granule movement to the cell surface and perforin trafficking to the lytic granule (PubMed:23632890). In addition, protects NK-cells from degranulation-associated damage induced by their own cytotoxic granule content (PubMed:23847195). Presents carbohydrate ligands to selectins (PubMed:7685349). {ECO:0000269|PubMed:2022921, ECO:0000269|PubMed:23632890, ECO:0000269|PubMed:23847195, ECO:0000269|PubMed:37390818, ECO:0000269|PubMed:7685349}. (Microbial infection) Acts as a receptor for Lassa virus glycoprotein (PubMed:24970085, PubMed:25972533, PubMed:27605678, PubMed:28448640). Also promotes fusion of the virus with host membrane in less acidic endosomes (PubMed:29295909). {ECO:0000269|PubMed:24970085, ECO:0000269|PubMed:25972533, ECO:0000269|PubMed:27605678, ECO:0000269|PubMed:28448640, ECO:0000269|PubMed:29295909}. (Microbial infection) Supports the FURIN-mediated cleavage of mumps virus fusion protein F by interacting with both FURIN and the unprocessed form but not the processed form of the viral protein F. .