Lysosomal membrane glycoprotein which plays an important role in lysosome biogenesis, autophagy, and cholesterol homeostasis. Presents carbohydrate ligands to selectins. Also implicated in tumor cell metastasis. (Microbial infection) Plays an essential role in efficient replication and spread of Marek's disease virus, by facilitating viral cell-to-cell spread. This protein shuttles between lysosomes, endosomes, and the plasma membrane (PubMed:2871029, PubMed:3107839). Colocalizes with OSBPL1A at the late endosome (PubMed:3107839). Belongs to the LAMP family.