Lysosomal membrane glycoprotein which plays a role in the unfolded protein response (UPR) that contributes to protein degradation and cell survival during proteasomal dysfunction. Plays a role in the process of fusion of the lysosome with the autophagosome, thereby modulating the autophagic process. Promotes hepatocellular lipogenesis through activation of the PI3K/Akt pathway. May also play a role in dendritic cell function and in adaptive immunity. Monomer. Interacts with FURIN. During dendritic cell maturation, detected on cytoplasmic vesicles (the MHC II compartment) that contain MHC II proteins, LAMP1, LAMP2 and LAMP3. Detected on lysosomes in mature dendritic cells. Belongs to the LAMP family.