CD107a, also known as Lysosome-Associated Membrane Protein 1 (LAMP-1) or LGP-120, is a 110-140 kD type I membrane glycoprotein. The mature CD107a is heavily glycosylated from a 40 kD core protein. It is expressed by macrophages, epithelial cells, endothelial cells, and some tumor cells. This molecule is located on the luminal side of lysosomes and has been suggested to play a role in the protection of the lysosome membrane from lysosomal hydrolases. CD107a is a ligand for galaptin. Upon activation, CD107a is transferred to the surface of the cell membrane. It plays a role in cell adhesion and regulation of tumor metastasis and mediates autoimmune disease progression.