CD107a, also known as Lysosome-Associated Membrane Protein 1 (LAMP-1) or LGP-120, is a 110-140 kD type I membrane glycoprotein. Mature CD107a is heavily glycosylated from a 40 kD core protein. It is expressed by activated platelets, activated lymphocytes, 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 lysosomal membrane from lysosomal hydrolases. Upon activation, CD107a is transferred to the cell membrane surface. It plays a role in cell adhesion and regulation of tumor metastasis, and mediates autoimmune disease progression. CD107a is a ligand for galaptin and E-selectin.