Lysosome associated membrane protein 1 (LAMP1) and LAMP2 are major constituents of the lysosomal membrane. The two have closely related structures, with 37% sequence homology.¹They are both transmembrane glycoproteins that are localized primarily in lysosomes and late endosomes. Newly synthesized molecules are mostly transported from the trans-Golgi network directly to endosomes and then to lysosomes. A second pathway involves the LAMPs being delivered from the Golgi to the cell surface, and then along the endocytic pathway to the lysosomes. A minor pathway involves transportviathe plasma membrane.²Upon stimulation, a rapid translocation of intracellular LAMPs to the cell membrane is dependent on a carboxyl-terminal tyrosine based motif (YXXI).³If there is a disturbance in this spacing, lysosome localization of LAMP1 is abolished and the mutant protein then cycles between the membrane and the endosome.²This stimulation has also been shown to have an associated release of histamine, leukotriene C₄and prostaglandin D₂, which shows that LAMP1 and LAMP2 are activation markers for normal mast cells.³They have also been linked to the inflammatory response in that they promote adhesion of human peripheral blood mononuclear cells (PBMC) to vascular endothelium and therefore possibly adhesion of PBMC to the site of inflammation.⁴

1.HÖning, S., Sandoval, I.V., and von Figura, K.A di-leucine-based motif in the cytoplasmic tail of LIMP-II and tyrosinase mediates selective binding of AP-3EMBO Journal17(5)1304-1314(1998) 2.Rohrer, J., Schweizer, A., Russel, D., et al.The targeting of lamp1 to lysosomes is dependent on the spacing of its cytoplasmic tail tyrosine sorting motif relative to the membraneJournal of Cell Biology132(4)565-576(1996) 3.GrÜtzkau, A., Smorodchenko, A., Lippert, U., et al.LAMP-1 and LAMP-2, but not LAMP-3, are reliable markers for activation-induced secretion of human mast cellsCytometry Part A61(1)62-68(2004) 4.Kannan, K., Stewart, R.M., Bounds, W., et al.Lysosome-associated membrane proteins h-LAMP1 (CD107a) and h-LAMP2 (CD107b) are activation-dependent cell surface glycoproteins in human peripheral blood mononuclear cells which mediate cell adhesion to vascular endotheliumCellular Immunology171(1)10-19(1996)