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Identification of two lysosomal membrane glycoproteins

By Jeff W. Chen, Theresa L. Murphy, Mark C. Wlllingham, Ira Pastan and J. Thomas August

Abstract

ABSTRACT TWO murine lysosome-assoeiated membrane proteins, LAMP-1 of 105,000-115,000 D and LAMP-2 of 100,000-110,000 D, have been identified by monoclonal antibodies that bind specifically to lysosomal membranes. Both glycoproteins were distinguished as integral membrane components solubilized by detergent solutions but not by various chaotropic agents. The lysosome localization was demonstrated by indirect immunofluorescent staining, co-localization of the antigen to sites of acridine orange uptake, and immunoelectron microscopy. Antibody binding was predominantly located at the limiting lysosomal membrane, distinctly separated from colloidal gold-labeled alpha-2-macroglobulin accumulated in the lumen during prolonged incubation. LAMP-1 and LAMP-2 also appeared to be present in low concentrations on Golgi trans-elements but were not detected in receptosomes marked by the presence of newly endocytose~malpha-2-macroglobulin, or in other cellular structures. LAMP-1 and LAMP-2 were distinguished as different molecules by two-dimensional gel analysis, 1251-tryptic peptide mapping, and sequential immunoprecipitations of ~2Sl-labeled cell extracts. Both glycoproteins were synthesized as a precursor protein of ~90,000 D, and showed a marked heterogeneity of apparent molecular weight expression in different cel

Year: 1985
OAI identifier: oai:CiteSeerX.psu:10.1.1.317.9596
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