THE LYSOSOMAL MEMBRANE-GLYCOPROTEINS LAMP-1 AND LAMP-2 ARE PRESENT INMOBILIZABLE ORGANELLES, BUT ARE ABSENT FROM THE AZUROPHIL GRANULES OFHUMAN NEUTROPHILS

The subcellular localization of two members of a highly glycosylated p rotein group present in lysosomal membranes in most cells, the lysosom e-associated membrane proteins 1 and 2 (Lamp-1 and Lamp-2), was examin ed in human neutrophil granulocytes. Antibodies that were raised again st purified Lamp-1 and Lamp-2 gave a distinct granular staining of the cytoplasm upon immunostaining of neutrophils. Subcellular fractionati on was used to separate the azurophil and specific granules from a lig ht-membrane fraction containing plasma membranes and secretory vesicle s, and Western blotting was used to determine the presence of the Lamp s in these fractions. The results show that Lamp-1 and Lamp-2 are pres ent in the specific-granule-enriched fraction and in the light-membran e fraction, but not in the azurophil granules. Separation of secretory vesicles from plasma membranes disclosed that the light-membrane Lamp s were present primarily in the secretary-vesicle-enriched fraction. D uring phagocytosis both Lamp-1 and Lamp-2 became markedly concentrated around the ingested particle and they both appear on the cell surface when the secretory organelles are mobilized.