title: Imaging of lytic granule exocytosis in CD8+ cytotoxic T lymphocytes reveals a modified form of full fusion.
abstract: Here we imaged the exocytosis of lytic granules from human CD8(+) cytotoxic T lymphocytes using rapid total internal reflection microscopy, Lamp-1 tagged with mGFP to follow the fate of the lytic granule membrane, and granzyme A, granzyme B or serglycin tagged with mRFP to follow the fate of lytic granule cargo. Lytic granules were released by full fusion with the plasma membrane, such that the entire granule content for all three cargos visualized was released on a subsecond time scale. The behavior of GFP-Lamp-1 was, however, more complex. While it entered the plasma membrane in all cases, the extent to which it then diffused away from the site of exocytosis varied from nearly complete to highly restricted. Finally, the diffusion properties upon release of the three cargos examined put an upper limit on the size of the macromolecular complex of granzyme and serglycin that is presented to the target cell.
authors.affiliation: Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Heath, Bethesda, MD 20892-8017, USA.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Martina
authors.forename: Xufeng S
authors.initials: XS
authors.lastname: Wu
authors.forename: Marta
authors.initials: M
authors.lastname: Catalfamo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Chang
authors.initials: C
authors.lastname: Yi
authors.forename: John A
authors.initials: JA
authors.lastname: Hammer
mesh_terms: D000818:Animals; D005089:Exocytosis / Q000276:immunology / Q000502:physiology*; D053804:Granzymes / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D008561:Membrane Fusion / Q000276:immunology / Q000502:physiology*; D051379:Mice; D008856:Microscopy, Fluorescence; D011509:Proteoglycans / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022142:Secretory Vesicles / Q000276:immunology / Q000502:physiology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000502:physiology*; D033921:Vesicular Transport Proteins / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D053804:Granzymes; D049452:Green Fluorescent Proteins; D051907:Lysosomal Membrane Proteins; D011509:Proteoglycans; D011993:Recombinant Fusion Proteins; D033921:Vesicular Transport Proteins; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1; C075430:serglycin