Abstract
Cytotoxic T lymphocytes and natural killer cells exert their cytotoxic activity through the polarized secretion of cytotoxic granules at the immunological synapse. Rab27a and hMunc13-4 are critical effectors of the exocytosis of cytotoxic granules. Here we show that the cytotoxic function of lymphocytes requires the cooperation of two types of organelles: the lysosomal cytotoxic granule and the endosomal 'exocytic vesicle'. Independently of Rab27a, hMunc13-4 mediated the assembly of Rab11(+) recycling and Rab27(+) late endosomal vesicles, constituting a pool of vesicles destined for regulated exocytosis. It also primed cytotoxic granule fusion, possibly through interaction with active Rab27a. Cytotoxic T lymphocyte-target cell recognition induced rapid polarization of both types of organelles, which coalesced near the cell-cell contact area. Our data provide insight into the regulation of the generation and release of cytotoxic granules by effector cytotoxic T lymphocytes and natural killer cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Cell Polarity
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Cells, Cultured
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Cytotoxicity, Immunologic / physiology*
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Endosomes / immunology
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Endosomes / metabolism
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Endosomes / ultrastructure
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Exocytosis / immunology*
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Fluorescent Antibody Technique
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Humans
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Immunoblotting
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Immunoprecipitation
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Killer Cells, Natural / immunology*
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Killer Cells, Natural / metabolism
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Killer Cells, Natural / ultrastructure
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Lymphocyte Activation / immunology
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Lysosomes / immunology
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Lysosomes / metabolism
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Lysosomes / ultrastructure
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Microscopy, Electron, Transmission
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Microscopy, Immunoelectron
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Nerve Tissue Proteins / immunology*
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Nerve Tissue Proteins / metabolism
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Polymerase Chain Reaction
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Secretory Vesicles / immunology*
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Secretory Vesicles / metabolism
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Secretory Vesicles / ultrastructure
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T-Lymphocytes, Cytotoxic / immunology*
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T-Lymphocytes, Cytotoxic / metabolism
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T-Lymphocytes, Cytotoxic / ultrastructure
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Transfection
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rab GTP-Binding Proteins / immunology
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rab GTP-Binding Proteins / metabolism
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rab27 GTP-Binding Proteins
Substances
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Nerve Tissue Proteins
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UNC13B protein, human
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rab27 GTP-Binding Proteins
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RAB27A protein, human
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rab GTP-Binding Proteins