title: The granzyme B-serglycin complex from cytotoxic granules requires dynamin for endocytosis.
abstract: Cytotoxic T lymphocytes and natural killer cells destroy target cells via the directed exocytosis of lytic effector molecules such as perforin and granzymes. The mechanism by which these proteins enter targets is uncertain. There is ongoing debate over whether the most important endocytic mechanism is nonspecific or is dependent on the cation-independent mannose 6-phosphate receptor. This study tested whether granzyme B endocytosis is facilitated by dynamin, a key factor in many endocytic pathways. Uptake of and killing by the purified granzyme B molecule occurred by both dynamin-dependent and -independent mechanisms. However most importantly, serglycin-bound granzyme B in high-molecular-weight degranulate material from cytotoxic T lymphocytes predominantly followed a dynamin-dependent pathway to kill target cells. Similarly, killing by live cytotoxic T lymphocytes was attenuated by a defect in the dynamin endocytic pathway, and in particular, the pathways characteristically activated by granzyme B were affected. We therefore propose a model where degranulated serglycin-bound granzymes require dynamin for uptake.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.
authors.forename: Kirstin
authors.initials: K
authors.lastname: Veugelers
authors.forename: Bruce
authors.initials: B
authors.lastname: Motyka
authors.forename: Christine
authors.initials: C
authors.lastname: Frantz
authors.forename: Irene
authors.initials: I
authors.lastname: Shostak
authors.forename: Tracy
authors.initials: T
authors.lastname: Sawchuk
authors.forename: R Chris
authors.initials: RC
authors.lastname: Bleackley
mesh_terms: D017209:Apoptosis / Q000276:immunology; D003594:Cytoplasmic Granules / Q000201:enzymology / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D034281:Dynamins / Q000235:genetics / Q000502:physiology*; D004705:Endocytosis / Q000276:immunology*; D053804:Granzymes; D006367:HeLa Cells; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology / Q000648:ultrastructure; D011509:Proteoglycans / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000648:ultrastructure; D014162:Transfection; D033921:Vesicular Transport Proteins
chemical_list: D011509:Proteoglycans; D033921:Vesicular Transport Proteins; C075430:serglycin; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases; D034281:Dynamins