title: Perforin pores in the endosomal membrane trigger the release of endocytosed granzyme B into the cytosol of target cells.
abstract: How the pore-forming protein perforin delivers apoptosis-inducing granzymes to the cytosol of target cells is uncertain. Perforin induces a transient Ca2+ flux in the target cell, which triggers a process to repair the damaged cell membrane. As a consequence, both perforin and granzymes are endocytosed into enlarged endosomes called 'gigantosomes'. Here we show that perforin formed pores in the gigantosome membrane, allowing endosomal cargo, including granzymes, to be gradually released. After about 15 min, gigantosomes ruptured, releasing their remaining content. Thus, perforin delivers granzymes by a two-step process that involves first transient pores in the cell membrane that trigger the endocytosis of granzyme and perforin and then pore formation in endosomes to trigger cytosolic release.
authors.affiliation: Immune Disease Institute and Program in Cellular and Molecular Medicine, Children's Hospital, Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Jerome
authors.initials: J
authors.lastname: Thiery
authors.forename: Dennis
authors.initials: D
authors.lastname: Keefe
authors.forename: Steeve
authors.initials: S
authors.lastname: Boulant
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Boucrot
authors.forename: Michael
authors.initials: M
authors.lastname: Walch
authors.forename: Denis
authors.initials: D
authors.lastname: Martinvalet
authors.forename: Ing Swie
authors.initials: IS
authors.lastname: Goping
authors.forename: R Chris
authors.initials: RC
authors.lastname: Bleackley
authors.forename: Tomas
authors.initials: T
authors.lastname: Kirchhausen
authors.forename: Judy
authors.initials: J
authors.lastname: Lieberman
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000276:immunology; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D003600:Cytosol / Q000276:immunology / Q000378:metabolism; D004705:Endocytosis / Q000276:immunology*; D011992:Endosomes / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D053804:Granzymes / Q000276:immunology* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007694:Killer Cells, Natural; D018942:Macrolides / Q000494:pharmacology; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D052899:Pore Forming Cytotoxic Proteins / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D051381:Rats
chemical_list: D018942:Macrolides; D052899:Pore Forming Cytotoxic Proteins; C510465:perforin, rat; D000643:Ammonium Chloride; C040929:bafilomycin A1; D053804:Granzymes