title: VAMP8-dependent fusion of recycling endosomes with the plasma membrane facilitates T lymphocyte cytotoxicity.
abstract: Cytotoxic T lymphocytes (CTLs) eliminate infected and neoplastic cells through directed release of cytotoxic granule contents. Although multiple SNARE proteins have been implicated in cytotoxic granule exocytosis, the role of vesicular SNARE proteins, i.e., vesicle-associated membrane proteins (VAMPs), remains enigmatic. VAMP8 was posited to represent the cytotoxic granule vesicular SNARE protein mediating exocytosis in mice. In primary human CTLs, however, VAMP8 colocalized with Rab11a-positive recycling endosomes. Upon stimulation, these endosomes rapidly trafficked to and fused with the plasma membrane, preceding fusion of cytotoxic granules. Knockdown of VAMP8 blocked both recycling endosome and cytotoxic granule fusion at immune synapses, without affecting activating signaling. Mechanistically, VAMP8-dependent recycling endosomes deposited syntaxin-11 at immune synapses, facilitating assembly of plasma membrane SNARE complexes for cytotoxic granule fusion. Hence, cytotoxic granule exocytosis is a sequential, multivesicle fusion process requiring VAMP8-mediated recycling endosome fusion before cytotoxic granule fusion. Our findings imply that secretory granule exocytosis pathways in other cell types may also be more complex than previously appreciated.
authors.affiliation: Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany Department of Medicine, Center For Infectious Medicine, 14186 Stockholm, Sweden.
authors.forename: Misty R
authors.initials: MR
authors.lastname: Marshall
authors.affiliation: Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany.
authors.forename: Varsha
authors.initials: V
authors.lastname: Pattu
authors.affiliation: Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany Department of Pathology, Brigham and Woman's Hospital, Boston, MA.
authors.forename: Mahantappa
authors.initials: M
authors.lastname: Halimani
authors.affiliation: Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Maier-Peuschel
authors.affiliation: Department of Medicine, Center For Infectious Medicine, 14186 Stockholm, Sweden.
authors.forename: Martha-Lena
authors.initials: ML
authors.lastname: Müller
authors.affiliation: Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Becherer
authors.affiliation: Membrane Biology Laboratory, Institute of Molecular and Cell Biology, Singapore 138673.
authors.forename: Wanjin
authors.initials: W
authors.lastname: Hong
authors.affiliation: Department of Biophysics, Saarland University, 66421 Homburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Hoth
authors.affiliation: Department of Anatomy, Saarland University, 66421 Homburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Tschernig
authors.affiliation: Department of Medicine, Center For Infectious Medicine, 14186 Stockholm, Sweden jrettig@uks.eu Yenan.Bryceson@ki.se.
authors.forename: Yenan T
authors.initials: YT
authors.lastname: Bryceson
authors.affiliation: Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany jrettig@uks.eu Yenan.Bryceson@ki.se.
authors.forename: Jens
authors.initials: J
authors.lastname: Rettig
mesh_terms: D015550:Cell Degranulation; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D011992:Endosomes / Q000378:metabolism*; D006801:Humans; D054992:Immunological Synapses / Q000378:metabolism; D008561:Membrane Fusion; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000378:metabolism; D050683:R-SNARE Proteins / Q000502:physiology*; D015398:Signal Transduction; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; C541732:STX11 protein, human; C112938:VAMP8 protein, human