title: Combinatorial SNARE complexes with VAMP7 or VAMP8 define different late endocytic fusion events.
abstract: Both heterotypic and homotypic fusion events are required to deliver endocytosed macromolecules to lysosomes and remodel late endocytic organelles. A trans-SNARE complex consisting of Q-SNAREs syntaxin 7, Vti1b and syntaxin 8 and the R-SNARE VAMP8 has been shown by others to be responsible for homotypic fusion of late endosomes. Using antibody inhibition experiments in rat liver cell-free systems, we confirmed this result, but found that the same Q-SNAREs can combine with an alternative R-SNARE, namely VAMP7, for heterotypic fusion between late endosomes and lysosomes. Co-immunoprecipitation demonstrated separate syntaxin 7 complexes with either VAMP7 or VAMP8 in solubilized rat liver membranes. Additionally, overexpression of the N-terminal domain of VAMP7, in cultured fibroblastic cells, inhibited the mixing of a preloaded lysosomal content marker with a marker delivered to late endosomes. These data show that combinatorial interactions of SNAREs determine whether late endosomes undergo homotypic or heterotypic fusion events.
authors.affiliation: Cambridge Institute for Medical Research and Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2XY, UK.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Pryor
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Mullock
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Bright
authors.forename: Margaret R
authors.initials: MR
authors.lastname: Lindsay
authors.forename: Sally R
authors.initials: SR
authors.lastname: Gray
authors.forename: Simon C W
authors.initials: SC
authors.lastname: Richardson
authors.forename: Abigail
authors.initials: A
authors.lastname: Stewart
authors.forename: David E
authors.initials: DE
authors.lastname: James
authors.forename: Robert C
authors.initials: RC
authors.lastname: Piper
authors.forename: J Paul
authors.initials: JP
authors.lastname: Luzio
mesh_terms: D000818:Animals; D002474:Cell-Free System / Q000276:immunology / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000276:immunology / Q000378:metabolism; D047468:Immunoprecipitation; D008247:Lysosomes / Q000276:immunology / Q000378:metabolism; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D016716:PC12 Cells; D021381:Protein Transport / Q000502:physiology; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D051381:Rats; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins / Q000276:immunology / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; C496926:Vamp7 protein, rat; C491830:Vamp8 protein, rat; D033921:Vesicular Transport Proteins