A SNARE complex mediating fusion of late endosomes defines conserved properties of SNARE structure and function.
Sets of SNARE proteins mediate membrane fusion by assembling into core complexes. Multiple SNAREs are thought to function in different intracellular trafficking steps but it is often unclear which of the SNAREs cooperate in individual fusion reactions. We report that syntaxin 7, syntaxin 8, vti1b and endobrevin/VAMP-8 form a complex that functions in the fusion of late endosomes. Antibodies specific for each protein coprecipitate the complex, inhibit homotypic fusion of late endosomes in vitro and retard delivery of endocytosed epidermal growth factor to lysosomes. The purified proteins form core complexes with biochemical and biophysical properties remarkably similar to the neuronal core complex, although each of the four proteins carries a transmembrane domain and three have independently folded N-terminal domains. Substitution experiments, sequence and structural comparisons revealed that each protein occupies a unique position in the complex, with syntaxin 7 corresponding to syntaxin 1, and vti1b and syntaxin 8 corresponding to the N- and C-terminal domains of SNAP-25, respectively. We conclude that the structure of core complexes and their molecular mechanism in membrane fusion is highly conserved between distant SNAREs.
Antonin
W
W
Department of Neurobiology, Max-Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
Holroyd
C
C
Fasshauer
D
D
Pabst
S
S
Von Mollard
G F
GF
Jahn
R
R
D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D011992:Endosomes / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011233:Precipitin Tests; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050600:SNARE Proteins; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D013696:Temperature; D014162:Transfection; D033921:Vesicular Transport Proteins
D000954:Antigens, Surface; D002352:Carrier Proteins; D007140:Immunoglobulin Fab Fragments; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; C494208:SNAP25 protein, human; D050600:SNARE Proteins; C494212:STX1A protein, human; C494210:Snap25 protein, rat; C494213:Stx1a protein, rat; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; C112938:VAMP8 protein, human; C491419:VTI1A protein, human; C491830:Vamp8 protein, rat; D033921:Vesicular Transport Proteins; C491417:Vti1a protein, rat; D004815:Epidermal Growth Factor; D005982:Glutathione Transferase