Phosphoinositides and SNARE chaperones synergistically assemble and remodel SNARE complexes for membrane fusion.
Yeast vacuole fusion requires 4 SNAREs, 2 SNARE chaperone systems (Sec17p/Sec18p/ATP and the HOPS complex), and 2 phosphoinositides, phosphatidylinositol 3-phosphate [PI(3)P] and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)]. By reconstituting proteoliposomal fusion with purified components, we now show that phosphoinositides have 4 distinct roles: PI(3)P is recognized by the PX domain of the SNARE Vam7p; PI(3)P enhances the capacity of membrane-bound SNAREs to drive fusion in the absence of SNARE chaperones; either PI(3)P or PI(4,5)P(2) can activate SNARE chaperones for the recruitment of Vam7p into fusion-competent SNARE complexes; and either PI(3)P or PI(4,5)P(2) strikingly promotes synergistic SNARE complex remodeling by Sec17p/Sec18p/ATP and HOPS. This ternary synergy of phosphoinositides and 2 SNARE chaperone systems is required for rapid fusion.
Mima
Joji
J
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, USA.
Wickner
William
W
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D046911:Macromolecular Substances / Q000378:metabolism; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D050767:Qc-SNARE Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25; D014617:Vacuoles / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism
D046911:Macromolecular Substances; D008565:Membrane Proteins; D018832:Molecular Chaperones; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D050767:Qc-SNARE Proteins; C075137:SEC17 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D050825:Synaptosomal-Associated Protein 25; C494205:VAM7 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C106336:phosphatidylinositol 3,5-diphosphate; C055525:phosphatidylinositol 3-phosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C064404:SEC18 protein, S cerevisiae