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The Sec1p/Munc18 (SM) protein, Vps45p, cycles on and off membranes during vesicle transport

The Sec1p/Munc18 (SM) protein, Vps45p, cycles on and off membranes during vesicle transport Protein phosphatase 1 (PP1, Glc7p) functions in the final stage of SNARE-mediated vesicle transport between docking and fusion. During this process, trans-SNARE complexes, formed between molecules in opposing membranes, convert to cis-complexes, with all participants in the same lipid bilayer. Here, we show that glc7 mutant cells accumulate SNARE complexes. These complexes are clearly different from those found in either wild-type or sec18–1 cells as the Sec1p/Munc18 (SM) protein Vps45p does not bind to them. Given that PP1 controls fusion, the SNARE complexes that accumulate in glc7 mutants likely represent trans-SNARE complexes. Vps45p dissociates from the membrane in the absence of PP1 activity, but rapidly reassociates after its reactivation. These data reveal that SM proteins cycle on and off membranes in a stage-specific manner during the vesicle transport reaction, and suggest that protein phosphorylation plays a key role in the regulation of this cycle. SNAREs; fusion; protein phosphatase 1; docking; membranes Footnotes ↵ * Abbreviations used in this paper: CPY, carboxypeptidase Y; HA, hemagglutinin; PP1, protein phosphatase 1; SM, Sec1p/Munc18. N.J. Bryant's present address is Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Davidson Building, University of Glasgow, Glasgow G12 8QQ, UK. E-mail: n.bryant@bio.gla.ac.uk Submitted: 13 December 2002 Accepted: 8 April 2003 Revision received 4 April 2003 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Cell Biology Rockefeller University Press

The Sec1p/Munc18 (SM) protein, Vps45p, cycles on and off membranes during vesicle transport

The Journal of Cell Biology , Volume 161 (4): 691 – May 26, 2003

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References (35)

Publisher
Rockefeller University Press
Copyright
© 2003 Rockefeller University Press
ISSN
0021-9525
eISSN
1540-8140
DOI
10.1083/jcb.200212078
pmid
12756236
Publisher site
See Article on Publisher Site

Abstract

Protein phosphatase 1 (PP1, Glc7p) functions in the final stage of SNARE-mediated vesicle transport between docking and fusion. During this process, trans-SNARE complexes, formed between molecules in opposing membranes, convert to cis-complexes, with all participants in the same lipid bilayer. Here, we show that glc7 mutant cells accumulate SNARE complexes. These complexes are clearly different from those found in either wild-type or sec18–1 cells as the Sec1p/Munc18 (SM) protein Vps45p does not bind to them. Given that PP1 controls fusion, the SNARE complexes that accumulate in glc7 mutants likely represent trans-SNARE complexes. Vps45p dissociates from the membrane in the absence of PP1 activity, but rapidly reassociates after its reactivation. These data reveal that SM proteins cycle on and off membranes in a stage-specific manner during the vesicle transport reaction, and suggest that protein phosphorylation plays a key role in the regulation of this cycle. SNAREs; fusion; protein phosphatase 1; docking; membranes Footnotes ↵ * Abbreviations used in this paper: CPY, carboxypeptidase Y; HA, hemagglutinin; PP1, protein phosphatase 1; SM, Sec1p/Munc18. N.J. Bryant's present address is Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Davidson Building, University of Glasgow, Glasgow G12 8QQ, UK. E-mail: n.bryant@bio.gla.ac.uk Submitted: 13 December 2002 Accepted: 8 April 2003 Revision received 4 April 2003

Journal

The Journal of Cell BiologyRockefeller University Press

Published: May 26, 2003

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