![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Vol. 16, Issue 2, 470-482, February 2005
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool L69 3BX, United Kingdom
Submitted August 10, 2004;
Revised October 29, 2004;
Accepted November 10, 2004
Monitoring Editor: Keith Mostov
Sec1/Munc18 (SM) proteins are involved in various intracellular membrane trafficking steps. Many SM proteins bind to appropriate syntaxin homologues involved in these steps, suggesting that SM proteins function as syntaxin chaperones. Organisms with mutations in SM genes, however, exhibit defects in either early (docking) or late (fusion) stages of exocytosis, implying that SM proteins may have multiple functions. To gain insight into the role of SM proteins, we introduced mutations modeled on those identified in Caenorhabditis elegans, Drosophila melanogaster, and Saccharomyces cerevisiae into mammalian Munc18-1. As expected, several mutants exhibited reduced binding to syntaxin1A. However, three mutants displayed wild-type syntaxin binding affinities, indicating syntaxin-independent defects. Expression of these mutants in chromaffin cells either increased the rate and extent of exocytosis or altered the kinetics of individual release events. This latter effect was associated with a reduced Mint binding affinity in one mutant, implying a potential mechanism for the observed alteration in release kinetics. Furthermore, this phenotype persisted when the mutation was combined with a second mutation that greatly reduced syntaxin binding affinity. These results clarify the data on the function of SM proteins in mutant organisms and indicate that Munc18-1 controls multiple stages of exocytosis via both syntaxin-dependent and -independent protein interactions.
The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).
* These authors contributed equally to this work.
Corresponding author. E-mail address: amorgan{at}liverpool.ac.uk.
This article has been cited by other articles:
|
|
 |
|
  A. Boyd, L. F. Ciufo, J. W. Barclay, M. E. Graham, L. P. Haynes, M. K. Doherty, M. Riesen, R. D. Burgoyne, and A. Morgan A Random Mutagenesis Approach to Isolate Dominant-Negative Yeast sec1 Mutants Reveals a Functional Role for Domain 3a in Yeast and Mammalian Sec1/Munc18 Proteins Genetics, September 1, 2008; 180(1): 165 - 178. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. McEwen and J. M. Kaplan UNC-18 Promotes Both the Anterograde Trafficking and Synaptic Function of Syntaxin Mol. Biol. Cell, September 1, 2008; 19(9): 3836 - 3846. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. W. Barclay Munc-18-1 Regulates the Initial Release Rate of Exocytosis Biophys. J., February 1, 2008; 94(3): 1084 - 1093. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Gulyas-Kovacs, H. de Wit, I. Milosevic, O. Kochubey, R. Toonen, J. Klingauf, M. Verhage, and J. B. Sorensen Munc18-1: Sequential Interactions with the Fusion Machinery Stimulate Vesicle Docking and Priming J. Neurosci., August 8, 2007; 27(32): 8676 - 8686. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Simonsen, R. C. Cumming, K. Lindmo, V. Galaviz, S. Cheng, T. E. Rusten, and K. D. Finley Genetic Modifiers of the Drosophila Blue Cheese Gene Link Defects in Lysosomal Transport With Decreased Life Span and Altered Ubiquitinated-Protein Profiles Genetics, June 1, 2007; 176(2): 1283 - 1297. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Sano, A. Syuzo-Takabatake, T. Nakaya, Y. Saito, S. Tomita, S. Itohara, and T. Suzuki Enhanced Amyloidogenic Metabolism of the Amyloid beta-Protein Precursor in the X11L-deficient Mouse Brain J. Biol. Chem., December 8, 2006; 281(49): 37853 - 37860. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. G. Garcia, A. M. Garcia-De-Diego, L. Gandia, R. Borges, and J. Garcia-Sancho Calcium signaling and exocytosis in adrenal chromaffin cells. Physiol Rev, October 1, 2006; 86(4): 1093 - 1131. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Tsuboi and M. Fukuda The Slp4-a Linker Domain Controls Exocytosis through Interaction with Munc18-1{middle dot}Syntaxin-1a Complex Mol. Biol. Cell, May 1, 2006; 17(5): 2101 - 2112. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F.-D. Huang, E. Woodruff, R. Mohrmann, and K. Broadie Rolling Blackout Is Required for Synaptic Vesicle Exocytosis J. Neurosci., March 1, 2006; 26(9): 2369 - 2379. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. J. O. Evans, J. W. Barclay, G. R. Prescott, S.-R. Jo, R. D. Burgoyne, M. J. Birnbaum, and A. Morgan Protein Kinase B/Akt Is a Novel Cysteine String Protein Kinase That Regulates Exocytosis Release Kinetics and Quantal Size J. Biol. Chem., January 20, 2006; 281(3): 1564 - 1572. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. R. L. Constable, M. E. Graham, A. Morgan, and R. D. Burgoyne Amisyn Regulates Exocytosis and Fusion Pore Stability by Both Syntaxin-dependent and Syntaxin-independent Mechanisms J. Biol. Chem., September 9, 2005; 280(36): 31615 - 31623. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Li, D. Gallwitz, and R. Peng Structure-based Functional Analysis Reveals a Role for the SM Protein Sly1p in Retrograde Transport to the Endoplasmic Reticulum Mol. Biol. Cell, September 1, 2005; 16(9): 3951 - 3962. [Abstract] [Full Text] [PDF]
|
|
