QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

doi: 10.1242/10.1242/jcs.00374

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JCS Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Coorssen, J. R. Articles by Zimmerberg, J. Search for Related Content PubMed PubMed Citation Articles by Coorssen, J. R. Articles by Zimmerberg, J.

Regulated secretion: SNARE density, vesicle fusion and calcium dependence

¹ Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, USA
² Unit on Biologic Computation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, USA
³ Department of Physiology and Biophysics, Neuroscience Research Group, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada

^* Authors for correspondence (e-mail: jcoorsse{at}ucalgary.ca or joshz{at}helix.nih.gov)

Accepted 20 January 2003

SNAREs such as VAMP, SNAP-25 and syntaxin are essential for intracellular trafficking, but what are their exact molecular roles and how are their interactions with other proteins manifest? Capitalizing on the differential sensitivity of SNAREs to exogenous proteases, we quantified the selective removal of identified SNAREs from native secretory vesicles without loss of fusion competence. Using previously established fusion assays and a high sensitivity immunoblotting protocol, we analyzed the relationship between these SNARE proteins and Ca²⁺-triggered membrane fusion. Neither the extent of fusion nor the number of intermembrane fusion complexes per vesicle were correlated with the measured density of identified egg cortical vesicle (CV) SNAREs. Without syntaxin, CVs remained fusion competent. Surprisingly, for one (but not another) protease the Ca²⁺ dependence of fusion was correlated with CV SNARE density, suggesting a native protein complex that associates with SNAREs, the architecture of which ensures high Ca²⁺ sensitivity. As SNAREs may function during CV docking in vivo, and as further proteolysis after SNARE removal eventually ablates fusion, we hypothesize that the triggered steps of regulated fusion (Ca²⁺ sensitivity and the catalysis and execution of fusion) require additional proteins that function downstream of SNAREs.

Key words: Secretory vesicles, Exocytosis, Membrane fusion, Sea urchins, Quantitative immunoblotting

Related articles in JCS:

Rethinking SNARE function

JCS 2003 116: 1001. [Full Text]  

This article has been cited by other articles:

				M. A. Churchward, T. Rogasevskaia, D. M. Brandman, H. Khosravani, P. Nava, J. K. Atkinson, and J. R. Coorssen Specific Lipids Supply Critical Negative Spontaneous Curvature--An Essential Component of Native Ca2+-Triggered Membrane Fusion Biophys. J., May 15, 2008; 94(10): 3976 - 3986. [Abstract] [Full Text] [PDF]

				P. Wang, N. R. Chintagari, D. Gou, L. Su, and L. Liu Physical and Functional Interactions of SNAP-23 with Annexin A2 Am. J. Respir. Cell Mol. Biol., October 1, 2007; 37(4): 467 - 476. [Abstract] [Full Text] [PDF]

				T. Rogasevskaia and J. R. Coorssen Sphingomyelin-enriched microdomains define the efficiency of native Ca2+-triggered membrane fusion J. Cell Sci., July 1, 2006; 119(13): 2688 - 2694. [Abstract] [Full Text] [PDF]

				L. V. Chernomordik and K. Melikov Are There Too Many or Too Few SNAREs in Proteoliposomes? Biophys. J., April 15, 2006; 90(8): 2657 - 2658. [Full Text] [PDF]

				X. Chen, D. Arac, T.-M. Wang, C. J. Gilpin, J. Zimmerberg, and J. Rizo SNARE-Mediated Lipid Mixing Depends on the Physical State of the Vesicles Biophys. J., March 15, 2006; 90(6): 2062 - 2074. [Abstract] [Full Text] [PDF]

				C. Reese and A. Mayer Transition from hemifusion to pore opening is rate limiting for vacuole membrane fusion J. Cell Biol., December 19, 2005; 171(6): 981 - 990. [Abstract] [Full Text] [PDF]

				M. A. Churchward, T. Rogasevskaia, J. Hofgen, J. Bau, and J. R. Coorssen Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion J. Cell Sci., October 15, 2005; 118(20): 4833 - 4848. [Abstract] [Full Text] [PDF]

				R. Qiu, W. Pei, L. Zhang, J. Lin, and G. Ji Identification of the Putative Staphylococcal AgrB Catalytic Residues Involving the Proteolytic Cleavage of AgrD to Generate Autoinducing Peptide J. Biol. Chem., April 29, 2005; 280(17): 16695 - 16704. [Abstract] [Full Text] [PDF]

				J. A. Szule and J. R. Coorssen Comment on "Transmembrane Segments of Syntaxin Line the Fusion Pore of Ca2+-Triggered Exocytosis" Science, October 29, 2004; 306(5697): 813b - 813b. [Full Text] [PDF]

				T. Whalley, K. Timmers, J. Coorssen, L. Bezrukov, D. H. Kingsley, and J. Zimmerberg Membrane fusion of secretory vesicles of the sea urchin egg in the absence of NSF J. Cell Sci., May 1, 2004; 117(11): 2345 - 2356. [Abstract] [Full Text] [PDF]

				J. A. Szule, S. E. Jarvis, J. E. Hibbert, J. D. Spafford, J. E. A. Braun, G. W. Zamponi, G. M. Wessel, and J. R. Coorssen Calcium-triggered Membrane Fusion Proceeds Independently of Specific Presynaptic Proteins J. Biol. Chem., June 27, 2003; 278(27): 24251 - 24254. [Abstract] [Full Text] [PDF]