Membrane fusion at neuronal synapses is a highly regulated process that is triggered by micromolar concentrations of calcium in the presynaptic cell. The SNARE proteins drive fusion and form the critical core of the fusion machinery;however, they are not directly regulated by calcium. Synaptotagmin 1 is a vesicle associated membrane protein that functions as the calcium sensor in neuronal exocytosis. It is anchored by a single transmembrane segment at its N-terminus and contains two C2 domains that have been shown to bind membranes in a calcium-dependent fashion. Synaptotagmin also interacts with SNAREs. At the present time, the nature of the synaptotagmin interactions that mediate fusion are not understood. The proposed work will utilize evolving magnetic resonance methods, such as site-directed spin labeling and pulse EPR, to evaluate a number of proposed mechanisms for the molecular function of sytnaptotagmin.
The specific aims are to test the importance of a bridging conformation that is observed for synaptotagmin 1, where the two C2 domains bind opposing bilayers. Proposed experiments will test the hypothesis that synaptotagmin 1 switches from SNARE to membrane interactions in the presence of calcium, and both membrane and SNARE associated structures for synaptotagmin 1 will be generated.
A final aim will examine the effects of synaptotagmin 1 on lipid bilayer properties and test the role of these effects in mediating membrane fusion. Membrane fusion is central to cellular processes such as intracellular transport, host defense (killing of microorganisms, immune response), and human physiology and disease (e.g., glucose regulation/diabetes, allergic response). Calcium -triggered neuronal fusion is a central process in neurobiology and it underlies synaptic transmission and potentiation. Regulated neuronal exocytosis is thought to be relevant to an understanding of schizophrenia, bipolar disorder, Huntington's disease, Parkinson's disease, Alzheimer's disease as well as range of other neurological disorders.

Public Health Relevance

The proposed work is directed at characterizing the molecular mechanisms by which neurons release neurotransmitters and communicate with each other in the central nervous system. The mechanisms of neurotransmitter release are relevant to understanding a wide range of neurological disorders, including schizophrenia, bipolar disorder, Huntington's disease, Parkinson's disease and Alzheimer's disease.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Program Projects (P01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-BCMB-S)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Virginia
United States
Zip Code
Moissoglu, Konstadinos; Kiessling, Volker; Wan, Chen et al. (2014) Regulation of Rac1 translocation and activation by membrane domains and their boundaries. J Cell Sci 127:2565-76
Park, Yongsoo; Vennekate, Wensi; Yavuz, Halenur et al. (2014) ?-SNAP interferes with the zippering of the SNARE protein membrane fusion machinery. J Biol Chem 289:16326-35
Liang, Binyong; Dawidowski, Damian; Ellena, Jeffrey F et al. (2014) The SNARE motif of synaptobrevin exhibits an aqueous-interfacial partitioning that is modulated by membrane curvature. Biochemistry 53:1485-94
Hernandez, Javier M; Kreutzberger, Alex J B; Kiessling, Volker et al. (2014) Variable cooperativity in SNARE-mediated membrane fusion. Proc Natl Acad Sci U S A 111:12037-42
Cafiso, David S (2014) Identifying and quantitating conformational exchange in membrane proteins using site-directed spin labeling. Acc Chem Res 47:3102-9
Dawidowski, Damian; Cafiso, David S (2013) Allosteric control of syntaxin 1a by Munc18-1: characterization of the open and closed conformations of syntaxin. Biophys J 104:1585-94
Kiessling, Volker; Ahmed, Saheeb; Domanska, Marta K et al. (2013) Rapid fusion of synaptic vesicles with reconstituted target SNARE membranes. Biophys J 104:1950-8
Honigmann, Alf; van den Bogaart, Geert; Iraheta, Emilio et al. (2013) Phosphatidylinositol 4,5-bisphosphate clusters act as molecular beacons for vesicle recruitment. Nat Struct Mol Biol 20:679-86
van den Bogaart, Geert; Meyenberg, Karsten; Diederichsen, Ulf et al. (2012) Phosphatidylinositol 4,5-bisphosphate increases Ca2+ affinity of synaptotagmin-1 by 40-fold. J Biol Chem 287:16447-53
van den Bogaart, Geert; Thutupalli, Shashi; Risselada, Jelger H et al. (2011) Synaptotagmin-1 may be a distance regulator acting upstream of SNARE nucleation. Nat Struct Mol Biol 18:805-12

Showing the most recent 10 out of 40 publications