Neurotransmitter release is acutely triggered by Ca2+ and is regulated during presynaptic plasticity processes that underlie some forms of information processing in the brain. Characterization of the mechanisms of release and its regulation is thus critical to understand brain function and will facilitate the development of therapies for neurological disorders with a presynaptic origin. The machinery that controls release contains a core formed by Munc18-1 and SNARE proteins, and specialized proteins that regulate release. Several of these proteins contain multiple C2 domains, which are widespread Ca and phospholipids binding modules but can 2+ also exhibit Ca2+-independent activities. These proteins include: i) Synaptotagmin-1, the Ca2+ sensor that triggers fast release;ii) Munc13-1 and related isoforms, which are essential for release and mediates diverse forms of presynaptic plasticity;and iii) ?RIMs, which are Rab3 effectors that also have key roles in release and presynaptic plasticity. The C2 domains of all these proteins are highly conserved and are hypothesized in this proposal to regulate neurotransmitter release at multiple levels through their Ca2+-dependent and Ca2+- independent interactions. The ultimate goals of the research proposed in this application are to test this hypothesis and, more generally, to elucidate the molecular mechanisms underlying key forms of regulation of neurotransmitter release. This research forms part of an integrated approach where the structural and reconstitution data performed in the PI's lab are correlated with genetic and physiological experiments performed in the laboratories of close collaborators. We propose three Specific Aims that focus on the following areas: 1. Mechanism of action of Synaptotagmin-1;2. Structural basis for Munc13-dependent regulation of neurotransmitter release;and 3. Reconstitution of Munc13-dependent regulation of neurotransmitter release. The proposed experiments will build on exciting results obtained during the previous funding period, including a preliminary structure of a Synaptotagmin-1/SNARE complex, key advances in crystallization of large Munc13-1 fragments, the reconstitution of synaptic vesicle fusion with the eight most central components of the release machinery, and preliminary data that reinforce the notion that Munc13s act as master regulators of release through a fascinating network of intramolecular and intermolecular interactions. We expect that this research will provide critical insights into the regulation of release in varied presynaptic plasticity processes, helping to establish fundamental principles on neuronal communication that are vital for brain function.

Public Health Relevance

The research proposed in this application will yield key insights into fundamental molecular mechanisms that underlie synaptic transmission and some forms of information processing in the brain. This knowledge is critical to understand how the brain and the nervous system in general function. Moreover, since many neurological disorders are treated with drugs that alter synaptic transmission, this research is expected to provide crucial clues for the development of novel strategies to understand and treat these disorders.

National Institute of Health (NIH)
Research Project (R01)
Project #
Application #
Study Section
Synapses, Cytoskeleton and Trafficking Study Section (SYN)
Program Officer
Talley, Edmund M
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Texas Sw Medical Center Dallas
Schools of Medicine
United States
Zip Code
Liu, Xiaoxia; Seven, Alpay Burak; Camacho, Marcial et al. (2016) Functional synergy between the Munc13 C-terminal C1 and C2 domains. Elife 5:
Brewer, Kyle D; Bacaj, Taulant; Cavalli, Andrea et al. (2015) Dynamic binding mode of a Synaptotagmin-1-SNARE complex in solution. Nat Struct Mol Biol 22:555-64
Rizo, Josep; Xu, Junjie (2015) The Synaptic Vesicle Release Machinery. Annu Rev Biophys 44:339-67
Mukherjee, Sohini; Zheng, Hui; Derebe, Mehabaw G et al. (2014) Antibacterial membrane attack by a pore-forming intestinal C-type lectin. Nature 505:103-7
Xu, Junjie; Bacaj, Taulant; Zhou, Amy et al. (2014) Structure and Ca²⁺-binding properties of the tandem C₂ domains of E-Syt2. Structure 22:269-80
Su, Lijing; Quade, Bradley; Wang, Huayi et al. (2014) A plug release mechanism for membrane permeation by MLKL. Structure 22:1489-500
Xu, Junjie; Brewer, Kyle D; Perez-Castillejos, Raquel et al. (2013) Subtle Interplay between synaptotagmin and complexin binding to the SNARE complex. J Mol Biol 425:3461-75
Ma, Cong; Su, Lijing; Seven, Alpay B et al. (2013) Reconstitution of the vital functions of Munc18 and Munc13 in neurotransmitter release. Science 339:421-5
Zhou, Amy; Brewer, Kyle D; Rizo, Josep (2013) Analysis of SNARE complex/synaptotagmin-1 interactions by one-dimensional NMR spectroscopy. Biochemistry 52:3446-56
Seven, Alpay B; Brewer, Kyle D; Shi, Liang et al. (2013) Prevalent mechanism of membrane bridging by synaptotagmin-1. Proc Natl Acad Sci U S A 110:E3243-52

Showing the most recent 10 out of 46 publications