Synaptic vesicles are distinct organelles that require multiple integral protein components to be functional. Despite this complexity, following exocytosis, synaptic vesicles are retrieved, recycled and reused swiftly within several seconds with high fidelity. The exact mechanisms that underlie this process remain poorly understood. In this renewal application, we propose to investigate mechanisms underlying synaptic vesicle exocytosis-endocytosis process by visualizing the fusion and retrieval of single synaptic vesicles using fluorescence imaging methodologies we developed in the last five years. In our hands, this imaging approach has become rather routine and versatile, amenable to molecular manipulations as well as multimodal imaging at physiological temperatures with high temporal resolution. Monitoring exo-endocytosis of single synaptic vesicles enables us to dissect permissive and instructive signals that regulate synaptic vesicle retrieval. Using this approach, our recent experiments suggested a limited role for the classical endocytosis machinery, while implying a critical role for the exocytotic fusion machinery, in regulation of quantal single vesicle endocytosis. In this renewal application, we will fully expand these initial findings and interrogate the mechanisms underlying single synaptic vesicle retrieval at physiological temperatures with high temporal resolution. To achieve this goal, we propose three specific aims. In the first aim, we will study the role of dynamins in single synaptic vesicle retrieval.
The second aim will focus on the role of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) fusion machinery in single synaptic vesicle retrieval. Finally, the third aim will investigate the roles of endosomal SNAREs in spontaneous synaptic vesicle retrieval. Collectively, these complementary experiments will elucidate the molecular mechanisms ensuring the fidelity and the time course of synaptic vesicle retrieval in central synapses. Information attained from these studies will provide new insight to the synaptic substrates that may be affected by a number of in neuropsychiatric and neurological disorders including major depressive disorder, autism and schizophrenia.

Public Health Relevance

Synaptic vesicles within individual presynaptic nerve terminals are divided into distinct pools with respect to their relative propensities for fusion. This project aims to uncover the mechanisms underlying the recycling of distinct synaptic vesicle populations. Information attained from these studies will help identification of molecular synaptic substrates that are affected by a number of neuropsychiatric and neurological disorders including major depression, mental retardation, autism and schizophrenia.

National Institute of Health (NIH)
National Institute of Mental Health (NIMH)
Research Project (R01)
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Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
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Driscoll, Jamie
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Vanderbilt University Medical Center
Schools of Medicine
United States
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Chanaday, Natali L; Kavalali, Ege T (2018) Presynaptic origins of distinct modes of neurotransmitter release. Curr Opin Neurobiol 51:119-126
Kavalali, Ege T (2018) Spontaneous neurotransmission: A form of neural communication comes of age. J Neurosci Res 96:331-334
Liu, Pei; Khvotchev, Mikhail; Li, Ying C et al. (2018) Copine-6 Binds to SNAREs and Selectively Suppresses Spontaneous Neurotransmission. J Neurosci 38:5888-5899
Chanaday, Natali L; Kavalali, Ege T (2018) Optical detection of three modes of endocytosis at hippocampal synapses. Elife 7:
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Li, Ying C; Kavalali, Ege T (2017) Synaptic Vesicle-Recycling Machinery Components as Potential Therapeutic Targets. Pharmacol Rev 69:141-160
Crawford, Devon C; Ramirez, Denise M O; Trauterman, Brent et al. (2017) Selective molecular impairment of spontaneous neurotransmission modulates synaptic efficacy. Nat Commun 8:14436
Afuwape, Olusoji A T; Wasser, Catherine R; Schikorski, Thomas et al. (2017) Synaptic vesicle pool-specific modification of neurotransmitter release by intravesicular free radical generation. J Physiol 595:1223-1238
Darios, Frederic D; Jorgacevski, Jernej; Flašker, Ajda et al. (2017) Sphingomimetic multiple sclerosis drug FTY720 activates vesicular synaptobrevin and augments neuroendocrine secretion. Sci Rep 7:5958
Horvath, Patricia M; Kavalali, Ege T; Monteggia, Lisa M (2017) CRISPR/Cas9 system-mediated impairment of synaptobrevin/VAMP function in postmitotic hippocampal neurons. J Neurosci Methods 278:57-64

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