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A role for the synaptic vesicle glycoprotein 2C (SV2C) in dopamine homeostasis and Parkinson's disease

Dunn, Amy Rose (2017)
Dissertation (190 pages)
Committee Chair / Thesis Adviser: Miller, Gary W
Committee Members: Chin, Lih-Shen ; Hess, Ellen ; Smith, Yoland ; Faundez, Victor
Research Fields: Neurosciences
Keywords: Parkinson's disease; Dopamine; SV2C
Program: Laney Graduate School, Biological and Biomedical Sciences (Neuroscience)
Permanent url: http://pid.emory.edu/ark:/25593/s0rpt

Abstract

The synaptic vesicle plays two important roles in dopamine neurons by: (1) packaging transmitter for neurotransmission, and (2) sequestering cytosolic toxicants from the rest of the cell. Impaired storage of dopamine occurs in Parkinson's disease (PD), and genetic mutations in the vesicular monoamine transporter 2 (VMAT2) lead to parkinsonism. Mutations in other vesicle-associated proteins, such as alpha-synuclein and LRRK2, are common causes of both familial and sporadic PD. Characterizing additional modulators of dopamine vesicle function may be important in further studying and identifying potential therapeutic targets in PD. The synaptic vesicle glycoprotein 2C (SV2C), a vesicular protein enriched in the basal ganglia, was recently identified as a genetic modifier of PD risk in smokers, suggesting an important role for SV2C in dopaminergic neurons. Polymorphisms in SV2C also alter patient sensitivity to L-DOPA, the primary pharmacotherapy for PD. SV2C may represent a novel mediator of basal ganglia neurotransmission; though its molecular function and potential role in PD is unknown. In the experiments described herein, I designed and optimized a specific SV2C antibody and detailed SV2C expression in rodents, nonhuman primates, and humans. In order to better understand the role of SV2C in dopamine homeostasis, neuronal vulnerability to degeneration, and PD pathogenesis, our laboratory developed and characterized mice lacking SV2C (SV2C-KO). Genetic ablation of SV2C resulted in a significant reduction in stimulated dopamine release as measured by fast-scan cyclic voltammetry, reduced striatal dopamine content, mild motor deficits, an altered neurochemical response to nicotine, and disrupted expression of alpha-synuclein. Further, SV2C-KO resulted in increased susceptibility to dopaminergic degeneration after intoxication with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a specific dopaminergic toxicant. I also present immunohistochemical data detailing SV2C's expression in human PD and in animal models of PD. SV2C expression was specifically disrupted in PD but preserved in other neurodegenerative diseases including Alzheimer's disease, progressive supranuclear palsy, and multiple system atrophy. A similar disruption in SV2C expression was observed in the striata of mice overexpressing mutated human alpha-synuclein. The results from our experiments identify SV2C as an important mediator of dopamine function and a potential contributor to dopamine cell death and PD pathogenesis, and suggest an important interaction between SV2C and alpha-synuclein.

Table of Contents

Table of Contents

Abstract............................................................................................................................................................

2

Acknowledgements.........................................................................................................................................

4

List of Figures..................................................................................................................................................

8

I. Chapter 1. Introduction: Vesicular function, Parkinson's disease, and the potential of SV2C as a novel vesicular target for Parkinson's disease pharmacotherapy...................................................

9

a. Background.................................................................................................................................................

10

b. Rationale & Hypothesis..............................................................................................................................

33

II. Chapter 2. Immunological analysis of the expression of SV2C in various species.......................

34

Abstract............................................................................................................................................................

35

Introduction.....................................................................................................................................................

36

Materials & Methods.......................................................................................................................................

38

Results.............................................................................................................................................................

43

Discussion........................................................................................................................................................

56

III. Chapter 3. SV2C modulates dopamine release and is disrupted in Parkinson's disease...............

60

Abstract............................................................................................................................................................

61

Introduction & Significance Statement.........................................................................................................

62

Materials & Methods........................................................................................................................................

64

Results..............................................................................................................................................................

72

Discussion........................................................................................................................................................

90

IV. Chapter 4. Genetic ablation of SV2C leads to enhanced vulnerability to neurodegeneration.........

98

Abstract............................................................................................................................................................

99

Introduction.....................................................................................................................................................

100

Materials & Methods........................................................................................................................................

102

Results..............................................................................................................................................................

105

Discussion........................................................................................................................................................

112

V. Chapter 5. The effect of SV2C-KO in non-dopaminergic transmitter systems.....................................

117

Abstract............................................................................................................................................................

118

Introduction.....................................................................................................................................................

120

Materials & Methods........................................................................................................................................

122

Results..............................................................................................................................................................

126

Discussion........................................................................................................................................................

137

VI. Discussion, Future Directions, and Concluding Remarks......................................................................

140

VII. Appendix A: Nicotine neuroprotection in SV2C-KO animals....................................................

144

Summary..........................................................................................................................................................

145

Figures..............................................................................................................................................................

149

VIII. References..............................................................................................................................................

154

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