Heterotrimeric G proteins are widely thought to play a critical role in regulating synaptic strength, yet relatively little is known about how these signaling pathways regulate synaptic vesicle exocytosis and recycling. We have undertaken a comprehensive analysis of how two G proteins (Ga0 and Gaq) regulate neurotransmitter release in the nematode C. elegans. We have shown that goa-1 Ga0 and egl-30 Gaq antagonistically regulate acetylcholine (ACh) release at C. elegans neuromuscular junctions (NMJs). We identified agonists that activate each of these pathways. Serotonin, acting via goa-1 Ga0, inhibits ACh release whereas muscarinic agonists, acting via egl-30 Gaq, stimulate ACh release. We showed that these G proteins are likely to directly regulate some aspect of synaptic vesicle recycling, since they control the abundance of a pre-synaptic syntaxin binding protein (UNC-l3) at ACh release sites. And we identified two proteins UNC-13 and protein kinase C (kin13 PKC) that are required for phorbol ester-mediated stimulation of ACh release. We propose three new aims to determine the mechanisms by which these G proteins regulate neurotransmitter release. First, we will determine what aspect of synaptic vesicle dynamics is regulated by goa-1 Ga0, egl-30 Gaq, UNC-13, and kin-13 PKC. Second, we will test the functional importance of the UNC-13:Syntaxin complex. Third, we will determine where and when kin-13 PKC acts to regulate ACh release. And we will test the functional importance of potential kin-13 PKC phosphorylation sites in SNAP-25 and UNC-18. In summary, G protein regulation of synaptic strength has been implicated in addiction, mood disorders, learning, and memory. Given the strong conservation of these pathways across phylogeny, it is likely that our experiments will provide new insights into the mechanisms underlying these fundamental aspects of signal transduction in the brain.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM054728-05
Application #
6401018
Study Section
Special Emphasis Panel (ZRG1-MDCN-1 (01))
Program Officer
Tompkins, Laurie
Project Start
1997-08-01
Project End
2002-07-31
Budget Start
2001-08-01
Budget End
2002-07-31
Support Year
5
Fiscal Year
2001
Total Cost
$289,551
Indirect Cost
Name
University of California Berkeley
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
094878337
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Tong, Xia-Jing; López-Soto, Eduardo Javier; Li, Lei et al. (2017) Retrograde Synaptic Inhibition Is Mediated by ?-Neurexin Binding to the ?2? Subunits of N-Type Calcium Channels. Neuron 95:326-340.e5
Hu, Zhitao; Vashlishan-Murray, Amy B; Kaplan, Joshua M (2015) NLP-12 engages different UNC-13 proteins to potentiate tonic and evoked release. J Neurosci 35:1038-42
Hu, Zhitao; Tong, Xia-Jing; Kaplan, Joshua M (2013) UNC-13L, UNC-13S, and Tomosyn form a protein code for fast and slow neurotransmitter release in Caenorhabditis elegans. Elife 2:e00967
Bai, Jihong; Hu, Zhitao; Dittman, Jeremy S et al. (2010) Endophilin functions as a membrane-bending molecule and is delivered to endocytic zones by exocytosis. Cell 143:430-41
Dittman, Jeremy S; Kaplan, Joshua M (2008) Behavioral impact of neurotransmitter-activated G-protein-coupled receptors: muscarinic and GABAB receptors regulate Caenorhabditis elegans locomotion. J Neurosci 28:7104-12
McEwen, Jason M; Kaplan, Joshua M (2008) UNC-18 promotes both the anterograde trafficking and synaptic function of syntaxin. Mol Biol Cell 19:3836-46
McEwen, Jason M; Madison, Jon M; Dybbs, Michael et al. (2006) Antagonistic regulation of synaptic vesicle priming by Tomosyn and UNC-13. Neuron 51:303-15
Dittman, Jeremy S; Kaplan, Joshua M (2006) Factors regulating the abundance and localization of synaptobrevin in the plasma membrane. Proc Natl Acad Sci U S A 103:11399-404
Madison, Jon M; Nurrish, Stephen; Kaplan, Joshua M (2005) UNC-13 interaction with syntaxin is required for synaptic transmission. Curr Biol 15:2236-42
Lackner, M R; Nurrish, S J; Kaplan, J M (1999) Facilitation of synaptic transmission by EGL-30 Gqalpha and EGL-8 PLCbeta: DAG binding to UNC-13 is required to stimulate acetylcholine release. Neuron 24:335-46