Cholinergic signaling mediated by ionotropic (nicotinic) acetylcholine receptors (iAChRs) plays key roles in the mammalian nervous system. iAChRs modulate neurotransmitter release at diverse synapse types across virtually every area of the brain and spinal cord, and in addition, regulate the activity of inhibitory interneurons in critical brain areas. Alterations in iAChR signaling are associated with a number of debilitating neurological disorders including Alzheimer's disease, schizophrenia and certain forms of epilepsy. Moreover, nicotine binding to nicotinic receptors in the nervous system initiates the cellular and molecular cascade that results in nicotine addiction. Despite the clear importance of iAChR signaling in normal brain physiology and health, there are major gaps in our understanding of the cellular mechanisms that regulate cholinergic signaling in the brain. We have made the exciting observation that iAChRs also regulate inhibitory neuron activity in the genetically tractable model organism Caenorhabditis elegans. We have developed a powerful system to study the trafficking, localization and function of these receptors in the dendrites of inhibitory neurons located in a simple 3-layer circuit that controls C. elegans movement. This proposal aims to use the genetic tools we have generated for manipulation of activity levels in this circuit, along with the powerful array of molecular genetic approaches available in C. elegans, to explore fundamental questions in iAChR biology. In this project we will (Aim 1) characterize iAChR subcellular localization, subunit composition, in vivo dynamics, and molecular pathways responsible for delivery of iAChRs to specific subcellular domains on inhibitory neurons;
(Aim 2) investigate how altered cholinergic innervation of GABA neurons leads to defects in the development or maintenance of GABA synapses;
(Aim 3) determine the role of a novel neurexin signaling pathway in shaping GABA synapse development. We expect that our studies of this experimentally tractable circuit in the worm will provide exciting new insights into mechanisms for biological regulation of iAChRs in the brain, and their important roles in regulating inhibitory signaling. Additionally, the identification and functional characterization of conserved genetic pathways that regulate synapse formation and function in our experiments will ultimately yield novel drug targets for therapeutic strategies designed to treat neurological disorders involving cholinergic signaling.

Public Health Relevance

The neurotransmitter acetylcholine plays conserved roles in mediating communication between neurons from nematodes to humans. Alterations in acetylcholine-mediated signaling are a hallmark of a wide variety of degenerative neurological disorders and nicotine addiction, yet we know very little about the molecular pathways that regulate this process in the mature nervous system or about how deficits alter connectivity in the developing nervous sytem. Our work will provide fundamental knowledge about mechanisms for regulation of acetylcholine-mediated signaling and is expected to provide critical insights into how defects in acetylcholine- mediated signaling cause disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS064263-08
Application #
9394038
Study Section
Synapses, Cytoskeleton and Trafficking Study Section (SYN)
Program Officer
Stewart, Randall R
Project Start
2009-09-15
Project End
2019-12-31
Budget Start
2018-01-01
Budget End
2018-12-31
Support Year
8
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Massachusetts Medical School Worcester
Department
Neurosciences
Type
Schools of Medicine
DUNS #
603847393
City
Worcester
State
MA
Country
United States
Zip Code
01655
Barbagallo, Belinda; Philbrook, Alison; Touroutine, Denis et al. (2017) Excitatory neurons sculpt GABAergic neuronal connectivity in the C. elegans motor circuit. Development 144:1807-1819
Francis, Michael M; Freeman, Marc R (2016) Dendrites actively restrain axon outgrowth and regeneration. Proc Natl Acad Sci U S A 113:5465-6
He, Siwei; Philbrook, Alison; McWhirter, Rebecca et al. (2015) Transcriptional Control of Synaptic Remodeling through Regulated Expression of an Immunoglobulin Superfamily Protein. Curr Biol 25:2541-8
Kowalski, Jennifer R; Dube, Hitesh; Touroutine, Denis et al. (2014) The Anaphase-Promoting Complex (APC) ubiquitin ligase regulates GABA transmission at the C. elegans neuromuscular junction. Mol Cell Neurosci 58:62-75
Bhattacharya, Raja; Touroutine, Denis; Barbagallo, Belinda et al. (2014) A conserved dopamine-cholecystokinin signaling pathway shapes context-dependent Caenorhabditis elegans behavior. PLoS Genet 10:e1004584
Donnelly, Jamie L; Clark, Christopher M; Leifer, Andrew M et al. (2013) Monoaminergic orchestration of motor programs in a complex C. elegans behavior. PLoS Biol 11:e1001529
Philbrook, Alison; Barbagallo, Belinda; Francis, Michael M (2013) A tale of two receptors: Dual roles for ionotropic acetylcholine receptors in regulating motor neuron excitation and inhibition. Worm 2:e25765
Petrash, Hilary A; Philbrook, Alison; Haburcak, Marian et al. (2013) ACR-12 ionotropic acetylcholine receptor complexes regulate inhibitory motor neuron activity in Caenorhabditis elegans. J Neurosci 33:5524-32
Jensen, Michael; Hoerndli, Frederic J; Brockie, Penelope J et al. (2012) Wnt signaling regulates acetylcholine receptor translocation and synaptic plasticity in the adult nervous system. Cell 149:173-87
Barbagallo, Belinda; Prescott, Hilary A; Boyle, Patrick et al. (2010) A dominant mutation in a neuronal acetylcholine receptor subunit leads to motor neuron degeneration in Caenorhabditis elegans. J Neurosci 30:13932-42