title: Extrasynaptic muscarinic acetylcholine receptors on neuronal cell bodies regulate presynaptic function in Caenorhabditis elegans.
abstract: Acetylcholine (ACh) is a potent neuromodulator in the brain, and its effects on cognition and memory formation are largely performed through muscarinic acetylcholine receptors (mAChRs). mAChRs are often preferentially distributed on specialized membrane regions in neurons, but the significance of mAChR localization in modulating neuronal function is not known. Here we show that the Caenorhabditis elegans homolog of the M1/M3/M5 family of mAChRs, gar-3, is expressed in cholinergic motor neurons, and GAR-3-GFP fusion proteins localize to cell bodies where they are enriched at extrasynaptic regions that are in contact with the basal lamina. The GAR-3 N-terminal extracellular domain is necessary and sufficient for this asymmetric distribution, and mutation of a predicted N-linked glycosylation site within the N-terminus disrupts GAR-3-GFP localization. In transgenic animals expressing GAR-3 variants that are no longer asymmetrically localized, synaptic transmission at neuromuscular junctions is impaired and there is a reduction in the abundance of the presynaptic protein sphingosine kinase at release sites. Finally, GAR-3 can be activated by endogenously produced ACh released from neurons that do not directly contact cholinergic motor neurons. Together, our results suggest that humoral activation of asymmetrically localized mAChRs by ACh is an evolutionarily conserved mechanism by which ACh modulates neuronal function.
authors.affiliation: Zilkha Neurogenetic Institute, Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Chan
authors.forename: Trisha A
authors.initials: TA
authors.lastname: Staab
authors.forename: Han
authors.initials: H
authors.lastname: Wang
authors.forename: Chiara
authors.initials: C
authors.lastname: Mazzasette
authors.forename: Zara
authors.initials: Z
authors.lastname: Butte
authors.forename: Derek
authors.initials: D
authors.lastname: Sieburth
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D009046:Motor Neurons / Q000378:metabolism* / Q000502:physiology; D009154:Mutation; D009469:Neuromuscular Junction / Q000378:metabolism / Q000502:physiology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism / Q000502:physiology*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011976:Receptors, Muscarinic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009435:Synaptic Transmission; D000099157:Sphingosine Kinase
chemical_list: D000109:Acetylcholine; D029742:Caenorhabditis elegans Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D011976:Receptors, Muscarinic; D000099157:Sphingosine Kinase; C477876:GAR-3 protein, C elegans