Abstract
We analyzed the synaptic physiology of unc-13 mutants in the nematode C. elegans. Mutants of unc-13 had normal nervous system architecture, and the densities of synapses and postsynaptic receptors were normal at the neuromuscular junction. However, the number of synaptic vesicles at neuromuscular junctions was two- to threefold greater in unc-13 mutants than in wild-type animals. Most importantly, evoked release at both GABAergic and cholinergic synapses was almost absent in unc-13 null alleles, as determined by whole-cell, voltage-clamp techniques. Although mutant synapses had morphologically docked vesicles, these vesicles were not competent for release as assayed by spontaneous release in calcium-free solution or by the application of hyperosmotic saline. These experiments support models in which UNC-13 mediates either fusion of vesicles during exocytosis or priming of vesicles for fusion.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 12 print issues and online access
$209.00 per year
only $17.42 per issue
Rent or buy this article
Prices vary by article type
from$1.95
to$39.95
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Brenner, S. The genetics of Caenorhabditis elegans. Genetics 77, 71–94 (1974).
Rose, A. M. & Baillie, D. L. Genetic organization of the region around UNC-15 (I), a gene affecting paramyosin in Caenorhabditis elegans . Genetics 96, 639– 648 (1980).
Hosono, R., Sassa, T. & Kuno, S. Spontaneous mutations of trichlorfon resistance in the nematode, Caenorhabditis elegans. Zoological Sci. 6, 697– 708 (1989).
Nguyen, M., Alfonso, A., Johnson, C. D. & Rand, J. B. Caenorhabditis elegans mutants resistant to inhibitors of acetylcholinesterase. Genetics 140, 527–535 (1995).
Maruyama, I. N. & Brenner, S. A phorbol ester/diacylglycerol-binding protein encoded by the unc-13 gene of Caenorhabditis elegans. Proc. Natl. Acad. Sci. USA 88, 5729– 5733 (1991).
Rizo, J. & Sudhof, T. C. C2-domains, structure and function of a universal Ca2+-binding domain. J. Biol. Chem. 273, 15879–15882 ( 1998).
Newton, A. C. Regulation of protein kinase C. Curr. Opin. Cell Biol. 9, 161–167 (1997).
Brose, N., Hofmann, K., Hata, Y. & Sudhof, T. C. Mammalian homologues of Caenorhabditis elegans unc-13 gene define novel family of C2-domain proteins. J. Biol. Chem. 270, 25273– 25280 (1995).
Augustin, I., Betz, A., Herrmann, C., Jo, T. & Brose, N. Differential expression of two novel Munc13 proteins in rat brain. Biochem. J. 337, 363–371 (1999).
Xu, X. Z. et al. Retinal targets for calmodulin include proteins implicated in synaptic transmission. J. Biol. Chem. 273, 31297–31307 (1998).
Aravamudan, B., Fergestad, T., Davis, W. S. & Broadie, K. Drosophila UNC-13 is essential for synaptic transmission. Nat. Neurosci. 2, 965–971 ( 1999).
Betz, A. et al. Munc13-1 is a presynaptic phorbol ester receptor that enhances neurotransmitter release. Neuron 21, 123 –136 (1998).
Ahmed, S. et al. The Caenorhabditis elegans unc-13 gene product is a phospholipid- dependent high-affinity phorbol ester receptor. Biochem. J. 287, 995–999 (1992).
Kazanietz, M. G., Lewin, N. E., Bruns, J. D. & Blumberg, P. M. Characterization of the cysteine-rich region of the Caenorhabditis elegans protein Unc-13 as a high affinity phorbol ester receptor. Analysis of ligand-binding interactions, lipid cofactor requirements, and inhibitor sensitivity. J. Biol. Chem. 270, 10777– 10783 (1995).
Nurrish, S., Segalat, L. & Kaplan, J. M. Serotonin inhibition of synaptic transmission: Gα o decreases the abundance of UNC-13 at release sites. Neuron 24, 231–242, ( 1999).
McIntire, S. L., Reimer, R. J., Schuske, K., Edwards, R. H. & Jorgensen, E. M. Identification and characterization of the vesicular GABA transporter. Nature 389, 870–876 (1997).
Jorgensen, E. M. et al. Defective recycling of synaptic vesicles in synaptotagmin mutants of Caenorhabditis elegans. Nature 378 , 196–199 (1995).
Jin, Y., Jorgensen, E., Hartwieg, E. & Horvitz, H. R. The Caenorhabditis elegans gene unc-25 encodes glutamic acid decarboxylase and is required for synaptic transmission but not synaptic development. J. Neurosci. 19, 539–548 (1999).
Richmond, J. E. & Jorgensen, E. M. One GABA and two acetylcholine receptors function at the C. elegans neuromuscular junction. Nat. Neurosci. 2, 791– 797 (1999).
Li, J. & Schwarz, T. L. Genetic evidence for an equilibrium between docked and undocked vesicles. Phil. Trans. R. Soc. Lond. B Biol. Sci. 354, 299–306 (1999).
Niles, W. D. & Smith, D. O. Effects of hypertonic solutions on quantal transmitter release at the crayfish neuromuscular junction. J. Physiol. (Lond.) 329, 185–202 (1982).
Stevens, C. F. & Tsujimoto, T. Estimates for the pool size of releasable quanta at a single central synapse and for the time required to refill the pool. Proc. Natl. Acad. Sci. USA 92, 846–849 (1995).
Rosenmund, C. & Stevens, C. F. Definition of the readily releasable pool of vesicles at hippocampal synapses. Neuron 16 , 1197–1207 (1996).
Augustin, I., Rosenmund, C., Sudhof, T. C. & Brose, N. Munc13-1 is essential for fusion competence of glutamatergic synaptic vesicles. Nature 400, 457–461 (1999).
Hata, Y., Slaughter, C. A. & Sudhof, T. C. Synaptic vesicle fusion complex contains unc-18 homologue bound to syntaxin. Nature 366, 347–351 (1993).
Ogawa, H., Harada, S., Sassa, T., Yamamoto, H. & Hosono, R. Functional properties of the unc-64 gene encoding a Caenorhabditis elegans syntaxin. J. Biol. Chem. 273, 2192–2198 (1998).
Pevsner, J. et al. Specificity and regulation of a synaptic vesicle docking complex. Neuron 13, 353–361 (1994).
Schulze, K. L. et al. rop, a Drosophila homolog of yeast Sec1 and vertebrate n-Sec1/Munc-18 proteins, is a negative regulator of neurotransmitter release in vivo. Neuron 13, 1099– 1108 (1994).
Wu, M. N. et al. Syntaxin 1A interacts with multiple exocytic proteins to regulate neurotransmitter release in vivo. Neuron 23, 593–605 (1999).
Betz, A., Okamoto, M., Benseler, F. & Brose, N. Direct interaction of the rat unc-13 homologue Munc13-1 with the N terminus of syntaxin. J. Biol. Chem. 272, 2520–2526 (1997).
Sassa, T. et al. Regulation of the UNC-18-Caenorhabditis elegans syntaxin complex by UNC- 13. J. Neurosci. 19, 4772 –4777 (1999).
Sollner, T., Bennett, M. K., Whiteheart, S. W., Scheller, R. H. & Rothman, J. E. A protein assembly-disassembly pathway in vitro that may correspond to sequential steps of synaptic vesicle docking, activation, and fusion. Cell 75, 409–418 (1993).
Bamber, B. A., Beg, A. A., Twyman, R. E. & Jorgensen, E. M. The Caenorhabditis elegans unc-49 locus encodes multiple subunits of a heteromultimeric GABA receptor. J. Neurosci. 19, 5348–5359 (1999).
Acknowledgements
We thank Becky Kohn and Jim Rand for sharing unpublished data. We thank Bharathi Aravamudan, Tim Fergestad and Kendal Broadie for interactions and discussions. We thank Wayne Davis, Doj Yoshikami and Karen Yook for comments on the manuscript. Rob Weimer provided confocal images, and Ann Rose provided the s69 allele. This work was supported by NIH grants RO3 MHS9820-01 (J.E.R.) and RO1 NS34307 (E.M.J.) and by the Damon Runyon Fund. Strains were obtained from the Caenorhabditis Genetics Center.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Richmond, J., Davis, W. & Jorgensen, E. UNC-13 is required for synaptic vesicle fusion in C. elegans. Nat Neurosci 2, 959–964 (1999). https://doi.org/10.1038/14755
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/14755
This article is cited by
-
Molecular and circuit mechanisms underlying avoidance of rapid cooling stimuli in C. elegans
Nature Communications (2024)
-
Identification of residues critical for the extension of Munc18-1 domain 3a
BMC Biology (2023)
-
Semantic representation of neural circuit knowledge in Caenorhabditis elegans
Brain Informatics (2023)
-
Inheritance of associative memories and acquired cellular changes in C. elegans
Nature Communications (2023)
-
All-optical closed-loop voltage clamp for precise control of muscles and neurons in live animals
Nature Communications (2023)