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A transmembrane protein required for acetylcholine receptor clustering in Caenorhabditis elegans


Clustering neurotransmitter receptors at the synapse is crucial for efficient neurotransmission. Here we identify a Caenorhabditis elegans locus, lev-10, required for postsynaptic aggregation of ionotropic acetylcholine receptors (AChRs). lev-10 mutants were identified on the basis of weak resistance to the anthelminthic drug levamisole, a nematode-specific cholinergic agonist that activates AChRs present at neuromuscular junctions (NMJs) resulting in muscle hypercontraction and death at high concentrations1,2,3. In lev-10 mutants, the density of levamisole-sensitive AChRs at NMJs is markedly reduced, yet the number of functional AChRs present at the muscle cell surface remains unchanged. LEV-10 is a transmembrane protein localized to cholinergic NMJs and required in body-wall muscles for AChR clustering. We also show that the LEV-10 extracellular region, containing five predicted CUB domains and one LDLa domain, is sufficient to rescue AChR aggregation in lev-10 mutants. This suggests a mechanism for AChR clustering that relies on extracellular protein–protein interactions. Such a mechanism is likely to be evolutionarily conserved because CUB/LDL transmembrane proteins similar to LEV-10, but lacking any assigned function, are expressed in the mammalian nervous system and might be used to cluster ionotropic receptors in vertebrates.

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Figure 1: Phenotypic characterization of lev-10 mutants.
Figure 2: Mutation of lev-10 results in the specific loss of levamisole-sensitive AChR clusters at neuromuscular junctions.
Figure 3: Levamisole-sensitive AChRs are functional but diffusely distributed in lev-10 body-wall muscle.
Figure 4: lev-10 encodes a CUB domain-rich transmembrane protein.
Figure 5: LEV-10 is a synaptic protein that requires levamisole-sensitive AChRs for proper localization but not for expression.

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We thank J. Lewis for the lev-10(x17) strain, M. Labouesse for the anti-VAH-5 antibodies, J. Rand for the anti-UNC-17 antibodies, M. Han for the pTG96 plasmid, Y. Kohara for the clone yk796a04, A. Fire for the GFP vectors, the Caenorhabditis Genetic Center for strains, R. Weimer for critical reading of the manuscript, and I. Nuez and H. Gendrot for technical help. C.G. was supported by a fellowship from the Ministère de la Recherche and by the Association pour la Recherche contre le Cancer. S.E. is an EMBO fellow. This work was funded by the Institut National de la Santé et de la Recherche Médicale and the Association Française contre les Myopathies. J.R. was supported by the NIH grant RO1NS41477-03.

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Correspondence to Jean-Louis Bessereau.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Table S1

lev-10 rescue experiments. This table presents the phenotypes of transgenic lev-10(kr26) mutants expressing wild-type or engineered LEV-10 proteins. (PDF 72 kb)

Supplementary Data

Mosaic analysis. This file contains detailed information on mosaic analysis of lev-10. (PDF 86 kb)

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Gally, C., Eimer, S., Richmond, J. et al. A transmembrane protein required for acetylcholine receptor clustering in Caenorhabditis elegans. Nature 431, 578–582 (2004).

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