A secreted complement-control-related protein ensures acetylcholine receptor clustering


Efficient neurotransmission at chemical synapses relies on spatial congruence between the presynaptic active zone, where synaptic vesicles fuse, and the postsynaptic differentiation, where neurotransmitter receptors concentrate. Diverse molecular systems have evolved to localize receptors at synapses, but in most cases, they rely on scaffolding proteins localized below the plasma membrane1,2,3. A few systems have been suggested to control the synaptic localization of neurotransmitter receptors through extracellular interactions, such as the pentraxins that bind AMPA receptors and trigger their aggregation4. However, it is not yet clear whether these systems have a central role in the organization of postsynaptic domains in vivo or rather provide modulatory functions5. Here we describe an extracellular scaffold that is necessary to cluster acetylcholine receptors at neuromuscular junctions in the nematode Caenorhabditis elegans. It involves the ectodomain of the previously identified transmembrane protein LEV-10 (ref. 6) and a novel extracellular protein, LEV-9. LEV-9 is secreted by the muscle cells and localizes at cholinergic neuromuscular junctions. Acetylcholine receptors, LEV-9 and LEV-10 are interdependent for proper synaptic localization and physically interact based on biochemical evidence. Notably, the function of LEV-9 relies on eight complement control protein (CCP) domains. These domains, also called ‘sushi domains’, are usually found in proteins regulating complement activity in the vertebrate immune system7. Because the complement system does not exist in protostomes, our results suggest that some of the numerous uncharacterized CCP proteins expressed in the mammalian brain might be directly involved in the organization of the synapse, independently from immune functions.

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Figure 1: lev-9 encodes a muscle-expressed protein containing a WAP domain and eight CCP domains.
Figure 2: LEV-9 localizes at cholinergic neuromuscular junctions.
Figure 3: LEV-9 is specifically required to localize L-AChRs at the neuromuscular junction.
Figure 4: LEV-9 and LEV-10 are interdependent for proper localization of L-AChRs.
Figure 5: LEV-9 physically interacts with LEV-10 and LEV-10 physically interacts with L-AChR.

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Data deposits

The EMBL database accession number for lev-9 cDNA is FN433774.


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We thank E. M. Jorgensen and D. Williams for the lev-9(ox171::Mos1) strain, M. Labouesse for the anti-VHA-5 antibodies, J. Rand for the anti-UNC-17 antibodies, A. Fire for the GFP vectors, the Caenorhabditis Genetic Center and W. R. Schafer for strains, I. Katic, M. Zhen and S. Marty for critical reading of the manuscript, and H. Gendrot and B. Mathieu for technical help. M.G. was supported by a fellowship from the Ministère de la Recherche and by the Association Française contre les Myopathies. G.R. is a Ministère de la Recherche fellow. This work was funded by an INSERM Avenir grant, the Agence Nationale de la Recherche (ANR-07-NEURO-032-01) and the Association Française contre les Myopathies. J.E.R. was supported by NIH RO1 MH073156.

Author Contributions M.G. performed most of the experiments. J.E.R. performed all the electrophysiology experiments (Fig. 3j, k and Supplementary Fig. 9d). G.R. generated and characterized the unc-63::YFP knock-in strain. M.G. and J.-L.B. wrote the manuscript. J.-L.B. supervised the project.

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Correspondence to Jean-Louis Bessereau.

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Gendrel, M., Rapti, G., Richmond, J. et al. A secreted complement-control-related protein ensures acetylcholine receptor clustering. Nature 461, 992–996 (2009). https://doi.org/10.1038/nature08430

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