Evidence for in Situ and in VitroAssociation between β-Dystroglycan and the Subsynaptic 43K Rapsyn Protein
CONSEQUENCE FOR ACETYLCHOLINE RECEPTOR CLUSTERING AT THE SYNAPSE*
- From ‡Biologie Cellulaire des Membranes, Département de Biologie Supramoléculaire et Cellulaire, Institut Jacques Monod, UMR 9922, CNRS et Université Paris VII, 2 Place Jussieu, 75251 Paris Cédex 05, France and§Biologia Cellulare, Istituto Superiore di Sanità, V. le Regina Elena 299, Roma 00161, Italy
Abstract
The accumulation of dystrophin and associated proteins at the postsynaptic membrane of the neuromuscular junction and their co-distribution with nicotinic acetylcholine receptor (AChR) clusters in vitro suggested a role for the dystrophin complex in synaptogenesis. Co-transfection experiments in which α- and β-dystroglycan form a complex with AChR and rapsyn, a peripheral protein required for AChR clustering (Apel, D. A., Roberds, S. L., Campbell, K. P., and Merlie, J. P. (1995)Neuron 15, 115–126), suggested that rapsyn functions as a link between AChR and the dystrophin complex. We have investigated the interaction between rapsyn and β-dystroglycan in TorpedoAChR-rich membranes using in situ and in vitroapproaches. Cross-linking experiments were carried out to study the topography of postsynaptic membrane polypeptides. A cross-linked product of 90 kDa was labeled by antibodies to rapsyn and β-dystroglycan; this demonstrates that these polypeptides are in close proximity to one another. Affinity chromatography experiments and ligand blot assays using rapsyn solubilized from TorpedoAChR-rich membranes and constructs containing β-dystroglycan C-terminal fragments show that a rapsyn-binding site is present in the juxtamembranous region of the cytoplasmic tail of β-dystroglycan. These data point out that rapsyn and dystroglycan interact in the postsynaptic membrane and thus reinforce the notion that dystroglycan could be involved in synaptogenesis.
Footnotes
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↵* This work was supported by the CNRS, the UniversitéDenis Diderot, the Association Française Contre les Myopathies (to J. C.), and by the Italian Telethon Grant 187 (to T. C. P.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed: Biologie Cellulaire des Membranes, Institut Jacques Monod, CNRS, Université Paris VII, 2, Place Jussieu, 75251 Paris Cédex 05, France. Tel.: 33-1-44 27 69 40; Fax: 33-1-44 27 59 94; E-mail:cartaud{at}ijm.jussieu.fr.
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↵1 The abbreviations used are: AChR, nicotinic acetylcholine receptor; DGC, dystrophin-glycoprotein complex; ECL, enhanced chemiluminescence detection; GST, glutathioneS-transferase; LiS, lithium diiodosalicylate; NMJ, neuromuscular junction; PAGE, polyacrylamide gel electrophoresis; SMPB, succinimidyl 4-(p-maleimidophenyl) butyrate; mAb, monoclonal antibody.
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- Received January 13, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
