title: Neuromuscular synapse integrity requires linkage of acetylcholine receptors to postsynaptic intermediate filament networks via rapsyn-plectin 1f complexes.
abstract: Mutations in the cytolinker protein plectin lead to grossly distorted morphology of neuromuscular junctions (NMJs) in patients suffering from epidermolysis bullosa simplex (EBS)-muscular dystrophy (MS) with myasthenic syndrome (MyS). Here we investigated whether plectin contributes to the structural integrity of NMJs by linking them to the postsynaptic intermediate filament (IF) network. Live imaging of acetylcholine receptors (AChRs) in cultured myotubes differentiated ex vivo from immortalized plectin-deficient myoblasts revealed them to be highly mobile and unable to coalesce into stable clusters, in contrast to wild-type cells. We found plectin isoform 1f (P1f) to bridge AChRs and IFs via direct interaction with the AChR-scaffolding protein rapsyn in an isoform-specific manner; forced expression of P1f in plectin-deficient cells rescued both compromised AChR clustering and IF network anchoring. In conditional plectin knockout mice with gene disruption in muscle precursor/satellite cells (Pax7-Cre/cKO), uncoupling of AChRs from IFs was shown to lead to loss of postsynaptic membrane infoldings and disorganization of the NMJ microenvironment, including its invasion by microtubules. In their phenotypic behavior, mutant mice closely mimicked EBS-MD-MyS patients, including impaired body balance, severe muscle weakness, and reduced life span. Our study demonstrates that linkage to desmin IF networks via plectin is crucial for formation and maintenance of AChR clusters, postsynaptic NMJ organization, and body locomotion.
authors.affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Mihailovska
authors.affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.
authors.forename: Marianne
authors.initials: M
authors.lastname: Raith
authors.affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.
authors.forename: Rocio G
authors.initials: RG
authors.lastname: Valencia
authors.affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.
authors.forename: Irmgard
authors.initials: I
authors.lastname: Fischer
authors.affiliation: Preclinical Phenotyping Facility, Campus Science Support Facilities, 1030 Vienna, Austria.
authors.forename: Mumna
authors.initials: M
authors.lastname: Al Banchaabouchi
authors.affiliation: Center for Brain Research and Institute of Immunology, Medical University of Vienna, 1030 Vienna, Austria.
authors.forename: Ruth
authors.initials: R
authors.lastname: Herbst
authors.affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria gerhard.wiche@univie.ac.at.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wiche
mesh_terms: D000818:Animals; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism*; D008297:Male; D018345:Mice, Knockout; D009043:Motor Activity; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D053580:Muscle Strength; D009469:Neuromuscular Junction / Q000378:metabolism*; D051190:Plectin / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms / Q000378:metabolism; D021381:Protein Transport
chemical_list: D009124:Muscle Proteins; C495333:Plec protein, mouse; D051190:Plectin; D020033:Protein Isoforms; C051609:peripheral membrane protein 43K