Silencing rapsyn in vivo decreases acetylcholine receptors and augments sodium channels and secondary postsynaptic membrane folding.
The receptor-associated protein of the synapse (rapsyn) is required for anchoring and stabilizing the nicotinic acetylcholine receptor (AChR) in the postsynaptic membrane of the neuromuscular junction (NMJ) during development. Here we studied the role of rapsyn in the maintenance of the adult NMJ by reducing rapsyn expression levels with short hairpin RNA (shRNA). Silencing rapsyn led to the average reduction of the protein levels of rapsyn (31% loss) and AChR (36% loss) at the NMJ within 2 weeks, corresponding to previously reported half life of these proteins. On the other hand, the sodium channel protein expression was augmented (66%) in rapsyn-silenced muscles. Unexpectedly, at the ultrastructural level a significant increase in the amount of secondary folds of the postsynaptic membrane in silenced muscles was observed. The neuromuscular transmission in rapsyn-silenced muscles was mildly impaired. The results suggest that the adult NMJ can rapidly produce postsynaptic folds to compensate for AChR and rapsyn loss.
Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands, Maastricht, The Netherlands. p.martinez@np.unimaas.nl
Pilar
P
Martínez-Martínez
Marko
M
Phernambucq
Laura
L
Steinbusch
Laurent
L
Schaeffer
Sonia
S
Berrih-Aknin
Hans
H
Duimel
Peter
P
Frederik
Peter
P
Molenaar
Marc H
MH
De Baets
Mario
M
Losen
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002038:Bungarotoxins / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004576:Electromyography / Q000379:methods; D018274:Electroporation / Q000379:methods; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron / Q000379:methods; D009124:Muscle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000276:immunology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000648:ultrastructure; D009469:Neuromuscular Junction / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D011950:Receptors, Cholinergic / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*
D000906:Antibodies; D002038:Bungarotoxins; D009124:Muscle Proteins; D034741:RNA, Small Interfering; D011950:Receptors, Cholinergic; D015222:Sodium Channels; C051609:peripheral membrane protein 43K; D049452:Green Fluorescent Proteins