Mesdc2 plays a key role in cell-surface expression of Lrp4 and postsynaptic specialization in myotubes

Low-density lipoprotein receptor-related protein 4 (Lrp4) is essential for pre- and post-synaptic specialization at the neuromuscular junction (NMJ), an indispensable synapse between a motor nerve and skeletal muscle. Muscle-specific receptor tyrosine kinase MuSK must form a complex with Lrp4 to organize postsynaptic specialization at NMJs. Here, we show that the chaperon Mesdc2 binds to the intracellular form of Lrp4 and promotes its glycosylation and cell-surface expression. Furthermore, knockdown of Mesdc2 suppresses cell-surface expression of Lrp4, activation of MuSK, and postsynaptic specialization in muscle cells. These results suggest that Mesdc2 plays an essential role in NMJ formation by promoting Lrp4 maturation. Structured summary of protein interactions: Lrp4 physically interacts with CANX, LRPAP1, CCAR2, MESDC2, PDIA4, RPN1 and SDF2L1 by anti tag coimmunoprecipitation (View interaction) Mesdc2 physically interacts with Lrp4 by anti tag coimmunoprecipitation (View interaction) Mesdc2 physically interacts with Lrp4 by anti bait coimmunoprecipitation (View interaction) (C) 2013 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.