A mammalian homolog of Drosophila tumorous imaginal discs, Tid1, mediates agrin signaling at the neuromuscular junction.
Motoneuron-derived agrin clusters nicotinic acetylcholine receptors (AChRs) in mammalian muscle cells. We used two-hybrid screens to identify a protein, tumorous imaginal discs (Tid1), that binds to the cytoplasmic domain of muscle-specific kinase (MuSK), a major component of the agrin receptor. Like MuSK, Tid1 colocalizes with AChRs at developing, adult, and denervated motor endplates. Knockdown of Tid1 by short hairpin RNA (shRNA) in skeletal muscle fibers dispersed synaptic AChR clusters and impaired neuromuscular transmission. In cultured myotubes, Tid1 knockdown inhibited AChR clustering, as well as agrin-induced activation of the Rac and Rho small GTPases and tyrosine phosphorylation of the AChR, without affecting MuSK activation. Tid1 knockdown also decreased Dok-7-induced clustering of AChRs. Overexpression of the N-terminal half of Tid1 induced agrin- and MuSK-independent phosphorylation and clustering of AChRs. These results demonstrate that Tid1 is an essential component of the agrin signaling pathway, crucial for synaptic development.
Linnoila
Jenny
J
Molecular Pharmacology Graduate Training Program, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA. jenny.linnoila@gmail.com
Wang
Ying
Y
Yao
Yun
Y
Wang
Zuo-Zhong
ZZ
D018171:Agrin / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D015536:Down-Regulation / Q000235:genetics; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009469:Neuromuscular Junction / Q000166:cytology / Q000196:embryology* / Q000254:growth & development; D009924:Organ Culture Techniques; D010766:Phosphorylation; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D034622:RNA Interference / Q000502:physiology; D011940:Receptor Aggregation / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D018171:Agrin; C485636:Dnaja3 protein, mouse; C511694:Dok-7 protein, mouse; D050956:HSP40 Heat-Shock Proteins; D009124:Muscle Proteins; D011950:Receptors, Cholinergic; C511695:MuSK protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D020558:GTP Phosphohydrolases