Agrin/Dok-7-induced JPH2 phosphorylation in muscle cells is involved in AChR clustering.

The neuromuscular junction (NMJ) performs the crucial function of controlling skeletal muscle contraction. NMJ formation depends on the Agrin/Lrp4/MuSK/Dok-7 signaling pathway. However, signaling downstream of Dok-7 remains incompletely understood. Here we used the phosphorylated iTRAQ technique to identify downstream molecules of Dok-7 in muscle cells. We found 16 Agrin/Dok-7-mediated serine/threonine phosphorylated proteins, and we validated the role of one phosphorylated protein, JPH2, in regulating AChR clustering. Our phosphoproteomics analysis sheds light on the underappreciated signaling network downstream of Agrin/Dok-7, thus providing new clues for understanding pathogenesis and developing treatment methods for neuromuscular diseases.