Sorbs1 and 2 interact with Crk-L and are required for Acetylcholine receptor cluster formation

Crk and CrkL are non-catalytic adapter proteins necessary for the formation of neuromuscular synapses which function downstream of MuSK, a receptor tyrosine kinase expressed in skeletal muscle, and the MuSK binding-protein Dok-7. How Crk/CrkL regulates neuromuscular endplate formation is not known. To better understand the roles of Crk/CrkL, we identified CrkL binding proteins using mass spectrometry, and have identified Sorbs1 and Sorbs2 as two functionally redundant proteins that associate with the initiating MuSK/Dok-7/Crk/CrkL complex, regulate AChR clustering in vitro, and are localized at synapses in vivo.