During development of the neuromuscular junction, neuronal splice variants of agrin initiate
the aggregation of acetylcholine receptors on the myotube surface. The muscle-specific
kinase is thought to be part of an agrin receptor complex, although the recombinant protein
does not bind agrin with high affinity. To specify its function, we induced phosphorylation
and activation of this kinase in the absence of agrin by incubating myotubes with antibodies
directed against its N-terminal sequence. Antibody-induced dimerization of the muscle …