Abstract
Agrin signals through the muscle-specific receptor tyrosine kinase (MuSK) to cluster acetylcholine receptors (AChRs) on the postsynaptic membrane of the neuromuscular junction (NMJ). This stands as the prevailing model of synapse induction by a presynaptic factor, yet the agrin-dependent MuSK signaling cascade is largely undefined. Abl1 (previously known as Abl) and the Abl1-related gene product Abl2 (previously known as Arg) define a family of tyrosine kinases that regulate actin structure and presynaptic axon guidance. Here we show that the Abl kinases are critical mediators of postsynaptic assembly downstream of agrin and MuSK. In mouse muscle, Abl kinases were localized to the postsynaptic membrane of the developing NMJ. In cultured myotubes, Abl kinase activity was required for agrin-induced AChR clustering and enhancement of MuSK tyrosine phosphorylation. Moreover, MuSK and Abl kinases effected reciprocal tyrosine phosphorylation and formed a complex after agrin engagement. Our findings suggest that Abl kinases provide the developing synapse with the kinase activity required for signal amplification and the intrinsic cytoskeletal regulatory capacity required for assembly and remodeling.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing*
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Agrin / physiology
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Animals
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Animals, Newborn / growth & development
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Animals, Newborn / metabolism
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Autonomic Denervation / methods
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Benzamides
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Blotting, Western / methods
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Brain / metabolism
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Bungarotoxins / metabolism
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Cell Aggregation / drug effects
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Cell Aggregation / physiology
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Cells, Cultured
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Cytoskeletal Proteins*
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Dose-Response Relationship, Drug
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Drug Interactions
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Enzyme Inhibitors / pharmacology
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Homeodomain Proteins / immunology
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Homeodomain Proteins / metabolism*
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Imatinib Mesylate
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Immunohistochemistry
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In Vitro Techniques
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Mice
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Muscle Denervation / methods
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Muscles / metabolism
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Myoblasts / metabolism
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Neurofilament Proteins / metabolism
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Neuromuscular Junction / physiology*
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Phosphorylation
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Piperazines / pharmacology
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-crk
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Pyrimidines / pharmacology
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Rabbits
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Radioimmunoassay
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Receptor Protein-Tyrosine Kinases / metabolism
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Receptors, Cholinergic / metabolism
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Synapses / physiology*
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Synaptophysin / metabolism
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Time Factors
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Transfection / methods
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Tyrosine / metabolism
Substances
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ABI1 protein, human
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Abi1 protein, mouse
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Abi2 protein, mouse
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Adaptor Proteins, Signal Transducing
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Agrin
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Benzamides
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Bungarotoxins
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Cytoskeletal Proteins
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Enzyme Inhibitors
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Homeodomain Proteins
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Neurofilament Proteins
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Piperazines
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-crk
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Pyrimidines
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Receptors, Cholinergic
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Synaptophysin
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Tyrosine
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Imatinib Mesylate
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MUSK protein, human
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Receptor Protein-Tyrosine Kinases