title: Analysis of a Shc family adaptor protein, ShcD/Shc4, that associates with muscle-specific kinase.
abstract: Shc family proteins serve as phosphotyrosine adaptor molecules in various receptor-mediated signaling pathways. In mammals, three distinct Shc genes have been described that encode proteins characterized by two phosphotyrosine-interaction modules, an amino-terminal phosphotyrosine binding (PTB) domain and a carboxy-terminal Src homology 2 domain. Here, we report the analysis of an uncharacterized fourth Shc family protein, ShcD/Shc4, that is expressed in adult brain and skeletal muscle. Consistent with this expression pattern, we find that ShcD can associate via its PTB domain with the phosphorylated muscle-specific kinase (MuSK) receptor tyrosine kinase and undergo tyrosine phosphorylation downstream of activated MuSK. Interestingly, additional sites of tyrosine phosphorylation, including a novel Grb2 binding site, are present on ShcD that are not found in other Shc family proteins. Activation of MuSK upon agrin binding at the neuromuscular junction (NMJ) induces clustering and tyrosine phosphorylation of acetylcholine receptors (AChRs) required for synaptic transmission. ShcD is coexpressed with MuSK in the postsynaptic region of the NMJ, and in cultured myotubes stimulated with agrin, expression of ShcD appears to be important for early tyrosine phosphorylation of the AChR. Thus, we have characterized a new member of the Shc family of docking proteins, which may mediate a specific aspect of signaling downstream of the MuSK receptor.
authors: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario, Canada. pawson@mshri.on.ca
authors: Nina
authors: N
authors: Jones
authors: W Rod
authors: WR
authors: Hardy
authors: Matthew B
authors: MB
authors: Friese
authors: Claus
authors: C
authors: Jorgensen
authors: Matthew J
authors: MJ
authors: Smith
authors: Neil M
authors: NM
authors: Woody
authors: Steven J
authors: SJ
authors: Burden
authors: Tony
authors: T
authors: Pawson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018171:Agrin / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D051380:GRB2 Adaptor Protein / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D009469:Neuromuscular Junction / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018171:Agrin; D051380:GRB2 Adaptor Protein; D011950:Receptors, Cholinergic; C519335:SHC4 protein, human; D055765:Shc Signaling Adaptor Proteins; C521729:Shc4 protein, mouse; D014443:Tyrosine; C511695:MuSK protein, mouse; D020794:Receptor Protein-Tyrosine Kinases