title: Src homology region 2 domains direct protein-protein interactions in signal transduction.
abstract: Cytoplasmic proteins that regulate signal transduction or induce cellular transformation, including cytoplasmic protein-tyrosine kinases, p21ras GTPase-activating protein (GAP), phospholipase C gamma, and the v-crk oncoprotein, possess one or two copies of a conserved noncatalytic domain, Src homology region 2 (SH2). Here we provide direct evidence that SH2 domains can mediate the interactions of these diverse signaling proteins with a related set of phosphotyrosine ligands, including the epidermal growth factor (EGF) receptor. In src-transformed cells GAP forms heteromeric complexes, notably with a highly tyrosine phosphorylated 62-kDa protein (p62). The stable association between GAP and p62 can be specifically reconstituted in vitro by using a bacterial polypeptide containing only the N-terminal GAP SH2 domain. The efficient phosphorylation of p62 by the v-Src or v-Fps tyrosine kinases depends, in turn, on their SH2 domains and correlates with their transforming activity. In lysates of EGF-stimulated cells, the N-terminal GAP SH2 domain binds to both the EGF receptor and p62. Fusion proteins containing GAP or v-Crk SH2 domains complex with similar phosphotyrosine proteins from src-transformed or EGF-stimulated cells but with different efficiencies. SH2 sequences, therefore, form autonomous domains that direct signaling proteins, such as GAP, to bind specific phosphotyrosine-containing polypeptides. By promoting the formation of these complexes, SH2 domains are ideally suited to regulate the activation of intracellular signaling pathways by growth factors.
authors.affiliation: Division of Molecular and Developmental Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: M F
authors.initials: MF
authors.lastname: Moran
authors.forename: C A
authors.initials: CA
authors.lastname: Koch
authors.forename: D
authors.initials: D
authors.lastname: Anderson
authors.forename: C
authors.initials: C
authors.lastname: Ellis
authors.forename: L
authors.initials: L
authors.lastname: England
authors.forename: G S
authors.initials: GS
authors.lastname: Martin
authors.forename: T
authors.initials: T
authors.lastname: Pawson
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D020690:GTPase-Activating Proteins; D016391:Genes, src; D006801:Humans; D009154:Mutation; D050736:Oncogene Protein v-crk; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D051381:Rats; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism; D020703:ras GTPase-Activating Proteins
chemical_list: D020690:GTPase-Activating Proteins; D050736:Oncogene Protein v-crk; D011506:Proteins; D015682:Retroviridae Proteins, Oncogenic; D020703:ras GTPase-Activating Proteins; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)