title: Differential sensitivity of Src-family kinases to activation by SH3 domain displacement.
abstract: Src-family kinases (SFKs) are non-receptor protein-tyrosine kinases involved in a variety of signaling pathways in virtually every cell type. The SFKs share a common negative regulatory mechanism that involves intramolecular interactions of the SH3 domain with the PPII helix formed by the SH2-kinase linker as well as the SH2 domain with a conserved phosphotyrosine residue in the C-terminal tail. Growing evidence suggests that individual SFKs may exhibit distinct activation mechanisms dictated by the relative strengths of these intramolecular interactions. To elucidate the role of the SH3:linker interaction in the regulation of individual SFKs, we used a synthetic SH3 domain-binding peptide (VSL12) to probe the sensitivity of downregulated c-Src, Hck, Lyn and Fyn to SH3-based activation in a kinetic kinase assay. All four SFKs responded to VSL12 binding with enhanced kinase activity, demonstrating a conserved role for SH3:linker interaction in the control of catalytic function. However, the sensitivity and extent of SH3-based activation varied over a wide range. In addition, autophosphorylation of the activation loops of c-Src and Hck did not override regulatory control by SH3:linker displacement, demonstrating that these modes of activation are independent. Our results show that despite the similarity of their downregulated conformations, individual Src-family members show diverse responses to activation by domain displacement which may reflect their adaptation to specific signaling environments in vivo.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Jamie A
authors.initials: JA
authors.lastname: Moroco
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America; Center for Vaccine Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Jodi K
authors.initials: JK
authors.lastname: Craigo
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, United States of America.
authors.forename: Roxana E
authors.initials: RE
authors.lastname: Iacob
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, United States of America.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wales
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, United States of America.
authors.forename: John R
authors.initials: JR
authors.lastname: Engen
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Smithgall
mesh_terms: D004789:Enzyme Activation / Q000235:genetics; D006801:Humans; D010455:Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D018909:src Homology Domains; D019061:src-Family Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D010455:Peptides; D019061:src-Family Kinases