title: Interaction between Brk kinase and insulin receptor substrate-4.
abstract: Breast tumor kinase (Brk) is a member of the Frk family of nonreceptor tyrosine kinases that is overexpressed in a high percentage of human breast tumors. The downstream substrates and effectors of Brk remain largely unidentified. In this study, we carried out immunoprecipitation and mass spectrometry experiments to identify new Brk binding partners. One interacting protein was insulin receptor substrate 4 (IRS-4), a member of the IRS family. We confirmed that Brk associates with IRS-4 in resting and insulin-like growth factor 1 (IGF-1)-stimulated HEK 293 cells. The SH3 and SH2 domains of Brk are both involved in the association. The tyrosine phosphorylation of Brk increases after stimulation with IGF-1, and in MCF-7 breast cancer cells we show that the presence of IRS-4 enhances this effect. Finally, we demonstrate that endogenous Brk and IRS-4 interact in A431 human epidermoid carcinoma cells.
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, State University of New York at Stony Brook, Stony Brook, NY 11794-8661, USA.
authors.forename: Haoqun
authors.initials: H
authors.lastname: Qiu
authors.forename: Francesca
authors.initials: F
authors.lastname: Zappacosta
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Su
authors.forename: Roland S
authors.initials: RS
authors.lastname: Annan
authors.forename: W Todd
authors.initials: WT
authors.lastname: Miller
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C526292:IRS1 protein, human; C107686:IRS4 protein, human; D055504:Insulin Receptor Substrate Proteins; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D007334:Insulin-Like Growth Factor I; D011505:Protein-Tyrosine Kinases; C088375:PTK6 protein, human