title: Physical interaction between epidermal growth factor receptor and DNA-dependent protein kinase in mammalian cells.
abstract: Binding of extracellular ligands to epidermal growth factor receptors (EGFR) activate signal transduction pathways associated with cell proliferation, and these events are inhibited by monoclonal antibodies against EGFR. Since efficient DNA repair in actively growing cells may require growth factor signaling, it was of interest to explore any linkage between EGFR-mediated signaling and DNA-dependent protein kinase (DNA-PK), an enzyme believed to be involved in repairing double strand breaks and V(D)J recombination. We report that anti-EGFR monoclonal antibodies (mAbs), and not EGFR ligands, trigger a specific early physical interaction between EGFR and a 350-kDa catalytic subunit of DNA or its regulatory heterodimeric complex Ku70/80, in a variety of cell types, both in vivo and in vitro. Inhibition of EGFR signaling by anti-EGFR mAb was accompanied by a reduction in the levels of the DNA-PK and its activity in the nuclear fraction. Confocal imaging revealed that a substantial amount of DNA-PK was co-localized with EGFR in anti-EGFR mAb-treated cells. Anti-EGFR mAb-induced physical interaction between EGFR and DNA-PK or Ku70/80 was dependent on the presence of EGFR, but not on the levels of EGFR. The EGFR associated with DNA-PK or Ku70/80 retains its intrinsic kinase activity. Our findings demonstrate the existence of a novel cellular pathway in mammalian cells that involves physical interactions between EGFR and DNA-PK or Ku70/80 in response to inhibition of EGFR signaling. Our present observations suggest a possible role of EGFR signaling in maintenance of the nuclear levels of DNA-PK, and interference in EGFR signaling may possibly result in the impairment of DNA repair activity in the nuclei in anti-EGFR mAb-treated cells.
authors.affiliation: Department of Clinical Investigation, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: D
authors.initials: D
authors.lastname: Bandyopadhyay
authors.forename: M
authors.initials: M
authors.lastname: Mandal
authors.forename: L
authors.initials: L
authors.lastname: Adam
authors.forename: J
authors.initials: J
authors.lastname: Mendelsohn
authors.forename: R
authors.initials: R
authors.lastname: Kumar
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D034961:Antigens, Nuclear; D001324:Autoantigens / Q000378:metabolism; D004265:DNA Helicases; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D000072200:Ku Autoantigen; D008024:Ligands; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D034961:Antigens, Nuclear; D001324:Autoantigens; D004268:DNA-Binding Proteins; D008024:Ligands; D009687:Nuclear Proteins; D014157:Transcription Factors; D066246:ErbB Receptors; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen