title: EGF receptor exposed to oxidative stress acquires abnormal phosphorylation and aberrant activated conformation that impairs canonical dimerization.
abstract: Crystallographic studies have offered understanding of how receptor tyrosine kinases from the ErbB family are regulated by their growth factor ligands. A conformational change of the EGFR (ErbB1) was shown to occur upon ligand binding, where a solely ligand-mediated mode of dimerization/activation was documented. However, this dogma of dimerization/activation was revolutionized by the discovery of constitutively active ligand-independent EGFR mutants. In addition, other ligand-independent activation mechanisms may occur. We have shown that oxidative stress (ox-stress), induced by hydrogen peroxide or cigarette smoke, activates EGFR differently than its ligand, EGF, thereby inducing aberrant phosphorylation and impaired trafficking and degradation of EGFR. Here we demonstrate that ox-stress activation of EGFR is ligand-independent, does not induce "classical" receptor dimerization and is not inhibited by the tyrosine kinase inhibitor AG1478. Thus, an unprecedented, apparently activated, state is found for EGFR under ox-stress. Furthermore, this activation mechanism is temperature-dependent, suggesting the simultaneous involvement of membrane structure. We propose that ceramide increase under ox-stress disrupts cholesterol-enriched rafts leading to EGFR re-localization into the rigid, ceramide-enriched rafts. This increase in ceramide also supports EGFR aberrant trafficking to a peri-nuclear region. Therefore, the EGFR unprecedented and activated conformation could be sustained by simultaneous alterations in membrane structure under ox-stress.
authors.affiliation: Center for Comparative Respiratory Biology and Medicine, Genome and Biomedical Sciences Facility, University of California School of Medicine, Davis, California, United States of America.
authors.forename: Simone
authors.initials: S
authors.lastname: Filosto
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Khan
authors.forename: Emiliana
authors.initials: E
authors.lastname: Tognon
authors.forename: Cathleen
authors.initials: C
authors.lastname: Becker
authors.forename: Majid
authors.initials: M
authors.lastname: Ashfaq
authors.forename: Tommer
authors.initials: T
authors.lastname: Ravid
authors.forename: Tzipora
authors.initials: T
authors.lastname: Goldkorn
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008024:Ligands; D051379:Mice; D008954:Models, Biological; D041681:NIH 3T3 Cells; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D011799:Quinazolines; D013696:Temperature; D020032:Tyrphostins / Q000494:pharmacology; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; D002518:Ceramides; D008024:Ligands; D011720:Pyrazoles; D011743:Pyrimidines; D011799:Quinazolines; D020032:Tyrphostins; C101044:RTKI cpd; D002784:Cholesterol; D006861:Hydrogen Peroxide; D066246:ErbB Receptors; D019061:src-Family Kinases