Reactive oxidants, such as hydrogen peroxide (H202) and peroxynitrite (ONOO-), are strongly associated with lung disease. Yet, the cellular and molecular mechanisms that link oxidant exposure to the development of lung disease are poorly understood. One direction of our studies has been to unravel the molecular mechanisms of oxidant-induced ceramide mediated apoptosis. The other direction, which is the focus of this application, aims to elucidate the molecular interactions between reactive oxidants and ErbB1, the epidermal growth factor receptor (EGFR), that drive aberrant growth control leading to airway epithelial hyperplasia. We propose that reactive oxidants act as independent participants in the """"""""input layer"""""""" of signals to the ErbB1 receptor but with a different outcome than that of physiologic ligands such as EGF. We have shown that in contrast to ligand-induced dimerization and phn._ohorylation of EGFR, H202 exposure results in an aberrantly phosphorylated EGFR, and ONOO- exposure generates a covalently cross-linked receptor. Moreover, we have recently observed that H202 inhibits the association of the ubiquitin E3 ligase, c-Cbl, with EGFR, and thus prevents the receptor's ubiquitination. These preliminary studies lead us to hypothesize that oxidant-induced aberrant phosphorylation of EGFR prevents its ubiquitination by c-Cbl and proteasomal (or lysosomal) down-regulation. This could result in continuous pro-growth signaling. To test this, we will determine the structure/function of EGFR following exposure to reactive oxidants. We will first map the specific sites of phosphorylation or dimerization targeted by reactive oxidants. Then, we will construct EGFR mutants of the affected sites and elucidate their roles in EGFR function. We will specifically test the hypothesis that by targeting aberrant phosphorylation sites, reactive oxidants prevent EGFR association with the proteasomal component, c-Cbl, and preclude ubiquitination and down-regulation of the receptor, thereby leading to airway epithelial hyperplasia. Structure/function characterization of oxidant-mediated alterations in EGFR sites of phosphorylation (or dimerization), followed by construction of the cognate tyrosine mutants, are important milestones that would link oxidant-specific changes to lung hyperplasia at a molecular level. In the long run, this approach should indicate precise targets for clinical intervention to control hyperplasia of epithelial cells in pulmonarydiseases.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL071871-02
Application #
6781718
Study Section
Lung Biology and Pathology Study Section (LBPA)
Program Officer
Harabin, Andrea L
Project Start
2003-08-01
Project End
2007-05-31
Budget Start
2004-06-01
Budget End
2005-05-31
Support Year
2
Fiscal Year
2004
Total Cost
$297,000
Indirect Cost
Name
University of California Davis
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
047120084
City
Davis
State
CA
Country
United States
Zip Code
95618
Chung, Samuel; Vu, Simon; Filosto, Simone et al. (2015) Src regulates cigarette smoke-induced ceramide generation via neutral sphingomyelinase 2 in the airway epithelium. Am J Respir Cell Mol Biol 52:738-48
Filosto, Simone; Ashfaq, Majid; Chung, Samuel et al. (2012) Neutral sphingomyelinase 2 activity and protein stability are modulated by phosphorylation of five conserved serines. J Biol Chem 287:514-22
Filosto, Simone; Khan, Elaine M; Tognon, Emiliana et al. (2011) EGF receptor exposed to oxidative stress acquires abnormal phosphorylation and aberrant activated conformation that impairs canonical dimerization. PLoS One 6:e23240
Filosto, Simone; Castillo, Sianna; Danielson, Aaron et al. (2011) Neutral sphingomyelinase 2: a novel target in cigarette smoke-induced apoptosis and lung injury. Am J Respir Cell Mol Biol 44:350-60
Filosto, Simone; Fry, William; Knowlton, Anne A et al. (2010) Neutral sphingomyelinase 2 (nSMase2) is a phosphoprotein regulated by calcineurin (PP2B). J Biol Chem 285:10213-22
Goldkorn, Tzipora; Filosto, Simone (2010) Lung injury and cancer: Mechanistic insights into ceramide and EGFR signaling under cigarette smoke. Am J Respir Cell Mol Biol 43:259-68
Levy, Michal; Khan, Elaine; Careaga, Milo et al. (2009) Neutral sphingomyelinase 2 is activated by cigarette smoke to augment ceramide-induced apoptosis in lung cell death. Am J Physiol Lung Cell Mol Physiol 297:L125-33
Khan, Elaine M; Lanir, Roni; Danielson, Aaron R et al. (2008) Epidermal growth factor receptor exposed to cigarette smoke is aberrantly activated and undergoes perinuclear trafficking. FASEB J 22:910-7
Castillo, S Sianna; Levy, Michal; Wang, Chunbo et al. (2007) Nitric oxide-enhanced caspase-3 and acidic sphingomyelinase interaction: a novel mechanism by which airway epithelial cells escape ceramide-induced apoptosis. Exp Cell Res 313:816-23
Castillo, S Sianna; Levy, Michal; Thaikoottathil, Jyoti V et al. (2007) Reactive nitrogen and oxygen species activate different sphingomyelinases to induce apoptosis in airway epithelial cells. Exp Cell Res 313:2680-6

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