Novel Role of EGFR in Virus-Induced Asthma Exacerbations

Yale University, New Haven CT

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Abstract

? DESCRIPTION (provided by applicant): The majority of asthma exacerbations are caused by viral infections, and childhood viral infections contribute to asthma pathogenesis. Virus-induced asthma exacerbations continue to account for significant morbidity and mortality, because effective antiviral therapies are not available. In asthma, airway epithelial Interferon-lambda (IFN-?) is deficient, which results in impaired antiviral immune responses. We have shown that viruses activate epidermal growth factor receptor (EGFR) to suppress IRF1-dependent IFN-?, which results in increased viral infection. In addition, we found that inhibiting EGFR increased IRF1 and IFN-? to suppress viral infection. This result has potential implications in asthma because EGFR signaling is increased in asthmatic epithelium. However, because of possible side effects with existing EGFR inhibitors, we investigated IFN-? to suppress EGFR, and found that IFN-? inhibits EGFR activation. An emerging area of EGFR biology is that this cell surface tyrosine kinase receptor traffics to the nucleus to influence key cell functions, which include calcium (Ca2+) signaling in the nucleus. Preliminary work found that inhibition of nuclear Ca2+ signaling attenuates EGFR suppression of IRF1, which implicates nuclear EGFR-dependent Ca2+ signaling to suppress IRF1. More recently, we found that sputum EGFR expression correlates with asthma severity. Because macrophages are the predominant cell type in sputum, we investigated EGFR signaling in macrophages. Preliminary experiments showed functional EGFR in sputum and PBMC-derived macrophages. In addition, increased EGFR activation suppressed IRF1, which parallels our findings in airway epithelium. Therefore, the hypothesis of this proposal is that EGFR signaling is integral to susceptibility to viral infectionin asthma via suppression of IRF1-dependent IFN-? in both airway epithelial cells and macrophages. In Aim 1, we will use a murine model of virus-induced asthma exacerbations to study the effect of EGFR inhibition on inflammation. A genetic approach will suppress airway epithelial EGFR, and we will study intranasal EGFR siRNA and IFN-?. Aim 2 will investigate nuclear EGFR-dependent Ca2+ signaling to suppress IRF1 and IFN-? using confocal microscopy, constructs, and siRNA that target EGFR trafficking to the nucleus and inhibit nuclear Ca2+ signaling. This will include experiments to study the effect of IFN-? to inhibit nuclear EGFR in airway epithelium. Aim 3 will investigate EGFR signaling in sputum and blood macrophages from asthmatics and healthy individuals, which will include the effect of IFN-? on nuclear EGFR in macrophages. Finally, using a genetic model to remove EGFR in macrophages, we will study the cell-specific contribution of EGFR signaling in the mouse model of virus-induced asthma exacerbations. These studies will elucidate: 1) the effectiveness of EGFR inhibition to suppress inflammation in virus-induced asthma exacerbations, which will provide insights for novel therapies, 2) a new mechanism for nuclear EGFR-dependent Ca2+ signaling to influence antiviral immunity, and 3) the role of macrophage EGFR signaling in asthma, which will expand our current model of EGFR biology.