Abstract 176: β-Adrenergic Receptor--Mediated Regulation of Cardiac Gene Expression Is Gefitinib Sensitive

Abstract

BetaAR-mediated transactivation of epidermal growth factor receptor (EGFR) has been shown to promote cardioprotection in a mouse model of heart failure, however the mechanism(s) responsible for this pro-survival response are not known. We hypothesized that this transactivation event could impact a number of processes in the heart, including survival, via regulation of gene expression. To test the capacity of BetaAR-mediated EGFR transactivation to regulate this process, acute changes in cardiac gene expression were assessed via RNA sequencing in the hearts of C57BL/6 mice given i.p. injections of the BetaAR agonist isoproterenol (ISO, 1mg/kg) in the presence or absence of the EGFR antagonist gefitinib (Gef, 5mg/kg) for 1 hour. The total RNA from 4 hearts per treatment group (Control, ISO, Gef, Gef/ISO) were combined and underwent DNA library generation and SOLiD sequencing analysis, which revealed a substantial number of genes and isoforms regulated by each of the treatments. Interestingly, Gef alone significantly altered the expression of 270 genes compared to control suggesting potential Gef-dependent alterations in the heart during clinical use. ISO alone and Gef/ISO significantly altered 401 and 723 distinct genes compared to control, respectively. Further statistical analysis was performed between the ISO and Gef/ISO groups to assess true Gef sensitivity of ISO-regulated genes in the heart, confirming 173 genes significantly altered between the groups. Classification of these genes revealed 4 categories: ISO-dependent gene upregulation (1) or downregulation (2) antagonized by Gef, and ISO-dependent gene upregulation (3) or downregulation (4) promoted in presence of Gef. Identified within these categories were several genes known to be involved in the regulation of cardiac hypertrophy, apoptosis, sarcomeric structure and Ca2+-handling, which were selected for validation via qPCR. In conclusion, BetaAR-mediated EGFR transactivation induces rapid modulation of cardiac gene expression in response to catecholamine stimulation in vivo, with potential functional impacts on a number of cellular processes, while simultaneously acting to antagonize gene expression changes mediated via distinct BetaAR-mediated signaling pathways.