SUMMARY Cardiovascular disease remains the principal cause of death in the United States, with myocarditis contributing to 42% of all sudden deaths in young adults. Human adenovirus type 5 is a leading etiological agent of viral myocarditis, yet research is lacking due to host species specificity limiting the development of model systems for cardiac infection. The effect of active adenoviral infection on cardiomyocyte function and arrhythmogenesis that precedes immune responses and progression to heart failure is unknown. Gap junctions, predominantly comprising the protein connexin43 (Cx43) in the ventricular intercalated disc, facilitate action potential propagation during each heartbeat. An intimate association and interplay between gap junctions, other ID resident ion channels, and components of mechanical junctions is now well accepted. Alterations in ID mechanical and electrical coupling cause arrhythmias, and while it has been demonstrated that adenovirus directly targets adhesion late in infection, the relationship between adenoviral myocarditis and Cx43 gap junction, or other ion channel, function and regulation remains unexplored. Indeed, treatment for viral myocarditis is largely supportive, with no therapeutic interventions or antivirals demonstrating significant clinical efficacy to date. Through study of adenoviral infection of cardiac muscle at the molecular level, we will address significant gaps in the knowledge regarding mechanisms underlying the impact of infection on cardiomyocyte intercellular coupling and electrophysiology while identifying therapeutic targets to limit viral spread and/or rescue electrical coupling in diseased hearts. Our long term goal is to elucidate the pathological mechanisms of viral myocarditis and resulting arrhythmogenic subversion of cardiac ion channels and junctional structures. The objective of this R01 proposal is to determine how electrical and mechanical intercellular coupling is affected during acute adenoviral cardiac infection to precipitate an arrhythmogenic substrate. Our central hypothesis is that adenovirus hijacks junction protein expression and function leading to an arrhythmogenic substrate prior to gross pathological remodeling and the appreciable host immune responses. We will test this hypothesis with the following two Specific Aims: Aim 1: Determine the role of early adenoviral proteins in generation of an arrhythmogenic cellular landscape. The working hypothesis for this aim is that early adenoviral proteins activate a PI3K/β-catenin signaling axis targeting Cx43 and cardiac ion channel function, contributing to arrhythmogenesis. Aim 2: Determine the role of connexins and gap junction intercellular communication in adenoviral pathogenesis. The working hypothesis for this aim is that adenovirus stabilizes cellular junctions to facilitate viral spread while limiting intercellular communication to enhance viral replication.