Cardiac troponin i3 kinase in viral myocarditis

ABSTRACT Myocarditis is a leading cause of heart failure and sudden cardiac death, but many cases of myocarditis follow a benign course. It is unknown what factors control this variable susceptibility to severe disease. Without this knowledge, the ability to develop targeted therapies to prevent disease progression is greatly limited. Viral infection is the most common known cause of myocarditis, and much research has focused on the pathways involved in the heart’s response to viral infection. Many such studies have identified type I interferon signaling as critical for viral pathogenicity and susceptibility to myocarditis. Quantitative trait locus analysis suggested the cardiomyocyte-specific protein cardiac troponin i3 kinase (TNNI3K) as a potential candidate. In an initial study, I infected homozygous Tnni3k knockout and control wild-type mice with coxsackievirus B3 (CVB3) for 10 days and demonstrated a direct role of Tnni3k in viral myocarditis. I additionally showed that Tnni3k’s kinase activity is necessary for mounting an effective response. Preliminary cell-based transfection of Tnni3k with an interferon signaling response element (ISRE)-linked reporter showed that presence of Tnni3k led to increased ISRE expression after treatment with interferon-α. Therefore, I hypothesize that TNNI3K decreases susceptibility to viral myocarditis in a kinase-dependent manner by enhancing the interferon response in cardiomyocytes. I will address this hypothesis by testing the role of Tnni3k in vivo (Aim 1) and in vitro (Aim 2). Aim 1 of this proposal expands on the initial study by infecting Tnni3k knockout and control wild-type mice with CVB3 and assessing measures of myocarditis after 4 days and after 35 days. Additional mouse models modifying the kinase activity of Tnni3k have been generated and will also be tested with viral infection. One of these models is of particular interest, as it recapitulates a common SNP found in millions of humans. In Aim 2, I will confirm the influence of TNNI3K in the interferon pathway by treating wild-type and TNNI3K knockout induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) with CVB3 and evaluating gene expression of proteins in the interferon pathway. I will then probe for differentially phosphorylated proteins in wild-type and TNNI3K knockout iPSC-CMs following CVB3 infection. Differentially phosphorylated proteins will be silenced in iPSC-CMs to define their role in the interferon pathway specifically in cardiomyocytes. Results from this study will document a mechanism by which TNNI3K controls susceptibility to viral myocarditis. This model will enable future studies aimed at developing novel therapies targeting myocarditis progression at the molecular level. This fellowship award will support my development as an exceptional cardiologist-scientist.