CaMKIIδ, Stabilized by RNA N6-Methyladenosine Reader IGF2BP2, Boosts Coxsackievirus B3-Induced Myocardial Inflammation via Interacting with TIRAP

Calcium/calmodulin-dependent protein kinase II (CaMKII) has been demonstrated to be aberrantly activated in viral myocarditis (VMC), but the role of its subtype CaMKII delta in VMC remains unclear. VMC mice and cardiomyocytes models were induced by Coxsackievirus B3 (CVB3) treatment. Mice that underwent sham surgery and saline-treated cardiomyocytes served as controls. Body weight, survival, left ventricular ejection fraction (LVEF), and fractional shortening (LVFS) were measured, and HE staining was performed to evaluate heart function in VMC mice model and sham control. Inflammation factors in serum or cell supernatant were detected by ELISA. Expressions of CaMKII delta, Toll/interleukin-1 receptor domain containing adaptor protein (TIRAP), insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2), nuclear factor NF-kappaB (NF-kappa B) signals, and inflammation factors were examined by quantitative real time polymerase chain reaction (qRT-PCR) or western blot. CCK-8, EdU, and flow cytometry were used to evaluate cell behaviors. Co-immunoprecipitation (Co-IP), RNA immunoprecipitation (RIP), and RNA pull-down were utilized to validate molecule interaction. Methylated RNA immunoprecipitation (MeRIP) was performed to measure N6-methyladenosine (m6A) level of specific molecule. CaMKII delta was upregulated in VMC mice and CVB3-treated primary cardiomyocytes, of which knockdown improved cell viability, proliferation, and suppressed cell apoptosis in vitro, thereby alleviating myocarditis in vivo. The stability of CaMKII delta was attributed to the presence of IGF2BP2 through m6A modification. Loss of CaMKII delta repressed NF-kappa B pathway via negatively and directly regulating TIRAP to be involved in inflammatory damage. CaMKII delta, stabilized by m6A reader IGF2BP2, modulated NF-kappa B pathway via interacting with TIRAP to alter cell viability, proliferation, and apoptosis, thereby affecting VMC outcome.