1. Simulation of Ca-Calmodulin Dependent Protein Kinase II (CaMKII) on Rabbit Ventricular Ion Currents and Action Potentials E Grandi*, JL Puglisi*, S Wagner #, LS Maier #, S Severi § and DM Bers* * Department of Physiology, Loyola University Chicago, IL, USA # Department of Cardiology & Pneumology, Georg-August-University Göttingen, Germany § Biomedical Engineering Laboratory, DEIS, University of Bologna, Italy Stefano Morotti smorotti@gmail.com 31 Luglio 2009 C 3 MIG

2. CaMKII Ca 2+ /calmodulin dependent protein kinase II serine/threonine-specific protein kinase primarily regulated by the Ca 2+ /calmodulin complex Calmodulin (CaM) CALcium MODULated proteIN C 3 MIG

3. CaMKII Targets in the Heart Kohlhaas et al., 2006 Wagner et al., 2006b Wagner et al., 2006a cytosolic δ isoform C 3 MIG Ryanodine Receptors -> CICR (Calcium Induced - Calcium Relaese) Phospholamban -> SERCA (Sarco/Endoplasmic Reticulum Ca 2+ -ATPase)

4. Ion Currents and Action Potential Sodium (inward) current (I Na ) L-type Calcium (inward) current (I CaL ) Potassium (outward) transient current (I to1 ) C 3 MIG

5. Na + Channelopaties Inherited Diseases Long QT Syndrome (LQT3) Brugada Syndrome Conduction Disease Overlap Syndromes (1795insD in SCN5A) Acquired Diseases Drug-indiced LQTS Ischemia Heart Failure (over-expression of CaMKII) C 3 MIG

6. Na + Channelopaties shifted availability increased intermediate inactivation slowed recovery persistent current Loss of function faster heart rates -> Brugada Gain of function slower heart rates -> LQT I Na C 3 MIG

7. 5. Arrhythmia 1. Functional Analysis of I Na Mathematical Modeling 2. Markovian model of current 3. AP model Rabbit Ventricular AP Model Modified from Shannon et al., 2004 Na + channel model Modified from Clancy et al., 2002 4. Cardiac AP Matlab and Simulink were used for all numerical computations C 3 MIG

8. I Na Simulation Steady-state inactivation Steady-state activation Intermediate inactivation Recovery from inactivation C 3 MIG Experiments from Wagner et al., 2006 - Rabbit myocytes overexpressing CaMKII

9. I Na Simulation Experimental Simulated Experiments from Wagner et al., 2006 - Rabbit myocytes overexpressing CaMKII Fast inactivation Late current C 3 MIG

10. CaMKII-dependent I Na alterations on AP Simulated C 3 MIG

11. CaMKII-dependent I Na alterations on [Na + ] i ExperimentalSimulated Experiments from Wagner et al., 2006 - Rabbit myocytes overexpressing CaMKII C 3 MIG

12. Sim Exp I CaL Simulation Experiments from Kohlhaas et al., 2006 - Rabbit myocytes overexpressing CaMKII C 3 MIG

13. I to Simulation ExperimentalSimulated I to,total I to,slow I to,fast Experiments from Wagner et al., 2006 - Rabbit myocytes overexpressing CaMKII C 3 MIG Recovery from inactivation

14. CaMKII-dependent I Na, I CaL and I to alterations on AP Simulated Experiments from Wagner et al., 2006 - Rabbit myocytes overexpressing CaMKII [1 Hz] ExpSim 37ºC, physiological conditions [1 Hz] C 3 MIG

15. APD Sensitivity to Late I Na C 3 MIG

16. I to Heterogeneity / Down-regulation Simulated HF C 3 MIG

17. Conclusions  There are several potential pathways by which CaMKII may be arrhythmogenic: CaMKII effects on I Na, I CaL and I to combined with transmural heterogeneity of I to and I to down-regulation in HF may accentuate dispersion of repolarization and predispose to reentrant arrhythmias.  The in silico analysis provides a useful framework to consider pathways by which CaMKII may contribute to arrhythmogenesis and highlight novel potential therapeutic targets. C 3 MIG

18. Grazie per l’attenzione!