Troponin I phosphorylation as a novel novel cardiac inotrope

PROJECT SUMMARY In heart disease, the amount of blood pumped by the heart is not sufficient to supply the metabolic demands of the body. Current positive inotropes (dobutamine, milrinone) increase cardiac contraction by elevating the intracellular calcium contractile signal, however trials have demonstrated this elevated intracellular calcium also causes detrimental arrhythmia, impaired relaxation, and increased mortality rendering this inotropic approach unsuccessful as a long-term therapy. There are currently no approved therapies that directly increase the insufficient function of the heart in disease without long-term detrimental effects. The myofilament protein troponin I (TnI) is critical to relay the calcium activating signal into muscle contraction and is therefore a key regulator of in vivo cardiac muscle function. We have shown the site-specific phosphorylation of TnI increases cardiac muscle contraction without elevating intracellular calcium. Our preliminary data now demonstrates this TnI phosphorylation increases in vivo cardiac function in both normal and diseased hearts without long-term detrimental effects. This proposal will establish the novel effects and mechanism of this TnI site-specific phosphorylation to improve in vivo cardiac function in the normal and diseased mouse heart. We will further establish the effects and safety of this site-specific TnI phosphorylation on human cardiac tissue towards establishing this phosphorylation as a future therapeutic approach in human heart disease.