Grant: Project Grant

The muscle protein titin is the largest protein in our body, and plays important roles in regulating the passive mechanical properties of muscles. Cardiac titin is critical to heart health and heart diseases. Cardiac titin determines the size of the stroke volume and is a key factor of heart diastolic function. The mechanical properties of cardiac titin are highly regulated. Dysregulation of titin elasticity is an important contributor to various forms of heart diseases, such as cardiomyopathy. Oxidative stress, which arises when the balance between reactive oxygen species accumulation and anti-oxidant defense system is lost, is an important factor regulating titin elasticity and the passive stiffness of muscle. Due to its large size and high content of cysteine, titin is a prime target for oxidative stress. Cysteine can be oxidized into different oxidation products. Experimental evidences have shown that oxidative stress can alter titin elasticity and the stiffness of heart muscles. However, the detailed molecular mechanism for this oxidative regulation is largely unknow. Moreover, current experimental studies only investigate the oxidative effect that occur on the same titin molecule. However, in the muscle sarcomere, six titin molecules are organized in a parallel fashion, making it possible for the oxidation of cysteine to occur between two parallel titin molecules. Hence, in order to understand how oxidative stress modulates the mechanical properties of muscle, it is critical to investigate the effects of intermolecular oxidation on titin elasticity. We propose to use a novel combination of two-molecule atomic force microscopy, protein engineering, and muscle fiber mechanical testing to examine the mechanical effect of oxidative stress on cardiac titin as well as on muscle fibrils.