Grant: CIHR/Regional Partnership Program/Operating Grants

All cardiovascular cell types are capable of producing reactive oxygen species (ROS) and evidence suggests that these toxic molecules play an important role in the development and progression of heart disease. However, the precise mechanism of ROS action remains unknown. It has been shown that matrix metalloproteinase (MMP) activity is regulated by ROS. In 1997 we discovered a novel function of MMP-2. This finding suggests that MMP-2 may have considerable implications in understanding the mechanisms of cardiovascular diseases triggered by oxidative stress. We have shown that MMP-2 contributes to ischemia/reperfusion (I/R) injury. Later, we have shown that troponin I is degraded by MMP-2 in I/R injury. When I used a pharmaco-proteomics approach to analyze protein changes in I/R hearts we discovered that myosin light chain 1 (MLC1) is another target for MMP-2. Activity of MMPs is strictly regulated at multiple levels. What is new, and never investigated in relation to oxidative stress, is the regulation of proteinase activity by post-translational modifications (PTM) that renders previously protolysis-resistant proteins as substrates for these enzymes. I hypothesize that oxidative stress triggers specific PTMs of contractile proteins. Following these changes the proteins become substrates for MMPs. Oxidative stress also increases activity of MMPs; the increased activity contributes to the reduction of myocardial contractile function by degradation of contractile proteins. Thus oxidative stress can have a double effect on the regulation of intracellular action of MMP-2: first, to sensitize MLC1 to be a substrate for MMP-2 and second, to increase activity of the enzyme. I want to determine the PTMs of MLC1 triggered by oxidative stress and their role in degradation of MLC1 by MMP-2 as well as their effect on the mechanical function of the heart and to determine the mechanism by which MMP-2 activity increases in hearts subjected to oxidative stress.