Cardiomyocyte (CM) death has been identified in many clinically important cardiac conditions including heart failure and ischemic injury. Therefore, understanding the signaling pathways that control CM survival may have significant clinical implications. During the first project period, we learned that while acute activation of the serine-threonine kinase, Akt, is cardioprotective, chronic activation of Akt has deleterious effects associated with feedback inhibition of upstream IRS-1/PI 3-kinase (PI3K) signaling. These studies demonstrated the importance of additional PI3K-dependent but Akt-independent cardioprotective effectors. Integrin-linked kinase (ILK), a PI3K-dependent serine-threonine kinase, is one such candidate effector. Interestingly, ILK binds the cytoplasmic tail of p-integrins, raising the possibility that it links biomechanical stress to traditional kinase cascades. Our preliminary data suggest ILK is dynamically regulated in the heart and an important determinant of cardiomyocyte survival. The overall goals of the current proposal are to define the role of ILK in the heart at baseline, and in response to biomechanical and ischemic stress. This proposal is based on three hypotheses: 1) that ILK provides a PI3K-dependent, anti-apoptotic signal in cardiomyocytes (CM), 2) that common signaling mechanisms including ILK control CM survival after both biomechanical and ischemic stress, and that 3) ILK works through both Akt-dependent and -independent downstream pathways. To test these hypotheses, we will utilize mice with conditional, cardiac-specific inactivation of ILK, in combination with somatic gene transfer in models of CM death, ischemic injury, and biomechanical stress.
In Specific Aim 1, we will test, the hypothesis that ILK inhibits CM apoptosis in a PI3K-dependent manner, and define the downstream mechanisms responsible.
In Specific Aim 2, we will generate and characterize cardiac-specific ILK knockout mice.
In Specific Aim 3, we will test the hypothesis that inactivation of ILK in the heart will increase CM apoptosis after aortic banding thereby accelerating the development of heart failure.
In Specific Aim 4, we will test the hypothesis that loss of ILK signaling will increase acute ischemic injury through increased CM apoptosis. Heart failure is a growing cause of morbidity and mortality in the United States. Loss of CMs is cumulative and this likely contributes to the increasing prevalence of heart failure in our aging population. Understanding the role of specific pathways in CM survival may provide novel therapeutic approaches to preventing CM death, thereby preserving cardiac function and reducing the burden of heart failure.
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