Investigating the protective role of stress granules in cardiomyocytes

Ischemia-reperfusion injury occurs when the heart tissue’s demand for oxygen and nutrients fails to be met by blood flow inducing oxidative stress, inflammation, and cell death. The heart is primarily comprised of post- mitotic, non-regenerative cardiomyocytes, so it is necessary for these cells to recover from stress without inducing cell death to minimize the extent of tissue damage and maximize recovery of cardiac function. Other cell types respond to similar stress by assembling stress granules, which are transient, phase separated droplets of mRNA and RNA binding proteins in the cytosol. Stress granules are largely associated with protective function by several proposed mechanisms but can also be maladaptive. Rigorous direct tests of their function are lacking, especially in the context of the heart. Some reports indicate that the myocardium is partially protected from ischemia-reperfusion injury by activation of the Integrated Stress Response signaling pathway, which causes stress-induced stalling of translation, leading the stress granule assembly. However, it is unknown if activation of the integrated stress response leads to stress granule assembly in the heart, and if stress granules may protect or harm the heart during stress. My preliminary data demonstrates that stress granules assemble in several models of cardiomyocytes and in response to several stress types, including ischemia-reperfusion injury. Based on the reported protection of the myocardium by activation of the integrated stress response and my preliminary data, I hypothesize that stress granules assemble in cardiomyocytes after activation of the integrated stress response to promote cell viability. To approach this, in Aim 1, I will determine the dynamics of stress granule assembly and disassembly in cardiomyocytes and their dependence on activation of the integrated stress response. I will induce oxidative stress and simulate ischemia reperfusion injury in primary cardiomyocytes and use live cell and super resolution imaging of stress granule components and monitor markers of integrated stress response activation. I will also use small molecule perturbations of integrated stress response activation and stress granule assembly to test the interdependence of stress granules and the integrated stress response. In Aim 2, I will test if stress granules protect cardiomyocytes from ischemia-reperfusion injury. Using bi-directional modulation of stress granule assembly in primary cardiomyocytes, I will elucidate the specific contributions of stress granules to cardiomyocyte viability. I will also develop a mouse model of cardiac-specific stress granule assembly prevention and model ischemia-reperfusion injury to assess effects of stress granules on extent of cardiac tissue damage and cardiac function. Completion of these aims will be first investigation of stress granule dynamics and function in cardiomyocytes, and will determine if stress granules have a protective, maladaptive, or incidental function in cardiac stress, potentially identifying a novel therapeutic strategy for minimizing cardiomyocyte death and maximizing cardiac function. Project Number: 1F31HL182030-01 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Katey Stone | Institution: UNIVERSITY OF PENNSYLVANIA, PHILADELPHIA, PA | Award Amount: $49,538 | Activity Code: F31 | Study Section: Special Emphasis Panel[ZRG1 F10A-R (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1F31HL18203001