Role of Snf1-related Kinase as a Regulator of Chromatin Modifications and Dna-damage Response in Heart Injury

Introduction: Altered DNA damage response (DDR) can result in phenotypic changes that share features with age-associated pathological conditions, including metabolic and cardiovascular abnormalities. Snf1-related kinase (SNRK) is a serine/threonine kinase that belongs to the AMPK family. Our recent data demonstrates that SNRK expression is upregulated in heart failure (HF) and low energy states and that SNRK improves cardiac mitochondrial efficiency and cell survival. Here, we assessed the hypothesis that in response to stress, SNRK translocates to the nucleus where it modulates nuclear processes to enhance DNA repair and ultimately reduces cardiomyocyte death. Results: We first showed that the nuclear distribution of endogenous SNRK in cardiomyoblast is enhanced under low nutrient and oxidative stress. Next, we performed global phosphoproteomics analysis on cells with overexpression of wild type SNRK and mutant kinase-dead SNRK (D158A). We found significant increase of several phosphopeptides involved in nuclear processes, in particular in the regulation of chromatin remodeling and DDR. SNRK downregulation resulted in an increase in nucleus volume and heterochromatin content, with increased nuclear dysmorphia when subjected to oxidative stress. Despite having lower expression of DDR signal effectors p53 and Mdm2, these cells accumulated higher levels of pH2AX (DDR marker) and displayed higher cellular death after oxidative stress, consistent with increased DNA damage. Etoposide treatment in SNRK knockdown cells failed to induce p53 levels despite pH2AX accumulation. Additionally, pharmacological stabilization of p53 protein through nutlin-3A treatment did not increase p53 in SNRK knockdown cells. These findings suggest that SNRK regulates p53 expression, thereby acting as a new modulator of DDR. Conclusions: Our results demonstrate increased nuclear localization of SNRK under stress conditions, and that SNRK regulates phosphorylation of nuclear proteins involved in chromatin remodelling and DDR. Thus, SNRK may induce its pro-survival cardiac functions through regulation of chromatin architecture and enhancing DDR. Those novel findings can contribute to development of new therapies against HF.