Role of Arginine Methylation in Alcohol Pathogenesis

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PROJECT SUMMARY Alcoholic liver disease is a major clinical problem with unknown susceptibility factors. It displays marked variability in disease phenotype. Only about 15% of heavy drinkers develop disease while 85% appear to be protected, suggesting that there are mechanisms of adaptation to alcohol in majority of individuals. Arginine methylation is a common posttranslational modification (PTM) that regulates hundreds of proteins directly and many more via histone arginine methylation (epigenetic regulation). Protein arginine methyltransferase 1 (PRMT1) is the main enzyme responsible for about 90% of cellular arginine methylation. JMJD6 is the only known arginine demethylase Preliminary data indicate that patients with alcoholic liver disease have extremely low levels of PRMT1 protein compared other patient groups suggesting that PRMT1 might be involved in disease progression of these patients. Using hepatocyte specific knockout mouse model, we found that PRMT1 knockout in alcohol fed mice results in dramatic increase in hepatocyte death, steatosis, inflammation and fibrosis; and increased serum ALT levels suggesting that PRMT1 is protective against alcohol induced liver injury. This function of PRMT1 is specific to alcohol, and preliminary data suggests that it is mediated by alcohol induced dephosphorylation of PRMT1. We thus hypothesize that alcohol induced changes in PRMT1 activity are necessary for liver adaptation to alcohol. This project will specifically examine this hypothesis with the following specific aims: Specific Aim 1. To study the mechanism of PRMT1 mediated alcohol sensitivity. We will study non- histone targets and promoter arginine methylation and define the major pathways. Specific Aim 2. To define the role of PRMT1 phosphorylation in protection from alcohol induced liver injury. We hypothesize that dephosphorylated form is particularly protective from alcohol induced injury. Inhibiting the upstream kinase in this case is a promising future therapeutic strategy. Specific Aim 3. To define the role of arginine demethylation enzyme JMJD6 in susceptibility to alcohol induced liver injury. JMJD6 is another promising target. JMJD6 inhibition reverts the phenotype of PRMT1 knockout mice. We will study the mechanism of this regulation. Results of the proposed project will provide novel insights into the nature of the arginine methylation defects in alcoholic liver disease. It should determine whether PRMT1 and JMJD6 are essential regulators of the hepatocyte adaptation to alcohol and identify the primary targets. The project will set the stage for further studies to understand the alcohol susceptibility in patients and explore the potential targets for therapy. The ultimate goal is to use this information to develop clinical strategies to treat alcohol associated liver disease.