288-OR: Inflammation-Induced Repression of Insulin Production by Targeting Its mRNA to Stress Granules via ADP-Ribosylation Machinery

ADP-ribosylation has been shown to contribute to the development of Type 1 diabetes (T1D); however, the mechanism through which each component of the ADP ribosylation machinery contributes to the disease is poorly understood. Here, we aimed to investigate the contribution of specific ADP-ribosyltransferases in the development of T1D. We conducted comprehensive bioinformatics analyses on our previously published RNA-Seq, ATAC-Seq, H3K27ac-Seq, and proteomic data, followed by qPCR to investigate the regulation of ADP-ribosyltransferases in islets and β cells. We found that PARP12 expression was induced by both cytokines and omega-3 fatty acids, which are inducers and reducers of insulitis, respectively. RNAi depletion of PARP12, followed by proteomics analysis, revealed that a variety of stress granule proteins are regulated by PARP12. We performed fluorescence in situ hybridization, ADP-targeted RNA pulldown and pulse-chase proteomics to demonstrate that PARP12 ADP-ribosylates Insulin2 mRNA, targeting it to stress granules and blocking its translation. Stress granules are a characteristic feature of the integrative stress response and unfolded protein response in T1D. Here, we showed that PARP12 directs insulin mRNA to stress granules, impeding translation in response to cytokines. This may have implications for insulitis and T1D, such that an abrupt inhibition of insulin translation may amplify the stress and immune responses. These insights also provide avenues for therapeutic strategies aiming to improve insulin production.