PSUN83 Exploring the Role of PARP1-mediated ADP-ribosylation in Diet-induced Obesity

Abstract

Abstract Poly(ADP-ribosyl)ation (PARylation) is a posttranslational modification that regulates various cellular processes, including the differentiation of preadipocytes. PARylation involves the covalent attachment of a chain of ADP-ribose units to proteins by poly(ADP-ribose) polymerases (PARPs), mainly PARP1. We previously found that PARP1 activity decreases precipitously upon differentiation of preadipocytes, including 3T3-L1 cells, a preadipocyte cell line. Upon knockout or knockdown of Parp1, or chemical inhibition of PARP1, adipogenesis is dramatically increased. We have previously used a mouse lineage tracing model to show that knockout of Parp1 in preadipocytes promotes adipogenesis by expanding the pool of precursors, ultimately leading to accumulation of fat. PARP1 controls adipogenesis, in part, by PARylating two sites (E135A and E139A) in the regulatory domain of C/EBPβ, a proadipogenic transcription factor. Mutation of these sites enhances chromatin binding and transcriptional activity of C/EBPβ, as well as promotes a proadipogenic gene expression program and differentiation, in 3T3-L1 cells. However, we still do not know the role of PARP1-mediated site-specific PARylation in diet-induced obesity. We recently created a set of PAR-Trackers (PAR-Ts) that can detect changes in PAR levels during physiological processes in cells. We used PAR-T NanoLuc to observe dynamic changes in PAR levels during the differentiation of 3T3-L1 cells. We are now modifying the system to investigate PAR levels in the tissues of live animals. To investigate the physiological impact of loss of C/EBPβ PARylation in adipocytes, we have generated a knock-in mouse model for inducible tissue-specific expression of a C/EBPβ PARylation site mutant (Cebpb/E135A/E139A or C/EBPβ PAR mut). Using this model, we will investigate the impact of site-specific PARylation of C/EBPβ in mice fed a high fat diet. With these studies, we hope to reveal the specific roles of PARP1-mediated ADP-ribosylation in diet-induced obesity. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.