Oral Presentation 25th Annual Lorne Proteomics Symposium 2020

HNF4A sumoylation is regulated by fasting.   (#28)

Dylan J Harney 1 , Luke Hatchwell 1 , Michelle Cielesh 1 , Kieren Young 1 , Yen Chin C Koay 2 , John F O'Sullivan 2 3 , Mark Larance 1
  1. School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia
  2. Heart Research Institute, University of Sydney, Sydney, NSW, Australia
  3. Department of Cardiology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia

Intermittent fasting (IF) increases lifespan and decreases metabolic disease phenotypes, but the mechanisms mediating these effects are not fully characterized. Our laboratory has previously identified that hepatic nuclear factor 4A (HNF4A) has reduced activity during IF using unbiased liver proteomics and gene set enrichment analysis. Alongside the change in HNF4A activity, EODF caused comprehensive induction of de novo lipogenesis (DNL) and cholesterol biosynthesis pathways. HNF4A is known to regulate cholesterol metabolism, VLDL-particle formation and bile acid biosynthetic pathways that are related to some intermittent fasting phenotypes. Recently, a study identified SUMO2/3 modification of HNF4A at K365 which led to increased transcriptional activity of HNF4A. In this study, we have demonstrated that HNF4A sumoylation is greatly decreased by acute fasting, but not by intermittent fasting in mouse liver extracts. Furthermore, we demonstrated that SUMO-HNF4A had altered sub-cellular localisation compared to unmodified HNF4A, with the sumoylated form moving from the nucleus to the cytosol. Together, this suggests sumoylation of HNF4a may provide a regulatory mechanism by which HNF4a contributes to the intermittent fasting phenotype. We have identified two other transcription factors, peroxisome proliferation factor a (PPARa) and sterol regulatory element binding protein 1c (SREBP1c), which were also significantly regulated during EODF. Both these proteins have known inhibitory interactions with HNF4A and we will test whether these interactions help to mediate HNF4A inhibition through sumoylation. We will also examine whether sumoylation of HNF4A is necessary and sufficient for HNF4A nuclear-cytoplasmic trafficking.