Epac1 regulates cellular SUMOylation by promoting the formation of SUMO-activating nuclear condensates

Protein SUMOylation plays an essential role in maintaining cellular homeostasis when cells are under stress. However, precisely how SUMOylation is regulated, and a molecular mechanism linking cellular stress to SUMOylation remains elusive. Herein, we report that cAMP, a major stress-response second messenger, acts through Epac1 as a regulator of cellular SUMOylation. The Epac1-associated proteome is highly enriched with components of the SUMOylation pathway. Activation of Epac1 by intracellular cAMP triggers phase separation and the formation of nuclear condensates containing Epac1 and general components of the SUMOylation machinery to promote cellular SUMOylation. Furthermore, genetic knockout of Epac1 obliterates oxidized low-density lipoprotein induced cellular SUMOylation in macrophages, leading to suppression of foam cell formation. These results provide a direct nexus connecting two major cellular stress responses to define a molecular mechanism in which cAMP regulates the dynamics of cellular condensates to modulate protein SUMOylation.

Tissue-specific inhibition of protein sumoylation uncovers diverse SUMO functions during C. elegans vulval development

The sumoylation (SUMO) pathway is involved in a variety of processes during C. elegans development, such as gonadal and vulval fate specification, cell cycle progression and maintenance of chromosome structure. The ubiquitous expression of the sumoylation machinery and its involvement in many essential processes has made it difficult to dissect the tissue-specific roles of protein sumoylation and identify the specific target proteins. To overcome these challenges, we have established tools to block protein sumoylation and degrade sumoylated target proteins in a tissue-specific and temporally controlled manner. We employed the auxin-inducible protein degradation system (AID) to down-regulate AID-tagged SUMO E3 ligase GEI-17 or the SUMO ortholog SMO-1, either in the vulval precursor cells (VPCs) or in the gonadal anchor cell (AC). Tissue-specific inhibition of GEI-17 and SMO-1 revealed diverse roles of the SUMO pathway during vulval development, such as AC positioning, basement membrane (BM) breaching, vulval cell fate specification and epithelial morphogenesis. Inhibition of sumoylation in the VPCs resulted in an abnormal shape of the vulval toroids and ectopic cell fusions. Sumoylation of the ETS transcription factor LIN-1 at K169 mediates a subset of these SUMO functions, especially the proper contraction of the ventral vulA toroids. Thus, the SUMO pathway plays diverse roles throughout vulval development.

Upregulation of Small Ubiquitin-Like Modifier 2 and Protein SUMOylation as a Cardioprotective Mechanism Against Myocardial Ischemia-Reperfusion Injury

Background: Small ubiquitin-like modifier (SUMO) proteins modify proteins through SUMOylation as an essential protein post-translational modification (PTM) for regulating redox status, inflammation, and cardiac fibrosis in myocardial infarction. This study aimed to investigate whether natural product puerarin could alleviate myocardial ischemia/reperfusion injury (MI-RI) by targeting protein SUMOylation.Methods: Mouse MI-RI model was induced by ligating the left anterior descending (LAD) coronary artery and subsequently treated with puerarin at the dose of 100 mg/kg. Rat cardiomyocyte H9c2 cells were challenged by hypoxia/reoxygenation and treated with puerarin at concentrations of 10, 20, and 40 μM. The infarction area of mouse hearts was assessed by 2% TTC staining. Cell damage was analyzed for the release of lactate dehydrogenase (LDH) in serum and cell culture medium. Western blot technique was employed to detect the expression of SUMO2, phospho-ERK, pro-inflammatory biomarker COX2, fibrosis index galectin-3, apoptosis-related protein cleaved PARP-1. The activation of the estrogen receptor (ER) pathway was assayed by the dual-luciferase reporter system.Results: The present study validated that puerarin effectively reduced myocardial infarct size and LDH release in the mouse MI-RI model. In the cell culture system, puerarin effectively decreased the release of LDH and the protein level of COX2, galectin-3, and cleaved PARP-1. Mechanistic studies revealed that puerarin increased the expression of SUMO2, SUMOylation of proteins and the activation of ER/ERK pathway in cardiomyocytes. ER, ERK and SUMO2 inhibitors attenuated the cardioprotective effects of puerarin.Conclusion: Puerarin may alleviate myocardial injury by promoting protein SUMOylation through ER/ERK/SUMO2-dependent mechanism.

Acute ethanol stress induces sumoylation of conserved chromatin structural proteins in Saccharomyces cerevisiae

Stress is a ubiquitous part of life that disrupts cellular function and, if unresolved, can irreparably damage essential biomolecules and organelles. All organisms can experience stress in the form of unfavorable environmental conditions including exposure to extreme temperatures, hypoxia, reactive oxygen species, alcohol, or shifts in osmolarity. To survive, organisms must sense these changes then react and adapt. One highly conserved adaptive response to stress is through protein sumoylation, which is a post-translational modification by the small ubiquitin-like modifier (SUMO) protein. In this study, we examine the effects of acute ethanol stress on protein sumoylation in the budding yeast Saccharomyces cerevisiae. Although ethanol induces protein sumoylation, the targets and roles of sumoylation are largely unknown. Here, we found that cells exhibit a transient sumoylation response after exposure of cells to ≤ 7.5% volume/volume ethanol. The response peaks at 15 minutes and resolves by 60 minutes, indicating that cells have an adaptive response to low concentrations of ethanol. By contrast, the sumoylation response becomes chronic at 10% ethanol stress with no resolution by 60 minutes. To identify key targets of ethanol-induced sumoylation, we performed mass spectrometry analyses and identified 18 proteins with increased sumoylation after acute ethanol exposure, with 15 identified as known chromatin-associated proteins. Two of these proteins are the chromatin structural proteins Smc5 and Smc6, which are sumoylated by the activity of the SUMO ligase Mms21. Ethanol-induced Smc5/6 sumoylation occurs during G1 and G2M phases of the cell cycle but is abrogated during S phase despite the fact that other proteins are sumoylated during this phase. Acute ethanol exposure leads to formation of Rad52 foci indicating DNA damage similar to that observed with the addition of methyl methanesulfonate (MMS), which is an alkylating agent that damages DNA. Whereas MMS exposure induces the intra-S phase DNA damage checkpoint as observed by Rad53 phosphorylation, ethanol exposure does not induce the intra-S phase checkpoint and prevents Rad53 phosphorylation when added with MMS. From these results, we propose that ethanol induces a structural change in chromatin, possibly through DNA damage, and this causes sumoylation of conserved chromatin-associated proteins, including Smc5 and Smc6.