Premium
Role of sumoylated SOD2 in alcoholic liver disease and liver cancer
Author(s) -
Spissu Ylenia,
Cossu Carla,
Floris Andrea,
Tomasi Maria lauda
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.602.10
Subject(s) - sumo protein , sod2 , alcoholic liver disease , chemistry , superoxide dismutase , reactive oxygen species , ubiquitin , biochemistry , cancer research , microbiology and biotechnology , biology , enzyme , gene , medicine , cirrhosis
Background Manganese superoxide dismutase (MnSOD, SOD2) is the most important mitochondrial enzyme involved in the defense against reactive oxygen species (ROS) and it is well demonstrated to be a key protein in hepatocellular carcinoma (HCC) progression and in other several cancers development as colon adenocarcinoma. Alcohol abuse is one of the main causes of alcoholic liver disease (ALD) and represents the major risk factor of HCC development. Alcohol abuse generates high level of ROS as a consequence of increased enzymatic activity during the ethanol metabolism. SOD2 plays a crucial role in the build‐up of tolerance to ethanol catalyzing the dismutation of O 2 •− in H 2 O 2 . SUMOylation is a post‐translational modification that regulates a wide range of cellular processes involving the covalent attachment of a member of the SUMO (small ubiquitin‐like modifier; SUMO‐1, SUMO‐2 and SUMO‐3) family of proteins to lysine residues in specific target proteins via an enzymatic cascade. Increased ROS production enhances the global protein sumoylation profile. Our aim was to examine whether sumoylation could regulate SOD2 function in ALD and in HCC elucidating the molecular mechanism(s). Methods Chromatography by SUMO binding columns was performed to purify sumoylated proteins form total livers of Binge ethanol fed mouse model. Total liver, primary mouse hepatocytes, AML12, HepG2 cells (HCC cell line) and Huh7 cells were used to perform in vitro experiments. Protein and mRNA levels were measured using Western Blotting and RT‐PCR, respectively. SOD2 activity was measured by tetrazolium salt commercial kit and by native gel modified method. Results Using sumoylated purified‐proteins, we found that SOD2 is sumoylated in Binge ethanol fed mouse liver. In vitro experiments showed a different trend: ethanol treatment lowers SOD2 protein, mRNA levels and activity in total liver and primary mouse hepatocytes. In HepG2 cells SOD2 activity increases after ethanol treatment. Interestingly, SUMO‐3 silencing prevents ethanol stress‐damage increasing the SOD2 enzymatic activity raising protein stability in primary hepatocytes. In contrast, knockdown of SUMO‐1 lowers SOD2 enzymatic activity and protein level indicating that SUMO‐1 may plays an important role in the oxidative stress prevention. Conclusion We report for the first time that ethanol increases sumoylation of SOD2. Furthermore, in AML12 we demonstrated that sumoylation of SOD2 may control ethanol‐induced ROS induction. In addition, SUMO‐1 and SUMO‐3 control SOD2 protein stability and enzymatic activity in mouse hepatocytes and HepG2 cells. This new finding opens a new area of investigation examining the importance of SOD2 sumoylation in ALD and HCC, maybe suggesting SOD2 as potential therapeutic target to protect against induced‐oxidative stress liver damage. Support or Funding Information Supported by NIH grant 5 K01 AA022372‐04 (Maria Lauda Tomasi)