Methylglyoxal in cells elicits a negative feedback loop entailing transglutaminase 2 and glyoxalase 1.
Glyoxalase 1 (GlxI) is the key enzyme that converts the highly reactive α-oxo-aldehydes into the corresponding α-hydroxy acids using l-glutathione as a cofactor. In our preliminary data, GlxI was identified as a substrate of transglutaminase 2 (TG2), a ubiquitous enzyme with multiple functions. According to the catalytic properties of TG2, protein cross-linking, polyamine conjugation, and/or deamidation are potential post-translational modifications. In this article, we have demonstrated that TG2 catalyzes either polyamine conjugation or deamidation to GlxI depending on the presence of polyamines or not. Deamidation leads to activation of GlxI while polyamine conjugation results in activation of GlxI as well as stabilization of GlxI against denaturation treatment. In cultured HeLa cells, methylglyoxal challenge causes increase in intracellular levels of reactive oxygen species (ROS) and calcium leading to TG2 activation and subsequent transamidation and activation of GlxI. The inhibition of TG2 significantly weakens the cell resistance to the methylglyoxal challenge. Thus, GlxI is a novel substrate of TG2 and is activated by TG2 in vitro and in cellulo. Exposure to methylglyoxal elicits a negative feedback loop entailing ROS, calcium, TG2 and GlxI, thus leading to attenuation of the increase in the methylglyoxal level. The results imply that cancer cells highly express TG2 or GlxI can endure the oxidative stress derived from higher glycolytic flux and may gain extra growth advantage from the aerobic glycolysis.
Graduate Institute of Biochemical Sciences, Technology Commons, Center for Systems Biology, National Taiwan University, No.1, Section 4, Roosevelt Road, Taipei 106, Taiwan ; Technology Commons, Center for Systems Biology, National Taiwan University, No.1, Section 4, Roosevelt Road, Taipei 106, Taiwan.
Der-Yen
DY
Lee
Graduate Institute of Biochemical Sciences, Technology Commons, Center for Systems Biology, National Taiwan University, No.1, Section 4, Roosevelt Road, Taipei 106, Taiwan ; Center for Systems Biology, National Taiwan University, No.1, Section 4, Roosevelt Road, Taipei 106, Taiwan.
Geen-Dong
GD
Chang
D002118:Calcium / Q000378:metabolism; D025461:Feedback, Physiological / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007791:Lactoylglutathione Lyase / Q000378:metabolism*; D010658:Phenylglyoxal / Q000378:metabolism*; D011073:Polyamines / Q000378:metabolism; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D017382:Reactive Oxygen Species / Q000378:metabolism; D011503:Transglutaminases / Q000378:metabolism*
D011073:Polyamines; D017382:Reactive Oxygen Species; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins; C000597196:GLO1 protein, human; D007791:Lactoylglutathione Lyase; D010658:Phenylglyoxal; D002118:Calcium
Glyoxalase 1; Methylglyoxal; Oxidative stress; Transglutaminase 2