title: Regulation of Glo1 activity via tyrosine phosphorylation and the impact of methylglyoxal on cellular metabolism
creator: Garcia Cortizo, Fabiola Helena
subject: 000
subject: 000 Generalities, Science
subject: 500
subject: 500 Natural sciences and mathematics
subject: 570
subject: 570 Life sciences
subject: 610
subject: 610 Medical sciences Medicine
description: Methylglyoxal (MG) is a byproduct of glucose metabolism that displays high reactivity with many biological macromolecules, in particular proteins, giving rise to adducts known as advanced glycation end products (AGEs). Increased MG and AGEs are commonly observed in diabetes and, among diabetic patients, those affected by diabetic complications show the highest levels of MG and MG-adducts, raising the possibility that, besides hyperglycemia, a buildup of MG could play a direct causative role in the development of diabetes and its complications. Indeed, findings in Drosophila melanogaster and Danio rerio showed that disruption of glyoxalase I (Glo1), the rate limiting enzyme for MG detoxification, causes features of type 2 diabetes such as insulin resistance, hyperglycemia and obesity . Understanding how the activity of Glo1 is regulated and how exactly MG affects cellular metabolism is thus of the utmost importance to determine how MG detoxification goes awry in diabetes and how the ensuing MG accumulation contributes to the metabolic alterations typical of this disease. To this end, I worked on two complementary lines of investigation aimed at (1) assessing the role of post-translational modifications in the regulation of Glo1 activity and (2) studying which metabolic pathways are affected by high levels of MG in vitro and in mouse models of diabetes. My results show that phosphorylation of Glo1 at Y136 by multiple kinases, including those belonging to the Src family, promotes Glo1 activity. Consistent with impaired detoxification of MG in the pathogenesis of diabetes, I observed that phosphorylation at this residue and overall Glo1 activity are decreased when cells are cultured in high glucose (25 mM), as well as in diabetic mouse models. To study the metabolic alterations caused by MG, I generated cell lines knockout for Glo1 or acutely treated control cells with MG. Interestingly, chronic or acute exposure to MG was sufficient to increase glucose uptake, lactate production and impair fatty acid -oxidation. I found that MG inhibits the activity of pyruvate dehydrogenase (PDH), probably accounting for the increased glucose uptake and lactate production. The effect of MG on PDH activity is not mediated by altered phosphorylation of PDH, a well-established mode of regulating PDH activity, but rather by direct interaction of MG with the pyruvate dehydrogenase α (PDHA) subunit of PDH, together with formation of a DTT-sensitive modification on the PDH subunit dihydrolipoamide acetyltransferase (DLAT). I also observed decreased PDH activity in mouse models of diabetes, further strengthening the link between accumulation of MG and impaired PDH activity. Overall, my data point to a deleterious positive feedback loop whereby hyperglycemia leads to reduced Y136 Glo1 phosphorylation and activity, contributing to elevated MG levels,inhibition of PDH and changes of cellular metabolism to promote hyperglycemia and thus further production of MG.
date: 2024
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/33519/1/Dissertation_Fabiola%20Garcia%20-PDFA-1a.pdf
identifier: DOI:10.11588/heidok.00033519
identifier: urn:nbn:de:bsz:16-heidok-335199
identifier:   Garcia Cortizo, Fabiola Helena  (2024) Regulation of Glo1 activity via tyrosine phosphorylation and the impact of methylglyoxal on cellular metabolism.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/33519/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng