The activity of glyoxylase 1 is regulated by glucose-responsive phosphorylation on Tyr136

Abstract

Objective Methylglyoxal (MG) is a highly reactive α-oxoaldehyde that glycates proteins. MG has been linked to the development of diabetic complications: MG is the major precursor of advanced glycation end products (AGEs), a risk marker for diabetic complications in humans. Furthermore, flies and fish with elevated MG develop insulin resistance, obesity, and hyperglycemia. MG is detoxified in large part through the glyoxalase system, whose rate-limiting enzyme is glyoxalase I (Glo1). Hence, we aimed to study how Glo1 activity is regulated. Methods We studied the regulation and effect of post-translational modifications of Glo1 in tissue culture and in mouse models of diabetes. Results We show that Glo1 activity is promoted by phosphorylation on Tyrosine 136 via multiple kinases. We find that Glo1 Y136 phosphorylation responds in a bimodal fashion to glucose levels, increasing in cell culture from 0 mM to 5 mM (physiological) glucose, and then decreasing at higher glucose concentrations, both in cell culture and in mouse models of hyperglycemia. Conclusions These data, together with published findings that elevated MG leads to hyperglycemia, suggest the existence of a deleterious positive feedback loop whereby hyperglycemia leads to reduced Glo1 activity, contributing to elevated MG levels, which in turn promote hyperglycemia. Hence, perturbations elevating either glucose or MG have the potential to start an auto-amplifying feedback loop contributing to diabetic complications.

Accumulation of Non-Pathological Liver Fat Is Associated with the Loss of Glyoxalase I Activity in Humans

“…The loss of Glo1 activity was not associated with a change in protein expression, suggesting that the decline in activity may be due to detrimental post-translational modifications (PTMs), as previously reported [38][39][40][41][42][43]. Dityrosine (DT) was found to be the only PTM significantly positively correlated with BMI, indicating enhanced oxidative stress.…”

Angiotensin II reduces glyoxalase 1 activity and expression in vascular smooth muscle cells: Implications for diabetic vascular complications

“…Inhibition of ERK1/2 MAPK by PD98059 attenuated Glo1 activity and GSH levels, implying that ERK1/2 MAPK may modulate Glo1 activity. Multiple kinases can phosphorylate Glo1 and enhance its activity 32,33 . The catalytic activity and gene expression of Glo1 may differ in terms of being modulated by mechanisms such as phosphorylation.…”

“…Multiple kinases can phosphorylate Glo1 and enhance its activity. 32,33 The catalytic activity and gene expression of Glo1 may differ in terms of being modulated by mechanisms such as phosphorylation. Candesartan treatment alone did not change Glo1 activity but augmented the activity of Glo1 in bovine retinal endothelial cells, 8 suggesting that ERK1/2 MAPK can phosphorylate Glo1 to enhance its activity.…”

Malonyl-CoA is a conserved endogenous ATP-competitive mTORC1 inhibitor

“…In vitro assays for phosphorylation of Glo1 by Src were performed as described previously 98 . Briefly, bacterially purified His-tagged human Glo1 recombinant protein was mixed with 600 ng recombinant GST-tagged Src (0200-0000-1, ProQinase) in 1×kinase assay buffer (50 mM HEPES pH 7.4, 6 mM MgCl 2 , 6 mM β-glycerophosphate and 1 mM DTT) and 500 μM ATP in a total volume of 25 μl with the indicated concentrations of Mal-CoA, and incubated for 1 h at 30 °C.…”

“…The phosphorylation reaction was stopped by the addition of 2×Laemmli buffer and boiling the samples for 5 min at 95 °C. The samples were run on SDS–PAGE gels and immunoblotted for Src-dependent phosphorylation of Glo1 at Y316 using a homemade antibody 98 .…”