Methylglyoxal (MG) is a natural metabolite derived from glycolysis, and this 2-oxoaldehyde has been implicated in some diseases including diabetes. However, the physiological significance of MG for cellular functions is yet to be fully elucidated. We previously reported that MG activates the Mpk1 (MAPK) cascade in the yeast Saccharomyces cerevisiae To gain further insights into the cellular functions and responses to MG, we herein screened yeast-deletion mutant collections for susceptibility to MG. We found that mutants defective in the synthesis of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P₂) are more susceptible to MG. PtdIns(3,5)P₂ levels increased following MG treatment, and vacuolar morphology concomitantly changed to a single swollen shape. MG activated the Pkc1-Mpk1 MAPK cascade in which a small GTPase Rho1 plays a crucial role, and the MG-induced phosphorylation of Mpk1 was impaired in mutants defective in the PtdIns(3,5)P₂ biosynthetic pathway. Of note, heat shock-induced stress also provoked Mpk1 phosphorylation in a Rho1-dependent manner; however, PtdIns(3,5)P₂ was dispensable for the heat shock-stimulated activation of this signaling pathway. Our results suggest that PtdIns(3,5)P₂ is specifically involved in the MG-induced activation of the Mpk1 MAPK cascade and in the cellular adaptation to MG-induced stress.

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Journal Article

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Nomura W, Maeta K, Inoue Y

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