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J Biol Chem. 2016 Sep 16;291(38):20188-97. doi: 10.1074/jbc.M116.738799. Epub 2016 Aug 10.

Acidic pH Is a Metabolic Switch for 2-Hydroxyglutarate Generation and Signaling.

Author information

1
From the: Departments of Anesthesiology.
2
Biochemistry.
3
Biology, and.
4
Medicine, University of Rochester, Rochester, New York 14642.
5
From the: Departments of Anesthesiology, paul_brookes@urmc.rochester.edu.

Abstract

2-Hydroxyglutarate (2-HG) is an important epigenetic regulator, with potential roles in cancer and stem cell biology. The d-(R)-enantiomer (d-2-HG) is an oncometabolite generated from α-ketoglutarate (α-KG) by mutant isocitrate dehydrogenase, whereas l-(S)-2-HG is generated by lactate dehydrogenase and malate dehydrogenase in response to hypoxia. Because acidic pH is a common feature of hypoxia, as well as tumor and stem cell microenvironments, we hypothesized that pH may regulate cellular 2-HG levels. Herein we report that cytosolic acidification under normoxia moderately elevated 2-HG in cells, and boosting endogenous substrate α-KG levels further stimulated this elevation. Studies with isolated lactate dehydrogenase-1 and malate dehydrogenase-2 revealed that generation of 2-HG by both enzymes was stimulated severalfold at acidic pH, relative to normal physiologic pH. In addition, acidic pH was found to inhibit the activity of the mitochondrial l-2-HG removal enzyme l-2-HG dehydrogenase and to stimulate the reverse reaction of isocitrate dehydrogenase (carboxylation of α-KG to isocitrate). Furthermore, because acidic pH is known to stabilize hypoxia-inducible factor (HIF) and 2-HG is a known inhibitor of HIF prolyl hydroxylases, we hypothesized that 2-HG may be required for acid-induced HIF stabilization. Accordingly, cells stably overexpressing l-2-HG dehydrogenase exhibited a blunted HIF response to acid. Together, these results suggest that acidosis is an important and previously overlooked regulator of 2-HG accumulation and other oncometabolic events, with implications for HIF signaling.

KEYWORDS:

2-hydroxyglutarate; acidosis; cancer; epigenetics; hypoxia; metabolism

PMID:
27510037
PMCID:
PMC5025701
DOI:
10.1074/jbc.M116.738799
[Indexed for MEDLINE]
Free PMC Article

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