title: Acidic pH Is a Metabolic Switch for 2-Hydroxyglutarate Generation and Signaling.
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.
authors: From the: Departments of Anesthesiology.
authors: Sergiy M
authors: SM
authors: Nadtochiy
authors: Biochemistry.
authors: Xenia
authors: X
authors: Schafer
authors: Biology, and.
authors: Dragony
authors: D
authors: Fu
authors: Medicine, University of Rochester, Rochester, New York 14642.
authors: Keith
authors: K
authors: Nehrke
authors: Biochemistry.
authors: Joshua
authors: J
authors: Munger
authors: From the: Departments of Anesthesiology, paul_brookes@urmc.rochester.edu.
authors: Paul S
authors: 0000-0002-8639-8413
authors: PS
authors: Brookes
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D005977:Glutarates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D008291:Malate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D005977:Glutarates; D051793:Hypoxia-Inducible Factor 1; D007527:Isoenzymes; C019417:alpha-hydroxyglutarate; D000429:Alcohol Oxidoreductases; C052496:2-hydroxyglutarate dehydrogenase (NAD); D007770:L-Lactate Dehydrogenase; C409667:lactate dehydrogenase 1; D008291:Malate Dehydrogenase
keywords: 2-hydroxyglutarate; acidosis; cancer; epigenetics; hypoxia; metabolism