Mitochondrial Protein Lipoylation and the 2-Oxoglutarate Dehydrogenase Complex Controls HIF1α Stability in Aerobic Conditions

Abstract

SummaryHypoxia-inducible transcription factors (HIFs) control adaptation to low oxygen environments by activating genes involved in metabolism, angiogenesis, and redox homeostasis. The finding that HIFs are also regulated by small molecule metabolites highlights the need to understand the complexity of their cellular regulation. Here we use a forward genetic screen in near-haploid human cells to identify genes that stabilize HIFs under aerobic conditions. We identify two mitochondrial genes, oxoglutarate dehydrogenase (OGDH) and lipoic acid synthase (LIAS), which when mutated stabilize HIF1α in a non-hydroxylated form. Disruption of OGDH complex activity in OGDH or LIAS mutants promotes L-2-hydroxyglutarate formation, which inhibits the activity of the HIFα prolyl hydroxylases (PHDs) and TET 2-oxoglutarate dependent dioxygenases. We also find that PHD activity is decreased in patients with homozygous germline mutations in lipoic acid synthesis, leading to HIF1 activation. Thus, mutations affecting OGDHC activity may have broad implications for epigenetic regulation and tumorigenesis.

Regulatory mechanisms of hypoxia‐inducible factor 1 activity: Two decades of knowledge

“…For example, Koivunen et al showed that L‐2HG inhibits PHD activity, leading to an increase in HIF‐1α levels, whereas D‐2HG promotes PHD (Table ). Meanwhile, Burr et al reported similar, but controversial, findings showing that L‐2HG inhibits PHD, whereas D‐2HG has no effect (Table ). Regarding IDH3, we found that the aberrant activation of wild‐type IDH3 inactivated PHD activity by decreasing intracellular levels of 2‐OG, resulting in the stabilization of HIF‐1α (Table ).…”

MARCH6 and TRC8 facilitate the quality control of cytosolic and tail‐anchored proteins

“…Lentivirus was prepared by transfection using Mirus Trans‐IT ® ‐293 Transfection Reagent in HEK293ET cells as previously described . The viral supernatant was collected after 48 h and filtered (0.45‐μm filter), and cells were transduced by spin infection at 750 × g , 37°C for 1 h.…”

Mitochondria control acute and chronic responses to hypoxia

“…A systematic screen identified novel genes that led to normoxic HIF stabilization (Burr 2016). This screen identified mitochondrial oxoglutarate dehydrogenase (OGDH) and lipoic acid synthase (LIAS), which both, when mutated, lead to an accumulation of L-2-hydroxyglutarate (L-2-HG).…”

“…This screen identified mitochondrial oxoglutarate dehydrogenase (OGDH) and lipoic acid synthase (LIAS), which both, when mutated, lead to an accumulation of L-2-hydroxyglutarate (L-2-HG). Due to structural similarity to 2-oxoglutarate, L-2-HG is a competitive inhibitor of the 2-oxoglutarate dependent dioxygenase family of enzymes that include the PHDs (Burr 2016). This finding suggests that the TCA cycle dysfunction that leads to 2-HG metabolite accumulation is also a potential mediator of HIF activation in addition to ROS signaling pathways.…”