Oxidation of alpha-ketoglutarate is required for reductive carboxylation in cancer cells with mitochondrial defects

Andrew R. Mullen, Zeping Hu, Xiaolei Shi, Lei Jiang, Lindsey K. Boroughs, Zoltan Kovacs, Richard Boriack, Dinesh Rakheja, Lucas B. Sullivan, W. Marston Linehan, Navdeep S. Chandel, Ralph J DeBerardinis

Research output: Contribution to journalArticle

139 Scopus citations

Abstract

Mammalian cells generate citrate by decarboxylating pyruvate in the mitochondria to supply the tricarboxylic acid (TCA) cycle. In contrast, hypoxia and other impairments of mitochondrial function induce an alternative pathway that produces citrate by reductively carboxylating α-ketoglutarate (AKG) via NADPH-dependent isocitrate dehydrogenase (IDH). It is unknown how cells generate reducing equivalents necessary to supply reductive carboxylation in the setting of mitochondrial impairment. Here, weidentified shared metabolic features in cells using reductive carboxylation. Paradoxically, reductive carboxylation was accompanied by concomitant AKG oxidation in the TCA cycle. Inhibiting AKG oxidation decreased reducing equivalent availability and suppressed reductive carboxylation. Interrupting transfer of reducing equivalents from NADH to NADPH by nicotinamide nucleotide transhydrogenase increased NADH abundance and decreased NADPH abundance while suppressing reductive carboxylation. The data demonstrate that reductive carboxylation requires bidirectional AKG metabolism along oxidative and reductive pathways, with the oxidative pathway producing reducing equivalents used to operate IDH in reverse.

Original languageEnglish (US)
Pages (from-to)1679-1690
Number of pages12
JournalCell Reports
Volume7
Issue number5
DOIs
StatePublished - Jun 12 2014

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ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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