Calcium-insensitive splice variants of mammalian E1 subunit of 2-oxoglutarate dehydrogenase complex with tissue-specific patterns of expression

Dick Denton, Timothy J Pullen, Craig T Armstrong, Kate J Heesom, Guy A Rutter

Research output: Contribution to journalArticle (Academic Journal)peer-review

19 Citations (Scopus)
372 Downloads (Pure)

Abstract

The 2-oxoglutarate dehydrogenase (OGDH) complex is an important control point in vertebrate mitochondrial oxidative metabolism, including in the citrate cycle and catabolism of alternative fuels including glutamine. It is subject to allosteric regulation by NADH and the ATP/ADP ratio, and by Ca2+ through binding to the E1 subunit. The latter involves a unique Ca2+-binding site which includes D114ADLD (site 1). Here, we describe three splice variants of E1 in which either the exon expressing this site is replaced with another exon (loss of site 1, LS1) or an additional exon is expressed leading to the insertion of 15 amino acids just downstream of site 1 (Insert), or both changes occur together (LS1/Insert). We show that all three variants are essentially Ca2+-insensitive. Comparison of massive parallel sequence (RNA-Seq) databases demonstrates predominant expression of the Ca2+-sensitive archetype form in heart and skeletal muscle, but substantial expression of the Ca2+-insensitive variants in brain, pancreatic islets and other tissues. Detailed proteomic and activity studies comparing OGDH complexes from rat heart and brain confirmed the substantial difference in expression between these tissues. The evolution of OGDH variants was explored using bioinformatics, and this indicated that Ca2+-sensitivity arose with the emergence of chordates. In all species examined, this was associated with the co-emergence of Ca2+-insensitive variants suggesting a retained requirement for the latter in some settings. Tissue-specific expression of OGDH splice variants may thus provide a mechanism that tunes the control of the enzyme to the specialized metabolic and signalling needs of individual cell types.
Original languageEnglish
Article number9
Pages (from-to)1165-1178
Number of pages14
JournalBiochemical Journal
Volume473
Early online date26 Apr 2016
DOIs
Publication statusPublished - May 2016

Keywords

  • citrate cycle
  • allosteric regulation
  • RNA-Seq
  • proteomic analysis
  • heart
  • brain

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