2021 Oct 9;101354.
 doi: 10.1016/j.molmet.2021.101354. Online ahead of print.

An anaplerotic approach to correct the mitochondrial dysfunction in ataxia-telangiectasia (A-T)

A J Yeoabrey.yeo@uq.edu.au." href="https://pubmed.ncbi.nlm.nih.gov/34637921/#affiliation-1" ref="linksrc=author_aff" style="box-sizing: inherit; background-color: rgb(241, 241, 241); color: rgb(50, 58, 69); text-decoration: none; font-size: inherit; display: inline-block; line-height: 1; padding: 0.1rem 0.3rem; border-radius: 2px; transition: color 0.3s ease 0s; margin-right: 0px;">1G N Subramanian2K L Chong2M Gatei2R G Parton3D Coman4M F Lavinm.lavin@uq.edu.au." href="https://pubmed.ncbi.nlm.nih.gov/34637921/#affiliation-5" ref="linksrc=author_aff" style="box-sizing: inherit; background-color: rgb(241, 241, 241); color: rgb(50, 58, 69); text-decoration: none; font-size: inherit; display: inline-block; line-height: 1; padding: 0.1rem 0.3rem; border-radius: 2px; transition: color 0.3s ease 0s; margin-right: 0px;">5
Affiliations 

Affiliations

  • 1University of Queensland Centre for Clinical Research, University of Queensland, Herston, Brisbane, Australia. Electronic address: abrey.yeo@uq.edu.au.
  • 2University of Queensland Centre for Clinical Research, University of Queensland, Herston, Brisbane, Australia.
  • 3Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, University of Queensland, St Lucia, Brisbane, Australia.
  • 4Queensland Children's Hospital, Brisbane, Australia; Faculty of Medicine, University of Queensland, Herston, Brisbane, Australia.
  • 5University of Queensland Centre for Clinical Research, University of Queensland, Herston, Brisbane, Australia. Electronic address: m.lavin@uq.edu.au.
Free article

Abstract

Objective: ATM, the protein defective in the human genetic disorder, ataxia telangiectasia (A-T) plays a central role in the response to DNA double strand breaks (DSBs) and in protecting the cell against oxidative stress. We recently showed that A-T cells are hypersensitive to metabolic stress which can be accounted for by a failure to exhibit efficient endoplasmic reticulum (ER)-mitochondrial signalling and Ca2+ transfer in response to nutrient deprivation resulting in mitochondrial dysfunction. The objective of the current study is to use an anaplerotic approach using the fatty acid, heptanoate (C7), a metabolic product of the triglyceride, triheptanoin to correct the defect in ER-mitochondrial signalling and enhance cell survival of A-T cells in response to metabolic stress.

Methods: We treated control cells and A-T cells with the anaplerotic agent, heptanoate to determine their sensitivity to metabolic stress induced by inhibition of glycolysis with 2 deoxyglucose (2DG) using live-cell imaging to monitor cell survival for 72 hours using the Incucyte system. We examined ER-mitochondrial signalling in A-T cells exposed to metabolic stress using a suite of techniques including immunofluorescence staining of Grp75, ER-mitochondrial Ca2+ channel, the VAPB-PTPIP51 ER-mitochondrial tether complexes as well as proximity ligation assays between Grp75-IP3R1 and VAPB1-PTPIP51 to establish a functional interaction between ER and mitochondria. Finally, we also performed metabolomic analysis using LC-MS/MS to determine altered levels of TCA intermediates A-T cells compared to healthy control cells.

Results: We demonstrate here that heptanoate corrects all aspects of the defective ER-mitochondrial signalling observed in A-T cells. Heptanoate enhances ER-mitochondrial contacts; increases the flow of calcium from the ER to the mitochondrion; restores normal mitochondrial function and mitophagy and increases resistance of ATM-deficient cells and cells from A-T patients to metabolic stress-induced killing. The defect in mitochondrial function in ATM-deficient cells was accompanied by more reliance on aerobic glycolysis as shown by increased lactate dehydrogenase A (LDHA), accumulation of lactate and reduced levels of both acetyl CoA and ATP which are all restored by heptanoate.

Conclusions: These data together show that heptanoate corrects metabolic stress in A-T cells by restoring ER-mitochondria signalling and mitochondrial function and suggest that the parent compound, triheptanoin, has great potential as a novel therapeutic agent for patients with A-T.

Keywords: ATM; Ataxia-telangiectasia; endoplasmic reticulum; heptanoate (C7); mitochondrial dysfunction; mitochondrial interaction; nutrient deprivation.