Dysfunction in the mitochondrial Fe-S assembly machinery leads to formation of the chemoresistant truncated VDAC1 isoform without HIF-1α activation

PLoS One. 2018 Mar 29;13(3):e0194782. doi: 10.1371/journal.pone.0194782. eCollection 2018.

Abstract

Biogenesis of iron-sulfur clusters (ISC) is essential to almost all forms of life and involves complex protein machineries. This process is initiated within the mitochondrial matrix by the ISC assembly machinery. Cohort and case report studies have linked mutations in ISC assembly machinery to severe mitochondrial diseases. The voltage-dependent anion channel (VDAC) located within the mitochondrial outer membrane regulates both cell metabolism and apoptosis. Recently, the C-terminal truncation of the VDAC1 isoform, termed VDAC1-ΔC, has been observed in chemoresistant late-stage tumor cells grown under hypoxic conditions with activation of the hypoxia-response nuclear factor HIF-1α. These cells harbored atypical enlarged mitochondria. Here, we show for the first time that depletion of several proteins of the mitochondrial ISC machinery in normoxia leads to a similar enlarged mitochondria phenotype associated with accumulation of VDAC1-ΔC. This truncated form of VDAC1 accumulates in the absence of HIF-1α and HIF-2α activations and confers cell resistance to drug-induced apoptosis. Furthermore, we show that when hypoxia and siRNA knock-down of the ISC machinery core components are coupled, the cell phenotype is further accentuated, with greater accumulation of VDAC1-ΔC. Interestingly, we show that hypoxia promotes the downregulation of several proteins (ISCU, NFS1, FXN) involved in the early steps of mitochondrial Fe-S cluster biogenesis. Finally, we have identified the mitochondria-associated membrane (MAM) localized Fe-S protein CISD2 as a link between ISC machinery downregulation and accumulation of anti-apoptotic VDAC1-ΔC. Our results are the first to associate dysfunction in Fe-S cluster biogenesis with cleavage of VDAC1, a form which has previously been shown to promote tumor resistance to chemotherapy, and raise new perspectives for targets in cancer therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Caspase 3 / metabolism
  • Drug Resistance, Neoplasm*
  • Enzyme Activation / genetics
  • Gene Knockdown Techniques
  • HeLa Cells
  • Hep G2 Cells
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Iron / metabolism*
  • Mitochondria / drug effects
  • Mitochondria / metabolism*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Proteolysis / drug effects
  • Sequence Deletion*
  • Sulfur / metabolism*
  • Tumor Hypoxia / drug effects
  • Voltage-Dependent Anion Channel 1 / genetics
  • Voltage-Dependent Anion Channel 1 / metabolism*

Substances

  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Protein Isoforms
  • Sulfur
  • Iron
  • Voltage-Dependent Anion Channel 1
  • Caspase 3

Grant support

This work received support from Agence Nationale de la Recherche, ANR-13-BSV8-0017-01, CB and ICSN-CNRS Fellowship, IF.