Hypoxic-induced truncation of voltage-dependent anion channel 1 is mediated by both asparagine endopeptidase and calpain 1 activities
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Hadas Pahima1,*, Simona Reina2,3,*, Noa Tadmor1,*, Daniella Dadon-Klein1,*, Anna Shteinfer-Kuzmine1, Nathalie M. Mazure4,5, Vito De Pinto2 and Varda Shoshan-Barmatz1
1Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
2Department of Biomedicine and Biotechnology, University of Catania and National Institute for Biomembranes and Biosystems, Section of Catania, Catania 95125, Italy
3Department of Biological, Geological and Environmental Sciences, University of Catania, Catania 95125, Italy
4Institute for Research on Cancer and Aging of Nice, University of Nice Sophia-Antipolis, Centre Antoine Lacassagne, Nice 06189, France
5Present address: INSERM U1065, C3M, Nice 06204, France
*These authors contributed equally to this work
Varda Shoshan-Barmatz, email: firstname.lastname@example.org
Keywords: asparagine endopeptidase; calpain; hypoxia; VDAC1
Abbreviations: AEP: asparagine endopeptidase; VDAC1: voltage-dependent anion channel 1
Received: October 09, 2017 Accepted: January 25, 2018 Published: January 31, 2018
The voltage-dependent anion channel 1 (VDAC1), an outer mitochondria membrane (OMM) protein, serves as a mitochondrial gatekeeper, mediating the transport of nucleotides, Ca2+ and other metabolites across the OMM. VDAC1 also plays a central role in mitochondria-mediated apoptosis by facilitating the release of apoptotic proteins and by association with both pro- and anti-apoptotic proteins. Tumor cells, which are constantly exposed to hypoxic conditions, affect the cell via the transcription factor hypoxia-inducible factor (HIF) that induces transcriptional activity. In cultured cells and in lung cancer patients, hypoxia induces VDAC1 truncation at the C-terminus (VDAC1-ΔC). However, the molecular mechanisms involved in VDAC1-ΔC formation are unknown. Here, we show that hypoxia-induced VDAC1-ΔC formation is inhibited by the Ca2+ chelator BAPTA-AM, by calpain inhibitor-1, by inhibitor of the asparagine endopeptidase (AEP) and by si-RNA targeting HIF1-α or Ca2+-activated protease calpain-1 expression but not that of calpain-2. Finally, VDAC1-ΔC expressed in bacteria and reconstituted into a planar lipid bilayer exhibited decreased channel conductance relative to the full-length protein, yet retained voltage-dependent conductance. These findings suggest that hypoxia, acting via HIF-1α expression, leads to VDAC1 cleavage involving the activation of calpain 1 and AEP.
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