Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2025.04.15.648943

Structural basis of apoptosis induction by the mitochondrial voltage dependent anion channel

Daniilidis, M.·Guensel, U.·Broutzakis, G.·Janowski, R.·Leitl, K.·Fredriksson, K.·Niessing, D.·Gatsogiannis, C.·Hagn, F. X.
View original source ↗Export metadata ↓

Abstract

The voltage-dependent anion channel (VDAC) is the main gateway for metabolites across the mitochondrial outer membrane1. In addition, VDAC oligomers have been associated with apoptosis at mitochondrial stress conditions2. However, the mechanistic and structural basis of VDACs capability to induce apoptosis pathways remains poorly understood. Here, we show with biochemical and structural methods that VDAC1 oligomerization triggers the dissociation of its N-terminal -helix (VDAC1-N) from the channel interior. We used advanced lipid nanodiscs as a tool to selectively trap VDAC1 in its canonical helix-inserted and helix-exposed state to facilitate a structural characterization of both conformations by cryo-electron microscopy. The results show that slight changes in the shape and dynamics of the VDAC1 {beta}-barrel suffice to release the N-terminal helix to the channel exterior. This conformational switch addresses the long-standing question how VDAC1 can regulate partner protein binding. To confirm this hypothesis, we performed interaction studies between VDAC1 in both conformational states and the anti-apoptotic partner protein BclxL using nuclear magnetic resonance spectroscopy and could detect binding only for the helix-exposed state. These insights enabled the X-ray structure determination of the BclxL-VDAC1-N complex at high resolution and provided atomistic details on the VDAC1-N binding mode at the BH3-groove in BclxL. Further biochemical assays showed that VDAC1-N promotes pore formation of the pro-apoptotic Bcl2 protein Bak by neutralizing BclxLs inhibitory activity. These findings suggest that stress-induced oligomerization of VDAC can trigger the exposure of its N-terminal -helix leading to the neutralization of anti-apoptotic Bcl2 proteins. This mode-of-action is reminiscent of BH3-only sensitizer Bcl2 proteins3 that are efficient inducers of Bax/Bak-mediated mitochondrial outer membrane permeabilization and ultimately apoptosis.

Source connections

Explore related subjects

biophysicsPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Daniilidis, M., Guensel, U., Broutzakis, G., Janowski, R., Leitl, K., Fredriksson, K., Niessing, D., Gatsogiannis, C., Hagn, F. X.. 2025-04-17. Structural basis of apoptosis induction by the mitochondrial voltage dependent anion channel. https://doi.org/10.1101/2025.04.15.648943

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Scaling of structural variability of ecDNA polymer condensates with copy number boosts and stabilises oncogene regulatory contacts

Extrachromosomal DNAs (ecDNAs) form highly heterogeneous condensates in cancer cells that drive oncogene overexpression, yet how structural variability coexists with stable gene regulation remains unclear. Here, we develop a minimal polymer physics model of MYC-harbouring COLO320-DM ecDNAs, where BRD4-like complexes bind and bridge cognate sites along ecDNA rings. Above a critical binder concentration, ecDNAs phase separate into condensates exhibiting diverse conformations because of their thermodynamic folding degeneracy. Despite this variability, condensates retain conserved interaction scaffolds that give rise to reproducible contact patterns, including in-trans associated domains (I-TADs), genomic regions enriched in intermolecular regulatory contacts between distinct ecDNAs. We find that condensate 3D architecture follows universal scaling relations with ecDNA copy number, n, remaining robust to model parameter changes. Regulatory contacts within I TADs increase linearly with n, yet they are one order of magnitude stronger than in size matched control regions outside I TADs, whereas their relative fluctuations are markedly suppressed as n increases. This scaling produces enhanced, low-noise regulatory environments for oncogenes embedded within I-TADs, such as PVT1-MYC fusions, whereas the canonical MYC copy, located outside, is less amplified as experimentally observed. Our findings reveal universal polymer physics principles underlying ecDNA condensate organization, offering a mechanistic basis for selective oncogene amplification and potential advantages in cancer progression.

biophysics↗
bioRxiv2026

High-resolution mapping of RNA structural maturation during Cas9 assembly with ABEL-FRET

The structural flexibility of RNA is essential for forming ribonucleoprotein (RNP) complexes, which regulate diverse biological processes. This intrinsic property permits RNA to act as a dynamic scaffold along the assembly pathway as it folds into a specific structure for initial recognition by protein and undergoes conformational rearrangements for functional maturation as a complex. Yet, RNA flexibility and RNP multicomponent assembly create significant obstacles for traditional structural methods. To overcome these challenges, we applied recently developed ABEL-FRET spectroscopy to measure tether-free single-molecule Forster resonance energy transfer (smFRET) over extended observation times. Furthermore, ABEL-FRET enables the unique ability for simultaneous measurements of ultrahigh resolution smFRET and hydrodynamic size of individual complexes, which offers distinct advantages for studying dynamic RNA molecules that undergo assembly via sequential binding events. Using ABEL-FRET, we explored how the guide RNA (gRNA) of CRISPR genome editing system folds and modulates its structural flexibility to carry out the roles required for each assembly state from its unbound apo form to the functional Cas9 RNP state for target DNA cleavage. Multi-perspective view of gRNA structure gained by probing its two primary functional domains enabled to capture dramatic changes in gRNA flexibility that are highly dependent on its specific structural domains as well as assembly states. Collectively, our work with ABEL-FRET highlights the intrinsic link between the structural flexibility of RNA and its functionality in RNP assembly.

biophysics↗
bioRxiv2026

De novo design of functional RNAs through higher-order interactions

Designing RNA sequences that reliably adopt functional three-dimensional structures remains a central challenge in RNA engineering because folding depends on cooperative interactions beyond canonical base pairing. Here we present DS3dRNA, an interaction-based framework for de novo RNA sequence design that combines a three-body statistical potential with physics-guided sequence sampling and supports design against multiple conformations. Across the evaluated benchmarks, DS3dRNA outperformed representative RNA inverse-design methods in native-sequence recovery and agreement between predicted and target structures. Energy-sequence-quality analyses further showed that lower design energies generally accompanied higher sequence recovery and macro-averaged F1 scores (MacroF1). Experimentally tested Mango II designs retained high-affinity fluorogenic activity, and five twister ribozyme designs yielded mean endpoint cleavage fractions of 37.7-50.6%, compared with 23.5% for the wild type. These results establish explicit higher-order interaction scoring as a complementary approach to emerging data-driven RNA design methods and provide a framework for designing functional RNAs from experimental or predicted structural ensembles.

biophysics↗