Fredriksson, K. | Search bioRxiv

bioRxiv2025

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

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.

biophysics↗

bioRxiv2024

Self-association enhances early attentional selection through automatic prioritization of socially salient signals

Efficiently processing self-related information is critical for cognition, yet the earliest mechanisms enabling this self-prioritization remain unclear. By combining a temporal order judgement task with computational modelling based on the Theory of Visual Attention (TVA), we show how mere, arbitrary associations with the self can fundamentally alter attentional selection of sensory information into short-term memory/awareness, by enhancing the attentional weights and processing capacity devoted to encoding socially loaded information. This self-prioritization in attentional selection occurs automatically at early perceptual stages but reduces when active social decoding is required. Importantly, the processing benefits obtained from attentional selection via self-relatedness and via physical salience were additive, suggesting that social and perceptual salience captured attention via separate mechanisms. Furthermore, intra-individual correlations revealed an obligatory self-prioritization effect, whereby self-relatedness overpowered the contribution of perceptual salience in guiding attentional selection. Together, our findings provide evidence for the influence of self-relatedness during earlier, automatic stages of attentional section at the gateway to perception, distinct from later post-attentive processing stages.

neuroscience↗