Roux Lab, Geneva

@rouxlab.bsky.social

A mix of physics and biology, understanding shapes in biology, from molecules to tissues. http://www.orelrouxlab.org

So grateful to @epimechfc.bsky.social for citing our work! It’s a classic from the lab, forever thanks to @colomlab.bsky.social

epithelial mechanics fan club@epimechfc.bsky.social · 6mo ago

📄 The first study from @rouxlab.bsky.social in cells showed that planarizable Flipper probes report lipid composition, packing and phase state in GUVs, and respond to tension via changes in lipid order, both in model membranes and cells. @colomlab.bsky.social 🔗 bsky.app/profile/epim...

The crucial test: We fused Heimdall Hofund to a fission-defective yeast ESCRT-III protein (Did2). This chimera restored Mup1 trafficking to vacuoles back to wt! A short amphipathic helix, present in Asgard and retained as fragments in eukaryotes, acts as a minimal membrane fission trigger!

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Eukaryotic ESCRT-IIIA paralogs, known to form heteropolymers, retain Hofund elements at their N-termini. In yeast, mutating these elements blocks ESCRT-III-dependent Mup1 transport to vacuoles. So these elements matter in eukaryotes too.

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Is this Asgard-specific, or conserved with their eukaryotic paralogs? Hard to tell, since the exact molecular mechanism of fission by eukaryotic ESCRT-III remains blurry, probably due to its complexity. Let’s figure it out!

Meet Hofund, the N-terminal amphipathic helix of 15 aa in Heimdall ESCRT-IIIA (named after Heimdall’s sword). How do we know Hofund is the molecular trigger for fission? Remove Hofund → ESCRT-IIIA loses fission activity. Add Hofund alone → uncontrolled fission.

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Through membrane fission! We show in vitro that the Asgard Heimdallarchaeota (Heimdall) ESCRT-IIIA subunit is inherently capable of triggering fission upon subunit turnover driven by ATP hydrolysis by Vps4. And the key question: what actually destabilizes the membrane when ESCRT-IIIA turns over?

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We accompanied this dynamic live Flipper-TR FLIM imaging with lipid diffusion analysis, spatial lipidomics (shown below), and cool in vitro reconstitutions of tension gradients using supported lipid bilayers that are expanding

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