congrats Joshua!

All credits to the dreamteam that made this possible! what a pleasure and honor working with these people! 🥰
@diorgeps.bsky.social @mhakala.bsky.social @juanmagararc.bsky.social @joshuatran.bsky.social @mudgal17.bsky.social @Carlos Marcuello @Andrea Merino

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!

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.

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.

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?

In a recent work, @buzzbaum.bsky.social and colleagues showed an Asgard archaeon with internal vesicles.
www.biorxiv.org/content/10.1...
How might Asgard ESCRT-III have contributed to compartmentalization?

Thanks to all the team at @rouxlab.bsky.social and abroad: @pauguillamat.bsky.social @caterinatomba.bsky.social @giodang.bsky.social @colomlab.bsky.social @lizhinde.bsky.social @javierespadas.bsky.social and many more

Overall, the work shows that tension gradients arise from the combination of actin dynamics and strong cell–substrate adhesion, rather than from migration itself.
Link: rdcu.be/eRTQA

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

A key result: adherent cells maintain long-range membrane tension gradients even when they are not migrating! (micropatterned cells below)
In contrast, non-adherent migrating cells *do not* show these gradients.

Congrats Juanma! Thanks to all for your contributions in the long journey!