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Professor Roland Knorr, The University of Tokyo
Tuesday, May 04, 2021, 11:00am - 12:00pm
 

Ronald KnorrIntracellular capillary origami: how membranes and liquid compartments remodel mutually

Compartmentalisation is essential for eukaryotic cell function, allowing the division of metabolic and regulatory processes into membrane-bound, specialised compartments, such as organelles. In recent years, intracellular phase separation has garnered much attention as a non-membrane means of organising components through the formation of droplet-like compartments, which are functionally implicated in both health and disease. Evidence suggests that droplet clearance involves autophagy, a highly-conserved degradation system in which membrane sheets expand and bend to isolate portions of the cell interior inside autophagosomes.

Here, we investigate the mechanism of droplet sequestration by autophagosomes, in both living and synthetic cells. A minimal theoretical model shows that the surface tension of wetting droplets determines whether membrane sheets isolate droplets in a whole or piecemeal fashion. Further, we find that droplets can serve as an assembly platform for cytosol-degrading autophagosomes through fine-tuning of the membrane-droplet interaction, resulting in the reversal of the bending direction of autophagic membranes. Further, we demonstrate that embryonic plant vacuole remodelling underlies similar physical principles. I propose that droplet-mediated formation of autophagosomes and vacuole remodelling represent a previously undescribed class of processes that are driven by elastocapillarity, revealing the importance of wetting in cytosolic organization.

References:
Fujioka, Y; […] ; Knorr, R. L. et al. Phase separation organizes the site of autophagosome formation. Nature, 2020. https://doi.org/10.1038/s41586-020-1977-6
Agudo-Canalejo, J.; […]; Knorr, R. L. Wetting regulates autophagy of phase separated droplets and the cytosol. Nature, 2021. https://doi.org/10.1038/s41586-020-2992-3
Knorr, R. L. et al. Mutual Remodelling of Biomolecular Condensates and Membranes. in revision.

 

Hosted by Professor Zheng Shi

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