Vesicle condensation induced by synapsin: condensate size, geometry, and vesicle shape deformations

We study the formation of vesicle condensates induced by the protein synapsin, as a cell-free model system mimicking vesicle pool formation in the synapse. The system can be considered as an example of liquid–liquid phase separation (LLPS) in biomolecular fluids, where one phase is a complex fluid i...

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Published in:The European physical journal. E, Soft matter and biological physics Soft matter and biological physics, 2024-01, Vol.47 (1), p.8, Article 8
Main Authors: Alfken, Jette, Neuhaus, Charlotte, Major, András, Taskina, Alyona, Hoffmann, Christian, Ganzella, Marcelo, Petrovic, Arsen, Zwicker, David, Fernández-Busnadiego, Rubén, Jahn, Reinhard, Milovanovic, Dragomir, Salditt, Tim
Format: Article
Language:English
Subjects:
Adhesion
Biological and Medical Physics
Biophysics
Complex Fluids and Microfluidics
Complex Systems
Condensates
Festschrift in honor of Philip (Fyl) Pincus
Lipids
Liquid phases
Microscopy
Nanotechnology
Optical microscopy
Phase separation
Physics
Physics and Astronomy
Polymer Sciences
Proteins
Regular - Living Systems
Regular Article - Living Systems
Soft and Granular Matter
Surfaces and Interfaces
Thin Films
Vesicles
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Summary:We study the formation of vesicle condensates induced by the protein synapsin, as a cell-free model system mimicking vesicle pool formation in the synapse. The system can be considered as an example of liquid–liquid phase separation (LLPS) in biomolecular fluids, where one phase is a complex fluid itself consisting of vesicles and a protein network. We address the pertinent question why the LLPS is self-limiting and stops at a certain size, i.e., why macroscopic phase separation is prevented. Using fluorescence light microscopy, we observe different morphologies of the condensates (aggregates) depending on the protein-to-lipid ratio. Cryogenic electron microscopy then allows us to resolve individual vesicle positions and shapes in a condensate and notably the size and geometry of adhesion zones between vesicles. We hypothesize that the membrane tension induced by already formed adhesion zones then in turn limits the capability of vesicles to bind additional vesicles, resulting in a finite condensate size. In a simple numerical toy model we show that this effect can be accounted for by redistribution of effective binding particles on the vesicle surface, accounting for the synapsin-induced adhesion zone. Graphic abstract
ISSN:1292-8941
1292-895X
1292-895X
DOI:10.1140/epje/s10189-023-00404-5