Synapsin-1 and actin form ordered nanoscale assemblies

Authors

Mansour, D., Chowdhury, R., Chandrasekaran, A., Mimoso, T., Krah, D., Korobeinikov, A., Chhabra, A., Milovanovic, D., Köster, S., Shaib, A. H., Rizzoli, S. O., Rangamani, P.

Abstract

Liquid-liquid phase separation is a vital and ubiquitous principle of subcellular organization. Several actin-binding proteins have recently been shown to undergo liquid-liquid phase separation, forming micron-sized droplets that assemble actin into distinct network shapes. However, our knowledge of how these phase-separated proteins organize actin filaments at the nanoscale is rather limited. Here, we seek to address this knowledge gap by investigating synapsin-1 condensates through a combination of computational simulations and nanoscale imaging experiments. Our results show that while synapsin-1 condensates by themselves lack any special structural organization, the addition of actin filaments results in the generation of a regularly organized actin scaffold within the condensates. The organized scaffold forms both when actin and synapsin-1 are added simultaneously and when actin is added after the formation of synapsin condensates. Dissolving the condensates, by synapsin-1 removal, leaves the actin scaffold largely unaffected in both simulations and experiments, implying that this scaffold should guide droplet reformation when synapsin-1 is added back. Taken together, our findings suggest that the actin-rich component of the condensate retains a structural memory that promotes and guides the reassembly of synapsin-actin condensates. This structural memory may be important in the long-term maintenance of synaptic function in vivo.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 01 Oct 2026.

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