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Building Distinct Actin Filament Networks in a Common Cytoplasm

Periodic Reporting for period 4 - SegregActin (Building Distinct Actin Filament Networks in a Common Cytoplasm)

Reporting period: 2018-11-01 to 2020-04-30

The ability of cells to use the actin cytoskeleton for a diversity of cellular processes is due to the fact that actin filaments, although assembled from identical subunits, are organized in a wide variety of structures of appropriate geometrical, dynamical and rheological properties. Key players in this regulation are specific sets of actin binding proteins (ABPs) interacting with each actin networks, to modulate spatially and temporally their properties.
The objective of this project is to understand 1/ how cells can generate the formation of actin structures of appropriate ABP composition from a common pool of cytoplasmic components and 2/ the relationship between the ABP composition of an actin network, its geometrical and dynamical properties, and its response to mechanical deformations.
After 2.5 years of the project, the main achievements are:
• Development of super-resolution TIRF imaging to evaluate the range of allosteric interactions along an actin filament.
• Framework for stochastic in silico simulations to understand how families of actin binding proteins segregate on different actin networks.
• Reconstitution of branched Arp2/3 and linear formin actin networks in a common environment (bottom-up approach).
• Generation of a large collection of yeast mutants to later understand the effects, locally and globally, of the depletion of an ABP for a biological function (top-down approach).
• Adaptation of the use of yeast extract for branched network assembly to a force measurement device.

We successfully started almost all the parts of the projects and obtained interesting results. We expect that the first manuscripts from the team will be written and submitted soon.
This project will shed a new light on how cells organize their interior, and will represent a unique opportunity to understand how modifications in the expression of ABPs are associated with actin network defects.