Confinement Geometry Tunes Fascin-Actin Bundle Structures and Consequently the Shape of a Lipid Bilayer Vesicle

Yashar Bashirzadeh; Nadab H Wubshet; Allen P Liu

doi:10.3389/fmolb.2020.610277

Confinement Geometry Tunes Fascin-Actin Bundle Structures and Consequently the Shape of a Lipid Bilayer Vesicle

Front Mol Biosci. 2020 Nov 9:7:610277. doi: 10.3389/fmolb.2020.610277. eCollection 2020.

Authors

Yashar Bashirzadeh¹, Nadab H Wubshet¹, Allen P Liu^{1

2

3

4}

Affiliations

¹ Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, United States.
² Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.
³ Department of Biophysics, University of Michigan, Ann Arbor, MI, United States.
⁴ Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, United States.

Abstract

Depending on the physical and biochemical properties of actin-binding proteins, actin networks form different types of membrane protrusions at the cell periphery. Actin crosslinkers, which facilitate the interaction of actin filaments with one another, are pivotal in determining the mechanical properties and protrusive behavior of actin networks. Short crosslinkers such as fascin bundle F-actin to form rigid spiky filopodial protrusions. By encapsulation of fascin and actin in giant unilamellar vesicles (GUVs), we show that fascin-actin bundles cause various GUV shape changes by forming bundle networks or straight single bundles depending on GUV size and fascin concentration. We also show that the presence of a long crosslinker, α-actinin, impacts fascin-induced GUV shape changes and significantly impairs the formation of filopodia-like protrusions. Actin bundle-induced GUV shape changes are confirmed by light-induced disassembly of actin bundles leading to the reversal of GUV shape. Our study contributes to advancing the design of shape-changing minimal cells for better characterization of the interaction between lipid bilayer membranes and actin cytoskeleton.

Keywords: actin; encapsulation; fascin; giant unilamellar lipid vesicles; membrane deformation.