Tubulation pattern of membrane vesicles coated with bio filaments

TL;DR

This paper models how active biofilaments induce membrane tubulation in vesicles, revealing defect-driven deformation patterns and predicting dynamic shape oscillations through Monte Carlo simulations.

Contribution

It introduces a novel simulation framework linking filament activity and membrane topology to tubulation, emphasizing defect sites as deformation hotspots.

Findings

Filament intrinsic curvature influences tubulation patterns.

Nematic defect locations correlate with membrane deformation sites.

Model predicts shape oscillations in active filament-vesicle systems.

Abstract

Narrow membrane tubes are commonly pulled out from the surface of phospholipid vesicles using forces applied either through laser or magnetic tweezers or through the action of processive motor proteins. Recent examples have emerged where such tubes spontaneously grow from vesicles coated with bioactive cytoskeletal filaments (e.g. FtsZ, microtubule) in the presence GTP. We show how a soft vesicle deforms due to the interplay between its topology, local curvature and the forces due to the active filaments. We present results from Dynamically Triangulated Monte Carlo simulations of a spherical continuum membrane coated with a nematic field and show how the intrinsic curvature of the filaments and their ordering interactions drive membrane tubulation. We predict interesting patterns of nematic defects, on curved 2D membrane surfaces, which promote tube formation. Implication of our model for more dynamic cases where vesicles coated with an active mixture of microtubule and myosin show shape oscillation, are also discussed. All these cases point to a common theme that defect locations on 2D membrane surfaces are hot spots of membrane deformation activity.