Microtubule-based actin transport and localization in a spherical cell

TL;DR

This paper develops an analytical model to understand how microtubules influence actin filament transport and localization within spherical cells, revealing conditions that lead to actin concentration either at the center or the cortex.

Contribution

It introduces a theoretical framework for actin-microtubule interactions in spherical cells, elucidating mechanisms of actin localization driven by microtubule dynamics.

Findings

Actin concentrates at the cell center when diffusion dominates.

Actin localizes to the cell cortex when binding propensity is high.

The model predicts spatial organization based on microtubule density and actin dynamics.

Abstract

The interaction between actin filaments and microtubules is crucial for many eukaryotic cellular processes, such as, among others, cell polarization, cell motility and cellular wound healing. The importance of this interaction has long been recognised, yet very little is understood about both the underlying mechanisms and the consequences for the spatial (re)organization of the cellular cytoskeleton. At the same time, understanding the causes and the consequences of the interaction between different biomolecular components are key questions for \emph{in vitro} research involving reconstituted biomolecular systems, especially in the light of current interest in creating minimal synthetic cells. In this light, recent \emph{in vitro} experiments have shown that the actin-microtubule interaction mediated by the cytolinker TipAct, which binds to actin lattice and microtubule tip, causes the directed transport of actin filaments. We develop an analytical theory of dynamically unstable microtubules, nucleated from the center of a spherical cell, in interaction with actin filaments. We show that, depending on the balance between the diffusion of unbound actin filaments and propensity to bind microtubules, actin is either concentrated in the center of the cell, where the density of microtubules is highest, or becomes localized to the cell cortex.