Stall, spiculate or runaway - the fate of fibers growing towards fluctuating membranes

TL;DR

This paper analyzes the dynamic behavior of growing fibers near fluctuating membranes, identifying regimes of stalling, runaway growth, and spicule formation, with implications for cellular and artificial systems.

Contribution

It introduces a comprehensive model for fiber-membrane interactions, revealing distinct growth regimes and their biological relevance, supported by stochastic simulations.

Findings

Identification of three growth regimes: stalling, runaway, and spicule formation.

Application of the model to biological fibers such as actin, hemoglobin, and microtubules.

Validation of theoretical predictions with 3D stochastic simulations.

Abstract

We solve the dynamic equations of motion for a growing semi-flexible polymer, or fiber, approaching a fluctuating membrane at an angle. At late times we find three different regimes: fiber {\em stalling}, when fiber growth stops due to membrane resistence, {\em run-away}, in which the polymer bends away from the membrane, and another regime in which the membrane response is nonlinear and tubular membrane {\em spicules} are formed. We discuss which regions of the resulting `phase diagram' are explored by (i) single and bundled actin fibers in living cells, (ii) sickle hemoglobin fibers in red blood cells, and (iii) microtubules growing within artificial vesicles. We complement our analysis with full 3-dimensional stochastic simulations.