Fiber plucking by molecular motors yields large emergent contractility in stiff biopolymer networks

TL;DR

This paper reveals how molecular motors induce large-scale contractility in stiff biopolymer networks through force amplification mechanisms like fiber plucking, significantly enhancing cellular tension beyond linear elastic predictions.

Contribution

It uncovers a novel force amplification process at the filament level, demonstrating its role in emergent cellular contractility in stiff biopolymer networks.

Findings

Active forces cause nonlinear tension via fiber plucking.

Network-wide stresses exceed linear elastic expectations.

Multiple force amplification pathways coexist in biopolymer networks.

Abstract

The mechanical properties of the cell depend crucially on the tension of its cytoskeleton, a biopolymer network that is put under stress by active motor proteins. While the fibrous nature of the network is known to strongly affect the transmission of these forces to the cellular scale, our understanding of this process remains incomplete. Here we investigate the transmission of forces through the network at the individual filament level, and show that active forces can be geometrically amplified as a transverse motor-generated force force "plucks" the fiber and induces a nonlinear tension. In stiff and densely connnected networks, this tension results in large network-wide tensile stresses that far exceed the expectation drawn from a linear elastic theory. This amplification mechanism competes with a recently characterized network-level amplification due to fiber buckling, suggesting that that fiber networks provide several distinct pathways for living systems to amplify their molecular forces.