Elastic Behavior of Cross-Linked and Bundled Actin Networks

TLDR

Actin filament networks are common in cells, yet their elastic properties are poorly understood. The authors parameterize the full range of behavior in a state diagram and explain it with a robust model. These networks exhibit exceptional elastic behavior with two distinct regimes—bending of single filaments and stretching of entropic fluctuations—where stiffness can vary by decades with small changes in cross‑link concentration and increase markedly under external stress.

Abstract

Networks of cross-linked and bundled actin filaments are ubiquitous in the cellular cytoskeleton, but their elasticity remains poorly understood. We show that these networks exhibit exceptional elastic behavior that reflects the mechanical properties of individual filaments. There are two distinct regimes of elasticity, one reflecting bending of single filaments and a second reflecting stretching of entropic fluctuations of filament length. The mechanical stiffness can vary by several decades with small changes in cross-link concentration, and can increase markedly upon application of external stress. We parameterize the full range of behavior in a state diagram and elucidate its origin with a robust model.