Neurofilaments function as shock absorbers: compression response arising from disordered proteins

TL;DR

Disordered proteins in neuron cell skeletons act as shock absorbers, with their compression response governed by repulsive and attractive interactions, enabling large deformations without failure.

Contribution

This study reveals that disordered proteins form weakly cross-bridged hydrogels that serve as shock absorbers, highlighting their mechanical role in neuron cells.

Findings

High compression dominated by gas-like steric and ionic repulsions

Low compression influenced by specific attractive interactions

Truncation of protein segments increases hydrogel expansion

Abstract

What can cells gain by using disordered, rather than folded, proteins in the architecture of their skeleton? Disordered proteins take multiple co-existing conformations, and often contain segments which act as random-walk-shaped polymers. Using X-ray scattering we measure the compression response of disordered protein hydrogels, which are the main stress-responsive component of neuron cells. We find that at high compression their mechanics are dominated by gas-like steric and ionic repulsions. At low compression, specific attractive interactions dominate. This is demonstrated by the considerable hydrogel expansion induced by the truncation of critical short protein segments. Accordingly, the floppy disordered proteins form a weakly cross-bridged hydrogel, and act as shock absorbers that sustain large deformations without failure.