The Helical Superstructure of Intermediate Filaments

TL;DR

This paper reveals that intermediate filaments have a large-scale helical superstructure causing conformational anomalies, explained by an elastic shape instability called autocoiling, which aligns with ultrastructural observations.

Contribution

It uncovers a previously undetected helical superstructure in intermediate filaments and introduces the autocoiling mechanism as an explanation for their intrinsic curvature.

Findings

Intermediate filaments exhibit conformational anomalies in microfluidic channels.

A large-scale helical superstructure explains the anomalies.

Autocoiling, a surface stress-induced buckling, causes intrinsic filament curvature.

Abstract

Intermediate filaments are the least explored among the large cytoskeletal elements. We show here that they display conformational anomalies in narrow microfluidic channels. Their unusual behavior can be understood as the consequence of a previously undetected, large scale helically curved superstructure. Confinement in a channel orders the otherwise soft, strongly fluctuating helical filaments and enhances their structural correlations, giving rise to experimentally detectable, strongly oscillating tangent correlation functions. We propose an explanation for the detected intrinsic curving phenomenon - an elastic shape instability that we call autocoiling. The mechanism involves self-induced filament buckling via a surface stress located at the outside of the cross-section. The results agree with ultrastructural findings and rationalize for the commonly observed looped intermediate filament shapes.