Spectrins in Axonal Cytoskeletons: Dynamics Revealed by Extensions and Fluctuations

摘要

The macroscopic properties, the properties of individual components and howthose components interact with each other are three important aspects of acomposited structure. An understanding of the interplay between them isessential in the study of complex systems. Using axonal cytoskeleton as anexample system, here we perform a theoretical study of slender structures thatcan be coarse-grained as a simple smooth 3-dimensional curve. We first presenta generic model for such systems based on the fundamental theorem of curves. Weuse this generic model to demonstrate the applicability of the well-knownworm-like chain (WLC) model to the network level and investigate the situationwhen the system is stretched by strong forces (weakly bending limit). Wespecifically studied recent experimental observations that revealed thehitherto unknown periodic cytoskeleton structure of axons and measured thelongitudinal fluctuations. Instead of focusing on single molecules, we applyanalytical results from the WLC model to both single molecule and networklevels and focus on the relations between extensions and fluctuations. We showhow this approach introduces constraints to possible local dynamics of thespectrin tetramers in the axonal cytoskeleton and finally suggests simple butself-consistent dynamics of spectrins in which the spectrins in one spatialperiod of axons fluctuate in-sync.