Harvard WAM Seminars

Abstract

Mark Bathe, MIT

Cytoskeletal filament bundles: In search of Nature's design principles

Cytoskeletal actin and microtubule bundles play essential roles in numerous physiological processes including hearing, fertilization, cell migration and growth. Cells employ a multitude of accessory binding proteins and motors to regulate actively bundle properties to suit biological function. Here, I examine the experimentally observed mechanical properties of actin bundles and interpret results using molecular modeling. Bundles display elastic or plastic response depending on the rate and degree of deformation, where a generic competition between filament-stretching and crosslink-shearing determines three markedly different elastic regimes that are delineated by the relative values of two universal design parameters. In the inelastic regime, crosslinks reorganize microscopically to give rise to macroscopic creep. The elucidated properties have direct implications on the physiological behavior of active and passive cellular processes including filopodia and stereocilia that have heretofore been neglected. Ongoing research into the protein structural basis for bundle mechanics is addressed, along with the prospect of designing cytoskeletal bundles de novo for engineering purposes.