Microtubules can bear enhanced compressive loads in living cells because of lateral reinforcement

TLDR

Microtubules are thought to shape cell mechanics by resisting compressive forces, yet in vitro they buckle only at large scales, whereas in cells they appear highly curved and buckled under compressive loads. The study seeks to quantify the compressive forces microtubules experience in living cells and clarify their structural role. Intracellular microtubules bear large compressive loads, and their buckling wavelength is shortened by coupling to the elastic cytoskeleton, which dramatically increases the forces they can sustain, indicating a more significant structural contribution than previously thought.

Abstract

Cytoskeletal microtubules have been proposed to influence cell shape and mechanics based on their ability to resist large-scale compressive forces exerted by the surrounding contractile cytoskeleton. Consistent with this, cytoplasmic microtubules are often highly curved and appear buckled because of compressive loads. However, the results of in vitro studies suggest that microtubules should buckle at much larger length scales, withstanding only exceedingly small compressive forces. This discrepancy calls into question the structural role of microtubules, and highlights our lack of quantitative knowledge of the magnitude of the forces they experience and can withstand in living cells. We show that intracellular microtubules do bear large-scale compressive loads from a variety of physiological forces, but their buckling wavelength is reduced significantly because of mechanical coupling to the surrounding elastic cytoskeleton. We quantitatively explain this behavior, and show that this coupling dramatically increases the compressive forces that microtubules can sustain, suggesting they can make a more significant structural contribution to the mechanical behavior of the cell than previously thought possible.