Cytoskeletal microtubules have been proposed
to infl uence 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 signifi cantly 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 signifi cant structural contribution to the mechanical
behavior of the cell than previously thought possible