Mechanics of microtubule bundles in pillar cells from the inner ear.
The mechanical properties of cross-linked microtubule bundles were measured from outer pillar cells isolated from the mammalian inner ear. Measurements were made using a three-point bending test and were incorporated into a mathematical model designed to distinguish between the stiffness contributions from microtubules and their cross-linking proteins. Outer pillar cells were composed of 1000-3000 parallel bundled microtubules in a square array that was interdigitated and cross-linked with actin filaments. The average midpoint bending stiffness of intact cells was 7 x 10(-4) N/m. After removal of both the actin filaments and cross-links with detergent in the presence of DNase I, the square array was disrupted and the stiffness decreased by a factor of 4, to 1.7 x 10(-4) N/m. The bending modulus for individual microtubules was calculated to be 7 x 10(-23) Nm2, and the Young's modulus for these 15 protofilament microtubules was 2 x 10(9) Pa. The shear modulus between microtubules in intact cells was calculated to be 10(3) Pa. It was concluded that cross-linking proteins provided shear resistance between microtubules, which resulted in a fourfold increase in stiffness. The model can be used to estimate the mechanical properties of cross-linked microtubule bundles in cells from which direct measurements are not available.
Tolomeo
J A
JA
Department of Physiology, University of Bristol, England.
Holley
M C
MC
D000199:Actins / Q000737:chemistry / Q000502:physiology; D000818:Animals; D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D001703:Biophysics; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D003432:Cross-Linking Reagents; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D008870:Microtubules / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D008954:Models, Biological; D009925:Organ of Corti / Q000166:cytology* / Q000502:physiology*
D000199:Actins; D003432:Cross-Linking Reagents