Mechanisms of polarization of the shape of fibroblasts and epitheliocytes: Separation of the roles of microtubules and Rho-dependent actin-myosin contractility

Proc Natl Acad Sci U S A. 2002 Aug 6;99(16):10452-7. doi: 10.1073/pnas.152339899. Epub 2002 Jul 29.

Abstract

Cultured fibroblasts possess a characteristic polarized phenotype manifested by an elongate cell body with an anterior lamella whose cell edge is divided into protrusion-forming and inactive zones. Disruption of the fibroblast microtubule cytoskeleton leads to an increase in Rho-dependent acto-myosin contractile activity and concomitant loss of structural polarity. The functional relationship of myosin-driven contractile activity to loss of fibroblast anterior-posterior polarity is unknown. To dissect the roles of microtubule assembly and of Rho-dependent contractility on structural polarization of cells, polarized fibroblasts and nonpolarized epitheliocytes were treated with the microtubule-depolymerizing drug, nocodazole, and/or the Rho kinase inhibitor, Y-27632. Fibroblasts incubated with Y-27632 increased their degree of polarization by developing a highly elongate cell body with multiple narrow processes extended from the edges of the cell. Treatment of fibroblasts with nocodazole, alone or in combination with Rho kinase inhibitor, produced discoid or polygonal cells having broad, flattened lamellae that did not form long lamellar extensions. Single cultured epitheliocytes of the IAR-2 line do not display anterior-posterior polarization. When treated with Y-27632, the cells acquired a polarized, elongate shape with narrow protrusions and wide lamellas. Nocodazole alone or in combination with Y-27632 did not change the discoid shape of epitheliocytes, however treatment with Y-27632 produced thinning of the lamellar cytoplasm. We conclude that microtubules provide the necessary framework for polarization of fibroblasts and epitheliocytes, whereas Rho-regulated contractility modulates the degree of polarization of fibroblasts and completely inhibits polarization in epitheliocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Amides / pharmacology
  • Animals
  • Cell Line
  • Cell Polarity / drug effects
  • Cell Size / drug effects
  • Enzyme Inhibitors / pharmacology
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Intracellular Signaling Peptides and Proteins
  • Microtubules / drug effects
  • Microtubules / physiology*
  • Myosins / metabolism*
  • Nocodazole / pharmacology
  • Protein Serine-Threonine Kinases / antagonists & inhibitors*
  • Pyridines / pharmacology
  • Rats
  • rho-Associated Kinases

Substances

  • Actins
  • Amides
  • Enzyme Inhibitors
  • Intracellular Signaling Peptides and Proteins
  • Pyridines
  • Y 27632
  • Protein Serine-Threonine Kinases
  • rho-Associated Kinases
  • Myosins
  • Nocodazole