Polarity and nucleation of microtubules in polarized epithelial cells

Cell Motil Cytoskeleton. 1995;32(4):273-88. doi: 10.1002/cm.970320404.


Microtubules oriented in the apicobasal axis of columnar epithelial cells are arranged with a uniform polarity with minus ends toward the apical surface, suggesting that these cytoskeletal filaments might serve as a substrate for polarized movement of membrane vesicles within the cell. It is not known whether hepatocytes, a cuboidal epithelium in which transcellular transport is a requisite step in normal apical membrane biogenesis, contain microtubules arranged with a similar polarity. In the present study, we explore the question of microtubule polarity and possible mechanisms for nucleation in the epithelial cell lines WIF-B (hepatocyte), Caco-2 (intestine), and Madin-Darby canine kidney (MDCK). Caco-2 microtubules in the apicobasal axis had uniform polarity with minus ends nearest the apical surface. After cold and nocodazole-induced depolymerization, microtubule regrowth initiated in the apical region in all three cell types. The apex of WIF-B and Caco-2 cells contained two pools of gamma-tubulin: one associated with centrosomes and the other delocalized under the apical membrane. Non-centrosomal gamma-tubulin was present in complexes that sedimented between 10S and 29S; both forms could bind microtubules. The presence of both centrosomal and noncentrosomal gamma-tubulin in apical cytoplasm suggest multiple mechanisms by which microtubule nucleation might occur in epithelial cells.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Caco-2 Cells / chemistry
  • Caco-2 Cells / cytology*
  • Caco-2 Cells / ultrastructure
  • Carcinoma, Hepatocellular
  • Cell Polarity / physiology*
  • Centrosome / chemistry
  • Centrosome / ultrastructure
  • Dogs
  • Epithelial Cells
  • Epithelium / metabolism
  • Fluorescent Antibody Technique, Indirect
  • Humans
  • Kidney Tubules, Distal / cytology*
  • Microscopy, Electron
  • Microtubules / metabolism*
  • Microtubules / ultrastructure
  • Rats
  • Solubility
  • Tubulin / analysis


  • Tubulin