Relationship between intermediate filaments and microfilaments in cultured fibroblasts: evidence for common foci during cell spreading

Cell Motil Cytoskeleton. 1986;6(4):406-18. doi: 10.1002/cm.970060406.


Spreading and fully spread chick embryo fibroblasts (CEF) were examined by double-label fluorescence microscopy using the actin-specific probe rhodamine-phalloidin and an antibody directed against CEF intermediate filaments (IF). During midspreading, a striking relationship became discernible: statistical analysis showed that approximately half of the cell population exhibited one or more phase-dense, phalloidin-binding nodules that appeared to act as foci from which IF diverged. Coincidence between actin-containing structures and IF was not limited to these centers; IF could also frequently be seen running in close parallel arrays with stress fibers. Ultrastructural analysis confirmed the presence of non-membrane-bound out-pocketings along the length of stress fibers from which 10-nm IF diverged. These structures varied in size and shape, and displayed a dense, fine fibrillar appearance. IF and microfilaments (MF) were distinguished by size and by decoration of MF with myosin subfragment-1. Other IF-MF interactions were seen in cells of all stages: IF were observed to loop through stress fibers, most frequently at the cell margins. In colchicine-treated cells, IF became redistributed into cables that often ran parallel and appeared to merge with stress fibers. Cytochalasin D-treated CEF exhibited loose aggregates of actin-containing material that appeared to be associated with IF. These results suggest the possibility of an interaction between actin-containing structures and IF, particularly during cell spreading in cultured fibroblasts.

Publication types

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

MeSH terms

  • Actin Cytoskeleton / physiology*
  • Actin Cytoskeleton / ultrastructure
  • Animals
  • Cell Movement
  • Cells, Cultured
  • Chick Embryo
  • Cytoskeleton / physiology*
  • Fibroblasts / cytology
  • Intermediate Filaments / physiology*
  • Intermediate Filaments / ultrastructure
  • Microscopy, Electron
  • Microscopy, Fluorescence