Raf kinase inhibitor protein positively regulates cell-substratum adhesion while negatively regulating cell-cell adhesion

J Cell Biochem. 2008 Feb 15;103(3):972-85. doi: 10.1002/jcb.21470.


Raf kinase inhibitor protein (RKIP) regulates a number of cellular processes, including cell migration. Exploring the role of RKIP in cell adhesion, we found that overexpression of RKIP in Madin-Darby canine kidney (MDCK) epithelial cells increases adhesion to the substratum, while decreasing adhesion of the cells to one another. The level of the adherens junction protein E-cadherin declines profoundly, and there is loss of normal localization of the tight junction protein ZO-1, while expression of the cell-substratum adhesion protein beta1 integrin dramatically increases. The cells also display increased adhesion and spreading on multiple substrata, including collagen, gelatin, fibronectin and laminin. In three-dimensional culture, RKIP overexpression leads to marked cell elongation and extension of long membrane protrusions into the surrounding matrix, and the cells do not form hollow cysts. RKIP-overexpressing cells generate considerably more contractile traction force than do control cells. In contrast, RNA interference-based silencing of RKIP expression results in decreased cell-substratum adhesion in both MDCK and MCF7 human breast adenocarcinoma cells. Treatment of MDCK and MCF7 cells with locostatin, a direct inhibitor of RKIP and cell migration, also reduces cell-substratum adhesion. Silencing of RKIP expression in MCF7 cells leads to a reduction in the rate of wound closure in a scratch-wound assay, although not as pronounced as that previously reported for RKIP-knockdown MDCK cells. These results suggest that RKIP has important roles in the regulation of cell adhesion, positively controlling cell-substratum adhesion while negatively controlling cell-cell adhesion, and underscore the complex functions of RKIP in cell physiology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adherens Junctions / metabolism*
  • Animals
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Cadherins / metabolism
  • Cell Movement / drug effects
  • Cell-Matrix Junctions / drug effects
  • Cell-Matrix Junctions / metabolism*
  • Dogs
  • Down-Regulation
  • Epithelial Cells / metabolism
  • Extracellular Matrix / metabolism
  • Extracellular Matrix Proteins / chemistry
  • Extracellular Matrix Proteins / metabolism*
  • Humans
  • Integrin beta1 / metabolism
  • Kidney Neoplasms / metabolism
  • Kidney Neoplasms / pathology
  • Membrane Proteins / metabolism
  • Oxazolidinones / pharmacology
  • Phosphatidylethanolamine Binding Protein / metabolism*
  • Phosphatidylethanolamine Binding Protein / pharmacology
  • Phosphoproteins / metabolism
  • Protein Kinase Inhibitors / metabolism*
  • Protein Kinase Inhibitors / pharmacology
  • RNA Interference
  • Tumor Cells, Cultured
  • Up-Regulation
  • Wound Healing / drug effects
  • Zonula Occludens-1 Protein
  • raf Kinases / antagonists & inhibitors*


  • Cadherins
  • Extracellular Matrix Proteins
  • Integrin beta1
  • Membrane Proteins
  • Oxazolidinones
  • Phosphatidylethanolamine Binding Protein
  • Phosphoproteins
  • Protein Kinase Inhibitors
  • TJP1 protein, human
  • Zonula Occludens-1 Protein
  • locostatin
  • raf Kinases