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

• Published in: Journal of cellular biochemistry 2008-02, Vol.103 (3), p.972-985
• Main Authors: Mc Henry, Kevin T., Montesano, Roberto, Zhu, Shoutian, Beshir, Anwar B., Tang, Hui-Hui, Yeung, Kam C., Fenteany, Gabriel
• Format: Article
• Language: English
• Subjects: Adherens Junctions - metabolism; Animals; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Cadherins - metabolism; cell adhesion; cell migration; Cell Movement - drug effects; Cell-Matrix Junctions - drug effects; Cell-Matrix Junctions - metabolism; Dogs; Down-Regulation; Epithelial Cells - metabolism; extracellular matrix; 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; Raf kinase inhibitor protein; raf Kinases - antagonists & inhibitors; RNA Interference; Tumor Cells, Cultured; Up-Regulation; Wound Healing - drug effects; Zonula Occludens-1 Protein
• ISSN: 0730-2312; 1097-4644
• 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 β1 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. J. Cell. Biochem. 103: 972–985, 2008. © 2007 Wiley‐Liss, Inc.