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© The Rockefeller University Press, 0021-9525/1999/12/1325/ $5.00
The Journal of Cell Biology, Volume 147, Number 6, December 13, 1999 1325-1340

Original Article

Induction of Cell Scattering by Expression of ß1 Integrins in ß1-deficient Epithelial Cells Requires Activation of Members of the Rho Family of GTPases and Downregulation of Cadherin and Catenin Function

Clotilde Gimonda, Arjan van der Fliera, Sanne van Delfta, Cord Brakebuschb, Ingrid Kuikmana, John G. Collarda, Reinhard Fässlerb, and Arnoud Sonnenberga
a Division of Cell Biology, The Netherlands Cancer Institute, 1066 CX Amsterdam,The Netherlands
b Lund University Hospital, Section of Experimental Pathology, Lund S-22185, Sweden

Correspondence to: Arnoud Sonnenberg, Division of Cell Biology, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. Tel:(31) 20 512 1942 Fax:(31) 20 512 1944 E-mail:asonn{at}nki.nl.

Adhesion receptors, which connect cells to each other and to the surrounding extracellular matrix (ECM), play a crucial role in the control of tissue structure and of morphogenesis. In this work, we have studied how intercellular adhesion molecules and ß1 integrins influence each other using two different ß1-null cell lines, epithelial GE11 and fibroblast-like GD25 cells. Expression of ß1A or the cytoplasmic splice variant ß1D, induced the disruption of intercellular adherens junctions and cell scattering in both GE11 and GD25 cells. In GE11 cells, the morphological change correlated with the redistribution of zonula occluden (ZO)-1 from tight junctions to adherens junctions at high cell confluency. In addition, the expression of ß1 integrins caused a dramatic reorganization of the actin cytoskeleton and of focal contacts. Interaction of ß1 integrins with their respective ligands was required for a complete morphological transition towards the spindle-shaped fibroblast-like phenotype. The expression of an interleukin-2 receptor (IL2R)-ß1A chimera and its incorporation into focal adhesions also induced the disruption of cadherin-based adhesions and the reorganization of ECM–cell contacts, but failed to promote cell migration on fibronectin, in contrast to full-length ß1A. This indicates that the disruption of cell–cell adhesion is not simply the consequence of the stimulated cell migration. Expression of ß1 integrins in GE11 cells resulted in a decrease in cadherin and {alpha}-catenin protein levels accompanied by their redistribution from the cytoskeleton-associated fraction to the detergent-soluble fraction. Regulation of {alpha}-catenin protein levels by ß1 integrins is likely to play a role in the morphological transition, since overexpression of {alpha}-catenin in GE11 cells before ß1 prevented the disruption of intercellular adhesions and cell scattering. In addition, using biochemical activity assays for Rho-like GTPases, we show that the expression of ß1A, ß1D, or IL2R-ß1A in GE11 or GD25 cells triggers activation of both RhoA and Rac1, but not of Cdc42. Moreover, dominant negative Rac1 (N17Rac1) inhibited the disruption of cell–cell adhesions when expressed before ß1. However, all three GTPases might be involved in the morphological transition, since expression of either N19RhoA, N17Rac1, or N17Cdc42 reversed cell scattering and partially restored cadherin-based adhesions in GE11-ß1A cells. Our results indicate that ß1 integrins regulate the polarity and motility of epithelial cells by the induction of intracellular molecular events involving a downregulation of {alpha}-catenin function and the activation of the Rho-like G proteins Rac1 and RhoA.

Key Words: ß1 integrins, cadherins, epithelial cells, Rho-like GTPases, migration


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