CRB3A Controls the Morphology and Cohesion of Cancer Cells through Ehm2/p114RhoGEF-Dependent Signaling

Abstract

The transmembrane protein CRB3A controls epithelial cell polarization. Elucidating the molecular mechanisms of CRB3A function is essential as this protein prevents the epithelial-to-mesenchymal transition (EMT), which contributes to tumor progression. To investigate the functional impact of altered CRB3A expression in cancer cells, we expressed CRB3A in HeLa cells, which are devoid of endogenous CRB3A. While control HeLa cells display a patchy F-actin distribution, CRB3A-expressing cells form a circumferential actomyosin belt. This reorganization of the cytoskeleton is accompanied by a transition from an ameboid cell shape to an epithelial-cell-like morphology. In addition, CRB3A increases the cohesion of HeLa cells. To perform these functions, CRB3A recruits p114RhoGEF and its activator Ehm2 to the cell periphery using both functional motifs of its cytoplasmic tail and increases RhoA activation levels. ROCK1 and ROCK2 (ROCK1/2), which are critical effectors of RhoA, are also essential to modulate the cytoskeleton and cell shape downstream of CRB3A. Overall, our study highlights novel roles for CRB3A and deciphers the signaling pathway conferring to CRB3A the ability to fulfill these functions. Thereby, our data will facilitate further investigation of CRB3A functions and increase our understanding of the cellular defects associated with the loss of CRB3A expression in cancer cells.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00673-15.

ACKNOWLEDGMENTS

We are grateful to M. Caruso, A. Le Bivic, and B. Margolis for reagents. We also thank A. Turcotte for technical support. Confocal microscopy was performed at the CRCHU-Hôtel-Dieu imaging facility. DNA sequencing was carried out at the Genome Sequencing and Genotyping Platform of the CHU de Québec Research Centre.

This work was supported by an operating grant from the Cancer Research Society-Société de Recherche sur le Cancer (SRC-CRS) to P.L., who is a Fonds de Recherche du Québec-Santé junior 2 investigator.