R -Ras regulation of adherens junction formation

2006 2006

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Abstract (summary)

Coordination of cell-cell and cell-matrix adhesions is crucial for proper establishment and maintenance of epithelial tissue structure. Breakdown of this coordination can cause disruption of epithelial architecture, leading to the development of pathologies including tumor growth and metastasis. Currently, the pathways by which cell-cell and cell-matrix adhesions interact are poorly defined.

Activation of R-Ras, a member of the Ras family of small GTPases, disrupts ductal morphogenesis of mammary epithelial cells (MECs) in 3D collagen gels and promotes cell migration, causing loss of epithelial characteristics and acquisition of a migratory phenotype. I show in this thesis that constitutive activation of R-Ras in cells plated on collagen causes a decrease in adherens junction (AJ) formation and a corresponding increase in focal adhesions (FAs), i.e. a decrease in cell-cell adhesions and an increase in cell-matrix adhesions. This inverse relationship between AJs and FAs can be controlled by varying the concentration of collagen substrate on which the cells are cultured. It has been shown previously that R-Ras regulates the affinity and avidity of the α2β1 integrin, a collagen and laminin receptor that mediates MEC polarization in 3D collagen matrices. Inhibition of the α2β1 integrin through siRNA or addition of a blocking antibody, P1E6, causes a partial rescue of AJ formation on collagen in cells expressing activated R-Ras (38V), indicating that R-Ras enhancement of cell-matrix adhesions (FAs) down-regulates cell-cell adhesions (AJs). I show that R-Ras increases association of a FA component (α2 integrin) with the cytoskeleton and decreases association of AJ components with the cytoskeleton, suggesting that R-Ras regulates AJs by regulating the cytoskeleton. Consistent with this, disruption of R-Ras-enhanced actin polymerization with jasplakinolide rescues AJ formation and AJ component association with the cytoskeleton, indicating that R-Ras enhancement of α2β1-based cell-matrix contacts affects cell-cell contacts through regulation of the actin cytoskeleton.

In addition, I have shown that R-Ras regulation of cell-cell vs. cell-matrix adhesions may also be present on fibronectin, an α5β1 ligand. These data indicate that R-Ras may be a general regulator of cell-cell/cell-matrix balance in mammary epithelial cells.

Indexing (details)

Cellular biology;
Molecular biology
0419: Pharmacology
0379: Cellular biology
0307: Molecular biology
Identifier / keyword
Health and environmental sciences; Biological sciences; Adherens junction; Cell adhesion; R-Ras
R -Ras regulation of adherens junction formation
Wilson, Siobhan D.
Number of pages
Publication year
Degree date
School code
DAI-B 67/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Keely, Patricia J.
The University of Wisconsin - Madison
University location
United States -- Wisconsin
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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