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Roles of cell-cell adhesion-dependent tyrosine phosphorylation of Gab-1
M Shinohara1, A Kodama, T Matozaki
1Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, 2-2 Yamada-oka, Suita 565-0871, Japan.
Abstract:
Gab-1 is a multiple docking protein that is tyrosine phosphorylated by receptor tyrosine kinases such as c-Met, hepatocyte growth factor/scatter factor receptor, and epidermal growth factor receptor. We have now demonstrated that cell-cell adhesion also induces marked tyrosine phosphorylation of Gab-1 and that disruption of cell-cell adhesion results in its dephosphorylation. An anti-E-cadherin antibody decreased cell-cell adhesion-dependent tyrosine phosphorylation of Gab-1, whereas the expression of E-cadherin specifically induced tyrosine phosphorylation of Gab-1. A relatively selective inhibitor of Src family kinases reduced cell-cell adhesion-dependent tyrosine phosphorylation of Gab-1, whereas expression of a dominant-negative mutant of Csk increased it. Disruption of cell-cell adhesion, which reduced tyrosine phosphorylation of Gab-1, also reduced the activation of mitogen-activated protein kinase and Akt in response to cell-cell adhesion. These results indicate that E-cadherin-mediated cell-cell adhesion induces tyrosine phosphorylation by a Src family kinase of Gab-1, thereby regulating the activation of Ras/MAP kinase and phosphatidylinositol 3-kinase/Akt cascades.
Insights
Cell-cell adhesion, mediated by E-cadherin, triggers tyrosine phosphorylation of Gab-1 via Src family kinases. This process regulates key signaling pathways like Ras/MAP kinase and PI3K/Akt.
Area of Science:
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Gab-1 is a docking protein phosphorylated by receptor tyrosine kinases.
- The role of cell-cell adhesion in Gab-1 phosphorylation was previously unclear.
Purpose of the Study:
- To investigate the effect of cell-cell adhesion on Gab-1 tyrosine phosphorylation.
- To elucidate the signaling pathways involved in E-cadherin-mediated Gab-1 activation.
Main Methods:
- Utilized anti-E-cadherin antibodies to disrupt cell adhesion.
- Expressed E-cadherin to induce cell-cell adhesion.
- Employed Src family kinase inhibitors and dominant-negative Csk mutants.
- Assessed tyrosine phosphorylation of Gab-1 and activation of downstream kinases.
Main Results:
- Cell-cell adhesion strongly induced Gab-1 tyrosine phosphorylation; disruption of adhesion led to dephosphorylation.
- E-cadherin mediated this adhesion-dependent phosphorylation, involving Src family kinases.
- Inhibition of Src kinases decreased Gab-1 phosphorylation, while Csk inhibition increased it.
- Gab-1 phosphorylation correlated with the activation of Ras/MAP kinase and Akt pathways.
Conclusions:
- E-cadherin-mediated cell-cell adhesion activates Gab-1 through Src family kinases.
- This activation is crucial for downstream signaling cascades, including Ras/MAPK and PI3K/Akt.
- Gab-1 acts as a key integrator of cell adhesion and growth factor signaling.