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P. V. Rao, J. Christenbury, R. Maddala; RGK Proteins (Rad, Gem and Rem): A Ras-Related Subfamily of GTP-Binding Proteins With a Potential Role in Lens Epithelial Cell Elongation and Differentiation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2783.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the role of RGK subfamily of GTP-binding proteins, which are known to regulate voltage gated calcium channel activity and Rho GTPase-mediated reorganization of the cellular cytoskeleton, in lens epithelial cell elongation and differentiation.
Expression profiles of Rad, Gem, Rem1 and Rem2 in the mouse lens was determined by RT-PCR and cDNA microarray analysis. To explore the specific role of RGK proteins in lens epithelial cell elongation and differentiation, mouse lens primary epithelial cells were transfected by electroporation with plasmids encoding recombinant GFP-fused Gem and Rem2 proteins. The transfected cells were evaluated for changes in cell morphology, actin cytoskeletal reorganization, focal adhesions, and distribution of ERM (ezrin, radixin, moesin) proteins. Changes in lens differentiation markers such as γ-crystallin and beaded filament protein phakinin were determined by immunoblot analysis.
Both RT-PCR and cDNA microarray analyses were confirmed to express Gem, Rad, Rem1 and Rem2 with relative abundance of Rem2 in adult mouse lenses. Mouse lens epithelial cells expressing the recombinant Gem and Rem2 induced fiber cell-like elongation. In the preliminary studies, both Gem and Rem2 induced cortical actin complexes beneath the plasma membrane in association with actin depolymerization in the cell body. Similarly, focal adhesions and phosphorylated myosin light chain were found to be reorganizing along the plasma membrane. ERM proteins, the actin cytoskeleton and plasma membrane crosslinking proteins were also found to be redistributing to both the cortical complexes and plasma membrane from the cytosol and induce cell surface protrusions. Gem and Rem induced expression of lens differentiation markers including phakinin and γ-crystallin in the transfected lens epithelial cells.
Gem and Rem2, which act to regulate voltage gated calcium channel activity and Rho/Rho kinase activity, appear to induce lens epithelial elongation, cortical actin complexes and differentiation. These preliminary data indicate a potential role for the RGK family of GTP-binding in lens epithelial cell elongation and differentiation.
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