Purchase this article with an account.
R. Maddala, V.N. Reddy, P.V. Rao; Lysophospholipid Growth Factors and Edg Receptor-mediated Signaling in Human Lens Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1256.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Bioactive lysophospholipids, which signal through the endothelial differentiation gene (Edg) family of G-protein coupled receptors, play important roles in cell proliferation and survival as well as cytoskeletal organization. Inactivation of Rho GTPase in the mouse lens is associated with strong upregulation of Edg-4 receptor expression. To understand the possible role of Edg receptors in lens growth and development, here we determined the expression profile of Edg receptors in lens epithelial cells and studied the effects of their agonists on actin cytoskeletal organization, cell proliferation, and cell survival status in human lens epithelial cells. Methods: Expression of Edg receptors (Edg1 to 5) in both human lens tissue and in human lens epithelial cells (SRA 01 / 04) was determined by RT-PCR. The effects of lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P), physiological agonists of Edg receptors, on actin cytoskeleton and cell-cell junctions were analyzed by immunocytochemistry. LPA- and S1P-induced effects on DNA synthesis (BrdU incorporation), proliferation (histone H3 phosphorylation and MTS assay), and cell survival (AKT phosphorylation) were assessed in serum-starved lens epithelial cells. To determine whether Rho and Rac GTPase-mediated signaling is downstream of Edg receptors, Rho and Rac activation was determined by pull-down assays. Results: Expression of Edg isoforms 1-5 was readily detectable in human lens epithelial cells, while adult human lens tissue showed expression for only Edg isoforms 1 and 3. LPA and S1P both activated Rho and Rac GTPases, and both induced actin stress fibers and cell-ECM and cell-cell interactions in lens epithelial cells. Most of these effects of LPA and S1P were sensitive to Rho kinase inhibitor, Y-27632. In a limited number of experiments, BrdU incorporation, histone H3 phosphorylation, MTS-based cell proliferation, and AKT phosphorylation were increased when serum-starved lens cells were challenged with either LPA or S1P, with S1P eliciting stronger responses than LPA. Conclusions: This study confirms the expression of Edg receptors in the human lens and reveals their potential role in lens epithelial cell proliferation, survival, and cell-cell interactions. This study also indicates that lysophospholipids, in concert with Edg receptors, may serve as one of the important upstream regulators of Rho/Rho kinase-mediated signaling in maintaining lens growth and transparency.
This PDF is available to Subscribers Only