Purchase this article with an account.
C. Rivera, A.E. Griep; PDZ Domain Containing Proteins Are Required for Normal Cell Adhesions, Cell Polarity and Cell Differentiation in the Mouse Lens . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1066.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: PDZ domain containing proteins are scaffold molecules known to play a role in cell–cell adhesion, cell polarity and cell growth in Drosophila. The expression of the viral oncoprotein E6, which suppresses PDZ proteins, in the mouse lens epithelium leads to increased proliferation and defects in cell adhesion and differentiation. In this study we determined how cell adhesions are affected when PDZ proteins' are disrupted. We also analyzed signaling pathways that may be altered when such adhesions are affected that may contribute to the differentiation defects observed in PDZ disrupted lenses. Methods: Paraffin or frozen sections from E18.5 lenses of mice carrying an insertional mutation in dlg–1 (dlggt mice) and lenses from P5 nontransgenic (NT) and transgenic mice expressing E6 (E6 mice) were used to analyze the localization of Scrib, Dlg–1, N–cadherin, ZO–1, ß–catenin, α–catenin, ß1 integrin and ß–actin by immunofluorescence and confocal microscopy. The subcellular localization of N–cadherin, ZO–1, ß–catenin, α–catenin and ß–actin was assessed by immunoblotting of cytoskeletal and cytoplasmic associated protein fractions from NT and E6 lenses. The levels of ß1 integrin and phospho–FAK and phospho–Erk were determined by immunoblotting of whole lens and fiber cell compartment protein extracts, respectively. Results: In the presence of E6, the co–localization of Scrib and Dlg–1 with N–cadherin and the organization of the actin cytoskeleton were affected. While there was some overlap between N–cadherin and ß –catenin in the E6 lenses, the overlap of N–cadherin and α–catenin was greatly reduced. The majority of these defects were present in the transition zone, a region where the strengthening of adherens junctions has been shown to be important for proper lens cell differentiation. Scrib and ZO–1 were ectopically localized along the plasma membrane of E6 and dlggt lenses. Immunoblot analysis indicated that there was more cytoplasmic and less cytoskeletal associated α–catenin in the E6 lenses compared to NT. Confocal microscopy and immunoblotting also revealed that the levels of ß1 integrin were reduced in E6 lenses. The levels of phospho–FAK and phospho–Erk also appeared to be lower in the fiber cell compartment of E6 lenses than NT lenses. Conclusions: These results show that PDZ domain containing proteins are involved in maintaining cell polarity and cell junctions composed of N–cadherin and ß1 integrin. The disruption of PDZ proteins results in the destabilization of such junctions and the alteration of downstream signaling cascades that may contribute to the defects in cell differentiation.
This PDF is available to Subscribers Only