Purchase this article with an account.
I.F. Yamben, A. Griep; PDZ Domain Containing Proteins Function in Fiber Cell Maturation . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1988.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
PDZ proteins, such as Dlg–1, are scaffolding molecules that function in cell polarity, proliferation, and adhesion. Previously, we showed that transgenic expression of the viral oncoprotein E6, a dominant repressor of multiple PDZ proteins, in the lens epithelium and transition zone, affects the linkage of N–cadherin to the actin cytoskeleton. These effects were dependent on the ability of E6 to interact with PDZ proteins. As fiber cells differentiate, a different cytoskeletal linkage, cadherin to intermediate filament proteins, becomes prominent. Transgenic mice that specifically express E6 in the fiber cells (αAE6 mice) are characterized by a defect in denucleation. Herein, we use these mice, to begin to determine if PDZ proteins are involved in the regulation of cadherin–intermediate filament linkages.
Lenses from neonate nontransgenic and αAE6 mice were embedded in paraffin for either longitudinal or transverse orientation, sectioned, and analyzed for the localization of PDZ protein Dlg–1, N cadherin, γ–catenin, and the intermediate filament protein vimentin using immunofluorescence confocal microscopy. The subcellular distributions of γ–catenin, and vimentin were assessed by western blotting of triton soluble cytoplasmic and triton insoluble cytoskeletal associated fractions from lenses of nontransgenic and transgenic neonate mice and levels were compared to GAPDH and MIP26 as loading controls.
Nontransgenic lenses displayed strong colocalization of Dlg–1 and N–cadherin at the most posterior region of the lens and at the apical tips of the fiber cells. N–cadherin and γ–catenin both localized to fiber cell membranes. Vimentin localized primarily, but not exclusively, to membranes throughout the lens fibers. A narrow band of intense staining was observed at the basal tips of fiber cells. In the αAE6 transgenic mice, the hexagonal shape of the fiber cells was lost. Regions of N–cadherin and Dlg–1 colocalization were reduced at both the apical and basal tips of the fiber cells. N–cadherin and γ–catenin remained membrane bound. However, the region of intense vimentin staining was expanded and appeared more cytoplasmic. Western blot analysis confirmed that vimentin was more abundant in the cytoplasm of αAE6 mice.
These data suggest that PDZ proteins may be involved in the organization of cadherin–intermediate filament linkages. Taken together with our data showing that PDZ proteins affect cadherin–actin linkages, these new data suggest PDZ proteins may be broadly important for cadherin–cytoskeletal linkages in lens differentiation.
This PDF is available to Subscribers Only