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M. Leonard, A. Menko; Stabilization of N–Cadherin Junctions in Differentiating Lens Fiber Cells Through Linkage to –Catenin and Intermediate Filaments . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1068.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Stable cadherin junctions are essential for both the formation and the maintenance of lens cytoarchitecture. We have investigated the mechanism by which N–cadherin junctions are stabilized in differentiating lens fiber cells. Methods: Cadherin junction composition was determined in microdissected E10 chick embryo lenses by co–precipitation analysis. Cytoskeletal linkage was determined by sequential extraction in Triton, Triton–Octylglucoside, and SDS buffers. Results: We have previously shown that inducing assembly of N–cadherin junctions promotes initiation of lens cell differentiation and that, in vivo, these N–cadherin junctions increase their linkage to the actin cytoskeleton through the recruitment of α–catenin. While both ß–catenin and γ–catenin can link N–cadherin to α–catenin and the cytoskeleton, we now show that only γ–catenin is recruited to N–cadherin junctions in a differentiation specific manner. Using differential detergent fractionation we investigated whether a distinct class of N–cadherin junctional complexes was responsible for stabilizing cadherin junctions in differentiating lens fiber cells. As the lens cells differentiated, γ–catenin became triton insoluble, evidence of its increased linkage to the cytoskeleton. The γ–catenin pattern of triton insolubility was paralleled by N–cadherin, supporting our hypothesis that γ–catenin mediates the formation of stable associations between N–cadherin and the actin cytoskeleton in differentiating lens fiber cells. However, most interesting was our finding that a large fraction of both N–cadherin and γ–catenin was associated with the highly insoluble protein fraction of the lens fiber cells, a pattern that was paralleled by vimentin, an intermediate filament protein. Co–immunoprecipitation studies showed that in this fraction N–cadherin was associated with vimentin. While vimentin intermediate filaments are known to provide structural stability to desmosomes and hemidesmosomes, this is the first demonstration that vimentin can link to and stabilize N–cadherin junctions. Conclusions:Our data demonstrates that γ–catenin is a critical component of stable N–cadherin junctions, and that intermediate filament association with N–cadherin junctions may serve to strengthen cell–cell adhesions in lens fiber cell regions.
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