Purchase this article with an account.
Mark E. Ireland, Linda K. Mrock; Differentiation of Chick Lens Epithelial Cells: Involvement of the Epidermal Growth Factor Receptor and Endogenous Ligand. Invest. Ophthalmol. Vis. Sci. 2000;41(1):183-190.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
purpose. To characterize the constitutively activated epidermal growth
factor receptor in a lens epithelial cell population experiencing
initial stages of lens fiber formation, the chick lens annular pad.
methods. Phosphotyrosine levels of the receptor were examined with western blot
analysis and immunoprecipitation after ligand stimulation. Endogenous
receptor ligands were immunologically identified in whole cell lysates
of freshly isolated cells. The expression of lens fiber–specific
differentiation marker proteins was examined with western blot analysis
and enzyme-linked immunosorbent assay (ELISA) in short-term primary
cultures of annular pad cells exposed to ligand.
results. The major phosphotyrosine-containing protein in annular pad cells
comigrated with the epidermal growth factor receptor and increased its
phosphotyrosine content after epidermal growth factor treatment. Both
time- and dose-dependent responses were noted. The constitutive
activation of the receptor was determined in the presence of
phosphatase inhibitors. Endogenous transforming growth factor-α, but
not epidermal growth factor, was detected in freshly isolated cells.
Transforming growth factor-α (TGF-α) treatment produced greater
increases in receptor phosphotyrosine levels than equimolar levels of
epidermal growth factor. Finally, TGF-α treatment induced increased
expression of the beaded filament protein filensin when compared with
control cells. Filensin expression was increased further when cells
were costimulated with TGF-α and cAMP analogs.
conclusions. At least in the postnatal lens, endogenous TGF-α may affect overall
growth patterns by modulating differentiation-specific protein
expression. Furthermore, signaling pathways elicited by TGF-α and
cAMP analogs converge to cooperatively enhance lens fiber
This PDF is available to Subscribers Only