Abstract
Fibroblast growth factor (FGF) signaling is necessary for both proliferation and differentiation of lens cells. However, the molecular mechanisms by which FGFs exert their effects on the lens remain poorly understood. In this study, we show that FGF-2 repressed the expression of lens-specific genes at the proliferative phase in primary cultured lens cells. Using transfected cells, we also found that the activity of L-Maf, a lens differentiation factor, is repressed by FGF/ERK signaling. L-Maf is shown to be phosphorylated by ERK, and introduction of mutations into the ERK target sites on L-Maf promotes its stabilization. The stable L-Maf mutant protein promotes the differentiation of lens cells from neural retina cells. Taken together, these results indicate that FGF/ERK signaling negatively regulates the function of L-Maf in proliferative lens cells and that stabilization of the L-Maf protein is important for lens fiber differentiation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Cell Differentiation / physiology
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Cells, Cultured
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Chick Embryo
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Cysteine Endopeptidases
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Epithelial Cells / cytology
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Epithelial Cells / physiology
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Eye Proteins / genetics
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Eye Proteins / metabolism*
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Fibroblast Growth Factor 2 / metabolism*
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Gene Expression Regulation, Developmental*
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Genes, Reporter
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Humans
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Immunohistochemistry
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Lens, Crystalline / cytology
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Lens, Crystalline / growth & development*
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MAP Kinase Signaling System / physiology*
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Mitogen-Activated Protein Kinases / metabolism*
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Multienzyme Complexes / antagonists & inhibitors
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Phosphorylation
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Proteasome Endopeptidase Complex
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Recombinant Fusion Proteins / metabolism
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Serine / metabolism
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Threonine / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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delta-Crystallins / metabolism
Substances
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Eye Proteins
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Multienzyme Complexes
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Recombinant Fusion Proteins
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Transcription Factors
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delta-Crystallins
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Fibroblast Growth Factor 2
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Threonine
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Serine
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Mitogen-Activated Protein Kinases
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Cysteine Endopeptidases
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Proteasome Endopeptidase Complex