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S.B. Zanello, R. Nayak, P. Farthing–Nayak; Expression of 14.3.3 (Stratifin) in Normal and Pathologic Human Corneal Epithelium . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1587.
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© ARVO (1962-2015); The Authors (2016-present)
14.3.3σ or stratifin belongs to the family of 14.3.3 signaling proteins and is a marker of differentiation in cells of epithelial origin. In the skin, 14.3.3σ has been shown to be secreted by differentiated keratinocytes and to induce the expression of matrix metalloproteinase–1 in dermal fibroblasts. Recent attention has been drawn to 14.3.3σ since downregulation of its expression is causative of several different forms of cancer.
To study 14.3.3σ expression in corneal epithelium.
2–dimensional gel electrophoresis and mass spectrometry with Mascot search were performed to identify 14.3.3σ; Western blotting and immunohistochemistry of human corneas using a monoclonal antibody to 14.3.3σ were carried out to examine the presence of 14.3.3σ.
14.3.3σ appeared as a robust spot at 30 kDa and pI 4–5 in silver–stained 2D gels of whole cornea protein extracts from healthy individuals and patients with keratoconus, corneal dystrophy and corneal edema. Western blots of whole corneal extracts showed no apparent overall change in the level of expression of 14.3.3σ among the abovementioned samples. No immunoreactive 30 kDa band was shown in protein extracts from keratocytes in culture, indicating that the expression in the cornea was specifically of epithelial origin. This was confirmed by immunohistochemistry of corneal sections. Immunofluorescence was seen both in the cytoplasm and nucleus of epithelial cells. However, the labeling was more evenly distributed in the epithelium of corneas from healthy individuals than in dystrophic corneas, in which there were abundant cells where the staining was only localized to the cytoplasm and not in the nucleus. This specific cytoplasmic immunoreactivity was more notable in keratoconus corneal sections and a similar pattern was observed in corneal dystrophy and edema in older patients.
Our work presents evidence of 14.3.3σ expression in the corneal epithelium and of differences in 14.3.3σ cellular localization between healthy and affected corneas. Future studies will be directed to study whether alteration in 14.3.3σ expression and/or signaling pathways could affect the communication between the corneal epithelium and the stroma contributing to the development of certain corneal diseases. In addition, further efforts will be made to examine 14.3.3σ expression in corneal dysplasias and neoplasias.
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