Abstract
Tumor suppressor protein p53 is the key factor in the regulation of cell proliferation. Its concentration is low in the cytoplasm of most cell types. However, in corneal epithelium cells, abnormally high p53 content is detected. The aim of the present study was to characterize p53 distribution in the corneal epithelium. For this purpose, immunohistochemistry, western blot analysis and electronic microscope examinations were performed. A low level of p53 was identified in the lens, iris and retina; by contrast, a significantly high concentration of this protein was observed in the corneal epithelium. In opposite, MDM2 was identified in the lens, iris and retina while it is completely absent in the corneal epithelium. In addition, we found a significant amount of exosomes and other microvesicles containing p53 in the corneal mucin layer. We thus hypothesize that a significantly high level of p53 was caused by a combination of absents of MDM2 in parallel with p53 microvesicles storage.
Highlights
Tumor suppressor protein p53 is the key factor in the regulation of cell proliferation
It has been shown that the unstressed normal corneal epithelium of adult vertebrates is characterized, in contrast to other tissues, by high levels of p53 expression[4]
The gene produces a 53-kDa phosphoprotein that was first characterized as the major cellular protein associated with the T antigen encoded by simian virus 40 (SV40), a small DNA virus[13]
Summary
Tumor suppressor protein p53 is the key factor in the regulation of cell proliferation. Tumor suppressor protein p53, as a rule, is present in trace amounts in the vast majority of cells of adult organisms[1,2] a high synthesis of this protein is detected in certain tissues[3] This is explained by the high rate of degradation of p53 in cytoplasmic proteasomes[1]. A high level of p53 is detected in the cytoplasm of normal corneal epithelium cells of various vertebrate species[4] This protein, while present in significant quantities in the cytoplasm, does not exhibit its characteristic functional activities in unstressed normal conditions[5]. The aim of the present study was to characterize the features of p53 protein distribution in the corneal epithelium and corneal tear film and to examine the possible factors that contribute to a significant accumulation of this protein in the cytoplasm of epithelial cells of the cornea
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