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M. Massaro-Giordano, M. Montanari, C. M. Marshall, A. Giordano, M. Macaluso; TGF-ß1 and PMA Differentially Regulate PAI-2 Expression and Affect PAI-2/Rb Family Protein Interactions in Human Corneal and Conjunctival Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2739.
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© ARVO (1962-2015); The Authors (2016-present)
Plasminogen activator inhibitor type 2 (PAI-2) exhibits a different expression pattern in the cornea and conjunctiva. In corneal epithelium PAI-2 is present in differentiated cell layers and is primarily cytoplasmic. In the conjunctival epithelium PAI-2 expression is detected in the superficial and lower layers. The localization of PAI-2 in these epithelia remains an enigma but new evidence leads to the hypothesis that this inhibitor may regulate corneal and conjunctival cell proliferation. Recently, we showed that pRb family proteins interact with PAI-2 in both the cytoplasm and nucleus of normal primary human corneal and conjunctival epithelial cell cultures and we suggested a model of how pRb2/p130 and PAI-2 may cooperate in modulating PAI-2 gene expression by chromatin remodeling.
We assessed the effect of transforming growth factor- B1 (TGF-B1) and phorbol 12-myristate 13-acetate (PMA) treatment on the PAI-2 gene and protein expression by semi-quantitative RT-PCR and Western blot analysis in normal primary corneal and conjunctival cells. Moreover, we investigated if TGF-B1 and PMA treatment may affect PAI-2/Rb family protein/protein interactions by protein coimmunoprecipitation assays.
The results indicated that TGF-B1 down-regulates PAI-2 gene expression and decreases PAI-2 protein levels in both corneal and conjunctival cells. Interestingly, after TGF-B1 treatment we detected PAI-2 protein only in the nuclear fraction. Instead, PMA treatment induces up-regulation of PAI-2 gene expression and increases both PAI-2 nuclear and cytoplasmic protein levels. In addition, we found that after treatment with TGF-B1, PAI-2 was able to coimmunoprecipitate with pRb2/130 only in the nucleus of both corneal and conjunctival cells. PMA did not affect PAI-2/Rb family protein/protein interactions.
TGF-B1 and PMA may control a network of various signal transduction pathways, which by inducing reorganization of specific pRb2/130-multimolecular complexes on the PAI-2 promoter as well as changes in PAI-2/pRb family protein/ protein interactions can dictate a differential PAI-2 gene expression level under specific stimuli.
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