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P.V. Rao, R. Maddala, R. Herbst; Expression and Distribution of Isoprenylated Protein Tyrosine Phosphatases (PRLs) in Lens Tissue . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4325.
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Purpose:To understand the role of isoprenylated proteins in lens growth and function, herein we investigated the expression and distribution profile of isoprenylated low molecular weight protein tyrosine phosphatase (PRL) in lens tissue. Methods:Expression profiles of PRL 1, 2 and 3 in mouse and human lens and in human lens epithelial cells were determined by RT-PCR analysis. PRL-1 distribution in mouse lens and in human lens epithelial cells was studied by immunohistochemical analysis using rabbit polyclonal antibody raised against recombinant PRL-1. The effects of a farnesyl transferase inhibitor (FPT III) on PRL-1 subcellular distribution in human lens epithelial cells was determined immunocytochemically using confocal microscopy. PRL-1 expression under stress conditions was evaluated by Western blot analysis. Results:Initially analysis of an Affymetirx cDNA microarray of mouse lens transcripts revealed expression of three isoforms of PRL (PRL-1, 2 and 3), with PRL-1 being predominant. These microarray results were further substantiated by RT-PCR amplification of PRLs from human and mouse lens tissue and in human lens epithelial cells. Immunohistochemical localization of PRL-1 in day one old mouse lens cryosections revealed its presence in lens epithelial cells with strong expression in lens fibers. Subcellular localization of PRL-1 in human lens epithelial cells confirmed predominant localization to the nucleus and endoplasmic reticulum. Treatment of lens epithelial cells with farnesyl transferase inhibitor (FPT III) led to increased perinuclear relocalization of PRL-1. Interestingly, serum starvation and inhibition of farnesylation increased PRL-1 levels in lens epithelial cells. Expression of ATF-7, a known PRL-1 interacting transcription factor was confirmed in lens tissue by RT-PCR analysis. Conclusions:Isoprenylated protein tyrosine phosphatase, also known as phosphatase of regenerating liver (PRL), is an early inducible gene which has been thought to play an important role in proliferation, differentiation and in tumorogenesis. Expression of PRL-1 has been shown to be cell cycle dependent. To our knowledge this is the first report to document the expression of PRLs in lens and studies are ongoing to pursue our hypothesis that these protein phosphatases play important roles in lens growth and development.
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