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K. Kaarniranta, R.K. Sironen, J. Huuskonen, M.A. Elo, H.M. Karjalainen, T. Suuronen, M. Teräsvirta, M.J. Lammi, H. Uusitalo, A. Salminen; The cytoprotective role of heat shock proteins and geldanamycin in human retinal pigment epithelial cells subjected to protein phosphatase inhibitor . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3671.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Reversible protein phosphorylation is an essential mechanism to regulate biological activities of human proteins that affect various various cellular processes, including protein–protein interactions, cell signaling, gene transcription, cell growth and death. Disturbance of cellular homeostasis in retinal pigment epithelial (RPE) cells is involved in development of age–related macular degeneration (AMD). We examined the heat shock protein 70 (Hsp70) stress response and cytotoxicity in human RPE cells subjected to protein phosphatase inhibitor okadaic acid (OA). Moreover, influence of a specific Hsp90 inhibitor geldanamycin (GA), a benzoquinone ansamycin, in cytoprotection was assessed. Methods: Northern blotting was used to analyze the steady–state levels of hsp70 mRNA. Western blotting was used to analysis of Hsp70 protein levels. Lactate dehydrogenase release was measured from culture medium using a non–radioactive cytotoxicity assay. Caspase–3 enzyme activity was measured by assaying the cleavage of a fluorescent peptide substrate, and cellular viability was determined by MTT assay. Results: OA exposure caused Hsp70 stress response prior to the detection of cytotoxicity. Interestingly, GA treatment attenuated clearly OA –induced cytotoxicity in the RPE cells. Alterations in caspase–3 activity were not observed. Conclusions: This study suggests that protein phosphatase inhibitors may present new insights in pathogenesis of AMD. Moreover, Hsp70 and Hsp90 are related to cytoprotection of RPE cells in response to the protein phosphatase inhibitor.
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