Geldanamycin activates Hsp70 response and attenuates okadaic acid-induced cytotoxicity in human retinal pigment epithelial cells.

Abstract

Reversible protein phosphorylation regulates the biological activities of many human proteins involved in crucial cellular processes, e.g., protein-protein interactions, cell signaling, gene transcription, cell growth, and death. A malfunction of cellular homeostasis in retinal pigment epithelial (RPE) cells is involved in the age-related retinal degeneration. In this study, we examined cytotoxicity in human RPE cells subjected to the protein phosphatase inhibitor, okadaic acid (OA). Moreover, the influence of Hsp90 inhibitor geldanamycin (GA), a benzoquinone ansamycin, in cytoprotection was assessed. Hsp70 protein levels were analyzed by Western blot. Cellular viability was determined by LDH and MTT assays. To study apoptotic cell death, caspase-3 enzyme activity was measured by assaying the cleavage of a fluorescent peptide substrate and Hoechst dye was used to visualize nuclear morphology. OA treatment caused morphological changes and induced cytotoxicity by caspase-3-independent manner in the RPE cells. No evidence of nuclear fragmentation was observed in response to OA. Interestingly, GA treatment accumulated Hsp70 protein and attenuated OA-induced cytotoxicity. This study suggests that Hsp70 and Hsp90 are closely related to cytoprotection of RPE cells in response to protein phosphatase inhibition.

• Authors: Kai Kaarniranta, Tuomas Ryhänen, Reijo K Sironen, Tiina Suuronen, Mika A Elo, Hannu M Karjalainen, Mikko J Lammi, Markku Teräsvirta, Hannu Uusitalo, Antero Salminen
• Journal: Brain research. Molecular brain research (Brain Res Mol Brain Res) Vol. 137 Issue 1-2 Pg. 126-31 (Jun 13 2005) ISSN: 0169-328X [Print] Netherlands
• PMID: 15950770 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Benzoquinones
• Cysteine Proteinase Inhibitors
• Enzyme Inhibitors
• HSP70 Heat-Shock Proteins
• HSP90 Heat-Shock Proteins
• Lactams, Macrocyclic
• Quinones
• Okadaic Acid
• Phosphoprotein Phosphatases
• CASP3 protein, human
• Caspase 3
• Caspases
• geldanamycin

Topics

• Benzoquinones
• Caspase 3
• Caspases (drug effects, metabolism)
• Cell Death (drug effects, physiology)
• Cell Line
• Cell Nucleus (drug effects, metabolism)
• Cell Survival (drug effects, physiology)
• Cysteine Proteinase Inhibitors (pharmacology)
• Cytoprotection (drug effects, physiology)
• Enzyme Activation (drug effects, physiology)
• Enzyme Inhibitors (toxicity)
• Epithelial Cells (drug effects, metabolism)
• HSP70 Heat-Shock Proteins (drug effects, metabolism)
• HSP90 Heat-Shock Proteins (drug effects, metabolism)
• Humans
• Lactams, Macrocyclic
• Okadaic Acid (antagonists & inhibitors, toxicity)
• Phosphoprotein Phosphatases (antagonists & inhibitors, metabolism)
• Phosphorylation (drug effects)
• Pigment Epithelium of Eye (drug effects, metabolism)
• Quinones (pharmacology)
• Retinal Degeneration (enzymology, physiopathology)
• Up-Regulation (drug effects, physiology)