Hypoxia-regulated activity of PKCepsilon in the lens.

Abstract

PURPOSE:

To show that hypoxia is necessary to prevent opacification of the lens. Protein kinase C (PKC)-epsilon serves a role that is distinct from PKC-gamma when both PKC isoforms are expressed in the lens. PKCepsilon serves a very important role in hypoxic conditions, helping to prevent opacification of the lens.

METHODS:

Digital image analysis, confocal microscopy, dye transfer assay, coimmunoprecipitation, Western blot analysis, and enzyme activity assays were used, respectively, to study opacification of the lens, intercellular communications, cellular localization of connexin-43 (Cx43), and the interactions between PKCepsilon, PKCgamma, and Cx43 in the lens epithelial cells.

RESULTS:

Hypoxic conditions (1%-5% of oxygen) were very important in maintaining clarity of the lenses of wild-type (WT) mice. Normoxic conditions induced opacification of the WT lens. Lenses from the PKCepsilon-knockout mice underwent rapid opacification, even in hypoxic conditions. Hypoxia did not induce apoptosis in the lens epithelial cells, judging by the absence of active caspase-3, and it did not change intercellular communication and did not affect the number and localization of junctional Cx43 plaques in the lens epithelial cell culture. Hypoxia activated PKCepsilon, whereas phorbol ester (TPA), oxidation (H(2)O(2)), and insulin-like growth factor-1 (IGF-1) activated PKCgamma and decreased the activity of PKCepsilon. Hypoxia did not induce the phosphorylation of the Cx43.

CONCLUSIONS:

Hypoxia-induced activation of PKCepsilon is very important in surviving hypoxia and maintaining the clarity of the lens. However, PKCgamma is utilized in the control of Cx43 gap junctions.

• Authors: Vladimir Akoyev, Satyabrata Das, Snehalata Jena, Laura Grauer, Dolores J Takemoto
• Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci) Vol. 50 Issue 3 Pg. 1271-82 (Mar 2009) ISSN: 1552-5783 [Electronic] United States
• PMID: 18997087 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Connexin 43
• Insulin-Like Growth Factor I
• Hydrogen Peroxide
• protein kinase C gamma
• Protein Kinase C
• Protein Kinase C-epsilon
• Tetradecanoylphorbol Acetate

Topics

• Animals
• Blotting, Western
• Cataract (prevention & control)
• Cell Culture Techniques
• Connexin 43 (metabolism)
• Epithelial Cells (drug effects, metabolism)
• Humans
• Hydrogen Peroxide (pharmacology)
• Hypoxia (metabolism)
• Insulin-Like Growth Factor I (pharmacology)
• Lens, Crystalline (enzymology)
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Microscopy, Confocal
• Phosphorylation
• Protein Kinase C (metabolism)
• Protein Kinase C-epsilon (metabolism)
• Rabbits
• Signal Processing, Computer-Assisted
• Tetradecanoylphorbol Acetate (pharmacology)