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P. E. Fort, M. K. Losiewicz, T. W. Gardner; Akt Isoforms Expression and Localization in the Retina: Role in Retinal Cells Sensitivity to Diabetes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5378.
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The goal of this study was to investigate the expression, localization and function of the different Akt isoforms in the retina and their dysregulation during diabetes. We previously showed that despite the fact that all 3 isoforms are expressed in the retina from control and diabetic animals, only Akt1 and Akt3 activity are decreased in correlation with the insulin receptor in diabetic conditions.
Western-blot and immunohistochemistry analysis, respectively, were used to determine levels of protein expression and cellular localization either on retinal sections, isolated cells or cell in culture. Cells in culture were transfected with different Akt constructs or siRNA to study the role of Akt(s) in different retinal cells.
Here we are reporting the cellular expression of the different Akt isoforms in the different cells of the retina in control animals. We demonstrated that all 3 isoforms are differentially expressed by several retinal cell types including neurons of the inner retina as well as Muller glial cells and astrocytes. These results were confirmed using different models of retinal cells in culture. Phopshorylation pattern study also lead to the demonstration of a new differentially regulated phosphorylation site retina and/or central nervous system specific. The phosphorylation pattern of the different Akt isoforms was also studied as an indicator of their activity and their regulation in basal and cellular stress conditions.
This studies points out several new specificities and mechanisms by which Akt(s) represent a crucial node of the insulin signaling pathway.
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