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Anne Petersen, Julia Adeloef, Madeleine Zetterberg; The immunoproteasome in human lens epithelial cells during oxidative stress. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2028.
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© ARVO (1962-2015); The Authors (2016-present)
The immunoproteasome is known to generate peptides for antigen presentation. However, it has also been proposed to have additional functions such as response to stress. The efficiency of the immunoproteasome to degrade oxidatively damaged proteins and peptides makes it an interesting mechanism in cataractogenesis.The aim of the study was to examine the presence, protein expression, proteolytic activity and intracellular location of the immunoproteasome in the human lens and cultured human lens epithelial cells (HlECs) with and without oxidative stress.
Expression of the immunoproteasome and constitutive proteasome subunits β1i/β1, β2i/β2 and β5i/β5 were studied by western blot in lens fibre extracts from phacoemulsification surgery, in fresh lens capsule pieces with adherent cells obtained during cataract surgery and in oxidatively stressed native HLECs in culture.The chymotrypsin-like activity of the immuno- and constitutive protesome was examined for oxidative stress response and to study the relative contribution of the immuno- and constitutive protesome of the total proteasome activity, specific inhibitors, ONX-0914 and MG-132 were used.Intracellular location of protesome subunits, β5i/β5, was studied by immunocytochemistry.Immunoproteasome subunits are expressed in lens fibre extracts from phacoemulsification surgery as well as in fresh lens capsule pieces with adherent cells.
The immunoproteasome expression in cultured HLECs is also upregulated by oxidative stress in contrast to the constitutive proteasome.The chymotrypsin-like activity of the immuno- and constitutive protesome is decreased with increased oxidative stress and the relative activity contribution of the two proteasome types is about equal of total proteasome activity.Immunocytochemical labelling of the immunoproteasome subunit β5i showed mainly cytosolic localization whereas the constitutive subunit β5 was predominantly localized in the nucleus. When challenged by increasing H2O2 concentrations, the immunoproteasome expression was increased.
The present study shows that the immunoproteasome is present in the human lens and that it is upregulated by oxidative stress whereas the chymotrypsin-like activity is decreased. The activity of the immuno- and constitutive protesome is equally affected by oxidative stress. These findings indicate a role for the immunoproteasome in oxidative stress management in the lens.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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