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The immunoproteasome in human lens epithelial cells during oxidative stress

Journal article
Authors Anne Petersen
Madeleine Zetterberg
Published in Investigative Ophthalmology and Visual Science
Volume 57
Issue 11
Pages 5038-5045
ISSN 0146-0404
Publication year 2016
Published at Institute of Neuroscience and Physiology, Department of Clinical Neuroscience and Rehabilitation
Pages 5038-5045
Language en
Links dx.doi.org/10.1167/iovs.16-19536
Keywords Constitutive proteasome, Human lens, Human lens epithelial cells, Immunoproteasome, Oxidative stress
Subject categories Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy), Biochemistry and Molecular Biology

Abstract

PURPOSE. The immunoproteasome is known to generate peptides for antigen presentation. However, it has also been proposed to have additional functions such as stress response. The propensity of the immunoproteasome for degradation of oxidatively damaged proteins and peptides makes it interesting in the context of cataract formation and prevention. This study hypothesized that the immunoproteasome is present in human cataractous lenses and that oxidative stress will induce its expression, affect its proteolytic activity and its intracellular location in native cultured human lens epithelial cells (HLECs). METHODS. The expression of the immunoproteasome and the constitutive proteasome subunits β1i/β1, β2i/β2, and β5i/β5 were studied by using Western blotting. The chymotrypsin-like activity was investigated for possible oxidative stress response. Inhibitors specific for the immuno- and constitutive proteasome, ONX-0914 and MG-132, respectively, were used to study their relative contributions to total proteasome activity. The intracellular location of the proteasomal subunits β5i and β5 was studied by immunocytochemistry. RESULTS. Immunoproteasome subunits were detected both in the lens epithelium and in the lens fibers derived from cataract surgery. Oxidative stress to cultured HLECs upregulated the immunoproteasome but not the constitutive proteasome. The chymotrypsin-like activity decreased with increased oxidative stress and the two proteasome types contributed equally to total proteasome activity. Immunocytochemical labeling of subunit β5i showed mainly cytosolic localization, whereas subunit β5 was localized predominantly in the nucleus. H2O2-induced challenge increased the expression of the immunoproteasome. CONCLUSIONS. The present findings indicate a role for the immunoproteasome in oxidative stress management in the lens. © 2016, Association for Research in Vision and Ophthalmology Inc. All rights reserved.

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