Mechanisms Involved in Spontaneous and Viscum album Agglutinin-I-Induced Human Neutrophil Apoptosis: Viscum album Agglutinin-I Accelerates the Loss of Antiapoptotic Mcl-1 Expression and the Degradation of Cytoskeletal Paxillin and Vimentin Proteins Via Caspases
Autor: | Katarina Hostanska, Valérie Lavastre, Martin Pelletier, Denis Girard, Reinhard Saller |
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Rok vydání: | 2002 |
Předmět: |
Neutrophils
Immunology Intermediate Filaments Ribosome Inactivating Proteins Apoptosis Microtubules Membrane Potentials chemistry.chemical_compound Tumor Cells Cultured Humans Vimentin Immunology and Allergy Cytoskeleton Caspase Plant Proteins Toxins Biological Protein Synthesis Inhibitors chemistry.chemical_classification Inhibitor of apoptosis domain Reactive oxygen species Brefeldin A biology Intrinsic apoptosis Intracellular Membranes Vinculin Flow Cytometry Phosphoproteins Mistletoe Mitochondria Neoplasm Proteins Up-Regulation Cell biology Ribosome Inactivating Proteins Type 2 Cytoskeletal Proteins Proto-Oncogene Proteins c-bcl-2 chemistry Caspases biology.protein Myeloid Cell Leukemia Sequence 1 Protein Plant Preparations Paxillin Reactive Oxygen Species |
Zdroj: | The Journal of Immunology. 168:1419-1427 |
ISSN: | 1550-6606 0022-1767 |
Popis: | Viscum album agglutinin-I (VAA-I) is a plant lectin that possesses interesting potential therapeutic properties and immunomodulatory activities. We have recently found that VAA-I is a potent inducer of human neutrophil apoptosis, but the mechanism(s) involved require further elucidation. In this study, we found that VAA-I alters mitochondrial transmembrane potential and increases intracellular levels of reactive oxygen species (ROS). Despite these observations, treatment with the mitochondrial stabilizer, bongkrekic acid, or with catalase, known to degrade H2O2, fails to reverse VAA-I-induced apoptosis. Moreover, VAA-I was found to induce apoptosis in PLB-985 cells deficient in gp91phox, indicating that the lectin acts via an ROS-independent mechanism. Pretreatment of neutrophils with brefeldin A, an inhibitor of vesicular transport, was found to reverse VAA-I-induced apoptosis. Protein expression of Mcl-1 was decreased by VAA-I. The role of caspases in the degradation of cytoskeletal proteins during both spontaneous and VAA-I-induced neutrophil apoptosis was also investigated. Paxillin and vimentin were markedly degraded by VAA-I when compared with neutrophils that undergo spontaneous apoptosis, but not vinculin or α- and β-tubulin. Caspases were involved in cytoskeletal protein degradation because preincubation with the pan-caspase inhibitor N-benzyloxycarbonyl-V-A-D-O-methylfluoromethyl ketone was found to reverse protein cleavage. We conclude that VAA-I needs to be internalized to mediate apoptosis and that its activity is not dependent on a cell surface receptor-mediated pathway. Also, we conclude that VAA-I induces apoptosis by ROS-independent and Mcl-1-dependent mechanisms and that caspases are involved in cytoskeletal protein degradation in both spontaneous and VAA-I-induced neutrophil apoptosis. |
Databáze: | OpenAIRE |
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