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Author: Zahedi, René P. × End date: 2019 × Start date: 2016 × DDC: 610 ×

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Now showing 1 - 4 of 4
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    Cytomegalovirus downregulates IRE1 to repress the unfolded protein response
    (San Francisco, CA : Public Library of Science, 2013) Stahl, Sebastian; Burkhart, Julia M.; Hinte, Florian; Tirosh, Boaz; Mohr, Hermine; Zahedi, René P.; Sickmann, Albert; Ruzsics, Zsolt; Budt, Matthias; Brune, Wolfram
    During viral infection, a massive demand for viral glycoproteins can overwhelm the capacity of the protein folding and quality control machinery, leading to an accumulation of unfolded proteins in the endoplasmic reticulum (ER). To restore ER homeostasis, cells initiate the unfolded protein response (UPR) by activating three ER-to-nucleus signaling pathways, of which the inositol-requiring enzyme 1 (IRE1)-dependent pathway is the most conserved. To reduce ER stress, the UPR decreases protein synthesis, increases degradation of unfolded proteins, and upregulates chaperone expression to enhance protein folding. Cytomegaloviruses, as other viral pathogens, modulate the UPR to their own advantage. However, the molecular mechanisms and the viral proteins responsible for UPR modulation remained to be identified. In this study, we investigated the modulation of IRE1 signaling by murine cytomegalovirus (MCMV) and found that IRE1-mediated mRNA splicing and expression of the X-box binding protein 1 (XBP1) is repressed in infected cells. By affinity purification, we identified the viral M50 protein as an IRE1-interacting protein. M50 expression in transfected or MCMV-infected cells induced a substantial downregulation of IRE1 protein levels. The N-terminal conserved region of M50 was found to be required for interaction with and downregulation of IRE1. Moreover, UL50, the human cytomegalovirus (HCMV) homolog of M50, affected IRE1 in the same way. Thus we concluded that IRE1 downregulation represents a previously undescribed viral strategy to curb the UPR.
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    Gene network activity in cultivated primary hepatocytes is highly similar to diseased mammalian liver tissue
    (Heidelberg : Springer, 2016) Godoy, Patricio; Widera, Agata; Schmidt-Heck, Wolfgang; Campos, Gisela; Meyer, Christoph; Cadenas, Cristina; Reif, Raymond; Stöber, Regina; Hammad, Seddik; Pütter, Larissa; Gianmoena, Kathrin; Marchan, Rosemarie; Ghallab, Ahmed; Edlund, Karolina; Nüssler, Andreas; Thasler, Wolfgang E.; Damm, Georg; Seehofer, Daniel; Weiss, Thomas S.; Dirsch, Olaf; Dahmen, Uta; Gebhardt, Rolf; Chaudhari, Umesh; Meganathan, Kesavan; Sachinidis , Agapios; Kelm, Jens; Hofmann, Ute; Zahedi, René P.; Guthke, Reinhard; Blüthgen, Nils; Dooley, Steven; Hengstler, Jan G.
    It is well known that isolation and cultivation of primary hepatocytes cause major gene expression alterations. In the present genome-wide, time-resolved study of cultivated human and mouse hepatocytes, we made the observation that expression changes in culture strongly resemble alterations in liver diseases. Hepatocytes of both species were cultivated in collagen sandwich and in monolayer conditions. Genome-wide data were also obtained from human NAFLD, cirrhosis, HCC and hepatitis B virus-infected tissue as well as mouse livers after partial hepatectomy, CCl4 intoxication, obesity, HCC and LPS. A strong similarity between cultivation and disease-induced expression alterations was observed. For example, expression changes in hepatocytes induced by 1-day cultivation and 1-day CCl4 exposure in vivo correlated with R = 0.615 (p < 0.001). Interspecies comparison identified predominantly similar responses in human and mouse hepatocytes but also a set of genes that responded differently. Unsupervised clustering of altered genes identified three main clusters: (1) downregulated genes corresponding to mature liver functions, (2) upregulation of an inflammation/RNA processing cluster and (3) upregulated migration/cell cycle-associated genes. Gene regulatory network analysis highlights overrepresented and deregulated HNF4 and CAR (Cluster 1), Krüppel-like factors MafF and ELK1 (Cluster 2) as well as ETF (Cluster 3) among the interspecies conserved key regulators of expression changes. Interventions ameliorating but not abrogating cultivation-induced responses include removal of non-parenchymal cells, generation of the hepatocytes’ own matrix in spheroids, supplementation with bile salts and siRNA-mediated suppression of key transcription factors. In conclusion, this study shows that gene regulatory network alterations of cultivated hepatocytes resemble those of inflammatory liver diseases and should therefore be considered and exploited as disease models.
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    Proteomic insights into non-small cell lung cancer: New ideas for cancer diagnosis and therapy from a functional viewpoint
    (Amsterdam : Elsevier, 2014) Linxweiler, Johannes; Kollipara, Laxmikanth; Zahedi, René P.; Lampel, Pavel; Zimmermann, Richard; Greiner, Markus
    We recently characterized SEC62 as an oncogene in non-small-cell lung cancer (NSCLC). Here we aimed to gain further insight into the molecular mechanisms of the cancer-related functions of this oncogene. We performed 2D-DIGE proteome analysis of tumor material from patients with NSCLC and of HEK293 cells stably overexpressing plasmid-encoded SEC62, combined with investigation of the Sec62 interactome. Furthermore, we analyzed the proteomic effects of siRNA-mediated depletion of the Sec62-interacting protein Sec63. We identified a comprehensive list of differentially regulated proteins, providing new insights into the molecular mechanisms of the cancer-related functions of Sec62 in cell migration, drug resistance, and Ca2+-homeostasis.
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    Biological pathways modulated by antipsychotics in the blood plasma of schizophrenia patients and their association to a clinical response
    (London : Nature Publishing Group, 2015) Martins-de-Souza, Daniel; Solari, Fiorella A.; Guest, Paul C.; Zahedi, René P.; Steiner, Johann
    Proteomics is a valuable tool to unravel molecular mechanisms involved in human disorders. Considering the mediocre effectiveness of antipsychotics, which are the main class of drug used to treat schizophrenia, we analyzed a cohort of 58 schizophrenia patients who had blood collected before and after 6 weeks of antipsychotic treatment using a shotgun mass spectrometry proteomic profiling approach. Our aim was to unravel molecular pathways involved with an effective drug response. The results showed that all patients had essentially the same biochemical pathways triggered Independent of the antipsychotic response outcome. However, we observed that these pathways were regulated in different directions in blood samples from those who responded well to antipsychotics, compared with those who had a poorer outcome. These data are novel, timely and may help to guide new research efforts in the design of new treatments or medications for schizophrenia based on biologically relevant pathways.