Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Viral Bcl-2-Mediated Evasion of Autophagy Aids Chronic Infection of γHerpesvirus 68  [PDF]
Xiaofei E equal contributor,Seungmin Hwang equal contributor,Soohwan Oh equal contributor,Jong-Soo Lee,Joseph H. Jeong,Yousang Gwack,Timothy F. Kowalik,Ren Sun,Jae U. Jung ,Chengyu Liang
PLOS Pathogens , 2009, DOI: 10.1371/journal.ppat.1000609
Abstract: γ-herpesviruses (γHVs) have developed an interaction with their hosts wherein they establish a life-long persistent infection and are associated with the onset of various malignancies. One critical virulence factor involved in the persistency of murine γ-herpesvirus 68 (γHV68) is the viral homolog of the Bcl-2 protein (vBcl-2), which has been implicated to counteract both host apoptotic responses and autophagy pathway. However, the relative significance of the two activities of vBcl-2 in viral persistent infection has yet to be elucidated. Here, by characterizing a series of loss-of-function mutants of vBcl-2, we have distinguished the vBcl-2-mediated antagonism of autophagy from the vBcl-2-mediated inhibition of apoptosis in vitro and in vivo. A mutant γHV68 virus lacking the anti-autophagic activity of vBcl-2 demonstrates an impaired ability to maintain chronic infections in mice, whereas a mutant virus lacking the anti-apoptotic activity of vBcl-2 establishes chronic infections as efficiently as the wild-type virus but displays a compromised ability for ex vivo reactivation. Thus, the vBcl-2-mediated antagonism of host autophagy constitutes a novel mechanism by which γHVs confer persistent infections, further underscoring the importance of autophagy as a critical host determinant in the in vivo latency of γ-herpesviruses.
A Gammaherpesvirus Bcl-2 Ortholog Blocks B Cell Receptor-Mediated Apoptosis and Promotes the Survival of Developing B Cells In Vivo  [PDF]
Carrie B. Coleman,Jennifer E. McGraw,Emily R. Feldman,Alexa N. Roth,Lisa R. Keyes,Katrina R. Grau,Stephanie L. Cochran,Thomas J. Waldschmidt,Chengyu Liang,J. Craig Forrest,Scott A. Tibbetts
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1003916
Abstract: Gammaherpesviruses such as Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV, HHV-8) establish lifelong latency in their hosts and are associated with the development of several types of malignancies, including a subset of B cell lymphomas. These viruses are thought to co-opt the process of B cell differentiation to latently infect a fraction of circulating memory B cells, resulting in the establishment of a stable latency setpoint. However, little is known about how this infected memory B cell compartment is maintained throughout the life of the host. We have previously demonstrated that immature and transitional B cells are long-term latency reservoirs for murine gammaherpesvirus 68 (MHV68), suggesting that infection of developing B cells contributes to the maintenance of lifelong latency. During hematopoiesis, immature and transitional B cells are subject to B cell receptor (BCR)-mediated negative selection, which results in the clonal deletion of autoreactive B cells. Interestingly, numerous gammaherpesviruses encode homologs of the anti-apoptotic protein Bcl-2, suggesting that virus inhibition of apoptosis could subvert clonal deletion. To test this, we quantified latency establishment in mice inoculated with MHV68 vBcl-2 mutants. vBcl-2 mutant viruses displayed a marked decrease in the frequency of immature and transitional B cells harboring viral genome, but this attenuation could be rescued by increased host Bcl-2 expression. Conversely, vBcl-2 mutant virus latency in early B cells and mature B cells, which are not targets of negative selection, was remarkably similar to wild-type virus. Finally, in vivo depletion of developing B cells during chronic infection resulted in decreased mature B cell latency, demonstrating a key role for developing B cells in the maintenance of lifelong latency. Collectively, these findings support a model in which gammaherpesvirus latency in circulating mature B cells is sustained in part through the recurrent infection and vBcl-2-mediated survival of developing B cells.
Serum levels of bcl-2 and cellular oxidative stress in patients with viral hepatitis  [cached]
Osman H,Gabr O,Lotfy S,Gabr S
Indian Journal of Medical Microbiology , 2007,
Abstract: Purpose: This study was conducted to investigate the presence of bcl-2 protein in the serum of patients with viral hepatitis and to find out if there is any correlation between bcl-2 protein levels and cellular oxidative stress in the pathogenesis of viral hepatitis. Methods: This study was carried out on 130 patients with viral hepatitis, 70 with chronic hepatitis, 30 with liver cirrhosis and 30 with hepatocellular carcinoma (HCC) in addition to 20 healthy persons as the control. Serum bcl-2 protein was estimated by enzyme-linked immunosorbent assay, serum malondialdehyde (MDA), nitric oxide (NO) and antioxidant enzymes (GSH, GSH-px, GR and SOD) were measured using spectrophotometric analysis. Results: bcl-2 protein level was significantly elevated in the serum of HCC, cirrhosis and chronic hepatitis groups as compared to control group. There were significant positive correlations between higher bcl-2 protein level and viral hepatitis markers (HBsAg, anti-HCV antibodies) in HCC and cirrhotic patients as compared to chronic hepatitis group. An increase in oxidative stress markers (MDA, NO) and a decrease in antioxidant enzyme activities (SOD, GSH and GSH-px) were observed. However, there was a negative correlation between bcl-2 levels and GR in all studied patient groups. Conclusions: The release of oxidative free radicals, deficiency in antioxidant enzymes and the expression of bcl-2 protein might play a role in the pathogenesis of viral hepatitis. The ability to measure bcl-2 protein in the serum could be useful as a prognostic marker of cancer patients.
Microarray analysis of the in vivo sequence preferences of a minor groove binding drug
Todd T Eckdahl, Adam D Brown, Steven N Hart, Kelly J Malloy, Martha Shott, Gloria Yiu, Laura Hoopes, Laurie J Heyer
BMC Genomics , 2008, DOI: 10.1186/1471-2164-9-32
Abstract: Here we describe the use of microarray analysis to discover yeast genes that are affected by treatment with the MGBD berenil, thereby allowing the investigation of its sequence requirements for binding in vivo. A novel approach to sequence analysis allowed us to address hypotheses about genes that were directly or indirectly affected by drug binding. The results show that the sequence features of A/T richness and heteropolymeric character discovered by in vitro berenil binding studies are found upstream of genes hypothesized to be directly affected by berenil but not upstream of those hypothesized to be indirectly affected or those shown to be unaffected.The data support the conclusion that effects of berenil on gene expression in yeast cells can be explained by sequence patterns discovered by in vitro binding experiments. The results shed light on the sequence and structural rules by which berenil binds to DNA and affects the transcriptional regulation of genes and contribute generally to the development of MGBDs as tools for basic and applied research.Improved understanding of the sequence rules by which small molecules bind to DNA and alter patterns of gene expression advances both basic and applied research. In both of these contexts, molecules that bind noncovalently in the DNA minor groove with sequence-selective recognition have drawn considerable attention [1]. Minor groove binding drugs (MGBDs) have served as useful models for protein components of the transcriptional machinery since they can be more experimentally tractable than their macromolecular counterparts. For example, the understanding of the mechanism of action of TATA box binding protein, a general transcription factor required for proper initiation of transcription by RNA polymerase II, has been furthered using the MGBDs distamycin A, Hoechst 33258, and netropsin [2]. The observation that the MGBD berenil affects mitochondrial function and aerobic respiration in yeast suggests that it alters gen
An MRI-visible non-viral vector for targeted Bcl-2 siRNA delivery to neuroblastoma
Shen M, Gong FM, Pang PF, Zhu KS, Meng XC, Wu C, Wang J, Shan H, Shuai XT
International Journal of Nanomedicine , 2012, DOI: http://dx.doi.org/10.2147/IJN.S32900
Abstract: n MRI-visible non-viral vector for targeted Bcl-2 siRNA delivery to neuroblastoma Original Research (2777) Total Article Views Authors: Shen M, Gong FM, Pang PF, Zhu KS, Meng XC, Wu C, Wang J, Shan H, Shuai XT Published Date July 2012 Volume 2012:7 Pages 3319 - 3332 DOI: http://dx.doi.org/10.2147/IJN.S32900 Received: 12 April 2012 Accepted: 14 May 2012 Published: 02 July 2012 Min Shen,1,* Faming Gong,3,* Pengfei Pang,1,* Kangshun Zhu,1 Xiaochun Meng,1 Chun Wu,1 Jin Wang,1 Hong Shan,1,2 Xintao Shuai3,4 1Molecular Imaging Lab, Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China; 2Institute of Intervention Radiology, Sun Yat-sen University, Guangzhou, China; 3PCFM Lab of Ministry of Education, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, China; 4Center of Biomedical Engineering, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China *These authors contributed equally to this work Abstract: Polyethylene glycol-grafted polyethylenimine (PEG-g-PEI) which was functionalized with a neuroblastoma cell-specific ligand, the GD2 single chain antibody (scAbGD2), was synthesized in order to effectively deliver Bcl-2 siRNA into neuroblastoma cells. This polymer was complexed first with superparamagnetic iron oxide nanoparticle (SPION) to get a MRI-visible targeted non-viral vector (scAbGD2-PEG-g-PEI-SPION) and then with Bcl-2 siRNA to form nanoparticles showing low cytotoxicity. The targeting capacity of scAbGD2-PEG-g-PEI-SPION was successfully verified in vivo and in vitro by magnetic resonance imaging. The single chain antibody encoded targeted polyplex was more effective in transferring Bcl-2 siRNA than the nontargeting one in SK-N-SH cells, a human neuroblastoma cell line, resulting in a 46.34% inhibition in the expression of Bcl-2 mRNA. Consequently, a high level of cell apoptosis up to 50.76% and a significant suppression of tumor growth were achieved, which indicates that scAbGD2-PEG-g-PEI-SPION is a promising magnetic resonance imaging-visible non-viral vector for targeted neuroblastoma siRNA therapy and diagnosis.
Behavior of Solvent-Exposed Hydrophobic Groove in the Anti-Apoptotic Bcl-XL Protein: Clues for Its Ability to Bind Diverse BH3 Ligands from MD Simulations  [PDF]
Dilraj Lama, Vivek Modi, Ramasubbu Sankararamakrishnan
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0054397
Abstract: Bcl-XL is a member of Bcl-2 family of proteins involved in the regulation of intrinsic pathway of apoptosis. Its overexpression in many human cancers makes it an important target for anti-cancer drugs. Bcl-XL interacts with the BH3 domain of several pro-apoptotic Bcl-2 partners. This helical bundle protein has a pronounced hydrophobic groove which acts as a binding region for the BH3 domains. Eight independent molecular dynamics simulations of the apo/holo forms of Bcl-XL were carried out to investigate the behavior of solvent-exposed hydrophobic groove. The simulations used either a twin-range cut-off or particle mesh Ewald (PME) scheme to treat long-range interactions. Destabilization of the BH3 domain-containing helix H2 was observed in all four twin-range cut-off simulations. Most of the other major helices remained stable. The unwinding of H2 can be related to the ability of Bcl-XL to bind diverse BH3 ligands. The loss of helical character can also be linked to the formation of homo- or hetero-dimers in Bcl-2 proteins. Several experimental studies have suggested that exposure of BH3 domain is a crucial event before they form dimers. Thus unwinding of H2 seems to be functionally very important. The four PME simulations, however, revealed a stable helix H2. It is possible that the H2 unfolding might occur in PME simulations at longer time scales. Hydrophobic residues in the hydrophobic groove are involved in stable interactions among themselves. The solvent accessible surface areas of bulky hydrophobic residues in the groove are significantly buried by the loop LB connecting the helix H2 and subsequent helix. These observations help to understand how the hydrophobic patch in Bcl-XL remains stable in the solvent-exposed state. We suggest that both the destabilization of helix H2 and the conformational heterogeneity of loop LB are important factors for binding of diverse ligands in the hydrophobic groove of Bcl-XL.
Inhibition of NF-κB Activation In Vivo Impairs Establishment of Gammaherpesvirus Latency  [PDF]
Laurie T Krug,Janice M Moser,Shelley M Dickerson,Samuel H Speck
PLOS Pathogens , 2007, DOI: 10.1371/journal.ppat.0030011
Abstract: A critical determinant in chronic gammaherpesvirus infections is the ability of these viruses to establish latency in a lymphocyte reservoir. The nuclear factor (NF)-κB family of transcription factors represent key players in B-cell biology and are targeted by gammaherpesviruses to promote host cell survival, proliferation, and transformation. However, the role of NF-κB signaling in the establishment of latency in vivo has not been addressed. Here we report the generation and in vivo characterization of a recombinant murine gammaherpesvirus 68 (γHV68) that expresses a constitutively active form of the NF-κB inhibitor, IκBαM. Inhibition of NF-κB signaling upon infection with γHV68-IκBαM did not affect lytic replication in cell culture or in the lung following intranasal inoculation. However, there was a substantial decrease in the frequency of latently infected lymphocytes in the lung (90% reduction) and spleens (97% reduction) 16 d post intranasal inoculation. Importantly, the defect in establishment of latency in lung B cells could not be overcome by increasing the dose of virus 100-fold. The observed decrease in establishment of viral latency correlated with a loss of activated, CD69hi B cells in both the lungs and spleen at day 16 postinfection, which was not apparent by 6 wk postinfection. Constitutive expression of Bcl-2 in B cells did not rescue the defect in the establishment of latency observed with γHV68-IκBαM, indicating that NF-κB–mediated functions apart from Bcl-2–mediated B-cell survival are critical for the efficient establishment of gammaherpesvirus latency in vivo. In contrast to the results obtained following intranasal inoculation, infection of mice with γHV68-IκBαM by the intraperitoneal route had only a modest impact on splenic latency, suggesting that route of inoculation may alter requirements for establishment of virus latency in B cells. Finally, analyses of the pathogenesis of γHV68-IκBαM provides evidence that NF-κB signaling plays an important role during multiple stages of γHV68 infection in vivo and, as such, represents a key host regulatory pathway that is likely manipulated by the virus to establish latency in B cells.
Structural and Biochemical Bases for the Inhibition of Autophagy and Apoptosis by Viral BCL-2 of Murine γ-Herpesvirus 68  [PDF]
Bonsu Ku equal contributor,Jae-Sung Woo equal contributor,Chengyu Liang,Kwang-Hoon Lee,Hyang-Suk Hong,Xiaofei E,Key-Sun Kim,Jae U Jung,Byung-Ha Oh
PLOS Pathogens , 2008, DOI: 10.1371/journal.ppat.0040025
Abstract: All gammaherpesviruses express homologues of antiapoptotic B-cell lymphoma-2 (BCL-2) to counter the clearance of infected cells by host antiviral defense machineries. To gain insights into the action mechanisms of these viral BCL-2 proteins, we carried out structural and biochemical analyses on the interactions of M11, a viral BCL-2 of murine γ-herpesvirus 68, with a fragment of proautophagic Beclin1 and BCL-2 homology 3 (BH3) domain-containing peptides derived from an array of proapoptotic BCL-2 family proteins. Mainly through hydrophobic interactions, M11 bound the BH3-like domain of Beclin1 with a dissociation constant of 40 nanomole, a markedly tighter affinity compared to the 1.7 micromolar binding affinity between cellular BCL-2 and Beclin1. Consistently, M11 inhibited autophagy more efficiently than BCL-2 in NIH3T3 cells. M11 also interacted tightly with a BH3 domain peptide of BAK and those of the upstream BH3-only proteins BIM, BID, BMF, PUMA, and Noxa, but weakly with that of BAX. These results collectively suggest that M11 potently inhibits Beclin1 in addition to broadly neutralizing the proapoptotic BCL-2 family in a similar but distinctive way from cellular BCL-2, and that the Beclin1-mediated autophagy may be a main target of the virus.
Dynamic Expression of BCL6 in Murine Conventional Dendritic Cells during In Vivo Development and Activation  [PDF]
Ting-ting Zhang, Dong Liu, Samuele Calabro, Stephanie C. Eisenbarth, Giorgio Cattoretti, Ann M. Haberman
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0101208
Abstract: The transcriptional repressor BCL6 plays an essential role in the development of germinal center B cells and follicular helper T cells. However, much less is known about the expression and function of BCL6 in other cell types. Here we report that during murine dendritic cell (DC) ontogeny in vivo, BCL6 is not expressed in bone marrow hematopoietic stem cells, common DC precursors and committed precursors of conventional DCs (pre-cDCs), but is elevated in peripheral pre-cDCs. BCL6 protein levels rise as pre-cDCs differentiate into cDCs in secondary lymphoid organs. Elevated protein levels of Bcl6 are observed in all cDC subsets, with CD8α+ cDCs displaying the greatest levels. Co-staining of Ki-67 revealed BCL6hi cDCs to be more proliferative than BCL6lo cDCs. After adjuvant inoculation, BCL6 levels are significantly reduced in the CD11cint MHC class IIhi CD86hi cDCs. Activation-induced BCL6 reduction correlated with reduced proliferation. A LPS injection study further confirmed that, in response to microbial stimuli, BCL6 levels are dynamically regulated during the maturation of CD11cint MHC class IIhi splenic cDCs. This reduction of BCL6 levels in cDCs does not occur after LPS injection in MyD88?/? TRIF?/? mice. Thus, regulation of Bcl6 protein levels is dynamic in murine cDCs during development, maturation and activation in vivo.
Rates of CTL Killing in Persistent Viral Infection In Vivo  [PDF]
Marjet Elemans ,Arnaud Florins,Luc Willems,Becca Asquith
PLOS Computational Biology , 2014, DOI: doi/10.1371/journal.pcbi.1003534
Abstract: The CD8+ cytotoxic T lymphocyte (CTL) response is an important defence against viral invasion. Although CTL-mediated cytotoxicity has been widely studied for many years, the rate at which virus-infected cells are killed in vivo by the CTL response is poorly understood. To date the rate of CTL killing in vivo has been estimated for three virus infections but the estimates differ considerably, and killing of HIV-1-infected cells was unexpectedly low. This raises questions about the typical anti-viral capability of CTL and whether CTL killing is abnormally low in HIV-1. We estimated the rate of killing of infected cells by CD8+ T cells in two distinct persistent virus infections: sheep infected with Bovine Leukemia Virus (BLV) and humans infected with Human T Lymphotropic Virus type 1 (HTLV-1) which together with existing data allows us to study a total of five viruses in parallel. Although both BLV and HTLV-1 infection are characterised by large expansions of chronically activated CTL with immediate effector function ex vivo and no evidence of overt immune suppression, our estimates are at the lower end of the reported range. This enables us to put current estimates into perspective and shows that CTL killing of HIV-infected cells may not be atypically low. The estimates at the higher end of the range are obtained in more manipulated systems and may thus represent the potential rather than the realised CTL efficiency.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.