scholarly journals Complement Regulation by Kaposi's Sarcoma-Associated Herpesvirus ORF4 Protein

2003 ◽  
Vol 77 (1) ◽  
pp. 592-599 ◽  
Author(s):  
O. Brad Spiller ◽  
Mairi Robinson ◽  
Elizabeth O'Donnell ◽  
Steven Milligan ◽  
B. Paul Morgan ◽  
...  
Keyword(s):  
Immune Response ◽  
Kaposi's Sarcoma ◽  
Transmembrane Domain ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Protein Isoforms ◽  
Orf4 Protein ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Orf4 Gene

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is associated with three types of human tumor: Kaposi's sarcoma, multicentric Castleman's disease, and primary effusion lymphoma. The virus encodes a number of proteins that participate in disrupting the immune response, one of which was predicted by sequence analysis to be encoded by open reading frame 4 (ORF4). The predicted ORF4 protein shares homology with cellular proteins referred to as regulators of complement activation. In the present study, the transcription profile of the ORF4 gene was characterized, revealing that it encodes at least three transcripts, by alternative splicing mechanisms, and three protein isoforms. Functional studies revealed that each ORF4 protein isoform inhibits complement and retains a C-terminal transmembrane domain. Consistent with the complement-regulating activity, we propose to name the proteins encoded by the ORF4 gene collectively as KSHV complement control protein (KCP). KSHV ORF4 is the most complex alternatively spliced gene encoding a viral complement regulator described to date. KCP inhibits the complement component of the innate immune response, thereby possibly contributing to the in vivo persistence and pathogenesis of this virus.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Inhibits Interleukin-4-Mediated STAT6 Phosphorylation To Regulate Apoptosis and Maintain Latency

2010 ◽  
Vol 84 (21) ◽  
pp. 11134-11144 ◽  
Author(s):  
Qiliang Cai ◽  
Subhash C. Verma ◽  
Ji-Young Choi ◽  
Michelle Ma ◽  
Erle S. Robertson
Keyword(s):  
Immune Response ◽  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Cellular Growth ◽  
Interleukin 4 ◽  
Nuclear Antigen ◽  
Viral Agent ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Cytokine-mediated JAK/STAT signaling controls numerous important biologic responses like immune function, cellular growth, and differentiation. Inappropriate activation of this signaling pathway is associated with a range of malignancies. Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious viral agent associated with Kaposi's sarcoma and may also contribute to B-cell disorders, which include primary effusion lymphoma (PEL) and multicentric Castleman's disease. However, regulation of cytokine-mediated lymphocytic immune response by KSHV is not fully understood. In this report, we demonstrate that KSHV suppresses the interleukin-4 (IL-4)-stimulated immune response of B-lymphocyte activation and cell proliferation. Moreover, we show that the latency-associated nuclear antigen (LANA) encoded by KSHV is essential for viral blocking of IL-4-induced signaling. LANA reduces phosphorylation of the signal transducers and activators of transcription 6 (STAT6) on Y-641 and concomitantly its DNA binding ability. Importantly, knockdown of endogenous STAT6 dramatically increases the sensitivity of PEL cells to low-serum stress or chemical-mediated cellular apoptosis and reactivation of KSHV from latent replication. Thus, these findings suggest that the IL-4/STAT6 signaling network is precisely controlled by KSHV for survival, maintenance of latency, and suppression of the host cytokine immune response of the virus-infected cells.

scholarly journals Lytic Replication-Defective Kaposi's Sarcoma-Associated Herpesvirus: Potential Role in Infection and Malignant Transformation

2004 ◽  
Vol 78 (20) ◽  
pp. 11108-11120 ◽  
Author(s):  
Jian-Hong Deng ◽  
Yan-Jin Zhang ◽  
Xin-Ping Wang ◽  
Shou-Jiang Gao
Keyword(s):  
Malignant Transformation ◽  
Cell Lines ◽  
Kaposi's Sarcoma ◽  
Potential Role ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Screening Methods ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Defective viruses often have pivotal roles in virus-induced diseases. Although Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), defective KSHV has not been reported. Using differential genetic screening methods, we show that defective KSHV is present in KS tumors and PEL cell lines. To investigate the role of defective viruses in KSHV-induced pathogenesis, we isolated and characterized a lytic replication-defective KSHV, KV-1, containing an 82-kb genomic deletion of solely lytic genes. Cells harboring KV-1 escaped G0/G1 apoptosis induced by spontaneous lytic replication occurred in cells infected with regular KSHV but maintained efficient latent replication. Consequently, KV-1-infected cells had phenotypes of enhanced cell proliferation and transformation potentials. Importantly, KV-1 was packaged as infectious virions by using regular KSHV as helpers, and KV-1-like variants were detected in cultures of two of five KSHV cell lines and 1 of 18 KS tumors. These results point to a potential role for defective viruses in the regulation of KSHV infection and malignant transformation.

scholarly journals Mechanism of Angiopoietin-1 Upregulation in Kaposi's Sarcoma-Associated Herpesvirus-Infected PEL Cell Lines

2015 ◽  
Vol 89 (9) ◽  
pp. 4786-4797 ◽  
Author(s):  
Xin Zheng ◽  
Eriko Ohsaki ◽  
Keiji Ueda
Keyword(s):  
Cell Lines ◽  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Regulatory Region ◽  
Leukemia Cell ◽  
Kaposi’S Sarcoma ◽  
Dependent Manner ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Angiopoietin 1

ABSTRACTAngiopoietin-1 (ANGPT-1) is a secreted glycoprotein that was first characterized as a ligand of the Tie2 receptor. In a previous study using microarray analysis, we found that the expression of ANGPT-1 was upregulated in Kaposi's sarcoma-associated herpesvirus (KSHV)-infected primary effusion lymphoma (PEL) cell lines compared with that in uninfected Burkitt and other leukemia cell lines. Other authors have also reported focal expression of ANGPT-1 mRNA in biopsy specimens of Kaposi's sarcoma (KS) tissue from patients with AIDS. Here, to confirm these findings, we examined the expression and secretion levels of ANGPT-1 in KSHV-infected PEL cell lines and address the mechanisms ofANGPT-1transcriptional regulation. We also showed that ANGPT-1 was expressed and localized in the cytoplasm and secreted into the supernatant of KSHV-infected PEL cells. Deletion studies of the regulatory region revealed that the region encompassing nucleotides −143 to −125 of theANGPT-1-regulating sequence was responsible for this upregulation. Moreover, an electrophoretic mobility shift assay and chromatin immunoprecipitation, followed by quantitative PCR, suggested that some KSHV-infected PEL cell line-specific DNA-binding factors, such as OCT-1, should be involved in the upregulation ofANGPT-1in a sequence-dependent manner.IMPORTANCEWe confirmed that ANGPT-1 was expressed in and secreted from KSHV-infected PEL cells and that the transcriptional activity ofANGPT-1was upregulated. A 19-bp fragment was identified as the region responsible forANGPT-1upregulation through binding with OCT-1 as a core factor in PEL cells. This study suggests that ANGPT-1 is overproduced in KSHV-infected PEL cells, which could affect the pathophysiology of AIDS patients with PEL.

scholarly journals Identification and Characterization of the Orf49 Protein of Kaposi's Sarcoma-Associated Herpesvirus

2006 ◽  
Vol 80 (6) ◽  
pp. 3062-3070 ◽  
Author(s):  
Carlos M. González ◽  
Emily L. Wong ◽  
Brian S. Bowser ◽  
Gregory K. Hong ◽  
Shannon Kenney ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transcriptional Activation ◽  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Cycle ◽  
Transcription Activator ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Factor C ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. Kaposi's sarcoma is the most common neoplasm among human immunodeficiency virus-positive individuals. Like other herpesviruses, KSHV is able to establish a predominantly latent, life-long infection in its host. The KSHV lytic cycle can be triggered by a number of stimuli that induce the expression of the key lytic switch protein, the replication and transcription activator (RTA) encoded by Orf50. The expression of Rta is necessary and sufficient to trigger the full lytic program resulting in the ordered expression of viral proteins, release of viral progeny, and host cell death. We have characterized an unknown open reading frame, Orf49, which lies adjacent and in the opposite orientation to Orf50. Orf49 is expressed during the KSHV lytic cycle and shows early transcription kinetics. We have mapped the 5′ and 3′ ends of the unspliced Orf49 transcript, which encodes a 30-kDa protein that is localized to both the nucleus and the cytoplasm. Interestingly, we found that Orf49 was able to cooperate with Rta to activate several KSHV lytic promoters containing AP-1 sites. The Orf49-encoded protein was also able to induce transcriptional activation through c-Jun but not the ATF1, ATF2, or CREB transcription factor. We found that Orf49 could induce phosphorylation and activation of the transcription factor c-Jun, the Jun N-terminal kinase (JNK), and p38. Our data suggest that Orf49 functions to activate the JNK and p38 pathways during the KSHV lytic cycle.

scholarly journals Suberoyl bis-hydroxamic acid reactivates Kaposi’s sarcoma-associated herpesvirus through histone acetylation and induces apoptosis in lymphoma cells

2020 ◽  
Author(s):  
Shun Iida ◽  
Sohtaro Mine ◽  
Keiji Ueda ◽  
Tadaki Suzuki ◽  
Hideki Hasegawa ◽  
...  
Keyword(s):  
Histone Acetylation ◽  
Hydroxamic Acid ◽  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Mitochondrial Pathway ◽  
Dependent Manner ◽  
Transcription Activator ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

Kaposi’s sarcoma-associated herpesvirus (KSHV) is an etiologic agent of Kaposi’s sarcoma as well as primary effusion lymphoma (PEL), an aggressive B-cell neoplasm which mostly arises in immunocompromised individuals. Lytic replication of KSHV is also associated with a subset of multicentric Castleman diseases. At present, there is no specific treatment available for PEL and its prognosis is poor. In this study, we found that the histone deacetylase inhibitor suberoyl bis-hydroxamic acid (SBHA) induced KSHV reactivation in PEL cells in a dose-dependent manner. Next-generation sequencing analysis showed that more than 40% of all transcripts expressed in SBHA-treated PEL cells originated from the KSHV genome compared with less than 1% in untreated cells. Chromatin immunoprecipitation assays demonstrated that SBHA induced histone acetylation targeting the promoter region of the KSHV replication and transcription activator gene. However, there was no significant change in methylation status of the promoter region of this gene. In addition to its effect of KSHV reactivation, this study revealed that SBHA induces apoptosis in PEL cells in a dose-dependent manner, inducing acetylation and phosphorylation of p53, cleavage of caspases, and expression of pro-apoptotic factors such as Bim and Bax. These findings suggest that SBHA reactivates KSHV from latency and induces apoptosis through the mitochondrial pathway in PEL cells. Therefore, SBHA can be considered a new tool for induction of KSHV reactivation, and could provide a novel therapeutic strategy against PEL. IMPORTANCE Kaposi’s sarcoma and primary effusion lymphoma cells are latently infected with Kaposi’s sarcoma-associated herpesvirus (KSHV), whereas KSHV replication is frequently observed in multicentric Castleman disease. Although KSHV replication can be induced by some chemical reagents (e.g. 12-O-tetradecanoylphorbol-13-acetate), the mechanism of KSHV replication is not fully understood. We found that the histone deacetylase inhibitor suberoyl bis-hydroxamic acid (SBHA) induced KSHV reactivation with high efficiency, through histone acetylation in the promoter of the replication and transcription activator gene, compared with 12-O-tetradecanoylphorbol-13-acetate. SBHA also induced apoptosis through the mitochondrial pathway in KSHV-infected cells, with a lower EC50 than measured for viral reactivation. SBHA could be used in a highly efficient replication system for KSHV in vitro, and as a tool to reveal the mechanism of replication and pathogenesis of KSHV. The ability of SBHA to induce apoptosis at lower levels than needed to stimulate KSHV reactivation, indicates its therapeutic potential.

scholarly journals The Kaposi's Sarcoma-Associated Herpesvirus G Protein-Coupled Receptor Has Broad Signaling Effects in Primary Effusion Lymphoma Cells

2003 ◽  
Vol 77 (1) ◽  
pp. 57-67 ◽  
Author(s):  
Mark Cannon ◽  
Nicola J. Philpott ◽  
Ethel Cesarman
Keyword(s):  
G Protein ◽  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Cell Cycle Control ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
G Protein Coupled Receptor ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
G Protein Coupled

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV/human herpesvirus 8 [HHV-8]) is a gamma-2-herpesvirus responsible for Kaposi's sarcoma as well as primary effusion lymphoma (PEL). KSHV is a lymphotropic virus that has pirated many mammalian genes involved in inflammation, cell cycle control, and angiogenesis. Among these is the early lytic viral G protein-coupled receptor (vGPCR), a homologue of the human interleukin-8 (IL-8) receptor. When expressed, vGPCR is constitutively active and can signal via mitogen- and stress-activated kinases. In certain models it activates the transcriptional potential of NF-κB and activator protein 1 (AP-1) and induces vascular endothelial growth factor (VEGF) production. Despite its importance to the pathogenesis of all KSHV-mediated disease, little is known about vGPCR activity in hematopoietic cells. To study the signaling potential and downstream effects of vGPCR in such cells, we have developed PEL cell lines that express vGPCR under the control of an inducible promoter. The sequences required for tetracycline-mediated induction were cloned into a plasmid containing adeno-associated virus type 2 elements to enhance integration efficiency. This novel plasmid permitted studies of vGPCR activity in naturally infected KSHV-positive lymphocytes. We show that vGPCR activates ERK-2 and p38 in PEL cells. In addition, it increases the transcription of reporter genes under the control of AP-1, NF-κB, CREB, and NFAT, a Ca2+-dependent transcription factor important to KSHV lytic gene expression. vGPCR also increases the transcription of KSHV open reading frames 50 and 57, thereby displaying broad potential to affect viral transcription patterns. Finally, vGPCR signaling results in increased PEL cell elaboration of KSHV vIL-6 and VEGF, two growth factors involved in KSHV-mediated disease pathogenesis.

scholarly journals Induction of Paclitaxel Resistance by the Kaposi's Sarcoma-Associated Herpesvirus Latent Protein LANA2

2007 ◽  
Vol 82 (3) ◽  
pp. 1518-1525 ◽  
Author(s):  
C. Muñoz-Fontela ◽  
L. Marcos-Villar ◽  
F. Hernandez ◽  
P. Gallego ◽  
E. Rodriguez ◽  
...  
Keyword(s):  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Paclitaxel Resistance ◽  
Microtubule Stabilization ◽  
Cell Tissue ◽  
Transcriptional Pattern ◽  
Direct Binding ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is the causal agent of both KS and primary effusion lymphoma (PEL). Although treatment with paclitaxel has significant antitumor activity in KS, drug resistance represents a major obstacle for improving the overall response and survival of PEL patients. The transcriptional pattern of KSHV is cell/tissue specific, as revealed by the fact that the viral latent protein LANA2 is detected exclusively in B cells. This paper focuses on the mechanism of paclitaxel resistance observed in PEL cells. Here we show that LANA2 protein modulates microtubule dynamics through its direct binding to polymerized microtubules, preventing microtubule stabilization induced by paclitaxel. This is the first demonstration of paclitaxel resistance induced by a viral protein and suggests a link between the expression of LANA2 and the resistance of PEL cells to paclitaxel.

Angiogenesis and Hematopoiesis Induced by Kaposi’s Sarcoma-Associated Herpesvirus-Encoded Interleukin-6

Blood ◽  
1999 ◽  
Vol 93 (12) ◽  
pp. 4034-4043 ◽  
Author(s):  
Yoshiyasu Aoki ◽  
Elaine S. Jaffe ◽  
Yuan Chang ◽  
Karen Jones ◽  
Julie Teruya-Feldstein ◽  
...  
Keyword(s):  
Lymph Nodes ◽  
Interleukin 6 ◽  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Biological Activities ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
Nih3t3 Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

Kaposi’s sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 [HHV-8]) is a herpesvirus linked to the development of Kaposi’s sarcoma (KS), primary effusion lymphoma, and a proportion of Castleman’s disease. KSHV encodes viral interleukin-6 (vIL-6), which is structurally homologous to human and murine IL-6. The biological activities of vIL-6 are largely unknown. To gain insight into the biology of vIL-6, we expressed vIL-6 in murine fibroblasts NIH3T3 cells and inoculated stable vIL-6–producing clones into athymic mice. vIL-6 was detected selectively in the blood of mice injected with vIL-6–expressing clones. Compared with controls, vIL-6–positive mice displayed increased hematopoiesis in the myeloid, erythroid, and megakaryocytic lineages; plasmacytosis in spleen and lymph nodes; hepatosplenomegaly; and polyclonal hypergammaglobulinemia. vIL-6–expressing NIH3T3 cells gave rise to tumors more rapidly than did control cells, and vIL-6–positive tumors were more vascularized than controls. Vascular endothelial growth factor (VEGF) was detected at higher levels in the culture supernatant of vIL-6–expressing cells compared with controls, and immunohistochemical staining detected VEGF in spleen, lymph nodes, and tumor tissues from mice bearing vIL-6–producing tumors but not control tumors. Thus, vIL-6 is a multifunctional cytokine that promotes hematopoiesis, plasmacytosis, and angiogenesis. Through these functions, vIL-6 may play an important role in the pathogenesis of certain KSHV-associated disorders.

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