scholarly journals Human Herpesvirus 8 Envelope Glycoprotein K8.1A Interaction with the Target Cells Involves Heparan Sulfate

2001 ◽  
Vol 75 (16) ◽  
pp. 7517-7527 ◽  
Author(s):  
Fu-Zhang Wang ◽  
Shaw M. Akula ◽  
Naranatt P. Pramod ◽  
Ling Zeng ◽  
Bala Chandran

ABSTRACT Human herpesvirus-8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus K8.1 gene encodes for two immunogenic glycoproteins, gpK8.1A and gpK8.1B, originating from spliced messages. The 228-amino-acid (aa) gpK8.1A is the predominant form associated with the virion envelope, consisting of a 167-aa region identical to gpK8.1B and a 61-aa unique region (L. Zhu, V. Puri, and B. Chandran, Virology 262:237–249, 1999). HHV-8 has a broad in vivo and in vitro cellular tropism, and our studies showed that this may be in part due to HHV-8's interaction with the ubiquitous host cell surface molecule, heparan sulfate (HS). Since HHV-8 K8.1 gene is positionally colinear to the Epstein-Barr virus (EBV) gene encoding the gp350/gp220 protein involved in EBV binding to the target cells, gpK8.1A's ability to interact with the target cells was examined. The gpK8.1A without the transmembrane and carboxyl domains (ΔTMgpK8.1A) was expressed in a baculovirus system and purified. Radiolabeled purified ΔTMgpK8.1A protein bound to the target cells, which was blocked by unlabeled ΔTMgpK8.1A. Unlabeled ΔTMgpK8.1A blocked the binding of [3H]thymidine-labeled purified HHV-8 to the target cells. Binding of radiolabeled ΔTMgpK8.1A to the target cells was inhibited in a dose-dependent manner by soluble heparin, a glycosaminoglycan (GAG) closely related to HS, but not by other GAGs such as chondroitin sulfate A and C, N-acetyl heparin and de-N-sulfated heparin. Cell surface absorbed ΔTMgpK8.1A was displaced by soluble heparin. Radiolabeled ΔTMgpK8.1A also bound to HS expressing Chinese hamster ovary (CHO-K1) cells, and binding to mutant CHO cell lines deficient in HS was significantly reduced. The ΔTMgpK8.1A specifically bound to heparin-agarose beads, which was inhibited by HS and heparin, but not by other GAGs. Virion envelope-associated gpK8.1A was specifically precipitated by heparin-agarose beads. These findings suggest that gpK8.1A interaction with target cells involves cell surface HS-like moieties, and HHV-8 interaction with HS could be in part mediated by virion envelope-associated gpK8.1A.

2003 ◽  
Vol 77 (5) ◽  
pp. 3131-3147 ◽  
Author(s):  
Fu-Zhang Wang ◽  
Shaw M. Akula ◽  
Neelam Sharma-Walia ◽  
Ling Zeng ◽  
Bala Chandran

ABSTRACT Human herpesvirus 8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus, implicated in the pathogenesis of Kaposi's sarcoma, utilizes heparan sulfate-like molecules to bind the target cells via its envelope-associated glycoproteins gB and gpK8.1A. HHV-8-gB possesses the Arg-Gly-Asp (RGD) motif, the minimal peptide region of many proteins known to interact with subsets of host cell surface integrins. HHV-8 utilizes α3β1 integrin as one of the receptors for its entry into the target cells via its gB interaction and induces the activation of focal adhesion kinase (FAK) (S. M. Akula, N. P. Pramod, F.-Z. Wang, and B. Chandran, Cell 108:407-419, 2002). Since FAK activation is the first step in the outside-in signaling necessary for integrin-mediated cytoskeletal rearrangements, cell adhesions, motility, and proliferation, the ability of HHV-8-gB to mediate the target cell adhesion was examined. A truncated form of gB without the transmembrane and carboxyl domains (gBΔTM) and a gBΔTM mutant (gBΔTM-RGA) with a single amino acid mutation (RGD to RGA) were expressed in a baculovirus system and purified. Radiolabeled HHV-8-gBΔTM, gBΔTM-RGA, and ΔTMgpK8.1A proteins bound to the human foreskin fibroblasts (HFFs), human dermal microvascular endothelial (HMVEC-d) cells, human B (BJAB) cells, and Chinese hamster ovary (CHO-K1) cells with equal efficiency, which was blocked by preincubation of proteins with soluble heparin. Maxisorp plate-bound gBΔTM protein induced the adhesion of HFFs and HMVEC-d and monkey kidney epithelial (CV-1) cells in a dose-dependent manner. In contrast, the gBΔTM-RGA and ΔTMgpK8.1A proteins did not mediate adhesion. Adhesion mediated by gBΔTM was blocked by the preincubation of target cells with RGD-containing peptides or by the preincubation of plate-bound gBΔTM protein with rabbit antibodies against gB peptide containing the RGD sequence. In contrast, adhesion was not blocked by the preincubation of plate-bound gBΔTM protein with heparin, suggesting that the adhesion is mediated by the RGD amino acids of gB, which is independent of the heparin-binding domain of gB. Integrin-ligand interaction is dependent on divalent cations. Adhesion induced by the gBΔTM was blocked by EDTA, thus suggesting the role of integrins in the observed adhesions. Focal adhesion components such as FAK and paxillin were activated by the binding of gBΔTM protein to the target cells but not by gBΔTM-RGA protein binding. Inhibition of FAK phosphorylation by genistein blocked gBΔTM-induced FAK activation and cell adhesion. These findings suggest that HHV-8-gB could mediate cell adhesion via its RGD motif interaction with the cell surface integrin molecules and indicate the induction of cellular signaling pathways, which may play roles in the infection of target cells and in Kaposi's sarcoma pathogenesis.


Virology ◽  
2001 ◽  
Vol 282 (2) ◽  
pp. 245-255 ◽  
Author(s):  
Shaw M. Akula ◽  
Fu-Zhang Wang ◽  
Jeffrey Vieira ◽  
Bala Chandran

2001 ◽  
Vol 75 (23) ◽  
pp. 11583-11593 ◽  
Author(s):  
Alexander Birkmann ◽  
Kerstin Mahr ◽  
Armin Ensser ◽  
Svenja Yağuboğlu ◽  
Fritz Titgemeyer ◽  
...  

ABSTRACT An immunodominant envelope glycoprotein is encoded by the human herpesvirus 8 (HHV-8) (also termed Kaposi's sarcoma-associated herpesvirus) K8.1 gene. The functional role of glycoprotein K8.1 is unknown, and recognizable sequence homology to K8.1 is not detectable in the genomes of most other closely related gammaherpesviruses, such as herpesvirus saimiri or Epstein-Barr virus. In search for a possible function for K8.1, we expressed the ectodomain of K8.1 fused to the Fc part of human immunoglobulin G1 (K8.1ΔTMFc). K8.1ΔTMFc specifically bound to the surface of cells expressing glycosaminoglycans but not to mutant cell lines negative for the expression of heparan sulfate proteoglycans. Binding of K8.1ΔTMFc to mammalian cells could be blocked by heparin. Interestingly, the infection of primary human endothelial cells by HHV-8 could also be blocked by similar concentrations of heparin. The specificity and affinity of these interactions were then determined by surface plasmon resonance measurements using immobilized heparin and soluble K8.1. This revealed that K8.1 binds to heparin with an affinity comparable to that of glycoproteins B and C of herpes simplex virus, which are known to be involved in target cell recognition by binding to cell surface proteoglycans, especially heparan sulfate. We conclude that cell surface glycosaminoglycans play a crucial role in HHV-8 target cell recognition and that HHV-8 envelope protein K8.1 is at least one of the proteins involved.


2003 ◽  
Vol 77 (14) ◽  
pp. 8147-8152 ◽  
Author(s):  
Naoki Inoue ◽  
Jörn Winter ◽  
Renu B. Lal ◽  
Margaret K. Offermann ◽  
Shin Koyano

ABSTRACT To analyze the mechanisms of entry of human herpesvirus 8 (HHV-8), we established a reporter cell line T1H6 that contains the lacZ gene under the control of the polyadenylated nuclear RNA promoter, known to be strongly activated by a viral transactivator, Rta. We found that infection with cell-free virus, as well as cocultivation with HHV-8-positive primary effusion lymphoma cell lines, activated the lacZ gene of T1H6 in a sensitive and dose-dependent manner. Addition of Polybrene and centrifugation enhanced, but polysulfonate compounds inhibited, the HHV-8 infectivity. RGD-motif-containing polypeptides and integrins did not decrease the infectivity, suggesting the presence of an additional cellular receptor other than the reported one. The entry was dependent on pH acidification but not on the clathrin pathway. Although conditioned media obtained from human immunodeficiency virus (HIV)-infected cells did not have any effect on the early steps of HHV-8 infection, intracellular expression of a proviral HIV type 1, but not of Tat alone, increased the HHV-8-dependent reporter activation slightly, suggesting a potential of HIV-mediated enhancement of an early step of HHV-8 infection.


2000 ◽  
Vol 74 (23) ◽  
pp. 10920-10929 ◽  
Author(s):  
Szeman Ruby Chan ◽  
Bala Chandran

ABSTRACT Human herpesvirus 8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus (KSHV) ORF59 protein (PF-8) is a processivity factor for HHV-8 DNA polymerase (Pol-8) and is homologous to processivity factors expressed by other herpesviruses, such as herpes simplex virus type 1 UL42 and Epstein-Barr virus BMRF1. The interaction of UL42 and BMRF1 with their corresponding DNA polymerases is essential for viral DNA replication and the subsequent production of infectious virus. Using HHV-8-specific monoclonal antibody 11D1, we have previously identified the cDNA encoding PF-8 and showed that it is an early-late gene product localized to HHV-8-infected cell nuclei (S. R. Chan, C. Bloomer, and B. Chandran, Virology 240:118–126, 1998). Here, we have further characterized PF-8. This viral protein was phosphorylated both in vitro and in vivo. PF-8 bound double-stranded DNA (dsDNA) and single-stranded DNA independent of DNA sequence; however, the affinity for dsDNA was approximately fivefold higher. In coimmunoprecipitation reactions, PF-8 also interacted with Pol-8. In in vitro processivity assays with excess poly(dA):oligo(dT) as a template, PF-8 stimulated the production of elongated DNA products by Pol-8 in a dose-dependent manner. Functional domains of PF-8 were determined using PF-8 truncation mutants. The carboxyl-terminal 95 amino acids (aa) of PF-8 were dispensable for all three functions of PF-8: enhancing processivity of Pol-8, binding dsDNA, and binding Pol-8. Residues 10 to 27 and 279 to 301 were identified as regions critical for the processivity function of PF-8. Interestingly, aa 10 to 27 were also essential for binding Pol-8, whereas aa 1 to 62 and aa 279 to 301 were involved in binding dsDNA, suggesting that the processivity function of PF-8 is correlated with both the Pol-8-binding and the dsDNA-binding activities of PF-8.


1999 ◽  
Vol 73 (7) ◽  
pp. 6177-6181 ◽  
Author(s):  
Johnan A. R. Kaleeba ◽  
Eric P. Bergquam ◽  
Scott W. Wong

ABSTRACT The rhesus rhadinovirus strain 17577 (RRV strain 17577) genome is essentially colinear with human herpesvirus 8 (HHV8)/Kaposi’s sarcoma-associated herpesvirus (KSHV) and encodes several analogous open reading frames (ORFs), including the homologue of cellular interleukin-6 (IL-6). To determine if the RRV IL-6-like ORF (RvIL-6) is biologically functional, it was expressed either transiently in COS-1 cells or purified from bacteria as a glutathioneS-transferase (GST)-RvIL-6 fusion and analyzed by IL-6 bioassays. Utilizing the IL-6-dependent B9 cell line, we found that both forms of RvIL-6 supported cell proliferation in a dose-dependent manner. Moreover, antibodies specific to the IL-6 receptor (IL-6R) or the gp130 subunit were capable of blocking the stimulatory effects of RvIL-6. Reciprocal titrations of GST-RvIL-6 against human recombinant IL-6 produced a more-than-additive stimulatory effect, suggesting that RvIL-6 does not inhibit but may instead potentiate normal cellular IL-6 signaling to B cells. These results demonstrate that RRV encodes an accessory protein with IL-6-like activity.


1999 ◽  
Vol 73 (4) ◽  
pp. 3040-3053 ◽  
Author(s):  
Robert P. Searles ◽  
Eric P. Bergquam ◽  
Michael K. Axthelm ◽  
Scott W. Wong

ABSTRACT We have sequenced the long unique region (LUR) and characterized the terminal repeats of the genome of a rhesus rhadinovirus (RRV), strain 17577. The LUR as sequenced is 131,364 bp in length, with a G+C content of 52.2% and a CpG ratio of 1.11. The genome codes for 79 open reading frames (ORFs), with 67 of these ORFs similar to genes found in both Kaposi’s sarcoma-associated herpesvirus (KSHV) (formal name, human herpesvirus 8) and herpesvirus saimiri. Eight of the 12 unique genes show similarity to genes found in KSHV, including genes for viral interleukin-6, viral macrophage inflammatory protein, and a family of viral interferon regulatory factors (vIRFs). Genomic organization is essentially colinear with KSHV, the primary differences being the number of cytokine and IRF genes and the location of the gene for dihydrofolate reductase. Highly repetitive sequences are located in positions corresponding to repetitive sequences found in KSHV. Phylogenetic analysis of several ORFs supports the similarity between RRV and KSHV. Overall, the sequence, structural, and phylogenetic data combine to provide strong evidence that RRV 17577 is the rhesus macaque homolog of KSHV.


Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 605-605 ◽  
Author(s):  
Jian Feng Wang ◽  
Xuefeng Zhang ◽  
Bala Chandran ◽  
Jerome E. Groopman

Abstract Reactive oxygen species (ROS) can activate replication of certain viruses, induce the production of various inflammatory mediators and play a critical role in carcinogenesis and tumor development. Kaposi’s sarcoma (KS) is the most prevalent HIV-associated cancer and is caused by infection with human herpesvirus-8 (HHV-8/KSHV). KS tissue has been reported to possess increased levels of ROS. We studied if ROS generation is related to HHV-8 infection and its role in virus entry into endothelial cells. Incubation of dermal microvascular endothelial cells (DMECs) with highly purified HHV-8 induced rapid increases in the production of intracellular hydrogen peroxide (H2O2), one of the major forms of ROS. Intracellular H2O2 was also induced by the treatment of DMECs with the HHV-8 envelope glycoprotein B (gB). The gB protein possesses an RGD motif, binds to the integrin molecules, alpha3 and beta1, and is a major mediator of virus entry into target cells. To test if it was integrin ligation that induces the production of ROS, we treated DMECs with fibronectin or laminin, the respective natural ligands for alpha3 and beta1 integrins. We observed a similar induction of intracellular ROS in DMECs by either matrix protein. These results indicated that the HHV-8-induced production of ROS was, at least in part, mediated by stimulation of integrins through the RGD-containing viral gB protein. ROS have recently been shown to function as second messengers in cellular signaling. To assess at which steps of cell signaling ROS may be functioning, we studied the signaling cascade in DMECs activated by the HHV-8 gB protein. Previous studies have shown that HHV-8, through gB/integrin interaction, induces cytoskeletal rearrangement and activates focal adhesion kinase (FAK), Src kinase and Akt, which are critical for virus entry into the target cells. We found that the activation of FAK, c-Src or Akt by this viral protein was inhibited by pretreatment with N-acetyl-L-cysteine (NAC), a potent thiol antioxidant. These results suggested that generation of ROS was involved in HHV-8-triggered signaling. We next examined if a change in ROS production modulated HHV-8 virus entry. We used green fluorescent protein (GFP)-labeled HHV-8 at a multiplicity of infection of 5–6, and quantitated the infection by fluorescence analysis of the DMECs. Short term exposure to low concentrations of H2O2 enhanced HHV-8 infection in DMECs, while treatment with NAC significantly decreased infection. These data indicated that ROS generation participated in HHV-8-mediated signaling and entry into target cells. Our study demonstrates a novel role of ROS in virus pathogenesis and provides a framework for the development of novel antioxidant strategies in AIDS-KS treatment.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3773-3773
Author(s):  
Ronghua Tao ◽  
Zuzana Berkova ◽  
Shu Wang ◽  
Suizhao Wang ◽  
Jillian Wise ◽  
...  

Abstract Background: Expression of Human herpesvirus 8 (HHV-8) K1 causes hyperplasia of lymph nodes and lymphomas in mice. The exact mechanism of how K1 causes hyperplasia and lymphomas in K1 expressing mice is not known. The cytoplasmic immunoreceptor tyrosine-based activation motif (ITAM) of K1 was shown previously to be involved in activation of Nuclear Factor kappa B (NF-k-B). Moreover, we had shown recently that K1 suppresses Fas-mediated apoptosis through its extracellular immunoglobulin-like domain and that K1-transfected mice survived a lethal dose of agonistic anti-Fas antibody (Jo2). We thus hypothesized that development of hyperplasia and lymphomas in K1-expressing mice is driven by alterations of Fas signaling. Results: At 18 months, 10 K1 transgenic mice, 90% developed lymphoid hyperplasia (>3mm) and 60% developed lymphomas, while all (26) control mice remained hyperplasia and lymphoma free. In the extreme cases, K1 mice developed liver or mesenteric tumors (4 and 4 of 10 mice, respectively). Spleens of 78% of K1 mice were enlarged at 18 months and were on average 3.5 times heavier than spleens of non-expressing control mice (332 ± 200 mg vs. 94 ± 26 mg, P < 0.03). The H and E staining of spleen sections showed expansion to the periarteriolar lymphocyte sheath with disruption of normal follicular architecture. Staining of spleen sections with anti-kappa and anti-lambda light chain antibodies revealed presence of monoclonal foci in 3 out of 3 K1 mice (average 6 foci per single section of spleen), but none in the 4 control mice. Moreover, K1 protein was expressed in about 10% of splenic cells as judged from staining with anti-K1 antibody 2H5. To test the hypothesis that expression of K1 protein in spleens makes them resistant to Fas-mediated apoptosis, splenic cells of 6 month old K1 mice (n=3) and matched controls (n=3) were isolated and incubated with 50 ng/mL of agonistic anti-Fas antibody Jo2. At 12 hours of treatment, only 4 ± 1% of splenocytes from K1 mice versus 17 ± 2% of control splenocytes were undergoing apoptosis (P<0.01). At 24 hours of treatment, the difference was even more significant (11 ± 0.6% vs. 50 ± 6%, P<0.005). Splenocytes of K1 mice were indeed more resistant to Jo2 induced apoptosis than splenocytes from age-matched control mice. Of mice inoculated with a lethal dose of Jo2 antibody, 3 of 12 K1 transgenic (30%) and 13 of 22 control mice (60%) died (P<0.05), further confirming the protective effect of K1 against Fas-mediated apoptosis. We mapped the region that K1 uses to bind to Fas as an immunoglobulin (Ig) chainlike domain by expressing deletion mutants of K1. Overexpression of an Ig domaincontaining protein CD79b competed with K1-Fas binding in a dose-dependent manner. Two 20-amino acid peptides (N251, N253) representing the Ig domain of K1 competed with K1-Fas binding in immunoprecipitation/immunoblotting analysis. The N251 and N253 peptides (100 mM) enhanced anti-Fas antibody (CH-11, 50 ng/mL)-induced apoptosis of BJAB lymphoma cells that expressed K1 but not that of vector-transfected BJAB cells. Ig-deleted K1 (K1dIg)-transfected mice were not protected (0/6), and K1- transfected mice were protected (7/10, P < 0.01) against the lethal effects of agonistic anti-Fas (Jo2) antibody. K1dIg expressed in mice did not form complexes with Fas, suggesting that the Ig domain is essential for K1-Fas binding and suppression of apoptosis. Conclusion: These results confirm that K1 is associated with lymphoid hyperplasia and lymphoma and provide plausible explanation. K1 blocks Fas-mediated apoptosis and competing peptides can reinstate apoptosis.


Virology ◽  
2001 ◽  
Vol 284 (2) ◽  
pp. 235-249 ◽  
Author(s):  
Shaw M. Akula ◽  
Naranatt P. Pramod ◽  
Fu-Zhang Wang ◽  
Bala Chandran

Sign in / Sign up

Export Citation Format

Share Document