Cellular Receptors Involved in KSHV Infection

The process of Kaposi’s Sarcoma Herpes Virus’ (KSHV) entry into target cells is complex and engages several viral glycoproteins which bind to a large range of host cell surface molecules. Receptors for KSHV include heparan sulphate proteoglycans (HSPGs), several integrins and Eph receptors, cystine/glutamate antiporter (xCT) and Dendritic Cell-Specific Intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN). This diverse range of potential binding and entry sites allows KSHV to have a broad cell tropism, and entry into specific cells is dependent on the available receptor repertoire. Several molecules involved in KSHV entry have been well characterized, particularly those postulated to be associated with KSHV-associated pathologies such as Kaposi’s Sarcoma (KS). In this review, KSHV infection of specific cell types pertinent to its pathogenesis will be comprehensively summarized with a focus on the specific cell surface binding and entry receptors KSHV exploits to gain access to a variety of cell types. Gaps in the current literature regarding understanding interactions between KSHV glycoproteins and cellular receptors in virus infection are identified which will lead to the development of virus infection intervention strategies.

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Kaposi's Sarcoma-Associated Herpesvirus gH/gL: Glycoprotein Export and Interaction with Cellular Receptors

Journal of Virology ◽

10.1128/jvi.01170-08 ◽

2008 ◽

Vol 83 (1) ◽

pp. 396-407 ◽

Cited By ~ 49

Author(s):

Alexander Hahn ◽

Alexander Birkmann ◽

Effi Wies ◽

Dominik Dorer ◽

Kerstin Mahr ◽

...

Keyword(s):

Heparan Sulfate ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Target Cells ◽

Dependent Manner ◽

Viral Glycoprotein ◽

Cellular Receptors ◽

Kshv Infection ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT The attachment, entry, and fusion of Kaposi's sarcoma-associated herpesvirus (KSHV) with target cells are mediated by complex machinery containing, among others, viral glycoprotein H (gH) and its alleged chaperone, gL. We observed that KSHV gH, in contrast to its homologues in several other herpesviruses, is transported to the cytoplasm membrane independently from gL, but not vice versa. Mutational analysis revealed that the N terminus of gH is sufficient for gL interaction. However, the entire extracellular part of gH is required for efficient gL secretion. The soluble ectodomain of gH was sufficient to interact with the surfaces of potential target cells in a heparin-dependent manner, and binding was further enhanced by coexpression of gL. Surface plasmon resonance revealed a remarkably high affinity of gH for glycosaminoglycans. Heparan sulfate (HS) proteoglycans of the syndecan family act as cellular receptors for the gH/gL complex. They promoted KSHV infection, and expression of gH/gL on target cells inhibited subsequent KSHV infection. Whereas gH alone was able to bind to HS, we observed that only the gH/gL complex adhered to heparan sulfate-negative cells at lamellipodium-like structures.

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Kaposi's Sarcoma-Associated Herpesvirus Modulates Microtubule Dynamics via RhoA-GTP-Diaphanous 2 Signaling and Utilizes the Dynein Motors To Deliver Its DNA to the Nucleus

Journal of Virology ◽

10.1128/jvi.79.2.1191-1206.2005 ◽

2005 ◽

Vol 79 (2) ◽

pp. 1191-1206 ◽

Cited By ~ 114

Author(s):

Pramod P. Naranatt ◽

Harinivas H. Krishnan ◽

Marilyn S. Smith ◽

Bala Chandran

Keyword(s):

Cell Surface ◽

Cell Signaling ◽

Host Cell ◽

Rho Gtpases ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Target Cells ◽

Viral Dna ◽

Host Cell Signaling

ABSTRACT Human herpesvirus 8 (HHV-8; also called Kaposi's sarcoma-associated herpesvirus), which is implicated in the pathogenesis of Kaposi's sarcoma (KS) and lymphoproliferative disorders, infects a variety of target cells both in vivo and in vitro. HHV-8 binds to several in vitro target cells via cell surface heparan sulfate and utilizes the α3β1 integrin as one of its entry receptors. Interactions with cell surface molecules induce the activation of host cell signaling cascades and cytoskeletal changes (P. P. Naranatt, S. M. Akula, C. A. Zien, H. H. Krishnan, and B. Chandran, J. Virol. 77:1524-1539, 2003). However, the mechanism by which the HHV-8-induced signaling pathway facilitates the complex events associated with the internalization and nuclear trafficking of internalized viral DNA is as yet undefined. Here we examined the role of HHV-8-induced cytoskeletal dynamics in the infectious process and their interlinkage with signaling pathways. The depolymerization of microtubules did not affect HHV-8 binding and internalization, but it inhibited the nuclear delivery of viral DNA and infection. In contrast, the depolymerization of actin microfilaments did not have any effect on virus binding, entry, nuclear delivery, or infection. Early during infection, HHV-8 induced the acetylation of microtubules and the activation of the RhoA and Rac1 GTPases. The inactivation of Rho GTPases by Clostridium difficile toxin B significantly reduced microtubular acetylation and the delivery of viral DNA to the nucleus. In contrast, the activation of Rho GTPases by Escherichia coli cytotoxic necrotizing factor significantly augmented the nuclear delivery of viral DNA. Among the Rho GTPase-induced downstream effector molecules known to stabilize the microtubules, the activation of RhoA-GTP-dependent diaphanous 2 was observed, with no significant activation in the Rac- and Cdc42-dependent PAK1/2 and stathmin molecules. The nuclear delivery of viral DNA increased in cells expressing a constitutively active RhoA mutant and decreased in cells expressing a dominant-negative mutant of RhoA. HHV-8 capsids colocalized with the microtubules, as observed by confocal microscopic examination, and the colocalization was abolished by the destabilization of microtubules with nocodazole and by the phosphatidylinositol 3-kinase inhibitor affecting the Rho GTPases. These results suggest that HHV-8 induces Rho GTPases, and in doing so, modulates microtubules and promotes the trafficking of viral capsids and the establishment of infection. This is the first demonstration of virus-induced host cell signaling pathways in the modulation of microtubule dynamics and in the trafficking of viral DNA to the infected cell nucleus. These results further support our hypothesis that HHV-8 manipulates the host cell signaling pathway to create an appropriate intracellular environment that is conducive to the establishment of a successful infection.

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Focal Adhesion Kinase Is Critical for Entry of Kaposi's Sarcoma-Associated Herpesvirus into Target Cells

Journal of Virology ◽

10.1128/jvi.80.3.1167-1180.2006 ◽

2006 ◽

Vol 80 (3) ◽

pp. 1167-1180 ◽

Cited By ~ 65

Author(s):

Harinivas H. Krishnan ◽

Neelam Sharma-Walia ◽

Daniel N. Streblow ◽

Pramod P. Naranatt ◽

Bala Chandran

Keyword(s):

Focal Adhesion Kinase ◽

Focal Adhesion ◽

Viral Entry ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Target Cells ◽

Viral Dna ◽

Kshv Infection ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV-8) interacts with cell surface α3β1 integrin early during in vitro infection of human endothelial cells and fibroblasts and activates the focal adhesion kinase (FAK) that is immediately downstream in the outside-in signaling pathway by integrins, leading to the activation of several downstream signaling molecules. In this study, using real-time DNA and reverse transcription-PCR assays to measure total internalized viral DNA, viral DNA associated with infected nuclei, and viral gene expression, we examined the stage of infection at which FAK plays the most significant role. Early during KSHV infection, FAK was phosphorylated in FAK-positive Du17 mouse embryonic fibroblasts. The absence of FAK in Du3 (FAK−/−) cells resulted in about 70% reduction in the internalization of viral DNA, suggesting that FAK plays a role in KSHV entry. Expression of FAK in Du3 (FAK−/−) cells via an adenovirus vector augmented the internalization of viral DNA. Expression of the FAK dominant-negative mutant FAK-related nonkinase (FRNK) in Du17 cells significantly reduced the entry of virus. Virus entry in Du3 cells, albeit in reduced quantity, delivery of viral DNA to the infected cell nuclei, and expression of KSHV genes suggested that in the absence of FAK, another molecule(s) may be partially compensating for FAK function. Infection of Du3 cells induced the phosphorylation of the FAK-related proline-rich tyrosine kinase (Pyk2) molecule, which has been shown to complement some of the functions of FAK. Expression of an autophosphorylation site mutant of Pyk2 in which Y402 is mutated to F (F402 Pyk2) reduced viral entry in Du3 cells, suggesting that Pyk2 facilitates viral entry moderately in the absence of FAK. These results suggest a critical role for KSHV infection-induced FAK in the internalization of viral DNA into target cells.

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Human Herpesvirus 8 Envelope Glycoprotein B Mediates Cell Adhesion via Its RGD Sequence

Journal of Virology ◽

10.1128/jvi.77.5.3131-3147.2003 ◽

2003 ◽

Vol 77 (5) ◽

pp. 3131-3147 ◽

Cited By ~ 89

Author(s):

Fu-Zhang Wang ◽

Shaw M. Akula ◽

Neelam Sharma-Walia ◽

Ling Zeng ◽

Bala Chandran

Keyword(s):

Cell Adhesion ◽

Cell Surface ◽

Focal Adhesion ◽

Kaposi's Sarcoma ◽

Human Herpesvirus ◽

Kaposi’S Sarcoma ◽

Human Herpesvirus 8 ◽

Target Cells ◽

Herpesvirus 8 ◽

Rgd Sequence

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.

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Reactive Oxygen Species Are Induced by Kaposi's Sarcoma-Associated Herpesvirus Early during Primary Infection of Endothelial Cells To Promote Virus Entry

Journal of Virology ◽

10.1128/jvi.02958-12 ◽

2012 ◽

Vol 87 (3) ◽

pp. 1733-1749 ◽

Cited By ~ 37

Author(s):

Virginie Bottero ◽

Sayan Chakraborty ◽

Bala Chandran

Keyword(s):

Reactive Oxygen Species ◽

Endothelial Cells ◽

Kaposi's Sarcoma ◽

Reactive Oxygen ◽

Kaposi’S Sarcoma ◽

Target Cells ◽

Ros Production ◽

Oxygen Species ◽

Kshv Infection ◽

D Cells

ABSTRACTThe entry of Kaposi's sarcoma-associated herpesvirus (KSHV) into human dermal microvascular endothelial cells (HMVEC-d), naturalin vivotarget cells, via macropinocytosis is initiated through a multistep process involving the binding of KSHV envelope glycoproteins with cell surface α3β1, αVβ3, and αVβ5 integrin molecules and tyrosine kinase ephrin-A2 receptor, followed by the activation of preexisting integrin-associated signaling molecules such as focal adhesion kinase (FAK), Src, c-Cbl, phosphoinositide 3-kinase (PI-3K), and Rho-GTPases. Many viruses, including KSHV, utilize cellular reactive oxygen species (ROS) for viral genomic replication and survival within host cells; however, the role of ROS in early events of viral entry and the induction of signaling has not been elucidated. Here we show that KSHV induced ROS production very early during the infection of HMVEC-d cells and that ROS production was sustained over the observation period (24 h postinfection). ROS induction was dependent on the binding of KSHV to the target cells, since pretreatment of the virus with heparin abolished ROS induction. Pretreatment of HMVEC-d cells with the antioxidantN-acetylcysteine (NAC) significantly inhibited KSHV entry, and consequently gene expression, without affecting virus binding. In contrast, H2O2treatment increased the levels of KSHV entry and infection. In addition, NAC inhibited KSHV infection-induced translocation of αVβ3 integrin into lipid rafts, actin-dependent membrane perturbations, such as blebs, observed during macropinocytosis, and activation of the signal molecules ephrin-A2 receptor, FAK, Src, and Rac1. In contrast, H2O2treatment increased the activation of ephrin-A2, FAK, Src, and Rac1. These studies demonstrate that KSHV infection induces ROS very early during infection to amplify the signaling pathways necessary for its efficient entry into HMVEC-d cells via macropinocytosis.

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Cells of the Innate and Adaptive Immune Systems in Kaposi’s Sarcoma

Journal of Immunology Research ◽

10.1155/2020/8852221 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Owen Ngalamika ◽

Sody Munsaka

Keyword(s):

Kaposi's Sarcoma ◽

Immune Cell ◽

Kaposi’S Sarcoma ◽

Cell Types ◽

Etiologic Agent ◽

Immune Systems ◽

Kshv Infection ◽

Adaptive Immune ◽

Different Cell Types ◽

Adaptive Immune Systems

Kaposi’s sarcoma (KS) is an angioproliferative malignancy whose associated etiologic agent is the Kaposi’s sarcoma-associated herpesvirus (KSHV). KS is the most prevalent malignancy among HIV-infected individuals globally and is considered an AIDS-defining malignancy. The different forms of KS including HIV-associated KS, iatrogenic (immunosuppression-related) KS, and classical KS in elderly males suggest that immune cell dysregulation is among the key components in promoting KS development in KSHV-infected individuals. It is therefore expected that different cell types of the immune system likely play distinct roles in promoting or inhibiting KS development. This narrative review is focused on discussing cells of the innate and adaptive immune systems in KSHV infection and KS pathogenesis, including how these cells can be useful in the control of KSHV infection and treatment of KS.

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Human Mesenchymal Stem Cells of Diverse Origins Support Persistent Infection with Kaposi’s Sarcoma-Associated Herpesvirus and Manifest Distinct Angiogenic, Invasive, and Transforming Phenotypes

mBio ◽

10.1128/mbio.02109-15 ◽

2016 ◽

Vol 7 (1) ◽

Cited By ~ 12

Author(s):

Myung-Shin Lee ◽

Hongfeng Yuan ◽

Hyungtaek Jeon ◽

Ying Zhu ◽

Seungmin Yoo ◽

...

Keyword(s):

Stem Cells ◽

Mesenchymal Stem Cells ◽

Tumor Cells ◽

Malignant Transformation ◽

Kaposi's Sarcoma ◽

Human Mesenchymal Stem Cells ◽

Kaposi’S Sarcoma ◽

Target Cells ◽

Kshv Infection ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi’s sarcoma (KS), a highly angiogenic and invasive tumor often involving different organ sites, including the oral cavity, is caused by infection with Kaposi’s sarcoma-associated herpesvirus (KSHV). Diverse cell markers have been identified on KS tumor cells, but their origin remains an enigma. We previously showed that KSHV could efficiently infect, transform, and reprogram rat primary mesenchymal stem cells (MSCs) into KS-like tumor cells. In this study, we showed that human primary MSCs derived from diverse organs, including bone marrow (MSCbm), adipose tissue (MSCa), dental pulp, gingiva tissue (GMSC), and exfoliated deciduous teeth, were permissive to KSHV infection. We successfully established long-term cultures of KSHV-infected MSCa, MSCbm, and GMSC (LTC-KMSCs). While LTC-KMSCs had lower proliferation rates than the uninfected cells, they expressed mixtures of KS markers and displayed differential angiogenic, invasive, and transforming phenotypes. Genetic analysis identified KSHV-derived microRNAs that mediated KSHV-induced angiogenic activity by activating the AKT pathway. These results indicated that human MSCs could be the KSHV target cells in vivo and established valid models for delineating the mechanism of KSHV infection, replication, and malignant transformation in biologically relevant cell types. IMPORTANCE Kaposi’s sarcoma is the most common cancer in AIDS patients. While KSHV infection is required for the development of Kaposi’s sarcoma, the origin of KSHV target cells remains unclear. We show that KSHV can efficiently infect human primary mesenchymal stem cells of diverse origins and reprogram them to acquire various degrees of Kaposi’s sarcoma-like cell makers and angiogenic, invasive, and transforming phenotypes. These results indicate that human mesenchymal stem cells might be the KSHV target cells and establish models for delineating the mechanism of KSHV-induced malignant transformation.

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Integrin αVβ3 Binds to the RGD Motif of Glycoprotein B of Kaposi's Sarcoma-Associated Herpesvirus and Functions as an RGD-Dependent Entry Receptor

Journal of Virology ◽

10.1128/jvi.01673-07 ◽

2007 ◽

Vol 82 (3) ◽

pp. 1570-1580 ◽

Cited By ~ 90

Author(s):

H. Jacques Garrigues ◽

Yelena E. Rubinchikova ◽

C. Michael DiPersio ◽

Timothy M. Rose

Keyword(s):

Cho Cells ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Glycoprotein B ◽

Target Cells ◽

Kshv Infection ◽

Rgd Motif ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus ◽

Blocking Antibodies

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) envelope-associated glycoprotein B (gB) is involved in the initial steps of binding to host cells during KSHV infection. gB contains an RGD motif reported to bind the integrin α3β1 during virus entry. Although the ligand specificity of α3β1 has been controversial, current literature indicates that α3β1 ligand recognition is independent of RGD. We compared α3β1 to the RGD-binding integrin, αVβ3, for binding to envelope-associated gB and a gB(RGD) peptide. Adhesion assays demonstrated that β3-CHO cells overexpressing αVβ3 specifically bound gB(RGD), whereas α3-CHO cells overexpressing α3β1 did not. Function-blocking antibodies to αVβ3 inhibited the adhesion of HT1080 fibrosarcoma cells to gB(RGD), while antibodies to α3β1 did not. Using affinity-purified integrins and confocal microscopy, αVβ3 bound to gB(RGD) and KSHV virions, demonstrating direct receptor-ligand interactions. Specific αVβ3 antagonists, including cyclic and dicyclic RGD peptides and αVβ3 function-blocking antibodies, inhibited KSHV infection by 70 to 80%. Keratinocytes from α3-null mice lacking α3β1 were fully competent for infection by KSHV, and reconstitution of α3β1 function by transfection with α3 cDNA reduced KSHV infectivity from 74% to 55%. Additional inhibitory effects of α3β1 on the cell surface expression of αVβ3 and on αVβ3-mediated adhesion of α3-CHO cells overexpressing α3β1 were detected, consistent with previous reports of transdominant inhibition of αVβ3 function by α3β1. These observations may explain previous reports of an inhibition of KSHV infection by soluble α3β1. Our studies demonstrate that αVβ3 is a cellular receptor mediating both the cell adhesion and entry of KSHV into target cells through binding the virion-associated gB(RGD).

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A Kaposi's Sarcoma-Associated Herpesvirus Infection Mechanism Is Independent of Integrins α3β1, αVβ3, and αVβ5

Journal of Virology ◽

10.1128/jvi.00803-18 ◽

2018 ◽

Vol 92 (17) ◽

Cited By ~ 17

Author(s):

Allison Alwan TerBush ◽

Florianne Hafkamp ◽

Hee Jun Lee ◽

Laurent Coscoy

Keyword(s):

Kaposi's Sarcoma ◽

Expression Patterns ◽

Kaposi’S Sarcoma ◽

Cell Types ◽

Eph Receptors ◽

Kshv Infection ◽

Receptor Usage ◽

Infection Mechanism ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACTHost receptor usage by Kaposi's sarcoma-associated herpesvirus (KSHV) has been best studied using primary microvascular endothelial and fibroblast cells, although the virus infects a wide variety of cell types in culture and in natural infections. In these two infection models, KSHV adheres to the cell though heparan sulfate (HS) binding and then interacts with a complex of EphA2, xCT, and integrins α3β1, αVβ3, and αVβ5 to catalyze viral entry. We dissected this receptor complex at the genetic level with CRISPR-Cas9 to precisely determine receptor usage in two epithelial cell lines. Surprisingly, we discovered an infection mechanism that requires HS and EphA2 but is independent of αV- and β1-family integrin expression. Furthermore, infection appears to be independent of the EphA2 intracellular domain. We also demonstrated that while two other endogenous Eph receptors were dispensable for KSHV infection, transduced EphA4 and EphA5 significantly enhanced infection of cells lacking EphA2.IMPORTANCEOur data reveal an integrin-independent route of KSHV infection and suggest that multiple Eph receptors besides EphA2 can promote and regulate infection. Since integrins and Eph receptors are large protein families with diverse expression patterns across cells and tissues, we propose that KSHV may engage with several proteins from both families in different combinations to negotiate successful entry into diverse cell types.

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