scholarly journals Human Herpesvirus 8 Interleukin-6 Contributes to Primary Effusion Lymphoma Cell Viability via Suppression of Proapoptotic Cathepsin D, a Cointeraction Partner of Vitamin K Epoxide Reductase Complex Subunit 1 Variant 2

2013 ◽  
Vol 88 (2) ◽  
pp. 1025-1038 ◽  
Author(s):  
D. Chen ◽  
Y. Gao ◽  
J. Nicholas
Keyword(s):  
Vitamin K ◽  
Interleukin 6 ◽  
Cathepsin D ◽  
Primary Effusion Lymphoma ◽  
Human Herpesvirus ◽  
Human Herpesvirus 8 ◽  
Vitamin K Epoxide Reductase ◽  
Herpesvirus 8 ◽  
Primary Effusion Lymphoma Cell ◽  
Epoxide Reductase

scholarly journals Promotion of Endoplasmic Reticulum-Associated Degradation of Procathepsin D by Human Herpesvirus 8-Encoded Viral Interleukin-6

2015 ◽  
Vol 89 (15) ◽  
pp. 7979-7990 ◽  
Author(s):  
Daming Chen ◽  
John Nicholas
Keyword(s):  
Endoplasmic Reticulum ◽  
Interleukin 6 ◽  
Cathepsin D ◽  
Primary Effusion Lymphoma ◽  
Human Herpesvirus ◽  
Human Herpesvirus 8 ◽  
Herpesvirus 8 ◽  
Gp130 Receptor ◽  
Epoxide Reductase ◽  
Productive Replication

ABSTRACTThe interleukin-6 homologue (viral interleukin-6 [vIL-6]) of human herpesvirus 8 is implicated in viral pathogenesis due to its proproliferative, inflammatory, and angiogenic properties, effected through gp130 receptor signaling. In primary effusion lymphoma (PEL) cells, vIL-6 is expressed latently and is essential for normal cell growth and viability. This is mediated partly via suppression of proapoptotic cathepsin D (CatD) via cocomplexing of the endoplasmic reticulum (ER)-localized CatD precursor, pro-CatD (pCatD), and vIL-6 with the previously uncharacterized ER membrane protein vitamin K epoxide reductase complex subunit 1 variant 2 (VKORC1v2). vIL-6 suppression of CatD occurs also during reactivated productive replication in PEL cells and is likely to contribute to proreplication functions of vIL-6. Here, we report that vIL-6 suppresses CatD through vIL-6, VKORC1v2, and pCatD association with components of the ER-associated degradation (ERAD) machinery. In transfected cells, expression of vIL-6 along with CatD led to proteasome-dependent (inhibitor-sensitive) decreases in CatD levels and the promotion of pCatD polyubiquitination. Depletion of particular ERAD-associated isomerases, lectins, and translocon components, including ERAD E3 ubiquitin ligase HRD1, diminished suppression of CatD by vIL-6. Coprecipitation assays identified direct or indirect interactions of VKORC1v2, vIL-6, and pCatD with translocon proteins (SEL1L and/or HRD1) and ERAD-associated lectins OS9 and XTP3-B. Endogenous CatD expression in PEL cells was increased by depletion of ERAD components, and suppression of CatD by vIL-6 overexpression in PEL cells was dependent on HRD1. Our data reveal a new mechanism of ER-localized vIL-6 activity and further characterize VKORC1v2 function.IMPORTANCEHuman herpesvirus 8 (HHV-8) viral interleukin-6 (vIL-6), unlike cellular IL-6 proteins, is secreted inefficiently and sequestered mainly in the endoplasmic reticulum (ER), from where it can signal through the gp130 receptor. We have recently reported that vIL-6 also associates with a novel membrane protein termed vitamin K epoxide reductase complex subunit 1 variant 2 (VKORC1v2) and mediates suppression of VKORC1v2-cointeracting cathepsin D, a stress-released proapoptotic protein negatively impacting HHV-8 latently infected primary effusion lymphoma (PEL) cell viability and reactivated virus productive replication. Here, we have examined the mechanistic basis of the VKORC1v2–vIL-6 interaction-dependent suppression of cathepsin D and have found that this novel activity of vIL-6 is mediated through coassociation of VKORC1v2, procathepsin D, and vIL-6 with components of the ER-associated degradation (ERAD) machinery. Our findings provide information of significance for potential antiviral and therapeutic targeting of VKORC1v2-mediated vIL-6 activities and also indicate the nature of VKORC1v2 function in normal cell biology.

scholarly journals Differential Expression of Viral Bcl-2 Encoded by Kaposi's Sarcoma-Associated Herpesvirus and Human Bcl-2 in Primary Effusion Lymphoma Cells and Kaposi's Sarcoma Lesions

2002 ◽  
Vol 76 (5) ◽  
pp. 2551-2556 ◽  
Author(s):  
Isabelle Widmer ◽  
Marion Wernli ◽  
Felix Bachmann ◽  
Fred Gudat ◽  
Gieri Cathomas ◽  
...  
Keyword(s):  
Kaposi's Sarcoma ◽  
Mononuclear Cells ◽  
Primary Effusion Lymphoma ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
Human Herpesvirus 8 ◽  
Lymphoma Cells ◽  
Herpesvirus 8 ◽  
Primary Effusion Lymphoma Cell ◽  
Spindle Cells

ABSTRACT Expression of human herpesvirus 8 viral Bcl-2 protein was demonstrated in spindle cells of late-stage Kaposi's sarcoma lesions but not in primary effusion lymphoma cell lines. In contrast, strong expression of human Bcl-2 was found in stimulated primary effusion lymphoma cells, whereas in Kaposi's sarcoma lesions preferential mononuclear cells, and to a lesser extent spindle cells, stained positive.

scholarly journals Insulin-Like Growth Factor 2 Receptor Expression Is Promoted by Human Herpesvirus 8-Encoded Interleukin-6 and Contributes to Viral Latency and Productive Replication

2018 ◽  
Vol 93 (5) ◽  
Author(s):  
Qian Li ◽  
Daming Chen ◽  
Qiwang Xiang ◽  
John Nicholas
Keyword(s):  
Growth Factor ◽  
Cell Viability ◽  
Interleukin 6 ◽  
Primary Effusion Lymphoma ◽  
Human Herpesvirus ◽  
Human Herpesvirus 8 ◽  
Herpesvirus 8 ◽  
Latently Infected ◽  
Mannose 6 Phosphate ◽  
Productive Replication

ABSTRACTHuman herpesvirus 8 (HHV-8) viral interleukin-6 (vIL-6) localizes largely to the endoplasmic reticulum (ER) and here associates functionally with both the gp130 signal transducer and the novel ER membrane protein vitamin K epoxide reductase complex subunit 1 variant-2 (VKORC1v2). The latter interaction contributes to the viability of latently infected primary effusion lymphoma (PEL) cells and to HHV-8 productive replication, in part via promotion of ER-associated degradation (ERAD) of nascent pro-cathepsin D (pCatD) and consequent suppression of lysosome-localized proapoptotic mature CatD. Here we report that VKORC1v2 associates with insulin-like growth factor 2 receptor (IGF2R), also known as cation-independent mannose-6-phosphate receptor, which is involved in trafficking of mannose-6-phosphate-conjugated glycoproteins to lysosomes. VKORC1v2 effected reduced IGF2R expression in a manner dependent on VKORC1v2-IGF2R interaction, while vIL-6, which could inhibit VKORC1v2-IGF2R interaction, effected increased expression of IGF2R. These effects were independent of changes in IGF2R mRNA levels, indicating likely posttranslational mechanisms. In kinetic analyses involving labeling of either newly synthesized or preexisting IGF2R, vIL-6 promoted accumulation of the former while having no detectable effect on the latter. Furthermore, vIL-6 led to decreased K48-linked ubiquitination of IGF2R and suppression of ERAD proteins effected increased IGF2R expression and loss of IGF2R regulation by vIL-6. Depletion-based experiments identified IGF2R as a promoter of PEL cell viability and virus yields from lytically reactivated cultures. Our findings identify ER-transiting nascent IGF2R as an interaction partner of VKORC1v2 and target of vIL-6 regulation and IGF2R as a positive contributor to HHV-8 biology, thereby extending understanding of the mechanisms of VKORC1v2-associated vIL-6 function.IMPORTANCEHHV-8 vIL-6 promotes productive replication in the context of reactivated lytic replication in primary effusion lymphoma (PEL) and endothelial cells and sustains latently infected PEL cell viability. Viral IL-6 is also considered to contribute significantly to HHV-8-associated pathogenesis, since vIL-6 can promote cell proliferation, cell survival, and angiogenesis that are characteristic of HHV-8-associated Kaposi’s sarcoma, PEL and multicentric Castleman’s disease (MCD), in addition to proinflammatory activities observed in MCD-like “Kaposi’s sarcoma-associated herpesvirus-induced cytokine syndrome.” We show in the present study that vIL-6 can promote productive replication and latent PEL cell viability through upregulation of the mannose-6-phosphate- and peptide hormone-interacting receptor IGF2R, which is a positive factor in HHV-8 biology via these activities. VKORC1v2-enhanced ER-associated degradation of IGF2R and vIL-6 promotion of IGF2R expression through prevention of its interaction with VKORC1v2 and consequent rescue from degradation represent newly recognized activities of VKOCR1v2 and vIL-6.

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