Characterization of ER-localized Activity of HHV-8 Interleukin-6

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DESCRIPTION (provided by applicant): Human herpesvirus 8 (HHV-8) has been etiologically linked to Kaposi sarcoma, multicentric Castleman's disease, and primary effusion lymphoma (PEL). The virus encodes a homolog of interluekin-6 (viral IL-6, vIL-6), and this viral cytokine has been implicated in development and pathogenesis of HHV-8 associated neoplasias. vIL-6 is required for PEL cell growth and survival, and it is known to localize to the endoplasmic reticulum (ER) of these cells where it is competent to mediate its pro-growth and survival effects. The mechanism by which vIL-6 mediates these activities in latently infected PEL cells is unclear. However, we have recently identified a novel interaction partner of vIL-6, vitamin K epoxide reductase complex subunit 1 variant 2 (VKORC1v2), which also localizes to the ER and functions to promote PEL cell growth and survival by a mechanism involving its interaction with vIL-6. In a yeast two-hybrid screen and subsequently by co-precipitation assay, VKORC1v2 was also shown to interact with thioredoxin-like protein 1 (TMX1), an ER-localized protein known to participate in the reduction of disulfide bonds. ER localization and interaction of VKORC1v2 with TMX1 suggest that these proteins may play a role in the folding of vIL-6 and/or in regulating the ER stress response. Recent studies have also indicated that the IL-6 signal transducer, gp130, is required for the growth and maintenance of PEL cells although the specific role of vIL-6 in this process has not been determined. This F31 application proposes to further characterize the vIL-6:VKORC1v2 interaction at the molecular level, to determine the connection of VKORC1v2 and TMX1 with vIL-6 activity, and to elucidate the contribution and mechanism of vIL-6:gp130 signaling to PEL cell growth and viability. By understanding the molecular mechanisms of vIL-6 effects in virus biology and pathogenesis, new targets may be identified and exploited for therapeutic benefit to treat PEL and other HHV-8 associated diseases. PUBLIC HEALTH RELEVANCE: Human herpesvirus 8 (HHV-8) is associated with B cell malignancies (primary effusion lymphoma [PEL] and Multicentric Castleman's Disease [MCD]) and endothelial tumor (Kaposi sarcoma [KS]; the HHV-8 homolog of cellular interleukin-6 (viral IL-6, vIL-6) has been implicated as a driving factor in each of these diseases. Preliminary studies have shown that the interaction between vIL-6 and cellular vitamin K epoxide reductase complex 1 variant 2 (VKORC1v2) is crucial for this vIL-6 activity and that that the vIL-6 signal transducer is also essential for PEL cell growth and viability. The goal of the proposed research is to characterize the vIL-6:VKORC1v2 interaction and to elucidate the vIL-6-associated VKORC1v2- and gp130- mediated mechanisms that support PEL cell growth and survival; progress in these areas will be directly relevant to therapeutic advances that may stem from the development of strategies to combat and prevent HHV-8 associated diseases.