Poxvirus Tumor Necrosis Factor Receptor (TNFR)-Like T2 Proteins Contain a Conserved Preligand Assembly Domain That Inhibits Cellular TNFR1-Induced Cell Death

Westmead Millennium Institute, Westmead, NSW 2145, Australia.
Journal of Virology (Impact Factor: 4.44). 10/2006; 80(18):9300-9. DOI: 10.1128/JVI.02449-05
Source: PubMed


The poxvirus tumor necrosis factor receptor (TNFR) homologue T2 has immunomodulatory properties; secreted myxoma virus T2 (M-T2) protein binds and inhibits rabbit TNF-alpha, while intracellular M-T2 blocks virus-induced lymphocyte apoptosis. Here, we define the antiapoptotic function as inhibition of TNFR-mediated death via a highly conserved viral preligand assembly domain (vPLAD). Jurkat cell lines constitutively expressing M-T2 were generated and shown to be resistant to UV irradiation-, etoposide-, and cycloheximide-induced death. These cells were also resistant to human TNF-alpha, but M-T2 expression did not alter surface expression levels of TNFRs. Previous studies indicated that T2's antiapoptotic function was conferred by the N-terminal region of the protein, and further examination of this region revealed a highly conserved N-terminal vPLAD, which is present in all poxvirus T2-like molecules. In cellular TNFRs and TNF-alpha-related apoptosis-inducing ligand (TRAIL) receptors (TRAILRs), PLAD controls receptor signaling competency prior to ligand binding. Here, we show that M-T2 potently inhibits TNFR1-induced death in a manner requiring the M-T2 vPLAD. Furthermore, we demonstrate that M-T2 physically associates with and colocalizes with human TNFRs but does not prevent human TNF-alpha binding to cellular receptors. Thus, M-T2 vPLAD is a species-nonspecific dominant-negative inhibitor of cellular TNFR1 function. Given that the PLAD is conserved in all known poxvirus T2-like molecules, we predict that it plays an important function in each of these proteins. Moreover, that the vPLAD confers an important antiapoptotic function confirms this domain as a potential target in the development of the next generation of TNF-alpha/TNFR therapeutics.

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Available from: Lisa M Sedger
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    • "The MYXV protein M-T2 (M002R/L) is a secreted tumor necrosis factor receptor (TNFR) homolog that inhibits apoptosis by binding and subsequently inhibiting rabbit TNF via a conserved ligand-binding domain at the N-terminus of the viral protein [27-29]. A highly conserved viral preligand assembly domain (vPLAD) on the M-T2 protein is responsible for inhibiting intracellular apoptosis, making it the first described viral immunomodulatory protein for which two separate domains with distinct immune inhibiting functions are known [29,30]. "
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    • "Further studies have found that M-T2 also harbors a PLAD (PreLigand Assembly Domain) like-domain present in cellular TNF-Rs (Sedger et al., 2006). The PLAD domain of M-T2 can inhibit human TNF-R-mediated cell death by interaction with the PLAD domains of both human TNF-R1 and TNF-R2 (Sedger et al., 2006). Crm-like TNF inhibitors namely CrmB, CrmC, CrmD and CrmE also possess multiple ligand binding properties. "
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