title: Poxvirus tumor necrosis factor receptor (TNFR)-like T2 proteins contain a conserved preligand assembly domain that inhibits cellular TNFR1-induced cell death.
abstract: 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.
authors.affiliation: Westmead Millennium Institute, Westmead, NSW 2145, Australia. lisa_sedger@wmi.usyd.edu.au
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Sedger
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Osvath
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Xu
authors.forename: Grace
authors.initials: G
authors.lastname: Li
authors.forename: Francis K-M
authors.initials: FK
authors.lastname: Chan
authors.forename: John W
authors.initials: JW
authors.lastname: Barrett
authors.forename: Grant
authors.initials: G
authors.lastname: McFadden
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D017124:Conserved Sequence; D006801:Humans; D008214:Lymphocytes / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011212:Poxviridae / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011817:Rabbits; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha