The serpins (serine proteinase inhibitors) are a superfamily of proteins (350 -500 amino acids in size) that fold into a conserved structure and employ a unique suicide substrate-like inhibitory mechanism. The serpins were last reviewed in 1994 (1). More recent studies show: 1) an expanded distribution within the kingdoms of metazoa and plantae, as well as certain viruses, 2) a surprising effect on the covalently bound target proteinase, and 3) novel biochemical and biological functions.Most serpins inhibit serine proteinases of the chymotrypsin family. However, cross-class inhibitors have been identified. The viral serpin CrmA and, to a lesser extent, PI9 (SERPINB9) inhibit the cysteine proteinase, caspase 1 (2), and SCCA1

Cytotoxic T lymphocytes (CTL) can trigger an apoptotic signal through the Fas receptor or by the exocytosis of granzyme B and perforin. Caspase activation is an important component of both pathways. Granzyme B, a serine proteinase contained in granules, has been shown to proteolytically process and activate members of the caspase family in vitro. In order to gain an understanding of the contributions of caspases 8 and 3 during granule-induced apoptosis in intact cells, we have used target cells that either stably express the rabbitpox virus-encoded caspase inhibitor SPI-2 or are devoid of caspase 3. The overexpression of SPI-2 in target cells significantly inhibited DNA fragmentation, phosphatidylserine externalization, and mitochondrial disruption during Fas-mediated cell death. In contrast, SPI-2 expression in target cells provided no protection against granzyme-mediated apoptosis, mitochondrial collapse, or cytolysis, leading us to conclude that SPI-2-inhibited caspases are not an essential requirement for the granzyme pathway. Caspase 3-deficient MCF-7 cells were found to be resistant to CTL-mediated DNA fragmentation but not to CTL-mediated cytolysis and loss of the mitochondrial inner membrane potential. Furthermore, we demonstrate that granzyme B directly cleaves the proapoptotic molecule Bid, bypassing the need for caspase 8 activation of Bid. These results provide evidence for a two-pronged strategy for mediating target cell destruction and provide evidence of a direct link between granzyme B activity, Bid cleavage, and caspase 3 activation in whole cells.

Immunomodulatory proteins encoded by the larger DNA viruses interact with a wide spectrum of immune effector molecules that regulate the antiviral response in the infected host. Here we show that certain poxviruses, including myxoma virus. Shope fibroma virus, rabbitpox virus, vaccinia virus (strain Lister), cowpox virus, and raccoonpox virus, express a new family of secreted proteins which interact with members of both the CC and CXC superfamilies of chemokines. However, swinepox virus and vaccinia virus (strain WR) do not express this activity Using a recombinant poxviruses, the myxoma M-T1 and rabbitpox virus 35kDa secreted proteins were identified as prototypic members of this family of chemokine binding proteins. Members of this T1/35kDa family of poxvirus-secreted proteins share multiple stretches of identical sequence motifs, including eight conserved cysteine residues, but are otherwise unrelated to any cellular genes in the database. The affinity of the CC chemokine RANTES interaction with M-T1 was assessed by Scatchard analysis and yielded a Kd of approximately 73 nM. In rabbits infected with a mutant rabbitpox virus, in which the 35kDa gene is deleted, there was an increased number of extravasating leukocytes in the deep dermis during the early phases of infection. These observations suggest that members of the T1/35kDa class of secreted viral proteins bind multiple members of the chemokine superfamily in vitro and modulate the influx of inflammatory cells into virus-infected tissues in vivo.

Chemokines (chemotactic cytokines) comprise a large family of proteins that recruit and activate leukocytes, giving chemokines a major role in both immune response and inflammation-related diseases. The poxvirus-encoded viral CC chemokine inhibitor (vCCI) binds to many CC chemokines with high affinity, acting as a potent inhibitor of chemokine action. We have used heteronuclear multidimensional NMR to determine the structure of an orthopoxvirus vCCI in complex with a human CC chemokine, MIP-1␤ (macrophage inflammatory protein 1␤). vCCI binds to the chemokine with 1:1 stoichiometry, forming a complex of 311 aa. vCCI uses residues from its ␤-sheet II to interact with a surface of MIP-1␤ that includes residues adjacent to its N terminus, as well as residues in the 20 s region and the 40 s loop. This structure reveals the strategy used by vCCI to tightly bind numerous chemokines while retaining selectivity for the CC chemokine subfamily.inflammation ͉ protein:protein complex ͉ NMR ͉ chemokine-binding protein

1-Phosphohistidine and 3-phosphohistidine Phosphohistidine has been isolated as the solid lithium have been synthesized by reaction of histidine with salt and has been characterized by composition, ultraphosphoramidate. The two isomers have been sepaviolet and nuclear magnetic resonance spectra, titrarated by paper electrophoresis and anion-exchange tion curve, and rate of hydrolysis over a wide range of chromatography. The synthetic phosphohistidine isopH values. a-N-Acetyl-3-phosphohistidine, l-methylmer which is identical with the compound isolated from 3-phosphohistidine, a-AT-acetyl-1-methyl-3-phosphomitochondria and from a succinate thiokinase preparahistidine, and the isomers of phosphohistidine methyl tion has been identified as 3-phosphohistidine. 3-ester have been prepared and some properties reported.

Natural killer (NK) cells are an important element in the immune defense against the orthopox family members vaccinia virus (VV) and ectromelia virus (ECTV). NK cells are regulated through inhibitory and activating signaling receptors, the latter involving NKG2D and the natural cytotoxicity receptors (NCR), NKp46, NKp44 and NKp30. Here we report that VV infection results in an upregulation of ligand structures for NKp30 and NKp46 on infected cells, whereas the binding of NKp44 and NKG2D was not significantly affected. Likewise, infection with ectromelia virus (ECTV), the mousepox agent, enhanced binding of NKp30 and, to a lesser extent, NKp46. The hemagglutinin (HA) molecules from VV and ECTV, which are known virulence factors, were identified as novel ligands for NKp30 and NKp46. Using NK cells with selectively silenced NCR expression and NCR-CD3ζ reporter cells, we observed that HA present on the surface of VV-infected cells, or in the form of recombinant soluble protein, was able to block NKp30-triggered activation, whereas it stimulated the activation through NKp46. The net effect of this complex influence on NK cell activity resulted in a decreased NK lysis susceptibility of infected cells at late time points of VV infection when HA was expression was pronounced. We conclude that poxviral HA represents a conserved ligand of NCR, exerting a novel immune escape mechanism through its blocking effect on NKp30-mediated activation at a late stage of infection.

The activation of multiple interleukin-1b converting enzyme-related proteases (caspases) in apoptotic mammalian cells raises questions as to whether the multiple active caspases have distinct roles in apoptotic execution as well as how these proteases are organized in apoptotic signaling pathways. Here we used an a nity-labeling agent, YV(bio)KD-aomk, to investigate the caspases activated during apoptotic cell death. YV(bio)KD-aomk identi®ed six distinct polypeptides corresponding to active caspases in Fas-stimulated Jurkat T cells. On staurosporine treatment, four polypeptides were detected. Competition experiments showed that the labeled caspases have distinct substrate preferences. Stepwise appearance of the labeled caspases in each cell death event was consistent with the view that the activated caspases are organized into protease cascades. Moreover, we found that stepwise activation of caspases similar to that induced by Fas ligation is triggered by exposing non-apoptotic Jurkat cell extracts to caspase-8 (MACH/FLICE/Mch5). Conversely, CrmA protein, a viral suppressor of Fas-induced apoptosis, inhibited the protease activity of caspase-8. Overall, these ®ndings provide evidence that caspase-8, a CrmA-sensitive protease, is responsible for initiating the stepwise activation of multiple caspases in Fas-stimulated cells.

Background The development of molecular probes capable of recognizing virus-infected cells is essential to meet the serious clinical, therapeutic, and national-security challenges confronting virology today. We report the development of DNA aptamers as probes for the selective targeting of virus-infected living cells. Methods To create aptamer probes capable of recognizing virus-infected cells, we used cell-SELEX (systematic evolution of ligands via exponential enrichment), which uses intact infected live cells as targets for aptamer selection. In this study, vaccinia virus– infected and –uninfected lung cancer A549 cells were chosen to develop our model probes. Results A panel of aptamers has been evolved by means of the infected cell–SELEX procedure. The results demonstrate that the aptamers bind selectively to vaccinia virus–infected A549 cells with apparent equilibrium dissociation constants in the nanomolar range. In addition, these aptamers can specifically recognize a variety of target infected cell lines. The aptamers' target is most likely a viral protein located on the cell surface. Conclusions The success of developing a panel of DNA-aptamer probes capable of recognizing virus-infected cells via a whole living cell–SELEX selection strategy may increase our understanding of the molecular signatures of infected cells. Our findings suggest that aptamers can be developed as molecular probes for use as diagnostic and therapeutic reagents and for facilitating drug delivery against infected cells.