Michael J. Tocci

Resistance to fever induction and impaired acute-phase response in interleukin-1β-deficient mice

We used gene targeting in embryonic stem cells to introduce an IL-1 beta null allele in mice. The IL-1 beta-deficient mice develop normally and are apparently healthy and fertile. The IL-1 beta null mice responded normally in models of contact and delayed-type hypersensitivity or following bacterial endotoxin LPS-induced inflammation. The IL-1 beta-deficient mice showed equivalent resistance to Listeria monocytogenes compared with wild-type controls. In contrast, when challenged with turpentine, which causes localized inflammation and tissue injury, the IL-1 beta mutant mice exhibited an impaired acute-phase inflammatory response and were completely resistant to fever development and anorexia. These results highlight a central role for IL-1 beta as a pyrogen and a mediator of the acute-phase response in a subset of inflammatory disease models, and support the notion that blocking the action of a single key cytokine can alter the course of specific immune and inflammatory responses.

Growth hormone gene expression in eukaryotic cells directed by the Rous sarcoma virus long terminal repeat or cytomegalovirus immediate-early promoter

The cytomegalovirus (CMV) immediate-early (IE) gene-regulatory region was found to be three- to fourfold more efficient than the Rous sarcoma retroviral long terminal repeat (LTR) in promoting expression of the bovine growth hormone (bGH) gene by rat GH3 cells.

Organization and expression of the major genes from the long inverted repeat of the human cytomegalovirus genome

The long inverted repeat (TRL:IRL) of the human cytomegalovirus (CMV) genome is a major transcription unit in productively infected human fibroblasts. Cloned DNA fragments of the CMV IRL and complementary DNA (cDNA) copies of RNAs transcribed from the TRL:IRL were used as probes in RNA filter hybridization experiments to characterize and map the RNAs transcribed from this region of the virus genome. In human fibroblasts, three poly A+ RNAs of 2.7, 2.0, and 1.2 kb were detected during the early (E) and late (L) phases of virus gene expression. Analysis of cloned cDNAs and RNA mapping studies indicate that the TRL:IRL can be divided into three transcriptionally active regions. The most highly transcribed region lies between 0.805 and 0.816 map units and encodes a major abundant poly A+ RNA of 2.7 kb that is expressed at E and L times postinfection (p.i.). The second region spans map coordinates 0.792-0.797 and encodes a 1.2-kb poly A+ RNA that is relatively low in abundance at E times p.i. but achieves nearly the same abundance as the 2.7-kb transcript at L times p.i. The third region encompasses map units 0.796-0.804 and encodes a less abundant poly A+ RNA of 2.0 kb that attains maximum expression at E times. The 1.2- and 2.7-kb RNAs are transcribed in the same direction, while the 2.0-kb RNA is transcribed in the opposite direction. The 2.7-, 2.0-, and 1.2-kb RNAs, as well as 5.7- and 1.8-kb transcripts were detected at immediate early times p.i. when human fibroblasts were treated with cycloheximide, but not in cells treated with anisiomycin.

Structure and function of interleukin-1β converting enzyme

Publisher Summary This chapter describes the structure and function of interleukin-1β (IL-1β) converting enzyme based on its purification, molecular cloning, three-dimensional structure, and functional deletion in mice. IL-1β is a major mediator of inflammatory disease. IL-1β is synthesized as an inactive 31-kDa precursor protein (pIL-1β). The precursor is cleaved by a highly specific proteinase, termed IL-1β converting enzyme (ICE). The discovery of ICE, a unique processing enzyme involved in the production of active IL-1β, provides a new approach to specifically block the production of this potent cytokine. ICE is a cysteine proteinase that cleaves pIL-1β twice within the prodomain at aspartic acid residues. The development of potent inhibitors based on the unique substrate specificity of ICE and genetically engineered mice deficient in the enzyme confirms the importance of the enzyme in pIL-1β processing and suggests that inhibitors of the enzyme may be useful in the treatment of inflammatory disease. The discovery and development of inhibitors against the enzyme hold great promise therapeutically. Potent inhibitors of the enzyme are useful in the treatment of a number of important inflammatory diseases and potentially in the management of leukemia.

Recent advances in the mechanism of action of cyclosporine and FK506.

The immunosuppressants cyclosporine and FK506 (tacrolimus) are extremely potent inhibitors of T-lymphocyte activation. Recent studies have shown that these agents are actually prodrugs that become active only when bound to specific members of the cyclophilin or FK506 binding protein receptor gene families. The cyclosporine-cyclophilin or FK506-FK506 binding protein receptor complexes interact with a key component of the T-cell antigen receptor signal transduction pathway, the calcium-calmodulin-dependent phosphoprotein phosphatase calcineurin. The drug-receptor complexes inhibit the phosphatase activity of calcineurin and thereby prevent transcriptional activation of the interleukin-2 gene.

Expression and Immunoaffinity Purification of Human Inducible Nitric-oxide Synthase INHIBITION STUDIES WITH 2-AMINO-5,6-DIHYDRO-4H-1,3-THIAZINE

Recombinant human inducible nitric-oxide synthase (rH-iNOS) was expressed in the baculovirus system and purified by a novel immunoaffinity column. rH-iNOS and its native counterpart from cytokine-stimulated primary hepatocytes exhibited similar molecular mass of 130 kDa on SDS-polyacrylamide gel electrophoresis, recognition by antipeptide antibodies, specific activities, and IC50 values for inhibitors. The active dimeric form exhibited a specific activity range of 114-260 nmol/min/mg at 37°C and contained 1.15 ± 0.04 mol of calmodulin/monomer. The enzyme exhibited a Soret λmax at 396 nm with a shoulder at 460 nm and contained 0.28-0.64 mol of heme/monomer. Dithionite reduction under CO yielded an absorbance maximum at 446 nm, indicating a P450-type heme. Imidazole induced a type II difference spectrum, reversible by L-Arg. 2-Amino-5,6-dihydro-4H-1,3-thiazine (ADT) was competitive versus L-Arg (Ki = 22.6 ± 1.9 nM), reversed the type II difference spectrum induced by imidazole (Kd = 17.7 nM), and altered the CO-ferrous absorbance of rH-iNOS. L-Arg did not perturb the CO-ferrous adduct directly, but it partially reversed the ADT-induced absorbance shift, indicating that both bind similarly to the protein but interact differently with the heme.

Protoplast fusion in microtiter plates for expression cloning in mammalian cells: demonstration of feasibility using membrane-bound alkaline phosphatase as a reporter enzyme.

Protoplast fusion is a method for directly transferring cloned DNA from bacteria to mammalian cells at high efficiency. Here, we have used membrane-bound alkaline phosphatase as a reporter enzyme in a miniprotoplast fusion assay. This work demonstrates the principle that large numbers of protoplast fusions can be done simultaneously and successfully, to assay for an activity encoded by an expression vector. The technique described here circumvents key hurdles to expression cloning. This method does not require a highly sensitive assay or a way of separating a rare expressing cell from the mixture of transfected cells containing other transfected genes. With a strong promoter, the protein encoded by the undiluted transfected cDNA should be produced at at least as high a level as it is endogenously produced in the cell from which its activity was first detected. Reference clones are stored, avoiding the need to separate out the cells that are successfully transfected; this also avoids the need to repurify the DNA from the transfected cell. Because of the use of microtiter plates, it is likely that such a method could be partially automated for many types of assays.

Characterization of a major early gene from the human cytomegalovirus long inverted repeat; predicted amino acid sequence of a 30-kDa protein encoded by the 1.2-kb mRNA

The human cytomegalovirus (CMV) long inverted repeat (TRL:IRL) encodes three major early mRNAs. One of these RNAs is a 1.2-kb transcript that maps between 0.792 and 0.797 map units on the human CMV genome. Primer extension experiments, in addition to nucleotide sequence analyses of cloned cDNA transcripts and human CMV IRL DNA fragments, demonstrated that the 1.2-kb mRNA was not spliced. A single major open reading frame of 254 amino acids was identified, encoding a basic polypeptide of approximately 30 kDa. This polypeptide contains 19% Arg, Lys, and His residues, and would have a net positive charge of 31 at neutral pH. Examination of the deduced amino acid sequence revealed several potential phosphorylation sites and a hydrophobic carboxy terminus which resembles a membrane anchor sequence. In vitro translation of human CMV infected cell RNA, hybrid selected with either cloned cDNA or human CMV IRL DNA fragments specific for the 1.2-kb mRNA, resulted in a unique translation product that migrated on SDS-polyacrylamide gels with an apparent molecular mass of 37 kDa. Potential transcriptional regulatory sequences were also identified upstream of the gene encoding the 30-kDa protein.

Unexpected up-regulation of gene expression by cyclosporin A and FK-506 in a T-cell lymphoma: Both immunosuppressants augment Ly-6E antigen induction by interferon-γ in the presence of ionomycin

Cyclosporin A (CsA) and FK-506 inhibit lymphokine gene activation in T-cells. In the present study, we investigated the effects of these immunosuppressants on the regulation of a non-lymphokine molecule, the Ly-6E surface antigen, in the YAC-1 T-cell lymphoma. These cells do not normally express Ly-6E mRNA or Ly-6E surface molecules but are induced to do so upon treatment with IFN-gamma. At submicromolar concentrations, CsA or FK-506 did not alter this induction. However, at higher concentrations (1-12 microM), they both increased the induction of Ly-6E mRNA expression. Cyclosporin A or FK-506 also markedly affected Ly-6E induction when the cultures were co-treated with the calcium ionophore, ionomycin. In the absence of CsA or FK-506, ionomycin suppressed Ly-6E induction by IFN-gamma. Both immunosuppressants reversed this inhibitory effect and increased Ly-6E mRNA and Ly-6E surface expression to levels that were 2- to 3-fold higher than in cells induced with IFN-gamma alone. In this system, the two immunosuppressants were active at pharmacologically relevant concentrations, similar to those inhibiting normal T-cell activation, with FK-506 being 30- to 50-fold more potent than CsA. The ability of CsA analogs to enhance Ly-6E induction in the presence of ionomycin also correlated with their immunosuppressive activity. Therefore, through mechanisms apparently related to those involved in their immunosuppressive action, both CsA and FK-506 convert the negative effect of ionomycin on IFN-gamma-mediated Ly-6E induction into an overall positive effect. The YAC-1 cell model, described here, provides a unique example of upregulation of gene expression by these two immunosuppressants.