4-1BB-mediated immunotherapy of rheumatoid arthritis

Collagen type II-induced arthritis is a CD4(+) T-cell-dependent chronic inflammation in susceptible DBA/1 mice and represents an animal model of human rheumatoid arthritis. We found that development of this condition, and even established disease, are inhibited by an agonistic anti-4-1BB monoclonal antibody. Anti-4-1BB suppressed serum antibodies to collagen type II and CD4(+) T-cell recall responses to collagen type II. Crosslinking of 4-1BB evoked an antigen-specific, active suppression mechanism that differed from the results of blocking the interaction between 4-1BB and its ligand, 4-1BBL. Anti-4-1BB monoclonal antibodies induced massive, antigen-dependent clonal expansion of CD11c(+)CD8(+) T cells and accumulation of indoleamine 2,3-dioxygenase in CD11b(+) monocytes and CD11c(+) dendritic cells. Both anti-interferon-gamma and 1-methyltryptophan, a pharmacological inhibitor of indoleamine 2,3-dioxygenase, reversed the anti-4-1BB effect. We conclude that the suppression of collagen-induced arthritis was caused by an expansion of new CD11c(+)CD8(+) T cells, and that interferon-gamma produced by these cells suppresses antigen-specific CD4(+) T cells through an indoleamine 2,3-dioxygenase-dependent mechanism.     

Molecular cloning and expression analysis of phospholipase Cdelta from mud loach, Misgurnus mizolepis

A gene encoding phosphoinositide-specific phospholipase C (PLC), designated ML-PLCδ, was cloned from mud loach (Misgurnus mizolepis) liver. A complete cDNA encoding ML-PLCδ was isolated by screening the cDNA library of mud loach liver and using the 5′-rapid amplification of cDNA ends (RACE) method. The full-length ML-PLCδ gene contains an open reading frame of 2325 base pairs encoding a 774 amino acid protein with a molecular mass of 88,072 Da; this corresponds to the size of the protein expressed in Escherichia coli BL21 (DE3) using pET28a vector. It contains all of the characteristic domains found in mammalian PLCδ isozymes (PH domain, EF-hands, X–Y catalytic region, and a C2 domain). A homology search revealed that ML-PLCδ shares relatively high sequence identity with mammalian PLCδ1 (51–52%) and catfish PLCδ (64%). The recombinant ML-PLCδ protein expressed as a histidine-tagged fusion protein in E. coli was purified to apparent homogeneity by Ni²⁺-NTA affinity chromatography. The recombinant ML-PLCδ showed a concentration-dependent PLC activity to phosphatidylinositol 4,5-bis-phosphate (PIP₂) and its activity was Ca²⁺-dependent, which was similar to mammalian PLCδ isozymes.     

Solid-phase refolding of cyclodextrin glycosyltransferase adsorbed on cation-exchange resin

Expression with a fusion partner is now a popular scheme to produce a protein of interest because it provides a generic tool for expression and purification. In our previous study, a strong polycationic tail has been harnessed for an efficient purification scheme. Here, the same polycation tail attached to a protein of interest is shown to hold versatility for a solid-phase refolding method that utilizes a charged adsorbent as a supporting material. Cyclodextrin glycosyltransferase (CGTase) fused with 10 lysine residues at the C-terminus (CGTK10ase) retains the ability to bind to a cation exchanger even in a urea-denatured state. When the denatured and adsorbed CGTK10ase is induced to refold, the bound CGTK10ase aggregates little even at a g/L range. The renatured CGTK10ase can also be simply recovered from the solid support by adding high concentration of NaCl. The CGTK10ase refolded on a solid support retains specific enzyme activity virtually identical to that of the native CGTK10ase. Several factors that are important in improving the refolding efficiency are explored. Experimental results indicate that nonspecific electrostatic interactions between the charge of the ion exchanger and the local charge of CGTase other than the polycationic tag should be reduced to obtain higher refolding yield. The solid-phase refolding method utilizing a strong polycationic tag resulted in a remarkable increase in the refolding performance. Taken together with the previous report in which a series of polycations were explored for efficient purification, expression of a target protein fused with a strong polycation provides a straightforward protein preparation scheme.     

Purification and characterization of ferredoxin-NAD(P)(+) reductase from the green sulfur bacterium Chlorobium tepidum

Ferredoxin-NAD(P)(+) reductase [EC 1.18.1.3, 1.18.1.2] was isolated from the green sulfur bacterium Chlorobium tepidum and purified to homogeneity. The molecular mass of the subunit is 42 kDa, as deduced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular mass of the native enzyme is approximately 90 kDa, estimated by gel-permeation chromatography, and is thus a homodimer. The enzyme contains one FAD per subunit and has absorption maxima at about 272, 385, and 466 nm. In the presence of ferredoxin (Fd) and reaction center (RC) complex from C. tepidum, it efficiently catalyzes photoreduction of both NADP(+) and NAD(+). When concentrations of NADP(+) exceeded 10 microM, NADP(+) photoreduction rates decreased with increased concentration. The inhibition by high concentrations of substrate was not observed with NAD(+). It also reduces 2,6-dichlorophenol-indophenol (DPIP) and molecular oxygen with either NADPH or NADH as efficient electron donors. It showed NADPH diaphorase activity about two times higher than NADH diaphorase activity in DPIP reduction assays at NAD(P)H concentrations less than 0.1 mM. At 0.5 mM NAD(P)H, the two activities were about the same, and at 1 mM, the former activity was slightly lower than the latter.     

SEK1/MKK4-mediated SAPK/JNK signaling participates in embryonic hepatoblast proliferation via a pathway different from NF-kappaB-induced anti-apoptosis

Mice lacking the stress-signaling kinase SEK1 die from embryonic day 10.5 (E10.5) to E12.5. Although a defect in liver formation is accompanied with the embryonic lethality of sek1(-/-) mice, the mechanism of the liver defect has remained unknown. In the present study, we first produced a monoclonal antibody specifically recognizing murine hepatoblasts for the analysis of liver development and further investigated genetic interaction ofsek1 with tumor necrosis factor-alpha receptor 1 gene (tnfr1) and protooncogene c-jun, which are also responsible for liver formation and cell apoptosis. The defective liver formation in sek1(-/-) embryos was not protected by additionaltnfr1 mutation, which rescues the embryonic lethality of mice lacking NF-kappaB signaling components. There was a progressive increase in the hepatoblast cell numbers of wild-type embryos from E10.5 to E12.5. Instead, impaired hepatoblast proliferation was observed in sek1(-/-) livers from E10.5, though fetal liver-specific gene expression was normal. The impaired phenotype in sek1(-/-) livers was more severe than in c-jun(-/-) embryos, and sek1(-/-) c-jun(-/-) embryos died more rapidly before E8.5. The hepatoblast proliferation required no hematopoiesis, since liver development was not impaired in AML1(-/-) mice that lack hematopoietic functions. Stimulation of stress-activated protein kinase/c-Jun N-terminal kinase by hepatocyte growth factor was attenuated in sek1(-/-) livers. Thus, SEK1 appears to play a crucial role in hepatoblast proliferation and survival in a manner apparently different from NF-kappaB or c-Jun.     

Role of the connectivity of secondary structure segments in the folding of alpha(1)-antitrypsin

The native form of serpins (serine protease inhibitors) is metastable, which is critical to their biological functions. Spontaneous conversion from the native form of serpins into a more stable conformation, called the "latent" form, is restricted. To examine whether the connectivity of strand 1 of beta-sheet C to the hydrophobic core is critical to the serpin's preferential folding to the metastable native conformation, we designed a circularly-permuted mutant of alpha(1)-antitrypsin, the prototype serpin, in which strand 1C is disconnected from the hydrophobic core. Conformation of the circular permutant was similar to that of the latent form, as revealed by equilibrium unfolding, limited proteolysis, and spectroscopic properties. Our results support the notion that rapid folding of the hydrophobic core with concomitant incorporation of strand 1C into beta-sheet C traps the serpin molecule into its native metastable conformation.     

A potent inhibitor of inducible nitric oxide synthase, ONO-1714, a cyclic amidine derivative

(1S,5S,6R,7R)-7-Chloro-3-imino-5-methyl-2-azabicyclo[4.1.0]heptane hydrochloride (ONO-1714), a novel cyclic amidine analogue, inhibits human inducible nitric oxide (iNOS) with a K(i) of 1.88 nM and rodent iNOS with similar potency in vitro. ONO-1714 was found to be 10-fold selective for human iNOS over human endothelial NOS (ecNOS). When the inhibitory activity of ONO-1714 was compared for iNOS, it was found to be 451-fold and >20,000-fold more potent than L-NMMA and aminoguanidine (AG), respectively. In terms of human iNOS selectivity, ONO-1714 was approximately 34- and 2-fold more selective for iNOS than L-NMMA and AG, respectively. ONO-1714 inhibited the LPS-induced elevation of plasma nitrate/nitrite in mice with an ID(50) value of 0.010 mg/kg, s.c. The maximum tolerated dose of ONO-1714 was 30 mg/kg, i.v. Thus, ONO-1714 represents one of the most potent iNOS inhibitors in vitro and in vivo to date and has great potentials for use as an inhibitor for clarifying the pathophysiological roles of iNOS and for use as a therapeutic agent.