Comparative proteomic analysis of GS-NSO murine myeloma cell lines with varying recombinant monoclonal antibody production rate

We have employed an inverse engineering strategy based on quantitative proteome analysis to identify changes in intracellular protein abundance that correlate with increased specific recombinant monoclonal antibody production (qMab) by engineered murine myeloma (NSO) cells. Four homogeneous NSO cell lines differing in qMab were isolated from a pool of primary transfectants. The proteome of each stably transfected cell line was analyzed at mid-exponential growth phase by two-dimensional gel electrophoresis (2D-PAGE) and individual protein spot volume data derived from digitized gel images were compared statistically. To identify changes in protein abundance associated with qMab clatasets were screened for proteins that exhibited either a linear correlation with cell line qMab or a conserved change in abundance specific only to the cell line with highest qMab. Several proteins with altered abundance were identified by mass spectrometry. Proteins exhibiting a significant increase in abundance with increasing qMab included molecular chaperones known to interact directly with nascent immunoglobulins during their folding and assembly (e.g., BiP, endoplasmin, protein disulfide isomerase). 2D-PAGE analysis showed that in all cell lines Mab light chain was more abundant than heavy chain, indicating that this is a likely prerequisite for efficient Mab production. In summary, these data reveal both the adaptive responses and molecular mechanisms enabling mammalian cells in culture to achieve high-level recombinant monoclonal antibody production. (C) 2004 Wiley Periodicals, Inc.

Recombinant Kunjin virus replicon vaccines induce protective T-cell immunity against human papillomavirus 16 E7-expressing tumour

The persistence of the E7 oncoprotein in transformed cells in human papillomavirus (HPV)-associated cervical cancer provides a tumour-specific antigen to which immunotherapeutic strategies may be directed. Self-replicating RNA (replicon) vaccine vectors derived from the flavivirus Kunjin (KUN) have recently been reported to induce T-cell immunity. Here, we report that inclusion of a CTL epitope of HPV16 E7 protein into a polyepitope encoded by a KUN vector induced E7-directed T-cell responses and protected mice against challenge with an E7-expressing epithelial tumour. We found replicon RNA packaged into virus-like particles to be more effective than naked replicon RNA or plasmid DNA constructed to allow replicon RNA transcription in vivo. Protective immunity was induced although the E7 CTL epitope was subdominant in the context of other CTL epitopes in the polyepitope. The results demonstrate the efficacy of the KUN replicon vector system for inducing protective immunity directed towards a virally encoded human tumour-specific antigen, and for inducing multi-epitopic CTL responses. (C) 2004 Elsevier Inc. All rights reserved.

Phase 1 study of HPV16-specific immunotherapy with E6E7 fusion protein and ISCOMATRIX (TM) adjuvant in women with cervical intraepithelial neoplasia

Purpose: Persistent infection of cervical epithelium with high risk human papillomavirus (HPV) results in cervical intraepithelial neoplasia (CIN) from which squamous cancer of the cervix can arise. A study was undertaken to evaluate the safety and immunogenicity of an HPV 16 immunotherapeutic consisting of a mixture of HPV16 E6E7 fusion protein and ISCOMATRIX(TM) adjuvant (HPV16 Immunotherapeutic) for patients with CIN. Experimental design: Patients with CIN (n = 3 1) were recruited to a randomised blinded placebo controlled dose ranging study of immunotherapy. Results: Immunotherapy was well tolerated. Immunised subjects developed HPV16 E6E7 specific immunity. Antibody, delayed type hypersensitivity, in vitro cytokine release, and CD8 T cell responses to E6 and E7 proteins were each significantly greater in the immunised subjects than in placebo recipients. Loss of HPV16 DNA from the cervix was observed in some vaccine and placebo recipients. Conclusions : The HPV16 Immunotherapeutic comprising HPV16E6E7 fusion protein and ISCOMATRIX(TM) adjuvant is safe and induces vaccine antigen specific cell mediated immunity. (C) 2004 Elsevier Ltd. All rights reserved.

The cytoskeleton and motor proteins of human schistosomes and their roles in surface maintenance and host-parasite interactions

Schistosomes are parasitic blood flukes, responsible for significant human disease in tropical and developing nations. Here we review information on the organization of the cytoskeleton and associated motor proteins of schistosomes, with particular reference to the organization of the syncytial tegument, a unique cellular adaptation of these and other neodermatan flatworms. Extensive EST databases show that the molecular constituents of the cytoskeleton and associated molecular systems are likely to be similar to those of other eukaryotes, although there are potentially some molecules unique to schistosomes and platyhelminths. The biology of some components, particular those contributing to host-parasite interactions as well as chemotherapy and immunotherapy are discussed. Unresolved questions in relation to the structure and function of the tegument relate to dynamic organization of the syncytial layer. (C) 2004 Wiley Periodicals, Inc.

APPL proteins link Rab5 to nuclear signal transduction via an endosomal compartment

Signals generated in response to extracellular stimuli at the plasma membrane are transmitted through cytoplasmic transduction cascades to the nucleus. We report the identification of a pathway directly linking the small GTPase Rab5, a key regulator of endocytosis, to signal transduction and mitogenesis. This pathway operates via APPL1 and APPL2, two Rab5 effectors, which reside on a subpopulation of endosomes. In response to extracellular stimuli such as EGF and oxidative stress, APPL1 translocates from the membranes to the nucleus where it interacts with the nucleosome remodeling and histone deacetylase multiprotein complex NuRD/MeCP1, an established regulator of chromatin structure and gene expression. Both APPL1 and APPL2 are essential for cell proliferation and their function requires Rab5 binding. Our findings identify an endosomal compartment bearing Rab5 and APPL proteins as an intermediate in signaling between the plasma membrane and the nucleus.

Enzymatic characterization and homology model of a catalytically active recombinant West Nile virus NS3 protease

West Nile Virus (WNV) is a mosquito-borne flavivirus with a rapidly expanding global distribution. Infection causes severe neurological disease and fatalities in both human and animal hosts. The West Nile viral protease (NS2B-NS3) is essential for post-translational processing in host-infected cells of a viral polypeptide precursor into structural and functional viral proteins, and its inhibition could represent a potential treatment for viral infections. This article describes the design, expression, and enzymatic characterization of a catalytically active recombinant WNV protease, consisting of a 40-residue component of cofactor NS2B tethered via a noncleavable nonapeptide (G(4)SG(4)) to the N-terminal 184 residues of NS3. A chromogenic assay using synthetic para-nitroanilide (pNA) hexapeptide substrates was used to identify optimal enzyme-processing conditions (pH 9.5, I < 0.1 M, 30% glycerol, 1 mM CHAPS), preferred substrate cleavage sites, and the first competitive inhibitor (Ac-FASGKR- H, IC50 &SIM; 1 μM). A putative three-dimensional structure of WNV protease, created through homology modeling based on the crystal structures of Dengue-2 and Hepatitis C NS3 viral proteases, provides some valuable insights for structure-based design of potent and selective inhibitors of WNV protease.

The alpha(2)delta auxiliary subunit reduces affinity of omega-conotoxins for recombinant N-type (Ca(v)2.2) calcium channels

The omega-conotoxins from fish-hunting cone snails are potent inhibitors of voltage-gated calcium channels. The omega-conotoxins MVIIA and CVID are selective N-type calcium channel inhibitors with potential in the treatment of chronic pain. The beta and alpha(2)delta-1 auxiliary subunits influence the expression and characteristics of the alpha(1B) subunit of N-type channels and are differentially regulated in disease states, including pain. In this study, we examined the influence of these auxiliary subunits on the ability of the omega-conotoxins GVIA, MVIIA, CVID and analogues to inhibit peripheral and central forms of the rat N-type channels. Although the beta3 subunit had little influence on the on- and off-rates of omega-conotoxins, coexpression of alpha(2)delta with alpha(1B) significantly reduced on- rates and equilibrium inhibition at both the central and peripheral isoforms of the N-type channels. The alpha(2)delta also enhanced the selectivity of MVIIA, but not CVID, for the central isoform. Similar but less pronounced trends were also observed for N-type channels expressed in human embryonic kidney cells. The influence of alpha(2)delta was not affected by oocyte deglycosylation. The extent of recovery from the omega-conotoxin block was least for GVIA, intermediate for MVIIA, and almost complete for CVID. Application of a hyperpolarizing holding potential ( - 120 mV) did not significantly enhance the extent of CVID recovery. Interestingly, [R10K] MVIIA and [O10K] GVIA had greater recovery from the block, whereas [K10R] CVID had reduced recovery from the block, indicating that position 10 had an important influence on the extent of omega-conotoxin reversibility. Recovery from CVID block was reduced in the presence of alpha(2)delta in human embryonic kidney cells and in oocytes expressing alpha(1B-b). These results may have implications for the antinociceptive properties of omega-conotoxins, given that the alpha(2)delta subunit is up-regulated in certain pain states.

Adenosine triphosphate acts as both a competitive antagonist and a positive allosteric modulator at recombinant N-methyl-D-aspartate receptors

ATP and glutamate are fast excitatory neurotransmitters in the central nervous system acting primarily on ionotropic P2X and glutamate [N-methyl-D-aspartate (NMDA) and non-NMDA] receptors, respectively. Both neurotransmitters regulate synaptic plasticity and long-term potentiation in hippocampal neurons. NMDA receptors are responsible primarily for the modulatory action of glutamate, but the mechanism underlying the modulatory effect of ATP remains uncertain. In the present study, the effect of ATP on recombinant NR1a + 2A, NR1a + 2B, and NR1a + 2C NMDA receptors expressed in Xenopus laevis oocytes was investigated. ATP inhibited NR1a + 2A and NR1a + 2B receptor currents evoked by low concentrations of glutamate but potentiated currents evoked by saturating glutamate concentrations. In contrast, ATP potentiated NR1a + 2C receptor currents evoked by nonsaturating glutamate concentrations. ATP shifted the glutamate concentration-response curve to the right, indicating a competitive interaction at the agonist binding site. ATP inhibition and potentiation of glutamate-evoked currents was voltage-independent, indicating that ATP acts outside the membrane electric field. Other nucleotides, including ADP, GTP, CTP, and UTP, inhibited glutamate-evoked currents with different potencies, revealing that the inhibition is dependent on both the phosphate chain and nucleotide ring structure. At high concentrations, glutamate outcompetes ATP at the agonist binding site, revealing a potentiation of the current. This effect must be caused by ATP binding at a separate site, where it acts as a positive allosteric modulator of channel gating. A simple model of the NMDA receptor, with ATP acting both as a competitive antagonist at the glutamate binding site and as a positive allosteric modulator at a separate site, reproduced the main features of the data.

Modified nicotine metabolism in transgenic tobacco plants expressing the human cytochrome P450 2A6 cDNA

In this study, the human cytochrome P450 (CYP) 2A6 was used in order to modify the alkaloid production of tobacco plants. The cDNA for human CYP2A6 was placed under the control of the constitutive 35S promoter and transferred into Nicotiana tabacum via Agrobacterium-mediated transformation. Transgenic plants showed formation of the recombinant CYP2A6 enzyme but no obvious phenotypic changes. Unlike wild-type tobacco, the transgenic plants accumulated cotinine, a metabolite which is usually formed from nicotine in humans. This result substantiates that metabolic engineering of the plant secondary metabolism via mammalian P450 enzymes is possible in vivo. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

A recombinant diheme SoxAX cytochrome - Implications for the relationship between EPR signals and modified heme-ligands

The multiheme SoxAX proteins are notable for their unusual heme ligation (His/Cys-persulfide in the SoxA subunit) and the complexity of their EPR spectra. The diheme SoxAX protein from Starkeya novella has been expressed using Rhodobacter capsulatus as a host expression system. rSoxAX was correctly formed in the periplasm of the host and contained heme c in similar amounts as the native SoxAX. ESI-MS showed that the full length rSoxA, in spite of never having undergone catalytic turnover, existed in several forms, with the two major forms having masses of 28 687 +/- 4 and 28 718 +/- 4 Da. The latter form exceeds the expected mass of rSoxA by 31 4 Da, a mass close to that of a sulfur atom and indicating that a fraction of the recombinant protein contains a cysteine persulfide modification. EPR spectra of rSoxAX contained all four heme-dependent EPR signals (LS1a, LS1b, LS2, LS3) found in the native SoxAX proteins isolated from bacteria grown under sulfur chemolithotrophic conditions. Exposure of the recombinant SoxAX to different sulfur compounds lead to changes in the SoxA mass profile as determined by ESI while maintaining a fully oxidized SoxAX visible spectrum. Thiosulfate, the proposed SoxAX substrate, did not cause any mass changes while after exposure to dimethylsulfoxide a + 112 +/- 4 Da form of SoxA became dominant in the mass spectrum. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Direct electrochemistry of enzymes from the cytochrome P4502C family

The human cytochromes P450 are responsible for the clearance of similar to 90% of xenobiotics yet comparatively little is known about their electrochemistry. Here we report the first direct electrochemistry of P450s from the 2C subfamily; one of the major groups of enzymes from this family. Specifically, the proteins that we have examined are recombinant human P450s 2C9, 2C 18 and 2C 19 and reversible Fe-III/II couples are seen in the absence of dioxygen. Even in the presence of trace amounts of dioxygen, a pronounced cathodic response is seen which is assigned to catalytic reduction of the bound dioxygen ligand by the ferrous P450. (c) 2005 Elsevier B.V. All rights reserved.

Cytochrome P450-mediated metabolism of haloperidol and reduced haloperidol to pyridinium metabolites

Haloperidol ( HP) has been reported to undergo cytochrome P450 (P450)-mediated metabolism to potentially neurotoxic pyridinium metabolites; however, the chemical pathways and specific enzymes involved in these reactions remain to be identified. The aims of the current study were to (i) fully identify the cytochrome P450 enzymes capable of metabolizing HP to the pyridinium metabolite, 4-(4-chlorophenyl)- 1-(4-fluorophenyl)-4-oxobutylpyridinium (HPP+), and reduced HP (RHP) to 4-(4-chlorophenyl)- 1-(4-fluorophenyl)-4-hydroxybutylpyridinium (RHPP+); and (ii) determine whether 4-(4-chlorophenyl)- 1-(4-fluorophenyl)-4-oxobutyl-1,2,3,6-tetrahydropyridine (HPTP) and 4-(4-chlorophenyl)1-( 4-fluorophenyl)-4-hydroxybutyl-1,2,3,6-tetrahydropyridine (RHPTP) were metabolic intermediates in these pathways. In vitro studies were conducted using human liver microsomal preparations and recombinant human cytochrome P450 enzymes (P450s 1A1, 1A2, 1B1, 2A6, 2B6, 2C9, 2C19 2D6, 2E1, 3A4, 3A5, and 3A7) expressed in bicistronic format with human NADPH cytochrome P450 reductase in Escherichia coli membranes. Pyridinium formation from HP and RHP was highly correlated across liver preparations, suggesting the same enzyme or enzymes were responsible for both reactions. Cytochrome P450s 3A4, 3A5, and 3A7 were the only recombinant enzymes which demonstrated significant catalytic activity under optimized conditions, although trace levels of activity could be catalyzed by NADPHP450 reductase alone. NADPH-P450 reductase-mediated activity was inhibited by reduced glutathione but not catalase or superoxide dismutase, suggesting O-2-dependent oxidation. No evidence was obtained to support the contention that HPTP and RHPTP are intermediates in these pathways. K-m values for HPP+ (34 +/- 5 mu M) and RHPP+ (64 +/- 4 mu M) formation by recombinant P450 3A4 agreed well with those obtained with human liver microsomes, consistent with P450 3A4 being the major catalyst of pyridinium metabolite formation in human liver.

Chemical synthesis and biosynthesis of the cyclotide family of circular proteins

Cyclotides are a recently discovered class of proteins that have a characteristic head-to-tail cyclized backbone stabilized by a knotted arrangement of three disulfide bonds. They are exceptionally resistant to chemical, enzymatic and thermal treatments because of their unique structural scaffold. Cyclotides have a range of bio-activities, including uterotonic, anti-HIV, anti-bacterial and cytotoxic activity but their insecticidal properties suggest that their natural physiological role is in plant defense. They are genetically encoded as linear precursors and subsequently processed to produce mature cyclic peptides but the mechanism by which this occurs remains unknown. Currently most cyclotides are obtained via direct extraction from plants in the Rubiaceae and Violaceae families. To facilitate the screening of cyclotides for structure-activity studies and to exploit them in drug design or agricultural applications a convenient route for the synthesis of cyclotides is vital. In this review the current chemical, recombinant and biosynthetic routes to the production of cyclotides are discussed.

Investigation of recombinant Schistosoma japonicum paramyosin fragments for immunogenicity and vaccine efficacy in mice

Schistosoma japonicum paramyosin, a 97 kDa myofibrillar protein, is a recognized vaccine candidate against schistosomiasis. To improve its expression and to identify protective epitopic regions on paramyosin, the published Chinese Schistosoma japonicum paramyosin cDNA sequence was redesigned using Pichia codon usage and divided into four overlapping fragments (fragments 1, 2, 3, 4) of 747, 651, 669 and 678 bp, respectively. These gene fragments were synthesized and expressed in Pichia pastoris (fragments 2 and 3) or E. coli (fragments 1 and 4). The recombinant proteins were produced at high level and purified using a two-step process involving Ni-NTA affinity chromatography and gel filtration. BALB/c mice were immunized subcutaneously three times at 2-week-intervals with the purified proteins formulated in adjuvant Quil A. The protein fragments were highly immunogenic, inducing high, though variable, ELISA antibody titres, and each was shown to resemble native paramyosin in terms of its recognition by the anti-fragment antibodies in Western blotting. The immunized mice were subjected to cercarial challenge 2 weeks after the final injection and promising protective efficacy in terms of significant reductions in worm burdens, worm-pair numbers and liver eggs in the vaccinated mice resulted. There was no apparent correlation between the antibody titres generated and protective efficacy, as all fragments produced effective but similar levels of protection.