Essential and non-essential interactions in interactome networks: the Escherichia coli division proteins FtsQ-FtsN interaction.

The Escherichia coli division protein FtsQ, which plays a central role in the septosome assembly, interacts with several protein partners of the division machinery. Its interaction with FtsB and FtsL allows the formation of the trimeric complex connecting the early cytoplasmic cell division proteins with the late, essentially periplasmic, ones. Little is known about the interactions that FtsQ contracts with other divisome components, besides the fact that all are localized in its periplasmic domain. In this domain, two independent subdomains, both involved in FtsQ, FtsI and FtsN interactions, were also identified. The study of FtsQ interaction-defective mutants constituted a basis to investigate the biological significance of its interactions. However, in the case of interactions where two independent sites are involved, mutation(s) in one domain can be suppressed by the presence of the still-functional second interaction region. To ascertain the biological role of these interactions, it is therefore necessary to select double mutants, where both sites are impaired. This paper describes the behaviour of FtsQ double mutants that have lost the ability to interact with FtsN, which is the last component in the hierarchy of divisome assembly, and is necessary to guarantee its stability and function.

Efficacy and safety of etanercept in moderate-to-severe asthma: a randomised, controlled trial.

Increased tumour necrosis factor-α levels have been observed in bronchial biopsies and induced sputum from subjects with severe asthma. We investigated etanercept (ETN) as a therapeutic option for treating moderate-to-severe persistent asthma. In this 12-week, randomised, double-blind, placebo-controlled, phase 2 trial, subjects (n=132) with moderate-to-severe persistent asthma received subcutaneous injections of 25 mg ETN or placebo twice weekly, and were evaluated at baseline, and at weeks 2, 4, 8 and 12. The primary end-point was the change from baseline to week 12 in pre-bronchodilator forced expiratory volume in 1 s (FEV1)% predicted. Secondary end-points included morning peak expiratory flow, FEV1% pred, Asthma Control Questionnaire (5-item version), asthma exacerbations, provocative concentration of methacholine causing a 20% decrease in FEV1, and the Asthma Quality of Life Questionnaire. No significant differences were observed between ETN and placebo for any of the efficacy end-points. ETN treatment was well tolerated, with no unexpected safety findings observed during the study. Clinical efficacy of ETN was not shown in subjects with moderate-to-severe persistent asthma over 12 weeks. However, ETN treatment was a well-tolerated therapy. Studies in specific subsets of patients with asthma with longer-term follow-up may be needed to fully evaluate the clinical efficacy of ETN in this population.

Once weekly administration of etanercept 50 mg is efficacious and well tolerated in patients with moderate-to-severe plaque psoriasis: a randomized controlled trial with open-label extension.

BACKGROUND: In previous studies, etanercept 25 mg twice weekly (BIW) or 50 mg BIW significantly reduced disease severity in patients with plaque psoriasis and demonstrated a favourable safety profile. OBJECTIVES: To assess the efficacy and safety of etanercept 50 mg administered once weekly (QW) compared with placebo in patients with moderate-to-severe plaque psoriasis over 24 weeks. METHODS: This study was conducted in two parts: (i) a 12-week, double-blind, placebo-controlled phase, in which patients received etanercept 50 mg QW or placebo QW; and (ii) a 12-week, open-label extension phase, in which all patients received etanercept 50 mg QW. Primary endpoint was a 75% or greater improvement from baseline in the Psoriasis Area and Severity Index (PASI 75) at week 12. Secondary endpoints included percentage PASI improvement and Physician's Global Assessment (PGA). RESULTS: One hundred and forty-two patients were analysed in the double-blind phase; 126 patients entered the open-label phase. At week 12, significantly more patients receiving etanercept 50 mg QW (37.5%) achieved PASI 75 response than patients receiving placebo (2.2%; P < 0.0001). At week 24, 71.1% in the etanercept-etanercept group and 44.4% in the placebo-etanercept group achieved PASI 75. Mean percentage of PASI improvement from baseline was 55.4% with etanercept vs. 9.4% worsening with placebo at week 12 (P < 0.0001), with 77.4% and 57.7% improvement in the etanercept-etanercept and placebo-etanercept groups at week 24. A PGA score of 0-1 (clear-almost clear) was achieved by 64% and 42% in the etanercept-etanercept and placebo-etanercept groups at week 24, respectively. Etanercept 50 mg QW was well tolerated. No deaths, serious infections, opportunistic infections (including tuberculosis), demyelinating disorders, malignancies or new safety signals were reported. CONCLUSIONS: Nearly three-quarters of patients with moderate-to-severe psoriasis receiving etanercept 50 mg QW achieved significant improvement in disease severity over 24 weeks. This study also showed a favourable tolerability and safety profile with etanercept 50 mg QW.

Reversal of Mu gem2ts-induced mutations.

Mutations induced by the integration of a Mu gem2ts mutant prophage can revert at frequencies around 1 x 10(-6), more than 10(4)-fold higher than that obtained with Mu wild-type. Several aspects characterize Mu gem2ts precise excision: (i) the phage transposase is not involved; (ii) the RecA protein is not necessary; and (iii) revertants remain lysogenic with the prophage inserted elsewhere in the host genome. In addition, prophage re-integration seems to be non-randomly distributed, whereas Mu insertion into the host genome is a transposition event without any sequence specificity. In this paper, we describe that the site of re-integration somehow depends on the original site of insertion. Two alternative models are proposed to explain the strong correlation between donor and receptor sites.

A method for DNA extraction from the desert cyanobacterium chroococcidiopsis and its application to identification of ftsZ

A method was developed for extraction of DNA from Chroococcidiopsis that overcomes obstacles posed by bacterial contamination and the presence of a thick envelope surrounding the cyanobacterial cells. The method is based on the resistance of Chroococcidiopsis to lysozyme and consists of a lysozyme treatment followed by osmotic shock that reduces the bacterial contamination by 3 orders of magnitude. Then DNase treatment is performed to eliminate DNA from the bacterial lysate. Lysis of Chroococcidiopsis cells is achieved by grinding with glass beads in the presence of hot phenol. Extracted DNA is further purified by cesium-chloride density gradient ultracentrifugation. This method permitted the first molecular approach to the study of Chroococcidiopsis, and a 570-bp fragment of the gene ftsZ was cloned and sequenced.

Mu gem2ts DNA integration is not necessary for induction of synchrony of cell division in Escherichia coli K12.

The gem2ts mutant of bacteriophage Mu induced synchrony of cell division on bacteria surviving infection. Induction of synchronous growth could also be observed as a response to the entire infected bacterial population, as in the case of infection of hic mutants, a peculiar class of gyrB alleles. After Mu wild-type or Mu gem2ts infection of hic mutants, there was a lack of viral DNA integration and replication, while phage gene expression (including that of A gene, coding for the transposase) seemed to be quite normal. These data indicate that the mechanism of bacterial synchronization induced by Mu gem2ts does not require integration nor replication of the phage DNA.

Global changes in gene expression in Escherichia coli K12 induced by bacteriophage Mu Gem protein.

We have studied the growth properties of some Mu lysogens with respect to the non-lysogenic strain and have observed that the division time in minimal medium was increased over 4-fold when the bacteria carried the prophage mutated in the gem gene (Mu gem3). Since this phage gene has previously been shown to be involved in modulation of expression of host genes, we have analysed the proteins extracted from lysogens and non-lysogens as a rapid assay of global gene expression. The pattern of proteins extracted showed marked quantitative variations between non-lysogens, lysogens for wild-type Mu and lysogens for phage Mu gem3. These effects were no longer as evident when the strains were grown in rich medium. This dramatic change in the physiological state of the lysogenic strain versus the non-lysogenic in particular growth conditions extends the concept of lysogeny. For many years, the prophage has been considered only as a potentially lethal factor, while here it also appears as a genetic element capable of profoundly modifying host biology.

Synchronous division induced in Escherichia coli K12 by phage Mu: analysis of DNA topology and gene expression during the cell cycle.

Bacteriophage Mu mutants in gene gem (Mu gemts2) induce cycles of synchronous divisions after infection of a bacterial population in steady-state conditions. In this paper, two classes of gyrB mutants, synchronizable and non-synchronizable, are described. The existence of the non-synchronizable class suggests that the gyrase B subunit is involved with Gem in the process of synchronization. Cyclical variations in DNA topology of a resident multicopy plasmid occur during synchronous growth and correlate with a modulation of the chromosomal lacZ gene expression. Transcription data for the cell division genes, ftsZ and envA, obtained studying first steps in synchronous growth after infection, show that synthesis of the two mRNA is not constant. The specific mRNA of envA seems to be stimulated soon after infection, whereas the two transcripts initiating upstream from ftsZ apparently decrease to a basal level. In both cases, however, synthesis of the mRNA virtually doubles at the time of cell division.

Mu gem3 as a tool to investigate the influence of chromosome supercoiling on gene expression in Escherichia coli K12.

We have developed a rapid method to investigate the influence of chromosome supercoiling on gene expression in Escherichia coli K12. This method exploits the ability of the gem3 mutant of the bacteriophage Mu, even in the prophagic state in immune cells, to induce relaxation of the host chromosome. The experiments can thus be performed under physiological conditions, and without the use of the drugs. In theory, this method can be applied to any bacterial gene. Here, we report the results obtained with four DNA replication and three cell division genes.

A spontaneous Escherichia coli K12 mutant which inhibits the excision-reintegration process of Mu gem2ts.

Escherichia coli K12 strains lysogenic for Mu gem2ts with the prophage inserted in a target gene (i.e., lacZ::Mu gem2ts lysogenic strains) revert to Lac+ by prophage precise excision with a relatively high frequency (about 1 x 10(-6)). The revertants obtained are still lysogens with the prophage inserted elsewhere in the bacterial chromosome. We have observed that, with the time of storage in stabs, bacterial cultures lysogenic for Mu gem2ts lose the ability to excise the prophage. The mutation responsible for this effect was co-transducible with the gyrB gene. After the removal of the prophage by P1 vir transduction from these strains, one randomly chosen clone, R3538, was further analyzed. It shows an increment of DNA supercoiling of plasmid pAT153, used as a reporter, and a reduced beta-galactosidase activity. On the other hand, R3538 is totally permissive to both lytic and lysogenic cycles of bacteriophage Mu.

Tiopronine-induced reduction of rheumatoid factor functional affinity and asialylated IgG in patients with rheumatoid arthritis.

Serum and synovial fluid (SF) from 16 rheumatoid arthritis patients were evaluated before and after a 2-month treatment with tiopronine (TP). The levels of rheumatoid factor (RF) declined, as did the functional affinity of the remaining RF (p less than 0.01 in serum and p less than 0.05 in SF). Concomitant restoration of the sialylation of IgG was observed (p less than 0.05 in serum and SF). Following an initial increase, a significant reduction was observed in the level of soluble interleukin-2 receptors in serum (p less than 0.05) and SF (p less than 0.05) after treatment with TP.

A possible linkage of HLA-DRB haplotypes with Tiopronin intolerance in rheumatoid arthritis.

To investigate the relationship between HLA class II genotypes and toxic intolerance during treatment with Tiopronin, a slow-acting drug used in the treatment of rheumatoid arthritis (RA), we studied 40 patients who were divided into two groups: a group of 22 patients without side effects and a group of 18 patients with intolerance to Tiopronin. The PCR-RFLP method was used to determine the HLA-DR, DQ and DP genotypes. The patients in the two groups had similar genetic backgrounds with an expected high frequency of DRI and DR4 alleles. However, DR1/DR4 heterozygosity was significantly increased in patients with intolerance (p = 0.03, Odds Ratio = 10.5). In addition, one intolerant patient had a DR1/DR7 genotype which shared DRw53 (DRB4*0101) with DR1/DR4. Furthermore, two subtypes of DR5, DRB1*1102 and DRB1*1201, were increased among intolerant patients (11.1% vs 0%, p = 0.03, OR = 13.97). In total, DR1/DRw53 heterozygotes, DRB1*1102 and DRB1*1201 represented 61.1% of intolerant patients. Therefore, a detailed HLA class II typing might be useful before RA treatment by Tiopronin to predict and avoid toxic side effects in the patients with increased risk. Further investigation is currently underway.

[A comparative controlled trial of 2 administration modalities of tiopronin in rheumatoid arthritis]. / Essai contrôlé comparatif de deux modalités d'administration de la tiopronine dans la polyarthrite rhumatoïde.

Thiopronin is a second line drug for rheumatoid arthritis with proven efficacy in controlled trials versus a placebo, D-penicillamine, or gold salts. This 4-month study was aimed mainly at comparing the efficacy and safety of two thiopronin regimens, i.e., 1 g/d for 2 weeks followed by 1.5 g/d (regimen A) versus 0.5 g/d for 1 month, 0.750 g/d during the second month, then 1 g/d (regimen B). Because earlier investigations have suggested a role for copper in the activity of D-penicillamine, a secondary goal of this study was to evaluate whether the clinical effects of thiopronin were related to changes in serum copper and ceruloplasmin levels. Among the 61 included patients, 32 received regimen A and 29 regimen B. The primary efficacy criterion was the physician's overall efficacy assessment. Efficacy was rated good or excellent in 65.5% of regimen A patients and 55.6% of regimen B patients. Eighteen of the 32 regimen A patients and 23 of the 29 regimen B patients experienced at least one adverse event (p = 0.055). Failure to tolerate the drug required withdrawal in 12 of the 32 regimen A patients (37.5%) versus 11 of the 29 regimen B patients (37.9%). Declines in serum copper and ceruloplasmin levels were not correlated with treatment efficacy or tolerance. These findings, together with previously reported data, suggest that treatment should be initiated in a dosage of 1 g/day and that thiopronin-related adverse events are not dose-dependent.

Prokaryotic division interactome: setup of an assay for protein-protein interaction mutant selection.

A method which enables selection of protein mutants impaired in their ability to interact with their normal protein partners is presented here. The method is the two-phage two-hybrid assay adapted for mutant selection. In the two-phage assay, the interaction between two proteins enables the formation of a functional hybrid lambdoid repressor that shuts down expression of a reporter gene governed by a chimeric promoter/operator region. To adapt the assay to interaction mutant selection, antibiotic resistance was used as a reporter gene. In this case, the interaction between the two proteins resulted in antibiotic sensitivity, whereas the loss of interaction conferred resistance to the bacterial strain. Therefore, turning on reporter gene expression highlights the loss of interaction due to a mutation in one of the genes for the two protein partners, and leads to direct selection of the mutants regardless of the mutant phenotype. In this paper, application of this method to isolation of interaction mutants in proteins involved in Escherichia coli K12 cytokinesis is reported.

FtsQ interaction mutants: a way to identify new antibacterial targets.

FtsQ is a highly conserved component of the divisome that plays a central role in the assembly of early and late cell division proteins. The biological activity of this protein is still largely unknown, but its ability to interact with many components of the divisome was described by both two-hybrid assays and co-immunoprecipitation experiments. This paper describes the behaviour of ftsQ point mutants, created by random mutagenesis without regard to their phenotype, in which FtsQ is impaired in its ability to interact with its Escherichia coli division partners. Our results allow the identification of FtsQ residues involved in the interaction with other partner proteins and the determination of the biological significance of these interactions. The knowledge derived by this study could constitute not only the basis for understanding how these proteins assemble in the divisome, but also a starting point for the design of new antibacterial drugs that disrupt the bacterial division machinery.

Three functional subdomains of the Escherichia coli FtsQ protein are involved in its interaction with the other division proteins.

FtsQ, an essential protein for the Escherichia coli divisome assembly, is able to interact with various division proteins, namely FtsI, FtsL, FtsN, FtsB and FtsW. In this paper, the FtsQ domains involved in these interactions were identified by two-hybrid assays and co-immunoprecipitations. Progressive deletions of the ftsQ gene suggested that the FtsQ self-interaction and its interactions with the other proteins are localized in three periplasmic subdomains: (i) residues 50-135 constitute one of the sites involved in FtsQ, FtsI and FtsN interaction, and this site is also responsible for FtsW interaction; (ii) the FtsB interaction is localized between residues 136 and 202; and (iii) the FtsL interaction is localized at the very C-terminal extremity. In this third region, the interaction site for FtsK and also the second site for FtsQ, FtsI, FtsN interactions are located. As far as FtsW is concerned, this protein interacts with the fragment of the FtsQ periplasmic domain that spans residues 67-75. In addition, two protein subdomains, one constituted by residues 1-135 and the other from 136 to the end, are both able to complement an ftsQ null mutant. Finally, the unexpected finding that an E. coli ftsQ null mutant can be complemented, at least transiently, by the Streptococcus pneumoniae divIB/ftsQ gene product suggests a new strategy for investigating the biological significance of protein-protein interactions.

Etanercept 50 mg once weekly is as effective as 25 mg twice weekly in patients with ankylosing spondylitis.

OBJECTIVE: To compare the efficacy, pharmacokinetics and safety of etanercept 50 mg once weekly with 25 mg twice weekly and placebo in patients with ankylosing spondylitis. METHODS: A 12-week, double-blind, placebo-controlled study compared the effects of etanercept 50 mg once weekly, etanercept 25 mg twice weekly and placebo in 356 patients with active ankylosing spondylitis (3:3:1 randomisation, respectively). The primary end point was the proportion of patients achieving a response at week 12 based on the Assessment in Ankylosing Spondylitis Working Group criteria (ASAS 20). The pharmacokinetics of etanercept 50 mg once weekly and 25 mg twice weekly were analysed. RESULTS: Baseline characteristics and disease activity were similar among the three groups: etanercept 50 mg once weekly, etanercept 25 mg twice weekly and placebo. The percentage of patients discontinuing therapy was 9.0%, 9.3% and 13.7% for the three respective groups. ASAS 20 response at 12 weeks was achieved by 74.2% of patients with etanercept 50 mg once weekly and 71.3% of those with etanercept 25 mg twice weekly, both significantly higher than the percentage of patients taking placebo (37.3%, p<0.001). Percentages of patients with ASAS 5/6 response (70.3%, 72.0% and 27.5%, respectively; p<0.001) and those with ASAS 40 response (58.1%, 53.3% and 21.6%, respectively; p<0.001) followed a similar pattern. Significant improvement (p<0.05) was seen in measures of disease activity, back pain, morning stiffness and C reactive protein levels as early as 2 weeks. Serum etanercept exposure was similar between the etanercept groups. Incidence of treatment-emergent adverse events, including infections, was similar among all three groups, and no unexpected safety issues were identified. CONCLUSIONS: Patients with ankylosing spondylitis can expect a comparable significant improvement in clinical outcomes with similar safety when treated with etanercept 50 mg once weekly or with 25 mg twice weekly.