Glutathione-like tripeptides as inhibitors of glutathionylspermidine synthetase. Part 1: Substitution of the glycine carboxylic acid group

Glutathionylspermidine synthetase/amidase (GspS) is an essential enzyme in the biosynthesis and turnover of trypanothione and represents an attractive target for the design of selective anti-parasitic drugs. We synthesised a series of analogues of glutathione (L-gamma-Glu-L-Leu-Gly-X) where the glycine carboxylic acid group (X) has been substituted for other acidic groups such as tetrazole, hydroxamic acid, acylsulphonamide and boronic acid. The boronic acid appears the most promising lead compound (IC(50) of 17.2 microM).     

Identification and expression of a factor of the DM family in the oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas is a successive not systematic protandric hermaphrodite. Searching for an ortholog to Dmrt1, a conserved sex determinism factor, we have identified the first complete cDNA of a DM factor in Lophotrochozoa which we have called Cg-DMl (Crassostrea gigas DMRT-like). It is 359aa long, with the DM domain common to all the family factors, and one DMA domain specific to members such as Dmrt4 and Dmrt5. Its gene presents one intron of 598 bp. Real time PCR and in situ hybridization have shown that Cg-DMl was expressed in both sexes, with a significantly higher expression in male than in female gonads at the end of the adult gametogenetic cycle and that a significant peak of expression was observed in spat between 1 and 2 months of age. These results suggest that Cg-DMl may be involved in the development of the gonad and may constitute preliminary clues for future work in order to better understand DM protein evolution.     

Structural basis for molecular recognition and presentation of histone H3 by WDR5

Histone methylation at specific lysine residues brings about various downstream events that are mediated by different effector proteins. The WD40 domain of WDR5 represents a new class of histone methyl-lysine recognition domains that is important for recruiting H3K4 methyltransferases to K4-dimethylated histone H3 tail as well as for global and gene-specific K4 trimethylation. Here we report the crystal structures of full-length WDR5, WDR5Delta23 and its complexes with unmodified, mono-, di- and trimethylated histone H3K4 peptides. The structures reveal that WDR5 is able to bind all of these histone H3 peptides, but only H3K4me2 peptide forms extra interactions with WDR5 by use of both water-mediated hydrogen bonding and the altered hydrophilicity of the modified lysine 4. We propose a mechanism for the involvement of WDR5 in binding and presenting histone H3K4 for further methylation as a component of MLL complexes.     

The Lysozyme-Induced Peptidoglycan N-Acetylglucosamine Deacetylase PgdA (EF1843) Is Required for Enterococcus faecalis Virulence

Lysozyme is a key component of the innate immune response in humans that provides a first line of defense against microbes. The bactericidal effect of lysozyme relies both on the cell wall lytic activity of this enzyme and on a cationic antimicrobial peptide activity that leads to membrane permeabilization. Among Gram-positive bacteria, the opportunistic pathogen Enterococcus faecalis has been shown to be extremely resistant to lysozyme. This unusual resistance is explained partly by peptidoglycan O-acetylation, which inhibits the enzymatic activity of lysozyme, and partly by d-alanylation of teichoic acids, which is likely to inhibit binding of lysozyme to the bacterial cell wall. Surprisingly, combined mutations abolishing both peptidoglycan O-acetylation and teichoic acid alanylation are not sufficient to confer lysozyme susceptibility. In this work, we identify another mechanism involved in E. faecalis lysozyme resistance. We show that exposure to lysozyme triggers the expression of EF1843, a protein that is not detected under normal growth conditions. Analysis of peptidoglycan structure from strains with EF1843 loss- and gain-of-function mutations, together with in vitro assays using recombinant protein, showed that EF1843 is a peptidoglycan N-acetylglucosamine deacetylase. EF1843-mediated peptidoglycan deacetylation was shown to contribute to lysozyme resistance by inhibiting both lysozyme enzymatic activity and, to a lesser extent, lysozyme cationic antimicrobial activity. Finally, EF1843 mutation was shown to reduce the ability of E. faecalis to cause lethality in the Galleria mellonella infection model. Taken together, our results reveal that peptidoglycan deacetylation is a component of the arsenal that enables E. faecalis to thrive inside mammalian hosts, as both a commensal and a pathogen.     

Helicobacter pylori Genotypes Associated with Gastric Histo-Pathological Damages in a Moroccan Population

H. pylori persistent infection induces chronic gastritis and is associated with peptic ulcer disease and gastric carcinoma development. The severity of these diseases is related to human’s genetic diversity, H. pylori genetic variability and environmental factors. To identify the prevalence of histo-pathological damages caused by H. pylori infection in Moroccan population, and to determine their association to H. pylori genotypes, a prospective study has been conducted during 3 years on patients attending the gastroenterology department of Hassan II University Hospital (CHU) of Fez, Morocco. A total of 801 Moroccan adults’ patients were recruited; H. pylori was diagnosed and genotyped by PCR in biopsy specimens and histological exam was performed. We found a high rate of glandular atrophy. Chronic inflammation, neutrophil activity and glandular atrophy showed statistically significant association with H. pylori infection. However, intestinal metaplasia was inversely associated to this infection and no association was observed with gastric cancer cases. A statistically significant association was found between intestinal metaplasia and vacAs1 and vac Am1 genotypes in patients aged 50 years and more but not in younger. This last genotype is also associated to gastric cancer. In this study, gastric cancer showed no significant association with H. pylori. Further studies are warranted to determine the role of other etiological agents such as Epstein-Barr virus, human papillomavirus and possibly environmental and dietetic factors in the occurrence of this pathology.     

Etude de la respiration, à l’état isolé, des haplotypes de l’abeille tunisienne Apis mellifera intermissa (Buttel Reepen 1906) (Hymenoptera : Apidae)

L’étude de la respiration de l’abeille domestique, Apis mellifera intermissa, à l’état isolé a été réalisée sur les quatre haplotypes existant en Tunisie : A1, A4, A8 et A9 et sous différentes températures : 0°, 10°, 15°, 20°, 25°, 30° et 35°C. Des mesures effectuées sur 1000 abeilles isolées (250 de chaque haplotype) ont montré que la consommation d’oxygène de l’abeille varie en fonction de la température. L’intensité respiratoire des haplotypes augmente progressivement à partir de 0°C pour atteindre son maximum à 15°C. Au-delà de cette température, la consommation d’oxygène de l’abeille diminue progressivement. Pour les basses températures (0° et 10°C), la respiration de l’abeille dépend aussi du facteur génétique et la consommation d’oxygène est faible mais ne s’annule pas. Cette étude a montré qu’il existe une différence de consommation d’oxygène entre les haplotypes A1 et A8 et les haplotypes A4 et A9 pour les basses températures. Le déclenchement de la thermogenèse chez les haplotypes A1 et A8 se produit à 15°C, alors que chez les haplotypes A4 et A9, il a lieu à une température plus basse et qui est de 10°C.     

Impact of TP53 codon 72 and MDM2 promoter 309 allelic dosage in a Moroccan population with hepatocellular carcinoma

Single-nucleotide polymorphisms (SNPs) in codon 72 of the TP53 gene (rs1042522) and in the promoter region of the MDM2 gene (SNP309; rs2279744) have been shown to play a role in the predisposition to many cancers. However, these findings were inconsistent in other tumor types, and ethnicity is suspected to be a critical factor influencing the effects of these SNPs on the cancer risk. The aim of the present study was to investigate whether these functional SNPs were associated with an enhanced risk of liver tumorigenesis in Moroccan patients. We have genotyped both polymorphisms in 96 patients with hepatocellular carcinoma (HCC) and 222 controls without HCC matched for age, gender and ethnicity by PCR-RFLP confirmed by sequencing. A joint effect between the MDM2 and TP53 polymorphisms and an increased risk of liver cancer was detected, with the odds ratio for the presence of both MDM2 309GG and TP53 72Pro/Pro genotypes being 10 (95% confidence interval 0.39-255.55). Interestingly, a significant increase in the HCC risk was observed when at least two deleterious alleles were present, indicating an allele dosage effect. There was no evidence for any association with early age of HCC onset when deleterious alleles of MDM2 SNP309 and TP53 Arg72Pro where present. Our findings suggest that the combination of TP53 72Pro and MDM2 309G polymorphisms enhance the risk of developing HCC. These results deserve further confirmation in other populations.     

Human Brucellosis in Maghreb: Existence of a Lineage Related to Socio-Historical Connections with Europe

Despite control/eradication programs, brucellosis, major worldwide zoonosis due to the Brucella genus, is endemic in Northern Africa and remains a major public health problem in the Maghreb region (Algeria/Morocco/Tunisia). Brucella melitensis biovar 3 is mostly involved in human infections and infects mainly small ruminants. Human and animal brucellosis occurrence in the Maghreb seems still underestimated and its epidemiological situation remains hazy. This study summarizes official data, regarding Brucella melitensis infections in Algeria, from 1989 to 2012, with the purpose to provide appropriate insights concerning the epidemiological situation of human and small ruminant brucellosis in Maghreb. Algeria and Europe are closely linked for historical and economical reasons. These historical connections raise the question of their possible impact on the genetic variability of Brucella strains circulating in the Maghreb. Other purpose of this study was to assess the genetic diversity among Maghreb B. melitensis biovar 3 strains, and to investigate their possible epidemiological relationship with European strains, especially with French strains. A total of 90 B. melitensis biovar 3 Maghreb strains isolated over a 25 year-period (1989–2014), mainly from humans, were analysed by MLVA-16. The obtained results were compared with genotypes of European B. melitensis biovar 3 strains. Molecular assays showed that Algerian strains were mainly distributed into two distinct clusters, one Algerian cluster related to European sub-cluster. These results led to suggest the existence of a lineage resulting from socio-historical connections between Algeria and Europe that might have evolved distinctly from the Maghreb autochthonous group. This study provides insights regarding the epidemiological situation of human brucellosis in the Maghreb and is the first molecular investigation regarding B. melitensis biovar 3 strains circulating in the Maghreb.