Molecular modeling of c-erbB2 receptor dimerization: Coiled-coil structure of wild and oncogenic transmembrane domains—Stabilization by interhelical hydrogen bonds in the oncogenic form

Dimerization models of c-erbB2 transmembrane domains (Leu651-Ile675) are studied by molecular mechanics and molecular dynamics simulations. Both wild and Glu mutated transmembrane helices exhibit the same relative orientation for favorable associations and dimerize preferentially in left-handed coiled-coil structures. The mutation point 659 belongs to the interfacing residues, and in the transforming domain, symmetric hydrogen bonds between Glu carboxylic groups stabilize the dimeric structure. The same helix packing found for the wild dimers, except side-chain—side-chain hydrogen bonds, suggests that the transmembrane domains dimerize according to similar process. Structural and energetical characterization of the models are presented. © 1997 John Wiley & Sons, Inc. Biopoly 42: 157–168, 1997     

Long-range structural and dynamical changes induced by cofactor binding in DNA methyltransferase M.HhaI

The bacterial DNA cytosine methyltransferase M.HhaI sequence-specifically modifies DNA in an S-adenosylmethionine dependent reaction. The enzyme stabilizes the target cytosine (GCGC) into an extrahelical position, with a concomitant large movement of an active site loop involving residues 80-99. We used multidimensional, transverse relaxation-optimized NMR experiments to assign nearly 80% of all residues in the cofactor-bound enzyme form, providing a basis for detailed structural and dynamical characterization. We examined details of the previously unknown effects of the cofactor binding with M.HhaI in solution. Addition of the cofactor results in numerous structural changes throughout the protein, including those decorating the cofactor binding site, and distal residues more than 30 A away. The active site loop is involved in motions both on a picosecond to nanosecond time scale and on a microsecond to millisecond time scale and is not significantly affected by cofactor binding except for a few N-terminal residues. The cofactor also affects residues near the DNA binding cleft, suggesting a role for the cofactor in regulating DNA interactions. The allosteric properties we observed appear to be closely related to the significant amount of dynamics and dynamical changes in response to ligand binding detected in the protein.     

Acute dyspnoea and single tracheal localisation of mantle cell lymphoma

We report a case of a 48-year-old Chinese female with end-stage renal disease and chronic anemia on hemodialysis. Clonazepam was prescribed for myoclonus disorder two weeks prior to her hospitalization. Subsequently, she was hospitalized for neutropenic fever with thrombocytopenia and worsening anemia. Bone marrow examination demonstrated a markedly hypocellular marrow (10-20% total cellularity). Clonazepam was discontinued, with gradual improvement of thrombocytopenia, and neutropenia in 1-2 weeks. To our knowledge, this is the first reported case of pancytopenia associated with clonazepam. We recommend patients taking clonazepam to be monitored with regular complete blood count to check for clinically significant pancytopenia or thrombocytopenia.     

Hepatic Gene Expression Profile in Mice Perorally Infected with Echinococcus multilocularis Eggs

Background

Alveolar echinococcosis (AE) is a severe chronic hepatic parasitic disease currently emerging in central and eastern Europe. Untreated AE presents a high mortality (>90%) due to a severe hepatic destruction as a result of parasitic metacestode proliferation which behaves like a malignant tumor. Despite this severe course and outcome of disease, the genetic program that regulates the host response leading to organ damage as a consequence of hepatic alveolar echinococcosis is largely unknown.

Methodology/Principal Findings

We used a mouse model of AE to assess gene expression profiles in the liver after establishment of a chronic disease status as a result of a primary peroral infection with eggs of the fox tapeworm Echinococcus multilocularis. Among 38 genes differentially regulated (false discovery rate adjusted p≤0.05), 35 genes were assigned to the functional gene ontology group <immune response>, while 3 associated with the functional group <intermediary metabolism>. Upregulated genes associated with <immune response> could be clustered into functional subgroups including <macrophages>, <APCs>, <lymphocytes, chemokines and regulation>, <B-cells> and <eosinophils>. Two downregulated genes related to <lymphocytes, chemokines and regulation> and <intermediary metabolism>, respectively. The <immune response> genes either associated with an <immunosupression> or an <immunostimulation> pathway. From the overexpressed genes, 18 genes were subsequently processed with a Custom Array microfluidic card system in order to assess respective expression status at the mRNA level relative to 5 reference genes (Gapdh, Est1, Rlp3, Mdh-1, Rpl37) selected upon a constitutive and stable expression level. The results generated by the two independent tools used for the assessment of gene expression, i.e., microarray and microfluidic card system, exhibited a high level of congruency (Spearman correlation rho = 0.81, p = 7.87e-5) and thus validated the applied methods.

Conclusions/Significance

Based on this set of biomarkers, new diagnostic targets have been made available to predict disease status and progression. These biomarkers may also offer new targets for immuno-therapeutic intervention.     

X-Linked Female-Sterile Loci in DROSOPHILA MELANOGASTER

We have examined the number of X-linked loci specifically required only during oogenesis. Complementation analyses among female-sterile (fs) mutations obtained in two mutagenesis screens--GANS' and MOHLER's--indicate that any fs locus represented by two or more mutant alleles in GANS' collection are usually present in MOHLER's collection. However, when a locus is represented by a single allele in one collection, it is generally not present in the other collection. We propose that this discrepancy is due to the fact that most "fs loci" represented by less than two mutant alleles are, in fact, vital (zygotic lethal) genes, and that the fs alleles are hypomorphic mutations of such genes. In support of this hypothesis we have identified lethal alleles at 12 of these "fs loci." The present analysis has possibly identified all maternal-effect lethal loci detectable by mutations on the X chromosome and has allowed us to reevaluate the number of "ovary-specific fs" loci in the Drosophila genome. Finally, germline clone analysis of a large number of fs mutations was performed in order to estimate the relative contribution of germline and somatic cell derivatives to oogenesis and to embryonic development. All the maternal-effect lethal loci tested are germline-dependent.     

Role of the OPG/RANK/RANKL triad in calcifications of the atheromatous plaques: comparison between carotid and femoral beds

Recent works demonstrated the difference of calcification genesis between carotid and femoral plaques, femoral plaques being more calcified. It has been clearly demonstrated that the molecular triad osteoprotegerin (OPG)/Receptor Activator of NFkB (RANK)/RANK Ligand (RANKL) exerts its activities in the osteoimmunology and vascular system. The aim of this study was to determine their expression and their potential role in calcifications of the atheromatous plaques located in two different peripheral arterial beds, carotid and femoral. The expression of OPG, RANK and RANKL was analyzed by immunochemistry in 40 carotid and femoral samples. Blood OPG and RANKL were quantified using specific ELISA assays. OPG staining was more frequently observed in carotid than in femoral plaques, especially in lipid core. Its expression correlated with macrophage infiltration more abundantly observed in carotid specimens. Surprisingly, serum OPG concentration was significantly lower in carotid population compared to femoral population while RANK and RANKL were equally expressed in both arterial beds. Carotid plaques that are less rich in calcium than femoral specimens, express more frequently OPG, this expression being correlated with the abundance of macrophages in the lesions. These data strengthen the key role played by OPG in the differential calcification in carotid and femoral plaques.