Nitrosylation of c heme in cd1-nitrite reductase is enhanced during catalysis

The reduction of nitrite into nitric oxide (NO) in denitrifying bacteria is catalyzed by nitrite reductase. In several species, this enzyme is a heme-containing protein with one c heme and one d₁ heme per monomer (cd₁NiR), encoded by the nirS gene.     

Consistent Association of Type 2 Diabetes Risk Variants Found in Europeans in Diverse Racial and Ethnic Groups

It has been recently hypothesized that many of the signals detected in genome-wide association studies (GWAS) to T2D and other diseases, despite being observed to common variants, might in fact result from causal mutations that are rare. One prediction of this hypothesis is that the allelic associations should be population-specific, as the causal mutations arose after the migrations that established different populations around the world. We selected 19 common variants found to be reproducibly associated to T2D risk in European populations and studied them in a large multiethnic case-control study (6,142 cases and 7,403 controls) among men and women from 5 racial/ethnic groups (European Americans, African Americans, Latinos, Japanese Americans, and Native Hawaiians). In analysis pooled across ethnic groups, the allelic associations were in the same direction as the original report for all 19 variants, and 14 of the 19 were significantly associated with risk. In summing the number of risk alleles for each individual, the per-allele associations were highly statistically significant (P<10⁻⁴) and similar in all populations (odds ratios 1.09–1.12) except in Japanese Americans the estimated effect per allele was larger than in the other populations (1.20; P_het = 3.8×10⁻⁴). We did not observe ethnic differences in the distribution of risk that would explain the increased prevalence of type 2 diabetes in these groups as compared to European Americans. The consistency of allelic associations in diverse racial/ethnic groups is not predicted under the hypothesis of Goldstein regarding “synthetic associations” of rare mutations in T2D.     

Receptor crosstalk: haloperidol treatment enhances A2A adenosine receptor functioning in a transfected cell model

A(2A) adenosine receptors are considered an excellent target for drug development in several neurological and psychiatric disorders. It is noteworthy that the responses evoked by A(2A) adenosine receptors are regulated by D(2) dopamine receptor ligands. These two receptors are co-expressed at the level of the basal ganglia and interact to form functional heterodimers. In this context, possible changes in A(2A) adenosine receptor functional responses caused by the chronic blockade/activation of D(2) dopamine receptors should be considered to optimise the therapeutic effectiveness of dopaminergic agents and to reduce any possible side effects. In the present paper, we investigated the regulation of A(2A) adenosine receptors induced by antipsychotic drugs, commonly acting as D(2) dopamine receptor antagonists, in a cellular model co-expressing both A(2A) and D(2) receptors. Our data suggest that the treatment of cells with the classical antipsychotic haloperidol increased both the affinity and responsiveness of the A(2A) receptor and also affected the degree of A(2A)-D(2) receptor heterodimerisation. In contrast, an atypical antipsychotic, clozapine, had no effect on A(2A) adenosine receptor parameters, suggesting that the two classes of drugs have different effects on adenosine-dopamine receptor interaction. Modifications to A(2A) adenosine receptors may play a significant role in determining cerebral adenosine effects during the chronic administration of antipsychotics in psychiatric diseases and may account for the efficacy of A(2A) adenosine receptor ligands in pathologies associated with dopaminergic system dysfunction. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11302-010-9201-z) contains supplementary material, which is available to authorized users.     

Assessing cytotoxicity of boron nitride nanotubes: Interference with the MTT assay

Thanks to a non-covalent wrapping with glycol-chitosan, highly biocompatible and highly concentrated dispersions of boron nitride nanotubes were obtained and tested on human neuroblastoma cells. A systematic investigation of the cytotoxicity of these nanovectors with several complementary qualitative and quantitative assays allowed a strong interference with the MTT metabolic assay to be highlighted, similar to a phenomenon already observed for carbon nanotubes, that would wrongly suggest toxicity of boron nitride nanotubes. These results confirm the high complexity of these new nanomaterials, and the needing of extensive investigations on their exciting potential applications in the biomedical field.     

The electric sense of the paddlefish: a passive system for the detection and capture of zooplankton prey.

Behavioral and electrophysiological experiments have shown that the elongated paddlefish rostrum, with its extensive population of ampullae of Lorenzini, constitutes a passive electrosensory antenna of great sensitivity and spatial resolution. As demonstrated in juvenile paddlefish, the passive electrosense serves a novel function in feeding serving as the primary, if not exclusive sensory modality for the detection and capture of zooplanktonic prey. Ampullary receptors are sensitive to the weak electrical fields of plankton from distances up to 9 cm, and juvenile paddlefish capture plankton individually with great swimming dexterity in the absence of vision or other stimulus signals. Paddlefish also detect and avoid metal obstacles, the electrical signatures of which are a potential hindrance to their feeding and reproductive migrations. The ampullary receptors, their peripheral innervation and central targets in the dorsal octavolateral nucleus, are described. We also describe the ascending and descending neuronal circuitry of the electrosensory system in the brain based on tracer studies using dextran amines.     

Anti-PlGF inhibits growth of VEGF(R)-inhibitor-resistant tumors without affecting healthy vessels

Novel antiangiogenic strategies with complementary mechanisms are needed to maximize efficacy and minimize resistance to current angiogenesis inhibitors. We explored the therapeutic potential and mechanisms of alphaPlGF, an antibody against placental growth factor (PlGF), a VEGF homolog, which regulates the angiogenic switch in disease, but not in health. alphaPlGF inhibited growth and metastasis of various tumors, including those resistant to VEGF(R) inhibitors (VEGF(R)Is), and enhanced the efficacy of chemotherapy and VEGF(R)Is. alphaPlGF inhibited angiogenesis, lymphangiogenesis, and tumor cell motility. Distinct from VEGF(R)Is, alphaPlGF prevented infiltration of angiogenic macrophages and severe tumor hypoxia, and thus, did not switch on the angiogenic rescue program responsible for resistance to VEGF(R)Is. Moreover, it did not cause or enhance VEGF(R)I-related side effects. The efficacy and safety of alphaPlGF, its pleiotropic and complementary mechanism to VEGF(R)Is, and the negligible induction of an angiogenic rescue program suggest that alphaPlGF may constitute a novel approach for cancer treatment.     

Helicobacter pylori EstV: identification, cloning, and characterization of the first lipase isolated from an epsilon-proteobacterium

Bacterial lipases are attracting an enormous amount of attention due to their wide biotechnological applications and due to their roles as virulence factors in some bacteria. Helicobacter pylori is a significant and widespread pathogen which produces a lipase(s) and phospholipases that seem to play a role in mucus degradation and the release of proinflammatory and cytotoxic compounds. However, no H. pylori lipase(s) has been isolated and described previously. Therefore, a search for putative lipase-encoding genes was performed by comparing the amino acid sequences of 53 known lipolytic enzymes with the deduced proteome of H. pylori. As a result, we isolated, cloned, purified, and characterized EstV, a novel lipolytic enzyme encoded by open reading frame HP0739 of H. pylori 26695, and classified it in family V of the bacterial lipases. This enzyme has the properties of a small, cell-bound carboxylesterase (EC 3.1.1.1) that is active mostly with short-chain substrates and does not exhibit interfacial activation. EstV is stable and does not require additional cofactors, and the maximum activity occurs at 50 degrees C and pH 10. This unique enzyme is the first lipase isolated from H. pylori that has been described, and it might contribute to ulcer development, as inhibition by two antiulcer substances (beta-aescin and glycyrrhizic acid) suggests. EstV is also the first lipase from an epsilon-proteobacterium to be described. Furthermore, this enzyme is a new member of family V, probably the least-known family of bacterial lipases, and the first lipase of this family for which kinetic behavior, inhibition by natural substances, and other key biochemical features are reported.     

RNA and DNA binding properties of HIV-1 Vif protein: a fluorescence study

The HIV-1 viral infectivity factor (Vif) is a small basic protein essential for viral fitness and pathogenicity. Some "non-permissive" cell lines cannot sustain replication of Vif(-) HIV-1 virions. In these cells, Vif counteracts the natural antiretroviral activity of the DNA-editing enzymes APOBEC3G/3F. Moreover, Vif is packaged into viral particles through a strong interaction with genomic RNA in viral nucleoprotein complexes. To gain insights into determinants of this binding process, we performed the first characterization of Vif/nucleic acid interactions using Vif intrinsic fluorescence. We determined the affinity of Vif for RNA fragments corresponding to various regions of the HIV-1 genome. Our results demonstrated preferential and moderately cooperative binding for RNAs corresponding to the 5'-untranslated region of HIV-1 (5'-untranslated region) and gag (cooperativity parameter omega approximately 65-80, and K(d) = 45-55 nM). In addition, fluorescence spectroscopy allowed us to point out the TAR apical loop and a short region in gag as primary strong affinity binding sites (K(d) = 9.5-14 nM). Interestingly, beside its RNA binding properties, the Vif protein can also bind the corresponding DNA oligonucleotides and their complementary counterparts with an affinity similar to the one observed for the RNA sequences, while other DNA sequences displayed reduced affinity. Taken together, our results suggest that Vif binding to RNA and DNA offers several non-exclusive ways to counteract APOBEC3G/3F factors, in addition to the well documented Vif-induced degradation by the proteasome and to the Vif-mediated repression of translation of these antiviral factors.     

Aminoglycoside binding to the HIV-1 RNA dimerization initiation site: thermodynamics and effect on the kissing-loop to duplex conversion

Owing to a striking, and most likely fortuitous, structural and sequence similarity with the bacterial 16 S ribosomal A site, the RNA kissing-loop complex formed by the HIV-1 genomic RNA dimerization initiation site (DIS) specifically binds 4,5-disubstituted 2-deoxystreptamine (2-DOS) aminoglycoside antibiotics. We used chemical probing, molecular modeling, isothermal titration calorimetry (ITC) and UV melting to investigate aminoglycoside binding to the DIS loop–loop complex. We showed that apramycin, an aminoglycoside containing a bicyclic moiety, also binds the DIS, but in a different way than 4,5-disubstituted 2-DOS aminoglycosides. The determination of thermodynamic parameters for various aminoglycosides revealed the role of the different rings in the drug–RNA interaction. Surprisingly, we found that the affinity of lividomycin and neomycin for the DIS (K_d ~ 30 nM) is significantly higher than that obtained in the same experimental conditions for their natural target, the bacterial A site (K_d ~ 1.6 µM). In good agreement with their respective affinity, aminoglycoside increase the melting temperature of the loop–loop interaction and also block the conversion from kissing-loop complex to extended duplex. Taken together, our data might be useful for selecting new molecules with improved specificity and affinity toward the HIV-1 DIS RNA.