Structural effects of an LQT-3 mutation on heart Na+ channel gating

Computational methods that predict three-dimensional structures from amino acid sequences have become increasingly accurate and have provided insights into structure-function relationships for proteins in the absence of structural data. However, the accuracy of computational structural models requires experimental approaches for validation. Here we report direct testing of the predictions of a previously reported structural model of the C-terminus of the human heart Na(+) channel. We focused on understanding the structural basis for the unique effects of an inherited C-terminal mutation (Y1795C), associated with long QT syndrome variant 3 (LQT-3), that has pronounced effects on Na(+) channel inactivation. Here we provide evidence that this mutation, in which a cysteine replaces a tyrosine at position 1795 (Y1795C), enables the formation of disulfide bonds with a partner cysteine in the channel. Using the predictions of the model, we identify the cysteine and show that three-dimensional information contained in the sequence for the channel protein is necessary to understand the structural basis for some of the effects of the mutation. The experimental evidence supports the accuracy of the predicted structural model of the human heart Na(+) channel C-terminal domain and provides insight into a structural basis for some of the mutation-induced altered channel function underlying the disease phenotype.     

Hypoxia and DNA-damaging agent bleomycin both increase the cellular level of the protein 4E-BP

The 4E-binding proteins (4E-BPs) regulate the cap-dependent eukaryotic initiation factor 4E (eIF4E). The level of 4E-BP protein is regulated during early development of sea urchin embryos. Fertilization leads to the rapid disappearance of the protein that reappears later in development. We show that two important cellular stresses, hypoxia and bleomycin prolonged checkpoint mobilization provoked the overexpression of the protein 4E-BP in developing sea urchin embryos. Hypoxia resulted after 1 h in a reversible gradual increase in the protein 4E-BP level. At 20 h, the protein 4E-BP had reached the level existing in the unfertilized eggs. Bleomycin used as a DNA-damaging agent for checkpoint activation, provoked cell cycle inhibition and after prolonged exposure (20 h), induced the expression of the protein 4E-BP. The effect of bleomycin on 4E-BP protein overexpression was dose-dependent between 0.4 and 1.2 mM. The role of the overexpression of the protein 4E-BP is discussed in relation with cellular stress responses.     

Peracetic acid stress-induced genetic rearrangements in Escherichia coli H10407 detected by RAPD and RFLP analyses

The discriminatory powers of random amplified polymorphic DNA (RAPD) analysis and restriction fragment length polymorphism (RFLP) were assessed for the detection and comparison of DNA modifications caused by an oxidative stress. DNA extracted from peracetic acid (PAA)-treated Escherichia coli H10407 was randomly amplified with the 10-mer primer OPZ14, which generated one stress-induced fragment. RFLP and RAPD profiles were hybridized by Southern blotting with the digoxigenin-labelled RAPD product. Untreated and PAA-treated cells had difference band profiles. The results indicate that RAPD analysis could be used as a discriminatory tool for investigating genetic rearrangements in E. coli caused by oxidative stress and that RFLP analysis could be used to confirm the rearrangements.     

Hepatitis C virus (HCV) core protein-induced, monocyte-mediated mechanisms of reduced IFN-alpha and plasmacytoid dendritic cell loss in chronic HCV infection

IFN-alpha production by plasmacytoid dendritic cells (PDCs) is critical in antiviral immunity. In the present study, we evaluated the IFN-alpha-producing capacity of PDCs of patients with chronic hepatitis C virus (HCV) infection in treatment-naive, sustained responder, and nonresponder patients. IFN-alpha production was tested in PBMCs or isolated PDCs after TLR9 stimulation. Treatment-naive patients with chronic HCV infection had reduced frequency of circulating PDCs due to increased apoptosis and showed diminished IFN-alpha production after stimulation with TLR9 ligands. These PDC defects correlated with the presence of HCV and were in contrast with normal PDC functions of sustained responders. HCV core protein, which was detectable in the plasma of infected patients, reduced TLR9-triggered IFN-alpha and increased TNF-alpha and IL-10 production in PBMCs but not in isolated PDCs, suggesting HCV core induced PDC defects. Indeed, addition of rTNF-alpha and IL-10 induced apoptosis and inhibited IFN-alpha production in PDCs. Neutralization of TNF-alpha and/or IL-10 prevented HCV core-induced inhibition of IFN-alpha production. We identified CD14+ monocytes as the source of TNF-alpha and IL-10 in the HCV core-induced inhibition of PDC IFN-alpha production. Anti-TLR2-, not anti-TLR4-, blocking Ab prevented the HCV core-induced inhibition of IFN-alpha production. In conclusion, our results suggest that HCV interferes with antiviral immunity through TLR2-mediated monocyte activation triggered by the HCV core protein to induce cytokines that in turn lead to PDC apoptosis and inhibit IFN-alpha production. These mechanisms are likely to contribute to HCV viral escape from immune responses.     

RBP-Jkappa-dependent notch signaling is dispensable for mouse early embryonic development

The Notch signaling pathway is an evolutionarily conserved signaling system which has been shown to be essential in cell fate specification and in numerous aspects of embryonic development in all metazoans thus far studied. We recently demonstrated that several components of the Notch signaling pathway, including the four Notch receptors and their five ligands known in mammals, are expressed in mouse oocytes, in mouse preimplantation embryos, or both. This suggested a possible implication of the Notch pathway in the first cell fate specification of the dividing mouse embryo, which results in the formation of the blastocyst. To address this issue directly, we generated zygotes in which both the maternal and the zygotic expression of Rbpsuh, a key element of the core Notch signaling pathway, were abrogated. We find that such zygotes give rise to blastocysts which implant and develop normally. Nevertheless, after gastrulation, these embryos die around midgestation, similarly to Rbpsuh-null mutants. This demonstrates that the RBP-Jkappa-dependent pathway, otherwise called the canonical Notch pathway, is dispensable for blastocyst morphogenesis and the establishment of the three germ layers, ectoderm, endoderm, and mesoderm. These results are discussed in the light of recent observations which have challenged this conclusion.     

Estimation of the causal effects on survival of two-stage nonrandomized treatment sequences for recurrent diseases

In the treatment of cancer, patients commonly receive a variety of sequential treatments. The initial treatments administered following diagnosis can vary, as well as subsequent salvage regimens given after disease recurrence. This article considers the situation where neither initial treatments nor salvage treatments are randomized. Assuming there are no unmeasured confounders, we estimate the joint causal effects on survival of initial and salvage treatments, that is, the effects of two-stage treatment sequences. For each individual treatment sequence, we estimate the survival distribution function and the mean restricted survival time. Different treatment sequences are then compared using these estimates and their corresponding covariances. Simulation studies were conducted to evaluate the performance of the methods, including their sensitivity to the violation of the assumption of no unmeasured confounders. The methods are illustrated by a retrospective study of patients with soft tissue sarcoma, which motivated this research.     

Dose ranging and efficacy study of high-dose coenzyme Q10 formulations in Huntington's disease mice

There is substantial evidence that a bioenergetic defect may play a role in the pathogenesis of Huntington's Disease (HD). A potential therapy for remediating defective energy metabolism is the mitochondrial cofactor, coenzyme Q10 (CoQ10). We have reported that CoQ10 is neuroprotective in the R6/2 transgenic mouse model of HD. Based upon the encouraging results of the CARE-HD trial and recent evidence that high-dose CoQ10 slows the progressive functional decline in Parkinson's disease, we performed a dose ranging study administering high levels of CoQ10 from two commercial sources in R6/2 mice to determine enhanced efficacy. High dose CoQ10 significantly extended survival in R6/2 mice, the degree of which was dose- and source-dependent. CoQ10 resulted in a marked improvement in motor performance and grip strength, with a reduction in weight loss, brain atrophy, and huntingtin inclusions in treated R6/2 mice. Brain levels of CoQ10 and CoQ9 were significantly lower in R6/2 mice, in comparison to wild type littermate control mice. Oral administration of CoQ10 elevated CoQ10 plasma levels and significantly increased brain levels of CoQ9, CoQ10, and ATP in R6/2 mice, while reducing 8-hydroxy-2-deoxyguanosine concentrations, a marker of oxidative damage. We demonstrate that high-dose administration of CoQ10 exerts a greater therapeutic benefit in a dose dependent manner in R6/2 mice than previously reported and suggest that clinical trials using high dose CoQ10 in HD patients are warranted.     

Phylogenetic analysis of the tenascin gene family: evidence of origin early in the chordate lineage

Background  

Tenascins are a family of glycoproteins found primarily in the extracellular matrix of embryos where they help to regulate cell proliferation, adhesion and migration. In order to learn more about their origins and relationships to each other, as well as to clarify the nomenclature used to describe them, the tenascin genes of the urochordate Ciona intestinalis, the pufferfish Tetraodon nigroviridis and Takifugu rubripes and the frog Xenopus tropicalis were identified and their gene organization and predicted protein products compared with the previously characterized tenascins of amniotes.     

A novel surface protein of Trichomonas vaginalis is regulated independently by low iron and contact with vaginal epithelial cells

Background  

Trichomonosis caused by Trichomonas vaginalis is the number one, non-viral sexually transmitted disease (STD) that affects more than 250 million people worldwide. Immunoglobulin A (IgA) has been implicated in resistance to mucosal infections by pathogens. No reports are available of IgA-reactive proteins and the role, if any, of this class of antibody in the control of this STD. The availability of an IgA monoclonal antibody (mAb) immunoreactive to trichomonads by whole cell (WC)-ELISA prompted us to characterize the IgA-reactive protein of T. vaginalis.