Membrane Incorporation, Channel Formation, and Disruption of Calcium Homeostasis by Alzheimer's β-Amyloid Protein

Oligomerization, conformational changes, and the consequent neurodegeneration of Alzheimer's β-amyloid protein (AβP) play crucial roles in the pathogenesis of Alzheimer's disease (AD). Mounting evidence suggests that oligomeric AβPs cause the disruption of calcium homeostasis, eventually leading to neuronal death. We have demonstrated that oligomeric AβPs directly incorporate into neuronal membranes, form cation-sensitive ion channels (“amyloid channels”), and cause the disruption of calcium homeostasis via the amyloid channels. Other disease-related amyloidogenic proteins, such as prion protein in prion diseases or α-synuclein in dementia with Lewy bodies, exhibit similarities in the incorporation into membranes and the formation of calcium-permeable channels. Here, based on our experimental results and those of numerous other studies, we review the current understanding of the direct binding of AβP into membrane surfaces and the formation of calcium-permeable channels. The implication of composition of membrane lipids and the possible development of new drugs by influencing membrane properties and attenuating amyloid channels for the treatment and prevention of AD is also discussed

Rab13 Is Involved in the Entry Step of Hepatitis C Virus Infection

Membrane transport probably participates in the lifecycle of hepatitis C virus (HCV). Rab proteins are essential host factors for HCV RNA replication, but these proteins’ roles in other steps of the HCV lifecycle are not clear. The tight junction (TJ) plays a key role in HCV infection. Rab13 regulates the endocytic recycling of the TJ-associated proteins. Here we investigated whether Rab13 is involved in the HCV entry step. We used HuH-7-derived RSc cells and Li23-derived D7 cells. To evaluate the effect of Rab13 in HCV infection, we transfected the cells with siRNA targeting Rab13 before HCV infection. The down-regulation of Rab13 inhibited HCV infection. The D7 cells had showed a greater inhibitory effect against HCV infection compared to that in the RSc cells by Rab13 knockdown. Next, to evaluate the effect of Rab13 after infection, we inoculated the cells with HCV before transfection of the siRNA. The down-regulation of Rab13 did not show any effects after HCV infection. We further examined whether Rab13 would influence HCV RNA replication by using HCV replicon-harboring cells. The results revealed that Rab13 did not affect the step of HCV RNA replication. These results suggest that Rab13 plays an important role in the step of HCV entry

Annexin A1 Negatively Regulates Viral RNA Replication of Hepatitis C Virus

Persistent infection with hepatitis C virus (HCV) often causes chronic hepatitis, and then shows a high rate of progression to liver cirrhosis and hepatocellular carcinoma. To clarify the mechanism of the persistent HCV infection is considered to be important for the discovery of new target(s) for the development of anti-HCV strategies. In the present study, we found that the expression level of annexin A1 (ANXA1) in human hepatoma cell line Li23-derived D7 cells was remarkably lower than that in parental Li23 cells, whereas the susceptibility of D7 cells to HCV infection was much higher than that of Li23 cells. Therefore, we hypothesized that ANXA1 negatively regulates persistent HCV infection through the inhibition of viral RNA replication. The results revealed that HCV production was significantly inhibited without a concomitant reduction in the amount of lipid droplets in the D7 cells stably expressing exogenous ANXA1. Further, we demonstrated that ANXA1 negatively regulated the step of viral RNA replication rather than that of viral entry in human hepatocytes. These results suggest that ANXA1 would be a novel target for the development of anti-HCV strategies

The oligosaccharides in a recombinant hepatitis B virus surface antigen (HBsAg) carrying the pre-S2 region derived from yeast

AbstractThe N- and O-linked oligosaccharides in a yeast-derived HBsAg M protein (pre-S2 + S) were analyzed. Two major structures of the N-linked oligosaccharides bound to residue Asn4 were determined to be high-mannose type oligosaccharides. Man7GlcNAc2 and Man8GlcNAc2, by two-dimensional sugar mapping of the corresponding pyridylamino oligosaccharides. Peptide mapping of the M protein, sequence analysis of the glycopeptides after β-elimination under reducing conditions and sugar-composition analysis revealed that the O-linked oligosaccharides were composed solely or mannose and bound to residue Ser5, Thr6, Thr7, Ser27, Ser28, Ser29 and Thr31 in the pre-S2 region

Temporal and Spatial Expression Patterns of Bone Morphogenetic Protein 3 in Developing Zebrafish

Bone morphogenetic proteins (BMPs) are important elements in bone biology. We herein report the expression profiles of zebrafish bmp3 (zbmp3) as demonstrated by real-time PCR and in situ hybridization. The expression of zbmp3 was highly detectable by real-time PCR from 1 day post-fertilization (1 dpf) to 2 weeks post-fertilization (2 wpf) and peaked at 1 wpf. For in situ hybridization experiments, zbmp3 was expressed in the otic vesicle at 1 dpf, 2 dpf, 3 dpf, and 5 dpf. It was also expressed in the pharyngeal arches, including the opercle, branchiostegal ray, and pectoral fins, at 2 dpf. Our results suggest that zbmp3 may play an important role in the skeletal biology of developing zebrafish

Fitting birth-death processes to panel data with applications to bacterial DNA fingerprinting

Continuous-time linear birth-death-immigration (BDI) processes are frequently used in ecology and epidemiology to model stochastic dynamics of the population of interest. In clinical settings, multiple birth-death processes can describe disease trajectories of individual patients, allowing for estimation of the effects of individual covariates on the birth and death rates of the process. Such estimation is usually accomplished by analyzing patient data collected at unevenly spaced time points, referred to as panel data in the biostatistics literature. Fitting linear BDI processes to panel data is a nontrivial optimization problem because birth and death rates can be functions of many parameters related to the covariates of interest. We propose a novel expectation--maximization (EM) algorithm for fitting linear BDI models with covariates to panel data. We derive a closed-form expression for the joint generating function of some of the BDI process statistics and use this generating function to reduce the E-step of the EM algorithm, as well as calculation of the Fisher information, to one-dimensional integration. This analytical technique yields a computationally efficient and robust optimization algorithm that we implemented in an open-source R package. We apply our method to DNA fingerprinting of Mycobacterium tuberculosis, the causative agent of tuberculosis, to study intrapatient time evolution of IS6110 copy number, a genetic marker frequently used during estimation of epidemiological clusters of Mycobacterium tuberculosis infections. Our analysis reveals previously undocumented differences in IS6110 birth-death rates among three major lineages of Mycobacterium tuberculosis, which has important implications for epidemiologists that use IS6110 for DNA fingerprinting of Mycobacterium tuberculosis.Comment: Published in at http://dx.doi.org/10.1214/13-AOAS673 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Empiric treatment of pulmonary TB in the Xpert era: Correspondence of sputum culture, Xpert MTB/RIF, and clinical diagnoses.

BackgroundClinical tuberculosis diagnosis and empiric treatment have traditionally been common among patients with negative bacteriologic test results. Increasing availability of rapid molecular diagnostic tests, including Xpert MTB/RIF and the new Xpert Ultra cartridge, may alter the role of empiric treatment.MethodsWe prospectively enrolled outpatients age > = 15 who were evaluated for pulmonary tuberculosis at three health facilities in Kampala, Uganda. Using sputum mycobacterial culture, interviews, and clinical record abstraction, we estimated the accuracy of clinical diagnosis relative to Xpert and sputum culture and assessed the contribution of clinical diagnosis to case detection.ResultsOver a period of 9 months, 99 patients were diagnosed with pulmonary tuberculosis and subsequently completed sputum culture; they were matched to 196 patients receiving negative tuberculosis evaluations in the same facilities. Xpert was included in the evaluation of 291 (99%) patients. Compared to culture, Xpert had a sensitivity of 92% (95% confidence interval 83-97%) and specificity of 95% (92-98%). Twenty patients with negative Xpert were clinically diagnosed with tuberculosis and subsequently had their culture status determined; two (10%) were culture-positive. Considering all treated patients regardless of Xpert and culture data completeness, and considering treatment initiations before a positive Xpert (N = 4) to be empiric, 26/101 (26%) tuberculosis treatment courses were started empirically. Compared to sputum smear- or Xpert-positive patients with positive cultures, empirically-treated, Xpert-negative patients with negative cultures had higher prevalence of HIV (67% versus 37%), shorter duration of cough (median 4 versus 8 weeks), and lower inflammatory markers (median CRP 7 versus 101 mg/L).ConclusionJudged against sputum culture in a routine care setting of high HIV prevalence, the accuracy of Xpert was high. Clinical judgment identified a small number of additional culture-positive cases, but with poor specificity. Although clinicians should continue to prescribe tuberculosis treatment for Xpert-negative patients whose clinical presentations strongly suggest pulmonary tuberculosis, they should also carefully consider alternative diagnoses