Motility and segregation of Hsp104-associated protein aggregates in budding yeast

During yeast cell division, aggregates of damaged proteins are segregated asymmetrically between the bud and the mother. It is thought that protein aggregates are cleared from the bud via actin cable-based retrograde transport toward the mother and that Bni1p formin regulates this transport. Here, we examined the dynamics of Hsp104-associated protein aggregates by video microscopy, particle tracking, and image correlation analysis. We show that protein aggregates undergo random walk without directional bias. Clearance of heat-induced aggregates from the bud does not depend on formin proteins but occurs mostly through dissolution via Hsp104p chaperon. Aggregates formed naturally in aged cells also exhibit random walk but do not dissolve during observation. Although our data do not disagree with a role for actin or cell polarity in aggregate segregation, modeling suggests that their asymmetric inheritance can be a predictable outcome of aggregates' slow diffusion and the geometry of yeast cells.     

Lingo2 variants associated with essential tremor and Parkinson��s disease

LINGO2, a member of LRR gene family, has been linked with both Essential tremor (ET) and Parkinson's disease (PD). However, there is a lack of conclusive evidence regarding the etiologic role of LINGO2 genetic variants. We investigated the association of LINGO2 variants with ET and PD in two independent Asian countries. A total of 1,262 subjects comprising 499 controls, 436 PD patients, and 327 ET patients were included. Eight LINGO2 variants, including four single-nucleotide polymorphisms (SNPs) and four coding variants, were initially analyzed in one Asian population. SNPs that showed positive association were then replicated in the second independent Asian population, and a pooled analysis was carried out. Out of the eight variants, two SNPs (rs7033345 and rs10812774) revealed significant or strong positive trend in the first Asian population, and these were analyzed in the second Asian population. In the pooled analysis, the CC genotype at rs7033345 had a higher risk of developing PD (OR?=?1.67, 95% CI?=?1.18, 2.35, p?=?0.003) and ET (OR?=?1.50, 95% CI?=?1.02, 2.20, p?=?0.04) under a recessive model. The C allele at rs10812774 increased the risk of ET (OR?=?1.56 95% CI?=?1.10, 2.22, p?=?0.01) via a recessive model. The effect size and direction of trend were in the same direction in each of the two populations. Our study demonstrated for the first time that rs7033345 is associated with PD and ET and rs10812774 with ET among Asians, suggesting that LINGO2 might act as a susceptibility gene for both conditions.     

LysGH15B,the SH3b Domain of Staphylococcal Phage Endolysin LysGH15, Retains High Affinity to Staphylococci

LysGH15, a phage endolysin, exhibits a particularly broad lytic spectrum against Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA). Sequence analysis reveals that this endolysin contains a C-terminal cell wall binding domain (SH3b), which causes the endolysin to bind to host strains. In this study, the substrate binding affinity of the SH3b domain (LysGH15B) was evaluated. A fusion protein of LysGH15B and green fluorescent protein (LysGH15B–GFP) were cloned and expressed in Escherichia coli. Laser scanning confocal microscopy was used to detect the fluorescence of the treated cells irradiated at different excitation wavelengths and to determine the binding activity of LysGH15B–GFP and GFP. We found that LysGH15B–GFP not only generated green fluorescence, but, more importantly, also displayed specific affinity to staphylococcal isolates, especially MRSA. In contrast, the single GFP did not display any binding activity. The high affinity was attributed to the portion of LysGH15B and the binding activity of the fusion protein was specific to staphylococci. This study provides an insight into the SH3b domain of LysGH15. The specific binding activity may cause LysGH15B to serve as an anchoring device, and offer an alternative approach for cell surface attachment onto staphylococci.     

2ME and 2OHE2 exhibit growth inhibitory effects and cell cycle arrest at G2/M in RL95-2 human endometrial cancer cells through activation of p53 and Chk1

Evidence is accumulating that estradiol (E2) may play a dual role in carcinogenic and anticarcinogenic effects by different metabolic pathways. It has been shown that some metabolites of E2 exert proliferative and others anti-proliferative properties on human cancer cells. In the present study, the effects of E2 and its four primary metabolites including 2-hydroxyestradiol (2OHE2), 4-hydroxyestradiol (4OHE2), 2-methoxyestradiol (2ME), and 4-methoxyestradiol (4ME) on proliferation and cell cycle in RL95-2 human endometrial cells were investigated. Our results indicate that 2ME and 2OHE2, but not E2, 4ME, and 4OHE2, exhibit the inhibitory effect through cell cycle arrest at G2/M. 2ME and 2OHE2-induced G2/M cell cycle arrest associated with activation of p53 (Ser15), upregulation of p21(WAF1/Cip1) (p21) and GADD45, inactivation of Cdc2 (Tyr15), as well as downregulation of Cyclin B1. 2ME and 2OHE2-mediated cell cycle arrest at G2/M was also related to activation of protein kinase Chk1 which is associated with p53 (Ser20) activation and downstream responses.     

Genistein inhibits mitochondrial-targeted oxidative damage induced by beta-amyloid peptide 25–35 in PC12 cells

The antioxidative properties of genistein (Gen) have been demonstrated by our previous studies and others, but its potential mechanism was not very clear. Because of the key role of mitochondria in oxidant production, we wondered if mitochondria were one of Gen’s neuroprotective targets. In the present study we investigated whether Gen has protective effects on mitochondria damaged by Aβ25-35. PC12 cells were pre-incubated with or without Gen for 2 h followed by the incubation with 20 μM Aβ25-35 for another 24 h before mitochondrial membrane fluidity (MMF), mitochondrial membrane potential (MMP) , and mitochondrial redox state were measured. The results showed that Gen alleviated the decrease of MMF induced by Aβ25-35, and maintained the MMP. Additionally, Gen promoted the mitochondrial antioxidative capability through increasing the GSH/GSSG ratio, GPx activity and MnSOD protein expression in mitochondria. Moreover, Gen reversed the changes of ChAT mRNA and AChE mRNA expression in cells induced by Aβ25-35. These results suggested that Gen can protect the mitochondrial membrane and maintain redox state in mitochondria damaged by Aβ25-35.     

Congestive heart failure with preserved ejection fraction is associated with severely impaired dynamic Starling mechanism

Sedentary aging leads to increased cardiovascular stiffening, which can be ameliorated by sufficient amounts of lifelong exercise training. An even more extreme form of cardiovascular stiffening can be seen in heart failure with preserved ejection fraction (HFpEF), which comprises ~40~50% of elderly patients diagnosed with congestive heart failure. There are two major interrelated hypotheses proposed to explain heart failure in these patients: 1) increased left ventricular (LV) diastolic stiffness and 2) increased arterial stiffening. The beat-to-beat dynamic Starling mechanism, which is impaired with healthy human aging, reflects the interaction between ventricular and arterial stiffness and thus may provide a link between these two mechanisms underlying HFpEF. Spectral transfer function analysis was applied between beat-to-beat changes in LV end-diastolic pressure (LVEDP; estimated from pulmonary artery diastolic pressure with a right heart catheter) and stroke volume (SV) index. The dynamic Starling mechanism (transfer function gain between LVEDP and the SV index) was impaired in HFpEF patients (n = 10) compared with healthy age-matched controls (n = 12) (HFpEF: 0.23 ± 0.10 ml·m?2·mmHg?1 and control: 0.37 ± 0.11 ml·m?2·mmHg?1, means ± SD, P = 0.008). There was also a markedly increased (3-fold) fluctuation of LV filling pressures (power spectral density of LVEDP) in HFpEF patients, which may predispose to pulmonary edema due to intermittent exposure to higher pulmonary capillary pressure (HFpEF: 12.2 ± 10.4 mmHg2 and control: 3.8 ± 2.9 mmHg2, P = 0.014). An impaired dynamic Starling mechanism, even more extreme than that observed with healthy aging, is associated with marked breath-by-breath LVEDP variability and may reflect advanced ventricular and arterial stiffness in HFpEF, possibly contributing to reduced forward output and pulmonary congestion.     

Structure and dynamics of nitrifier populations in a full-scale submerged membrane bioreactor during start-up

Changes of microbial characteristics in a full-scale submerged membrane bioreactor system (capacity, 60,000 m³ day⁻¹) treating sewage were monitored over the start-up period (96 days). Fluorescence in situ hybridization analysis showed that the percentages of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (nitrobacter-related population) in total bacteria counted with DAPI staining increased significantly from 1.9% and 0.9% to 4.5% and 2.8%, corresponding to an increase of the specific ammonium oxidizing rate (from 0.06 to 0.12 kg N kg⁻¹ mixed liquor suspended solids (MLSS) per day) and the specific nitrate forming rate (from 0.05 to 0.10 kg N kg⁻¹ MLSS day⁻¹). Both the denaturing gradient gel electrophoresis of polymerase chain reaction and clone library results showed that the AOB was dominated by the genus Nitrosomonas, the diversity of which increased markedly with operational time. Most of the day 2 clones were closely related with the uncultured Nitrosomonas sp. clone Ninesprings-49S amoA gene (AY356450.1) originated from activated sludge, while the day 96 clone library showed a more diverse distribution characterized by the appearance of the oligotrophic nitrifiers like the Nitrosomonas oligotropha- and Nitrosomonas ureae-like bacteria, perhaps due to the interception by membrane and the low food-to-microorganisms ratio environment. The above results show that the membrane bioreactor system was characterized by the increased diversity and percentage of nitrifiers, which made it possible to achieve a stable and high efficient nitrification. Ammonia-oxidizing archaea with the changing population structures were also detected, but their roles for ammonia oxidation in the system need further studies.     

The effect of membrane curvature on the conformation of antimicrobial peptides: implications for binding and the mechanism of action

Short cationic antimicrobial peptides (AMPs) are believed to act either by inducing transmembrane pores or disrupting membranes in a detergent-like manner. For example, the antimicrobial peptides aurein 1.2, citropin 1.1, maculatin 1.1 and caerin 1.1, despite being closely related, appear to act by fundamentally different mechanisms depending on their length. Using molecular dynamics simulations, the structural properties of these four peptides have been examined in solution as well as in a variety of membrane environments. It is shown that each of the peptides has a strong preference for binding to regions of high membrane curvature and that the structure of the peptides is dependent on the degree of local curvature. This suggests that the shorter peptides aurein 1.2 and citropin 1.1 act via a detergent-like mechanism because they can induce high local, but not long-range curvature, whereas the longer peptides maculatin 1.1 and caerin 1.1 require longer range curvature to fold and thus bind to and stabilize transmembrane pores.     

Antimicrobial and antibiofilm activity of pleurocidin against cariogenic microorganisms

Dental caries is a common oral bacterial infectious disease of global concern. Prevention and treatment of caries requires control of the dental plaque formed by pathogens such as Streptococcus mutans and Streptococcus sobrinus. Pleurocidin, produced by Pleuronectes americanus, is an antimicrobial peptide that exerts broad-spectrum activity against pathogenic bacteria and fungi. Moreover, pleurocidin shows less hemolysis and is less toxic than other natural peptides. In the present study, we investigated whether pleurocidin is an effective antibiotic peptide against common cariogenic microorganisms and performed a preliminary study of the antimicrobial mechanism. We assayed minimal inhibitory concentration (MIC), minimal bactericide concentration (MBC) and bactericidal kinetics and performed a spot-on-lawn assay. The BioFlux system was used to generate bacterial biofilms under controllable flow. Fluorescence microscopy and confocal laser scanning microscopy (CLSM) were used to analyze and observe biofilms. Scanning electron microscopy was used to observe the bacterial membrane. MIC and MBC results showed that pleurocidin had different antimicrobial activities against the tested oral strains. Although components of saliva could affect antimicrobial activity, pleurocidin dissolved in saliva still showed antimicrobial effects against oral microorganisms. Furthermore, pleurocidin showed a favorable killing effect against BioFlux flow biofilms in vitro. Our findings suggest that pleurocidin has the potential to kill dental biofilms and prevent dental caries.