AKT/SGK-sensitive phosphorylation of GSK3 in the regulation of L-selectin and perforin expression as well as activation induced cell death of T-lymphocytes

We identified the interaction between HBV X (HBx) protein and the oncogene AIB1 (amplified in breast cancer 1). A serine/proline motif (SSPSPS) in HBx was found to be required for the interaction. Two LXD motifs [LLXX(X)L, X means any amino acids], LLRNSL and LLDQLHTLL in AIB1 were also found to be involved in the HBx-AIB1 interaction. The HBx-AIB1 interaction was important for the activation of NFκB signal transduction, the HBx mutant that did not interact with AIB1showed dramatically lower NFκB activation activity than the WT HBx. These findings contribute to the new understanding on signal transduction activation mechanisms of HBx.     

Psychoacoustic sampling as a reliable,non-invasive method to monitor orthopteran species diversity in tropical forests

We evaluated trained listener—based acoustic sampling as a reliable and non-invasive method for rapid assessment of ensiferan species diversity in tropical evergreen forests. This was done by evaluating the reliability of identification of species and numbers of calling individuals using psychoacoustic experiments in the laboratory and by comparing psychoacoustic sampling in the field with ambient noise recordings made at the same time. The reliability of correct species identification by the trained listener was 100 % for 16 out of 20 species tested in the laboratory. The reliability of identifying the numbers of individuals correctly was 100% for 13 out of 20 species. The human listener performed slightly better than the instrument in detecting low frequency and broadband calls in the field, whereas the recorder detected high frequency calls with greater probability. To address the problem of pseudoreplication during spot sampling in the field, we monitored the movement of calling individuals using focal animal sampling. The average distance moved by calling individuals for 17 out of 20 species was less than 1.5 m in half an hour. We suggest that trained listener—based sampling is preferable for crickets and low frequency katydids, whereas broadband recorders are preferable for katydid species with high frequency calls for accurate estimation of ensiferan species richness and relative abundance in an area.     

Role of substrate recognition in modulating strigolactone receptor selectivity in witchweed

Witchweed, or Striga hermonthica, is a parasitic weed that destroys billions of dollars'' worth of crops globally every year. Its germination is stimulated by strigolactones exuded by its host plants. Despite high sequence, structure, and ligand-binding site conservation across different plant species, one strigolactone receptor in witchweed, ShHTL7, uniquely exhibits a picomolar EC50 for downstream signaling. Previous biochemical and structural analyses have hypothesized that this unique ligand sensitivity can be attributed to a large binding pocket volume in ShHTL7 resulting in enhanced ability to bind substrates, but additional structural details of the substrate-binding process would help explain its role in modulating the ligand selectivity. Using long-timescale molecular dynamics simulations, we demonstrate that mutations at the entrance of the binding pocket facilitate a more direct ligand-binding pathway to ShHTL7, whereas hydrophobicity at the binding pocket entrance results in a stable “anchored” state. We also demonstrate that several residues on the D-loop of AtD14 stabilize catalytically inactive conformations. Finally, we show that strigolactone selectivity is not modulated by binding pocket volume. Our results indicate that while ligand binding is not the sole modulator of strigolactone receptor selectivity, it is a significant contributing factor. These results can be used to inform the design of selective antagonists for strigolactone receptors in witchweed.     

Isolation and characterization of an enriched Golgi fraction from rat brain

A fraction rich in membranes of the Golgi apparatus was isolated from rat brain by discontinuous density gradient centrifugation. The fraction sedimented at the characteristic Golgi density of 1.11–1.15 (g/cm³, 5°C) and had specific activities of Golgi-marker enzymes (N-acetyllactosaminyl synthetase, glycoprotein (Fetuin) galactosyltransferase, thiamine pyrophosphatase), 6–7 times over those of th original homogenates. The recovery of the enzyme activities in this fraction ranged from 17 to 31%. The incorporation [³H]fucose into glycoproteins was 3-fold higher than in homogenate. Recovery and relative specific activities of marker enzymes for other subcellular organelles were low. Electron microscopic analysis of the fraction revealed the presence of Golgi structures, namely, large sacs or plates with attached tubules and “blebbing” of the tubules into the vesicles.     

Complex Pathways in Folding of Protein G Explored by Simulation and Experiment

The B1 domain of protein G has been a classic model system of folding for decades, the subject of numerous experimental and computational studies. Most of the experimental work has focused on whether the protein folds via an intermediate, but the evidence is mostly limited to relatively slow kinetic observations with a few structural probes. In this work we observe folding on the submillisecond timescale with microfluidic mixers using a variety of probes including tryptophan fluorescence, circular dichroism, and photochemical oxidation. We find that each probe yields different kinetics and compare these observations with a Markov State Model constructed from large-scale molecular dynamics simulations and find a complex network of states that yield different kinetics for different observables. We conclude that there are many folding pathways before the final folding step and that these paths do not have large free energy barriers.     

Role of Community Group Exposure in Reducing Sexually Transmitted Infection-Related Risk among Female Sex Workers in India

Background

Empowering female sex workers (FSWs) to address structural barriers and forming community groups (CGs) through community mobilization are seen as essential components of HIV prevention programs in India. Taking the membership of a CG as an exposure intervention, we hypothesized whether participation in a CG lead to reduced sexually transmitted infections (STIs) and increased treatment-seeking behavior among FSWs in three selected states of India — Andhra Pradesh, Maharashtra and Tamil Nadu.

Methods and Findings

The propensity score matching (PSM) approach examined the effect of CG membership, as against no membership, on STI-related risk, described as selected outcome measures — presence of any STI, self-reported STI symptoms, and treatment-seeking behavior among FSWs. A cross sectional bio-behavioral survey was administered in 2009–2010 and covered 7,806 FSWs through two-stage probability-based conventional and time location cluster sampling in 23 administrative districts of Andhra Pradesh, Maharashtra and Tamil Nadu. Only 2,939 FSWs were reported to be members of a CG and among them 4.5% had any STIs. A majority of FSWs were aged above 24 years (86.4%), had ever been married (73%), operated from a public place for solicitation (81.5%), and had ever received HIV test results (75.6%). The average effect of CG exposure was reduction in STI prevalence by 4%, while self-reported STI symptom treatment-seeking behavior increased by 13.7%.

Conclusion

FSWs who were exposed to a CG were at a substantially lower risk of STIs than those who were unexposed. The FSWs exposed to a CG had a higher chance of seeking STI treatment from public and private health facilities. Collectivization related challenges must be overcome to provide access to tailored STI prevention and care services.     

Inhibition of cystathionine-gamma-lyase leads to loss of glutathione and aggravation of mitochondrial dysfunction mediated by excitatory amino acid in the CNS

Oxidative stress has been implicated in the pathogenesis and progression of neurodegenerative disorders and antioxidants potentially have a major role in neuroprotection. Optimum levels of glutathione (gamma-glutamylcysteinyl glycine), an endogenous thiol antioxidant are required for the maintenance of the redox status of cells. Cystathionine gamma-lyase is the rate-limiting enzyme for the synthesis of cysteine from methionine and availability of cysteine is a critical factor in glutathione synthesis. In the present study, we have examined the role of cystathionine gamma-lyase in maintaining the redox homeostasis in brain, particularly with reference to mitochondrial function since the complex I of the electron transport chain is sensitive to redox perturbation. Inhibition of cystathionine gamma-lyase by l-propargylglycine caused loss of glutathione and decrease in complex I activity in the brain although the enzyme activity in mouse brain was 1% of the corresponding hepatic activity. We then examined the effect of this inhibition on the neurotoxicity mediated by the excitatory amino acid, l-beta-oxalyl amino-l-alanine, which is the causative factor of a type of motor neuron disease, neurolathyrism. l-beta-Oxalyl amino-l-alanine toxicity was exacerbated by l-propargylglycine measured as loss of complex I activity indicating the importance of cystathionine gamma-lyase in maintaining glutathione levels and in turn the mitochondrial function during excitotoxicity. Oxidative stress generated by l-beta-oxalyl amino-l-alanine itself inhibited cystathionine gamma-lyase, which could be prevented by prior treatment with thiol antioxidant. Thus, cystathionine gamma-lyase itself is susceptible to inactivation by oxidative stress and this can potentially exacerbate oxidant-induced damage. Cystathionine gamma-lyase is present in neuronal cells in human brain and its activity is several-fold higher compared to mouse brain. It could potentially play an important role in maintaining glutathione and protein thiol homeostasis in brain and hence afford neuroprotection.     

Dewetting Controls Plant Hormone Perception and Initiation of Drought Resistance Signaling

1. Download high-res image (204KB)
2. Download full-size image