Brain transcriptome-wide screen for HIV-1 Nef protein interaction partners reveals various membrane-associated proteins

HIV-1 Nef protein contributes essentially to the pathology of AIDS by a variety of protein-protein-interactions within the host cell. The versatile functionality of Nef is partially attributed to different conformational states and posttranslational modifications, such as myristoylation. Up to now, many interaction partners of Nef have been identified using classical yeast two-hybrid screens. Such screens rely on transcriptional activation of reporter genes in the nucleus to detect interactions. Thus, the identification of Nef interaction partners that are integral membrane proteins, membrane-associated proteins or other proteins that do not translocate into the nucleus is hampered. In the present study, a split-ubiquitin based yeast two-hybrid screen was used to identify novel membrane-localized interaction partners of Nef. More than 80% of the hereby identified interaction partners of Nef are transmembrane proteins. The identified hits are GPM6B, GPM6A, BAP31, TSPAN7, CYB5B, CD320/TCblR, VSIG4, PMEPA1, OCIAD1, ITGB1, CHN1, PH4, CLDN10, HSPA9, APR-3, PEBP1 and B3GNT, which are involved in diverse cellular processes like signaling, apoptosis, neurogenesis, cell adhesion and protein trafficking or quality control. For a subfraction of the hereby identified proteins we present data supporting their direct interaction with HIV-1 Nef. We discuss the results with respect to many phenotypes observed in HIV infected cells and patients. The identified Nef interaction partners may help to further elucidate the molecular basis of HIV-related diseases.

Comparing augmentation with non-antidepressants over sticking to antidepressants after treatment failure in depression: a naturalistic study

INTRODUCTION

Non-response to an antidepressant monotherapy in unipolar depression is quite common. Therefore strategies for subsequent treatment steps are necessary. However, there is a lack of direct comparisons of these different strategies. In this naturalistic study we compared the outcome to different strategies after failure of the primary antidepressant treatment.

METHODS

Failure of primary antidepressant monotherapy occurred in 135 patients. 98 of these patients have been administered 4 treatment strategies of the physicians' choice: lithium augmentation (Li-Augm), switching to another antidepressant (AD-Switch), combination of 2 antidepressants (AD-Comb) or augmentation with second generation antipsychotic (SGA-Augm). Primary outcome measure was the 17-item Hamilton rating scale for depression (HRSD).

RESULTS

Patients who received Li-Augm or augmentation with SGAs showed significantly greater improvement in HRSD and BDI compared to patients with antidepressant switch or antidepressant combination. Remission rates for Li-Augm and SGA-Augm were 89.3% and 86.2% compared to 40.7% for AD-Switch and 42.9% for AD-Comb.

DISCUSSION

Changing to another pharmacological class (Li-Augm or augmentation with SGAs) showed better treatment results than sticking to the class of antidepressants (AD-Switch and AD-Comb) after primary failure in response to antidepressant monotherapy in unipolar depression. The lack of randomization and absence of a non-response definition are design flaws. Controlled studies are required to confirm the findings of this trial.

Hydrophobic matching controls the tilt and stability of the dimeric platelet-derived growth factor receptor (PDGFR) β transmembrane segment

The platelet-derived growth factor receptor β is a member of the cell surface receptor tyrosine kinase family and dimerizes upon activation. We determined the structure of the transmembrane segment in dodecylphosphocholine micelles by liquid-state NMR and found that it forms a stable left-handed helical dimer. Solid-state NMR and oriented circular dichroism were used to measure the tilt angle of the helical segments in macroscopically aligned model membranes with different acyl chain lengths. Both methods showed that decreasing bilayer thickness (DEPC-POPC-DMPC) led to an increase in the helix tilt angle from 10° to 30° with respect to the bilayer normal. At the same time, reconstitution of the comparatively long hydrophobic segment became less effective, eventually resulting in complete protein aggregation in the short-chain lipid DLPC. Unrestrained molecular dynamics simulations of the dimer were carried out in explicit lipid bilayers (DEPC, POPC, DMPC, sphingomyelin), confirming the observed dependence of the helix tilt angle on bilayer thickness. Notably, molecular dynamics revealed that the left-handed dimer gets tilted en bloc, whereas conformational transitions to alternative (e.g. right-handed dimeric) states were not supported. The experimental data along with the simulation results demonstrate a pronounced interplay between the platelet-directed growth factor receptor β transmembrane segment and the bilayer thickness. The effect of hydrophobic mismatch might play a key role in the redistribution and activation of the receptor within different lipid microdomains of the plasma membrane in vivo.

Electrochemical properties of GaN nanowire electrodes--influence of doping and control by external bias

We report on the electrochemical characteristics of GaN nanowire (NW) ensembles grown by plasma-assisted molecular beam epitaxy on Si111 substrates and on the influence of Si and Mg doping. The NW electrochemical properties in terms of surface capacitance (C(S)), surface resistance (R(S)) are extracted from electrochemical impedance spectra. While Mg doping of GaN NWs does not cause a significant variation of these quantities, an increase of the Si concentration leads to an increase of C(S) and a simultaneous decrease of R(S), indicating the presence of charge carriers in the NWs. According to the extracted values for R(S) and C(S) the NWs are classified into resistive and conductive. For conductive NWs charge transfer to a ferricyanide redox couple in the electrolyte is demonstrated and the ensemble average of the flatband voltage was determined. Variation of the lateral surface potential due to application of an external bias via the electrolyte is demonstrated.

Transient structure and SH3 interaction sites in an intrinsically disordered fragment of the hepatitis C virus protein NS5A

Understanding the molecular mechanisms involved in virus replication and particle assembly is of primary fundamental and biomedical importance. Intrinsic conformational disorder plays a prominent role in viral proteins and their interaction with other viral and host cell proteins via transiently populated structural elements. Here, we report on the results of an investigation of an intrinsically disordered 188-residue fragment of the hepatitis C virus non-structural protein 5A (NS5A), which contains a classical poly-proline Src homology 3 (SH3) binding motif, using sensitivity- and resolution-optimized multidimensional NMR methods, complemented by small-angle X-ray scattering data. Our study provides detailed atomic-resolution information on transient local and long-range structure, as well as fast time scale dynamics in this NS5A fragment. In addition, we could characterize two distinct interaction modes with the SH3 domain of Bin1 (bridging integrator protein 1), a pro-apoptotic tumor suppressor. Despite being largely disordered, the protein contains three regions that transiently adopt α-helical structures, partly stabilized by long-range tertiary interactions. Two of these transient α-helices form a noncanonical SH3-binding motif, which allows low-affinity SH3 binding. Our results contribute to a better understanding of the role of the NS5A protein during hepatitis C virus infection. The present work also highlights the power of NMR spectroscopy to characterize multiple binding events including short-lived transient interactions between globular and highly disordered proteins.

Crosstalk in the retinal neurovascular unit - lessons for the diabetic retina

Diabetic retinopathy shares important features with neurodegenerative retinal diseases, including loss of ganglion cells and retinal thinning. The impact on vasoregression and subsequent ischemia-driven changes such as macular edema and proliferative retinopathy are not established. Studies using adult neurodegenerative animal models such as the transgenic TGR(CMV-PKD2(1/703)HA) rat imply early activation of the innate immunity system and the complement system as well as microglia playing a role in the damage of the retinal neurovascular unit.

The European gonococcal antimicrobial surveillance programme, 2009

Neisseria gonorrhoeae antimicrobial susceptibility is monitored in the European Union (EU) and the European Economic Area (EEA) by the European gonococcal antimicrobial surveillance programme (Euro-GASP). Results from 17 EU/EEA Member States in 2009 showed that 5% of isolates had decreased susceptibility to cefixime, an upward trend in the minimum inhibitory concentrations of ceftriaxone and a high prevalence of resistance to ciprofloxacin (63%)and azithromycin (13%). These results are of public health value and highlight the need for healthcare professionals to be aware of possible cefixime treatment failures. Euro-GASP is being implemented in additional EU/EEA Member States to achieve greater representativeness. In addition, Euro-GASP aims to set up a system which will allow biannual reporting of antimicrobial resistance in the EU/EEA, with a transition from centralised towards decentralised testing,and will link epidemiological data to laboratory data to enhance surveillance. The benefits of this approach include more timely detection of emerging trends in gonococcal resistance across the EU/EEA and the provision of a robust evidence base for informing national and European guidelines for therapy.

The European gonococcal antimicrobial surveillance programme, 2009

Neisseria gonorrhoeae antimicrobial susceptibility is monitored in the European Union (EU) and the European Economic Area (EEA) by the European gonococcal antimicrobial surveillance programme (Euro-GASP). Results from 17 EU/EEA Member States in 2009 showed that 5% of isolates had decreased susceptibility to cefixime, an upward trend in the minimum inhibitory concentrations of ceftriaxone and a high prevalence of resistance to ciprofloxacin (63%) and azithromycin (13%). These results are of public health value and highlight the need for healthcare professionals to be aware of possible cefixime treatment failures. Euro-GASP is being implemented in additional EU/EEA Member States to achieve greater representativeness. In addition, Euro-GASP aims to set up a system which will allow biannual reporting of antimicrobial resistance in the EU/EEA, with a transition from centralised towards decentralised testing, and will link epidemiological data to laboratory data to enhance surveillance. The benefits of this approach include more timely detection of emerging trends in gonococcal resistance across the EU/EEA and the provision of a robust evidence base for informing national and European guidelines for therapy.

1H, 13C, and 15N resonance assignment of a 179 residue fragment of hepatitis C virus non-structural protein 5A

Non-structural protein 5A (NS5A) plays an important role in the life cycle of hepatitis C virus. This proline-rich phosphoprotein is organized into three domains. Besides its role in virus replication and virus assembly, NS5A is involved in a variety of cellular regulation processes. Recent studies on domain 2 and 3 revealed that both belong to the class of intrinsically disordered proteins as they adopt a natively unfolded state. In particular, domain 2 together with its vicinal regions is responsible for NS5A's multiple interactions with other proteins necessary for virus persistence. The low chemical shift dispersion observed for instrinsically disordered proteins presents a challenge for NMR spectroscopy. Here we report sequential resonance assignment of a 179-residue fragment of NS5A, comprising the entire domain 2, using a set of sensitivity and resolution optimized 3D correlation experiments, as well as amino-acid-type editing in (1)H-(15)N correlation spectra. Our assignment reveals the presence of several segments with high propensity to form α-helical structure that may be of importance to the function of this protein fragment as a versatile interaction platform.

Management of pelvic lymphoceles after radical prostatectomy: a multicentre community based study

Introduction

Pelvic lymphoceles (LC) following radical prostatectomy (LC-RP) have an incidence up to 27%. LC-managements constitute 50% of surgical interventions performed in post-RP patients.

Objectives

To describe a therapeutic algorithm for LC-managements based on a community based representative retrospective study.

Patients and methods: Multicentre data from 304 patients with LC-RP were retrospectively examined for LC-managements. RPs were performed by various surgeons from 67 urological departments. All patients had undergone 3 weeks rehabilitation in a specialized hospital where the data base was generated. Indications and results of therapeutic manoeuvres were used to develop a general concept for planning therapy decisions.

Results

Median age was 64 years. Complications occurred in 9% (28/304) of patients. Median LC-volume was 36 ml (range 20-1800 ml). There were more complications for LCs with ≥100 ml volume than those < 100 ml (27% versus 17%, p = 0.346). Conservative therapy was the standard in uncomplicated cases (87%, 239 of 276 patients), while intervention was done in 13% (puncture and/or drainage, surgery). Surgical intervention was performed significantly more often in complicated cases (82%, 23 from 28 patients; p < 0.001). Based on these data, LCs can be stratified into 3 groups depending on the size and clinical presentation. Therapeutic decisions were used to develop the illustrated new therapy algorithm.

Conclusions

This study based treatment algorithm provides a rationale approach with an accurate LC-classification as regard the indications and decision making for the available LC-RP-therapies. This could facilitate management decisions. Evaluation of this concept prospectively in large patient cohort is mandatory.