Retroviral mRNA nuclear export elements regulate protein function and virion assembly

Rodent cells are notable for their inability to support normal assembly of HIV particles. In this report, we address possible causes for this defect by considering the hypothesis that mRNA-associated events occurring in the nucleus can regulate the activity of their encoded proteins in the cytoplasm. We show that altering the RNA nuclear export element used by HIV gag-pol mRNA from the Rev response element to the constitutive transport element restores both the trafficking of Gag to cellular membranes and efficient HIV assembly in murine cells. These results suggest that two phases of the HIV life cycle, RNA export and capsid assembly, that have hitherto been regarded as distinct are, in fact, linked. Thus, protein function and fate may depend upon the full and precise history of its encoding mRNA.     

An unusual cation channel mediates photic control of locomotion in Drosophila

A unique family of putative ion channels that are related to voltage-gated sodium and calcium channels has been identified in genomic and cDNA studies of metazoans. Aside from evidence for expression of family members in the nervous system, little is known about the operation of the channel or its functional significance. In the present study, this conserved family's sole Drosophila member, a gene known both as CG1517 and as Dmalpha1U, is shown to correspond to the narrow abdomen (na) gene and is the locus of a set of mutations that affect sensitivity to anesthetics. Immunohistochemistry of adult heads reveals that the channel is expressed in the neuropil of the central complex and optic lobe; expression is severely depressed in the mutants. In addition to previously described defects, the mutant phenotype is demonstrated here to include dysfunction in the coupling between light and locomotor behavior. Most dramatically, mutant flies have an inversion of relative locomotor activity in light versus dark. The involvement of the channel in daily rhythms of the fruit fly is especially provocative because the human ortholog lies in a candidate region linked to bipolar disorder, a disease frequently associated with altered diurnal behavior.     

Manipulation of dendritic cells as an approach to improved outcomes in transplantation

At the time of organ transplantation, a variety of non-parenchymal cells are transplanted simultaneously with the allograft. Recognition of the importance of these cells as potential immunostimulatory cells lead to the concept of 'passenger leukocytes' as the principal instigators of rejection. Passenger leukocytes include interstitial dendritic cells (DCs) and blood-derived monocytes/macrophages. As investigators have discovered the significance of DCs in influencing graft outcome, so have they begun to determine the best ways to influence DCs themselves. This review discusses the role of DCs in transplantation and then focuses on three different approaches for manipulating DCs to improve allograft survival: (1) targeting of chemokines involved in DC migration, (2) pharmacological arrest of DC maturation, and (3) genetic engineering of DCs.     

Microtubule-dependent transport of secretory vesicles in RBL-2H3 cells

Antigen-mediated activation of mast cells results in Ca²⁺-dependent exocytosis of preformed mediators of the inflammatory response. To investigate the role of secretory vesicle motility in this response, we have performed time-lapse confocal microscopy on RBL-2H3 cells transfected with a green fluorescent protein-Fas ligand fusion protein (GFP-FasL). Green fluorescent protein-labeled vesicles exhibit rapid, bidirectional movement in both resting and activated cells and can be localized adjacent to microtubules. Colchicine treatment inhibits the motility of secretory vesicles as measured by fluorescence recovery after photobleaching (FRAP). Colchicine also inhibits both the extent and the rate of exocytosis triggered by receptor activation or by Ca²⁺ ionophore, demonstrating that microtubule-dependent movement of secretory vesicles plays an important role in the exocytic response .     

Investigating plant-plant interference by metabolic fingerprinting

New analytical developments in post-genomic technologies are being introduced to the field of plant ecology. FT-IR fingerprinting coupled with chemometrics via cluster analysis is proposed as a tool for correlating global metabolic changes with abiotic or biotic perturbation and/or interactions. The current study concentrates on detecting chemical responses by inter-species competition between a monocotyledon Brachypodium distachyion and a dicotyledon Arabidopsis thaliana. Growth analysis of 42 days old plants showed differences in both species under competition. Clear changes in the FT-IR metabolic fingerprints of B. distachyion in competition with A. thaliana were observed, whilst there were no apparent chemical differences in the A. thaliana plant tissues. This study demonstrates the power of this approach in detecting changes in the global metabolic profiles of plants in response to biotic interactions, and we believe FT-IR is appropriate for rapid screening (10 s per sample) prior to targeted metabolite analyses.     

Debating Ethics in HIV Research: Gaps between Policy and Practice in Nigeria

HIV prevention is a critical health issue in Nigeria; a country that has one of the worst HIV epidemic profiles in the world. With 270,000 new infections in 2012, Nigeria is a prime site for HIV prevention research. One effect of the HIV epidemic has been to revolutionalise ethical norms for the conduct of research: it is now considered unethical to design and implement HIV related studies without community engagement. Unfortunately, there is very little commensurate effort in building the capacity of local persons to engage actively with researchers, and there is no existing platform to facilitate dialogue between researchers and communities engaged in research in Nigeria. In an effort to address this gap, we undertook a series of three community dialogues (Phase One) and two community‐researcher interface meetings (Phase Two) in Nigeria. This paper aims to give an empirical account of the dialogue from these community engagement processes and provide a resulting critique of the implementation of research ethics practices in Nigeria. It is anticipated that the outputs will: (i) support researchers in designing community‐based research protocols; (ii) inform ethics committees of key considerations during research protocol reviews from a community perspective; and (iii) inform policy makers and research sponsors about issues of primary concern to communities with respect to HIV research.     

Characterization of angiotensin-(1-7) receptor subtype in mesenteric arteries

Mesenteric arteries from male Sprague-Dawley rats were mounted in a pressurized myograph system. Ang-(1-7) concentration-dependent responses were determined in arteries preconstricted with endothelin-1 (10(-7)M). The receptor(s) mediating the Ang-(1-7) evoked dilation were investigated by pretreating the mesenteric arteries with specific antagonists of Ang-(1-7), AT(1) or AT(2) receptors. The effects of Ang-(3-8) and Ang-(3-7) were also determined. Ang-(1-7) caused a concentration-dependent dilation (EC(50): 0.95 nM) that was blocked by the selective Ang-(1-7) receptor antagonist D-[Ala(7)]-Ang-(1-7). Administration of a specific antagonist to the AT(2) receptor (PD123319) had no effect. On the other hand, losartan and CV-11974 attenuated the Ang-(1-7) effect. These results demonstrate that Ang-(1-7) elicits potent dilation of mesenteric resistance vessels mediated by a D-[Ala(7)]-Ang-(1-7) sensitive site that is also sensitive to losartan and CV-11974.     

Unique pattern of convergent envelope evolution in simian immunodeficiency virus-infected rapid progressor macaques: association with CD4-independent usage of CCR5

The rate of disease development in simian immunodeficiency virus (SIV) infection of macaques varies considerably among individual macaques. While the majority of macaques inoculated with pathogenic SIV develop AIDS within a period of 1 to 2 years, a minority exhibit a rapid disease course characterized by absence or transience of humoral and cellular immune responses and high levels of virus replication with widespread dissemination of SIV in macrophages and multinucleated giant cells. The goal of this study was to examine viral evolution in three SIVsmE543-3-inoculated rapid progressors to determine the contribution of viral evolution to the development of rapid disease and the effect of the absence of immune pressure upon viral evolution. PCR was used to amplify and clone the entire SIV genome from tissues collected at necropsy, and the course of viral evolution was assessed by env sequences cloned from sequential plasma samples of one rapid progressor (RP) macaque. The majority of sequence changes in RP macaques occurred in the envelope gene. Substitutions were observed in all three animals at specific conserved residues in envelope, including loss of a glycosylation site in V1/V2, a D-to-N/V substitution in a highly conserved GDPE motif, and a P-to-V/H/T substitution in the V3 loop analog. A cell-cell fusion assay revealed that representative env clones utilized CCR5 as a coreceptor, independent of CD4. The selection of specific substitutions in envelope in RP macaques suggests novel selection pressures on virus in such animals and suggests that viral variants that evolve in these animals may play a role in disease progression.     

Maturation in Action: CryoEM Study of a Viral Capsid Caught during Expansion

Bacteriophage HK97 maturation involves discrete intermediate particle forms, comparable to transitional states in protein folding, before reaching its mature form. The process starts by formation of a metastable prohead, poised for exothermic expansion triggered by DNA packaging. During maturation, the capsid subunit transitions from a strained to a canonical tertiary conformation and this has been postulated to be the driving mechanism for initiating expansion via switching hexameric capsomer architecture from skewed to 6-fold symmetric. We report the subnanometer electron-cryomicroscopy reconstruction of the HK97 first expansion intermediate before any crosslink formation. This form displays 6-fold symmetric hexamers, but capsid subunit tertiary structures exhibit distortions comparable to the prohead forms. We propose that coat subunit strain release acts in synergy with the first crosslinks to drive forward maturation. Finally, we speculate that the energetic features of this transition may result from increased stability of intermediates during maturation via enhanced inter-subunit interactions.