The SARS-coronavirus-host interactome: identification of cyclophilins as target for pan-coronavirus inhibitors

Coronaviruses (CoVs) are important human and animal pathogens that induce fatal respiratory, gastrointestinal and neurological disease. The outbreak of the severe acute respiratory syndrome (SARS) in 2002/2003 has demonstrated human vulnerability to (Coronavirus) CoV epidemics. Neither vaccines nor therapeutics are available against human and animal CoVs. Knowledge of host cell proteins that take part in pivotal virus-host interactions could define broad-spectrum antiviral targets. In this study, we used a systems biology approach employing a genome-wide yeast-two hybrid interaction screen to identify immunopilins (PPIA, PPIB, PPIH, PPIG, FKBP1A, FKBP1B) as interaction partners of the CoV non-structural protein 1 (Nsp1). These molecules modulate the Calcineurin/NFAT pathway that plays an important role in immune cell activation. Overexpression of NSP1 and infection with live SARS-CoV strongly increased signalling through the Calcineurin/NFAT pathway and enhanced the induction of interleukin 2, compatible with late-stage immunopathogenicity and long-term cytokine dysregulation as observed in severe SARS cases. Conversely, inhibition of cyclophilins by cyclosporine A (CspA) blocked the replication of CoVs of all genera, including SARS-CoV, human CoV-229E and -NL-63, feline CoV, as well as avian infectious bronchitis virus. Non-immunosuppressive derivatives of CspA might serve as broad-range CoV inhibitors applicable against emerging CoVs as well as ubiquitous pathogens of humans and livestock.     

Switches, excitable responses and oscillations in the Ring1B/Bmi1 ubiquitination system

In an active, self-ubiquitinated state, the Ring1B ligase monoubiquitinates histone H2A playing a critical role in Polycomb-mediated gene silencing. Following ubiquitination by external ligases, Ring1B is targeted for proteosomal degradation. Using biochemical data and computational modeling, we show that the Ring1B ligase can exhibit abrupt switches, overshoot transitions and self-perpetuating oscillations between its distinct ubiquitination and activity states. These different Ring1B states display canonical or multiply branched, atypical polyubiquitin chains and involve association with the Polycomb-group protein Bmi1. Bistable switches and oscillations may lead to all-or-none histone H2A monoubiquitination rates and result in discrete periods of gene (in)activity. Switches, overshoots and oscillations in Ring1B catalytic activity and proteosomal degradation are controlled by the abundances of Bmi1 and Ring1B, and the activities and abundances of external ligases and deubiquitinases, such as E6-AP and USP7.     

Structural analysis in nonsymbiotic hemoglobins: What can we learn from inner cavities?

Plants contain three classes of hemoglobins which are not associated with nitrogen fixing bacteria, and have been accordingly termed nonsymbiotic hemoglobins. The function of nonsymbiotic hemoglobins is as yet mostly unknown. A NO dioxygenase activity has been proposed and demonstrated for some of them in vitro. In this context, a sound molecular mechanism that relates the structure with the biological activity is crucial to suggest a given physiological role. Insight into such a mechanism is now facilitated by recent progress made in both experimental and computational techniques. These studies have highlighted a number of key structural features implicated in the function of nonsymbiotic hemoglobins. The bis-histidyl hexacoordination of the heme in both its ferric and ferrous states provides a powerful and general tool to modulate reactivity, protein dynamics, and shape of the cavities. In addition, the specific arrangement of distal cavity residues provides effective protection against autoxidation. Inspection of the static crystal structures available for both liganded and unliganded states seems unsufficient to explain the function of these proteins. Function appears to be intimately linked with protein flexibility, which influences the dynamical behavior of inner cavities, capable of delivering apolar reactants to the reaction site, and removing charged reaction products. In this mini review, we demonstrate how the integration of information derived from experimental assays and computational studies is valuable and can shed light into the linkage between structural plasticity of nonsymbiotic hemoglobins and their biological role.     

Overcoming seed dormancy in ex situ plant germplasm conservation programmes; an example in the endemic Argyranthemum (Asteraceae: Anthemideae) species from the Canary Islands

Germplasm of 21 diverse Argyranthemum taxa was collected from contrasting ecological zones in the Canary Islands. Seed dormancy was considerable in the majority of taxa. Extensive investigations, based on a germination test procedure algorithm for Asteraceae, with achenes from ray and disc florets of five contrasting taxa identified a procedure to promote full (85%) germination of the seeds from both ray and disc florets of all five taxa; viz, excision of the seeds from the achenes, followed by testing at 15°C with 2.6×10^-3 m GA₃ co-applied. Subsequent tests showed that this regime was effective in promoting full germination in seeds from both ray and disc florets of the remaining 16 taxa. The results are discussed in the context of ex situ plant germplasm conservation.     

Light- and singlet oxygen-mediated antifungal activity of phenylphenalenone phytoalexins.

The light-induced singlet oxygen production and antifungal activity of phenylphenalenone phytoalexins isolated from infected banana plants (Musa acuminata) are reported. Upon absorption of light energy all studied phenylphenalenones sensitise the production of singlet oxygen in polar and non-polar media. Antifungal activity of these compounds towards Fusarium oxysporum is enhanced in the presence of light. These results, together with the correlation of IC50 values under illumination with the quantum yield of singlet oxygen production and the enhancing effect of D2O on the antifungal activity, suggest the intermediacy of singlet oxygen produced by electronic excitation of the phenylphenalenone phytoalexins.     

Efectos del Modelo de Atención Centrado en la Persona en la calidad de vida de personas con deterioro cognitivo de centros gerontológicos

Introduction

The Model of Person Centered Care has attracted increasing interest for use in gerontology centers. Therefore, the contributions about its impact are scarce in our context. The objective of this paper is to establish the impact that the interventions associated with the Model of Person Centered Care in the «Etxean Ondo» Project have on the quality of life of residents with cognitive impairment.

Material and methods

One hundred and ninetten residents with cognitive impairment were selected: 59 in the control group and 60 in the experimental group. Subjects in each group were sorted by cognitive impairment: mild or severe. Changes were implemented in the physical and organizational environments for the promotion of autonomy and wellbeing. Quality of life was assessed before and 6 months after intervention using the Fumat Scales (mild cognitive impairment) and Qualid (severe cognitive impairment). The t-Student test was used for comparison of means.

Results

In intergroup comparisons, significant differences in the Fumat Scale for the control group with mild cognitive impairment were initially identified. These differences were not recorded in the post assessment. The experimental group with severe cognitive impairment was significantly improved in the Qualid Scale post assessment. In intragroup comparisons, significant improvements were evident in the quality of life of experimental subjects, both with severe cognitive impairment (Qualid) and mild (Fumat).

Conclusions

The findings support the effectiveness of the interventions and identify methodological and conceptual issues that have been considered to analyze the Model of Person Centered Care efects.     

Experiencia con el uso del registrador implantable de eventos en una serie de personas mayores con caídas y sospecha de síncopes de origen arrítmico

Objective

To review our experience on using an implantable loop recorder (ILR) in patients with recurrent falls, when an arrhythmogenic cause is suspected.

Material and methods

This is a retrospective, observational study of patients with repetitive unexplained falls, suspected syncope, or electrocardiographic abnormalities. All of them had been evaluated by a cardiologist, who decided to implant a loop recorder (ILR) for an accurate diagnosis.

Results

A total of 13 patients received an ILR. The average falls rate for the sample was 3.3. The mean age was 78 years, and 46% were female, with a mean follow-up period of 24 months. During this time, three patients did not suffer from a new fall. An arrhythmogenic diagnosis was obtained in 5 patients: bradycardia was identified in 4 cases, and tachycardia in one of them. The symptoms did not coincide with a documented arrhythmia in the rest of the patients.

Conclusion

ILR is a helpful tool to establish an arrhythmogenic cause of unexplained and recurrent falls, in this selected sample of older adults.     

Implication of an Asp residue in the ribonucleolytic activity of hirsutellin A reveals new electrostatic interactions at the active site of ribotoxins

Ribotoxins are fungal extracellular ribonucleases that specifically cleave ribosomes leading to cell-death via apoptosis. α-Sarcin is the ribotoxin studied in deepest detail, and therefore constitutes the referential protein for the whole family. It has been demonstrated that ribotoxin activity depends on a very precise structural microenvironment in which electrostatic interactions among residues in the active site are of the highest importance. Hirsutellin A (HtA) has been recently described as the smallest ribotoxin known to date, encompassing all the abilities of previously characterized members of this family into a shorter sequence. Comparison of HtA and α-sarcin three-dimensional structures suggested that residues presumably forming the catalytic triad of HtA would be His 42, Glu 66, and His 113. Within this same idea, the presence of an Asp residue (Asp 40) in a position equivalent to α-sarcin Tyr 48 is highlighted as a novelty in this field. In this work, substitution mutants H42Q, E66Q and H113Q, as well as double and triple mutants in all possible combinations, are studied regarding their ribonucleolytic activity and cytotoxicity. Implication of these three residues in the ribotoxin activity of HtA is confirmed, though none of them is strictly essential for ribosomal cleavage. Studies with mutants D40N and D40N/E66Q demonstrate an important role for Asp 40 in the activity of HtA and establish a new set of electrostatic interactions different from the one described for already known ribotoxins.