Functional and molecular identification of novel members of the ubiquitous membrane fusion proteins alpha- and gamma-SNAP (soluble N-ethylmaleimide-sensitive factor-attachment proteins) families in Dictyostelium discoideum.

The soluble N-ethylmaleimide-sensitive-factor-attachment proteins (SNAP) are eukaryotic soluble proteins required for membrane fusion. Based on their initial identification in bovine brain cytosol, they are divided in alpha/beta and gamma subfamilies. SNAPs act as adapters between N-ethylmaleimide-sensitive factor (NSF), a hexameric ATPase, and membrane SNARE proteins (SNAP receptors). Within the NSF/SNAP/SNARE complex, SNAPs contribute to the catalysis of an ATP-driven conformational change in the SNAREs, resulting in dissociation of the complex. We have constructed a Dictyostelium discoideum strain overexpressing a c-myc-tagged form of D. discoideum NSF (NSF-myc). Its immunoprecipitation from detergent-solubilized membrane extracts reveals two associated polypeptides with apparent molecular masses of 33 and 36 kDa (p33 and p36) that are absent in NSF-myc immunoprecipitates from cytosol. Analysis of trypsin-digested peptides by microsequencing and mass spectrometry and comparison with cDNA sequences identify p33 and p36 as the D. discoideum homologues of alpha- and gamma-SNAP, respectively. The alpha-/gamma-SNAP molar ratio is close to 3 in vegetative amoebae from this organism. The molecular identification of gamma-SNAP in plants (Arabidopsis thaliana) and insects (Drosophila melanogaster) documents, for the first time, the wide distribution of the gamma subtype. Altogether, these results suggest a specific role for gamma-SNAP, distinct from that of alpha-SNAP.     

Altered expression of Alzheimer's disease-related genes in the cerebellum of autistic patients: a model for disrupted brain connectome and therapy

Autism and Alzheimer''s disease (AD) are, respectively, neurodevelopmental and degenerative diseases with an increasing epidemiological burden. The AD-associated amyloid-β precursor protein-α has been shown to be elevated in severe autism, leading to the ‘anabolic hypothesis'' of its etiology. Here we performed a focused microarray analysis of genes belonging to NOTCH and WNT signaling cascades, as well as genes related to AD and apoptosis pathways in cerebellar samples from autistic individuals, to provide further evidence for pathological relevance of these cascades for autism. By using the limma package from R and false discovery rate, we demonstrated that 31% (116 out of 374) of the genes belonging to these pathways displayed significant changes in expression (corrected P-values <0.05), with mitochondria-related genes being the most downregulated. We also found upregulation of GRIN1, the channel-forming subunit of NMDA glutamate receptors, and MAP3K1, known activator of the JNK and ERK pathways with anti-apoptotic effect. Expression of PSEN2 (presinilin 2) and APBB1 (or F65) were significantly lower when compared with control samples. Based on these results, we propose a model of NMDA glutamate receptor-mediated ERK activation of α-secretase activity and mitochondrial adaptation to apoptosis that may explain the early brain overgrowth and disruption of synaptic plasticity and connectome in autism. Finally, systems pharmacology analyses of the model that integrates all these genes together (NOWADA) highlighted magnesium (Mg²⁺) and rapamycin as most efficient drugs to target this network model in silico. Their potential therapeutic application, in the context of autism, is therefore discussed.     

Copurification of rho protein and the rho-GDP dissociation inhibitor from bovine neutrophil cytosol. Effect of phosphoinositides on rho ADP-ribosylation by the C3 exoenzyme of Clostridium botulinum.

The substrate of the C3 exoenzyme from botulinum toxin is a protein which is particularly abundant in the cytosol of neutrophils [Stasia, M. J., Jouan, A., Bourmeyster, N., Boquet, P., & Vignais, P. V. (1991) Biochem. Biophys. Res. Commun. 180, 615-622]. Optimal conditions for the ADP-ribosylation of the C3 substrate have been established in order to follow the course of its purification from bovine neutrophil cytosol. In particular, phosphoinositides at micromolar concentrations were found to enhance the ADP-ribosylation capacity of the C3 substrate in crude neutrophil cytosol and partially purified fractions. A [32P]ADP-ribosylatable protein, migrating on SDS-PAGE with a mass of 24 kDa, was copurified with a 29-kDa protein by a series of chromatographic steps on DEAE-Sephacel, Biogel P60, and Mono Q. In the case of the C3 substrate, isoelectric focusing revealed two major labeled bands with pI values of 6.2 and 5.6; the pI of the 29-kDa protein was 4.8-5.0. On the basis of the amino acid sequence of peptides resolved after proteolytic digestion, the 24-kDa protein and the 29-kDa protein were identified respectively as rho and the GDP dissociation inhibitor (GDI), suggesting that rho and GDI copurify from bovine neutrophil cytosol in the form of a complex. The presence of a number of amino acid residues specific of rho A in the enzymatic digest originating from rho indicates that, among the rho proteins, at least rho A belongs to the GDI-rho complex.     

Adjunctive Corticotherapy for Community Acquired Pneumonia: A Systematic Review and Meta-Analysis

Background

Community-acquired pneumonia (CAP) induces lung and systemic inflammation, leading to high morbidity and mortality. We systematically reviewed the risks and benefits of adjunctive corticotherapy in the management of patients with CAP.

Methods

We systematically searched Pubmed, Embase and the Cochrane Library for randomized controlled trials comparing adjunctive corticotherapy and antimicrobial therapy with antimicrobial therapy alone in patients with CAP. The primary outcome was 30-day mortality. Secondary outcomes were length of hospital stay, time to clinical stability and severe complications.

Results

14 trials (2077 patients) were included. The reported 30-day mortality was 7.9% (80/1018) among patients treated with adjunctive corticotherapy versus 8.3% (85/1028) among patients treated with antimicrobial therapy alone (RR 0.84; 95%CI 0.55 to1.29). Adjunctive corticotherapy was associated with a reduction of severe complications (RR 0.36; 95%CI 0.23 to 0.56), a shorter length of stay (9.0 days; 95%CI 7.6 to 10.7 vs 10.6 days; 95%CI 7.4 to 15.3) and a shorter time to clinical stability (3.3 days; 95% CI 2.8 to 4.1 vs 4.3 days; 95%CI 3.6 to 5.1). The risk of hyperglycemia was higher among patients treated with adjunctive corticotherapy (RR 1.59; 95%CI 1.06 to 2.38), whereas the risk of gastro-intestinal bleeding was similar (RR 0.83; 95%CI 0.35 to 1.93). In the subgroup analysis based on CAP severity, a survival benefit was found among patients with severe CAP (RR 0.47; 95%CI 0.23 to 0.96).

Conclusion

Adjunctive corticotherapy is associated with a reduction of length of stay, time to clinical stability, and severe complications among patients with CAP, but the effect on mortality remains uncertain.     

Reproductive and age classes do not change spatial dynamics of foraging long-fingered bats (Myotis capaccinii)

Spatial dynamics of foraging long-fingered bats (Myotis capaccinii) were studied in the Eastern Iberian Peninsula. We analysed the locations of 45 radio-tracked individuals during three discrete periods through the breeding season and measured the spatial parameters related to their foraging behaviour in order to test whether variations in spatial use occur. Colony range, measured as the minimum convex polygon through all the radiolocations, was 345 km², but the area used during each period was smaller. During pre-breeding, foraging bats gathered at two stretches of different tributary rivers; during lactation, they scattered throughout the river system; and during weaning, they aggregated at a stretch of the main river. Individuals on average flew 5.7 km from roosts to foraging areas, with a maximum absolute distance of 22.7 km. Individual foraging ranges were measured linearly, because the bats foraged mostly along rivers; their values averaged 1.3 km/night and overlapped extensively between neighbouring bats (>65% on average). The sampling period, rather than the bats’ reproductive status, age, or sex, explained the observed variability in spatial distribution and size of hunting sites. We did not find differences in spatial parameters between lactating females and non-lactating bats, nor between juveniles and adults. This is the first study to split the independent effects of season and population class in order to enable unconfounded interpretations of the spatial dynamics of foraging reproductive females and juveniles. We speculate that the relationship between colony size and prey availability ruled the observed changes in foraging area through seasons. The considerable overlap in individual foraging ranges may be a necessary adaption to large colonies forced by the specific roost requirements of the long-fingered bat and the narrow foraging niche they appear to occupy.     

Microbial modification of host long-distance dispersal capacity

Background  

Dispersal plays a key role in shaping biological and ecological processes such as the distribution of spatially-structured populations or the pace and scale of invasion. Here we have studied the relationship between long-distance dispersal behaviour of a pest-controlling money spider,Erigone atra, and the distribution of maternally acquired endosymbionts within the wider meta-population. This spider persists in heterogeneous environments because of its ability to recolonise areas through active long-distance airborne dispersal using silk as a sail, in a process termed 'ballooning'.