Role of Interaction and Nucleoside Diphosphate Kinase B in Regulation of the Cystic Fibrosis Transmembrane Conductance Regulator Function by cAMP-Dependent Protein Kinase A

Cystic fibrosis results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-dependent protein kinase A (PKA) and ATP-regulated chloride channel. Here, we demonstrate that nucleoside diphosphate kinase B (NDPK-B, NM23-H2) forms a functional complex with CFTR. In airway epithelia forskolin/IBMX significantly increases NDPK-B co-localisation with CFTR whereas PKA inhibitors attenuate complex formation. Furthermore, an NDPK-B derived peptide (but not its NDPK-A equivalent) disrupts the NDPK-B/CFTR complex in vitro (19-mers comprising amino acids 36–54 from NDPK-B or NDPK-A). Overlay (Far-Western) and Surface Plasmon Resonance (SPR) analysis both demonstrate that NDPK-B binds CFTR within its first nucleotide binding domain (NBD1, CFTR amino acids 351–727). Analysis of chloride currents reflective of CFTR or outwardly rectifying chloride channels (ORCC, DIDS-sensitive) showed that the 19-mer NDPK-B peptide (but not its NDPK-A equivalent) reduced both chloride conductances. Additionally, the NDPK-B (but not NDPK-A) peptide also attenuated acetylcholine-induced intestinal short circuit currents. In silico analysis of the NBD1/NDPK-B complex reveals an extended interaction surface between the two proteins. This binding zone is also target of the 19-mer NDPK-B peptide, thus confirming its capability to disrupt NDPK-B/CFTR complex. We propose that NDPK-B forms part of the complex that controls chloride currents in epithelia.     

Analytical and preparative isoelectric focusing of peptides in immobilized pH gradients

A new method for peptide analysis and purification is described, based on isoelectric focusing in immobilized pH gradients. On the analytical scale, the peptide zones can now be revealed by an stain for primary and secondary amino group (e.g. ninydrin, fluorescamine, dansyl chloride) since the buffering species, unlike conventional carrier ampholytes, contain only carboxyl and tertiary amino groups. For preparative purposes, conditions have been described to remove most contaminants (e.g. unreacted monomers, non-cross-linked, short polyacrylamide chains) from the gel matrix before the electrophoretic run. However, ca. 2% of the gel dry mass is still present as extractable material. The focused peptides can be recovered in higly yields (ca. 90%) with a fairly high degree of purity (75%), the contaminants being mostly components eluted from the polyacrylamide gel.     

The interstitial crystal-nucleating sheet in molluscan Haliotis rufescens shell: A bio-polymeric composite

The interstitial green sheets in abalone shell nacre are shown to be bifacially differentiated trilaminate polymeric complexes, with glycoprotein layers sandwiching a central core containing chitin. They share some common feature with the organic matrix layers between the aragonite tablets in the nacre and the periostracum, and show similarities to the myostracum. Thus, although the green sheet is reported to be unique to the abalone shell, it represents an interesting model for the study of molluscan shell biomineralization processes. Indeed, during shell formation, prismatic and spherulitic aragonite precedes and follows the deposition of the interstitial green polymeric composite sheets, and there is evidence to suggest that these sheets demark the interruption of nacre synthesis and serve to nucleate the resumption of calcium carbonate crystal growth. The green polymeric interstitial sheet purified from the abalone shell was investigated by spectroscopic and imaging techniques: FTIR, confocal microscopy, scanning and transmission electron microscopy, and by pyrolysis combined with GC–MS. Structural and compositional differences are observed between the surfaces of the two sides of the interstitial polymeric composite sheets. Moreover, comparative crystallization experiments on the green sheet sides also reveal asymmetry with respect to the nucleation of calcium carbonate. These findings suggest that these bifacially differentiated interstitial composites may play an active role in the mineral assembly processes, with one of the surfaces acting as a crystal nucleator.     

Plant respiration: Controlled by photosynthesis or biomass?

Two simplifying hypotheses have been proposed for whole‐plant respiration. One links respiration to photosynthesis; the other to biomass. Using a first‐principles carbon balance model with a prescribed live woody biomass turnover, applied at a forest research site where multidecadal measurements are available for comparison, we show that if turnover is fast the accumulation of respiring biomass is low and respiration depends primarily on photosynthesis; while if turnover is slow the accumulation of respiring biomass is high and respiration depends primarily on biomass. But the first scenario is inconsistent with evidence for substantial carry‐over of fixed carbon between years, while the second implies far too great an increase in respiration during stand development—leading to depleted carbohydrate reserves and an unrealistically high mortality risk. These two mutually incompatible hypotheses are thus both incorrect. Respiration is not linearly related either to photosynthesis or to biomass, but it is more strongly controlled by recent photosynthates (and reserve availability) than by total biomass.     

Taxonomic differences shape the responses of freshwater aerobic anoxygenic phototrophic bacterial communities to light and predation

Aerobic anoxygenic phototrophic (AAP) bacteria are a phylogenetically diverse and ubiquitous group of prokaryotes that use organic matter but can harvest light using bacteriochlorophyll a. Although the factors regulating AAP ecology have long been investigated through field surveys, the few available experimental studies have considered AAPs as a group, thus disregarding the potential differential responses between taxonomically distinct AAP assemblages. Here, we used sequencing of the pufM gene to describe the diversity of AAPs in 10 environmentally distinct temperate lakes, and to investigate the taxonomic responses of AAP communities in these lakes when subjected to similar experimental manipulations of light and predator removal. The studied communities were clearly dominated by Limnohabitans AAP but presented a clear taxonomic segregation between lakes presumably driven by local conditions, which was maintained after experimental manipulations. Predation reduction (but not light exposure) caused significant compositional shifts across most assemblages, but the magnitude of these changes could not be clearly related to changes in bulk AAP abundances or taxonomic richness of AAP assemblages during experiments. Only a few operational taxonomic units, which differed taxonomically between lakes, were found to respond positively during experimental treatments. Our results highlight that different freshwater AAP communities respond differently to similar control mechanisms, highlighting that in‐depth knowledge on AAP diversity is essential to understand the ecology and potential role of these photoheterotrophs.     

Circulating miRNAs expression as potential biomarkers of mild traumatic brain injury

Molecular Biology Reports - TBI is the main cause of death and disability in individuals aged 1–45 in Western countries. One of the main challenges of TBI at present is the lack of specific...     

Human-mediated introgression of exotic chukar (Alectoris chukar, Galliformes) genes from East Asia into native Mediterranean partridges

Mediterranean red-legged (Alectoris rufa) and rock (Alectoris graeca) partridge populations are affected by genetic pollution. The chukar partridge (Alectoris chukar), a species only partly native to Europe, is the most frequently introgressive taxon detected in the genome of hybrid partridges. Both theoretical (evolutionary) and practical (resources management) matters spur to get insight into the geographic origin of the A. chukar hybridizing swarm. The phenotypic A. rufa populations colonizing the easternmost part of the distribution range of this species, the islands of Elba (Italy) and Corsica (France), were investigated. The analysis of both mitochondrial (mtDNA: Cytochrome-b gene plus Control Region: 2,250 characters) and nuclear (Short Tandem Repeats, STR; Random Amplified Polymorphic DNA, RAPD) genomes of 25 wild (Elba) and 20 captive (Corsica) partridges, disclosed spread introgression of chukar origin also in these populations. All mtDNA haplotypes of Elba and Corsica partridges along with those we obtained from other A. rufa (total, n = 111: Italy, Spain, France) and A. graeca (n = 6, Italy), were compared with the mtDNA haplotypes of chukars (n = 205) sampled in 20 countries. It was found that the A. chukar genes detected in red-legged (n = 43) and rock partridges (n = 4) of Spain, France and Italy as well as in either introduced (Italy) or native (Greece, Turkey) chukars (n = 35) were all from East Asia. Hence, a well-defined geographic origin of the exotic chukar genes polluting the genome of native Mediterranean A. rufa and A. graeca (inter-specific level) as well as A. chukar (intra-specific level), was demonstrated.     

Links between resources, C metabolism and the major components of bacterioplankton community structure across a range of freshwater ecosystems

We explored the patterns in bacterioplankton community metabolism (BCM) and four components of community structure [composition (BCC), metabolic capacities (MC), physiological structure (PS) and single-cell characteristics (SCC)], between lakes, rivers and marshes within a watershed in Québec, to assess the connections that exist between them and with the main resources (organic matter, nutrients). Habitat types were well segregated by both resources and BCM and their corresponding dissimilarity matrices were significantly correlated, suggesting that BCM tracks resource conditions in a consistent manner across ecosystem types. MC also segregated the various habitats and was correlated to BCM but less so to resources, whereas BCC at times resulted in a clear separation of habitats, but was rarely correlated to resources and never to BCM, suggesting a higher degree of ecosystem specificity at this particular level. Finally, there was no clear separation of habitats in terms of PS and SCC, and none covaried with resources or BCM. The habitat patterns based on these different components of structure were rarely correlated to each other, indicating weak deterministic connections between them. MC appears to mediate the link between resources and BCM more directly and consistently across systems; BCC appears to be more influenced by ecosystem-specific factors that weaken its overall connection to both resources and BCM, whereas PS and SCC show no discernible patterns. Our results thus suggest that the bottom-up regulation of BCM by resources is mediated by complex shifts within components of community structure that can be directional, ecosystem-specific or apparently random, which combined nevertheless result in a systematic overall response to resources in terms of C metabolism.