Shaping mechanisms of metal specificity in a family of metazoan metallothioneins: evolutionary differentiation of mollusc metallothioneins

Background  

The degree of metal binding specificity in metalloproteins such as metallothioneins (MTs) can be crucial for their functional accuracy. Unlike most other animal species, pulmonate molluscs possess homometallic MT isoforms loaded with Cu⁺ or Cd²⁺. They have, so far, been obtained as native metal-MT complexes from snail tissues, where they are involved in the metabolism of the metal ion species bound to the respective isoform. However, it has not as yet been discerned if their specific metal occupation is the result of a rigid control of metal availability, or isoform expression programming in the hosting tissues or of structural differences of the respective peptides determining the coordinative options for the different metal ions. In this study, the Roman snail (Helix pomatia) Cu-loaded and Cd-loaded isoforms (HpCuMT and HpCdMT) were used as model molecules in order to elucidate the biochemical and evolutionary mechanisms permitting pulmonate MTs to achieve specificity for their cognate metal ion.     

Contributions of the effector gene hopQ1-1 to differences in host range between Pseudomonas syringae pv. phaseolicola and P. syringae pv. tabaci

To study the role of type III-secreted effectors in the host adaptation of the tobacco ( Nicotiana sp.) pathogen Pseudomonas syringae pv. tabaci , a selection of seven strains was first characterized by multilocus sequence typing (MLST) to determine their phylogenetic affinity. MLST revealed that all strains represented a tight phylogenetic group and that the most closely related strain with a completely sequenced genome was the bean ( Phaseolus vulgaris ) pathogen P. syringae pv. phaseolicola 1448A. Using primers designed to 21 P. syringae pv. phaseolicola 1448A effector genes, it was determined that P. syringae pv. phaseolicola 1448A shared at least 10 effectors with all tested P. syringae pv. tabaci strains. Six of the 11 effectors that failed to amplify from P. syringae pv. tabaci strains were individually expressed in one P. syringae pv. tabaci strain. Although five effectors had no effect on phenotype, growth in planta and disease severity of the transgenic P. syringae pv. tabaci expressing hopQ1-1 _Pph1448A were significantly increased in bean, but reduced in tobacco. We conclude that hopQ1-1 has been retained in P. syringae pv. phaseolicola 1448A, as this effector suppresses immunity in bean, whereas hopQ1-1 is missing from P. syringae pv. tabaci strains because it triggers defences in Nicotiana spp. This provides evidence that fine-tuning effector repertoires during host adaptation lead to a concomitant reduction in virulence in non-host species.     

The GALA study: relationship between galectin-3 serum levels and short- and long-term outcomes of patients with acute heart failure

Objective: We tested the hypothesis that early measurement of galectin-3 at the emergency department (ED) during an episode of acute heart failure (AHF) allows predicting short- and long-term outcomes.

Methods: We performed an exploratory study including 115 patients consecutively diagnosed with AHF in a single ED. Clinical and analytical variables were recorded. The primary endpoint was 30-day all-cause mortality, and secondary endpoints were 30-day composite outcome (death, rehospitalization or ED reconsultation, whichever first) and 1-year mortality.

Results: Seven patients (6.1%) died within 30?days and 43 (37.4%) within 1?year. The 30-day composite endpoint was observed in 21.1% of patients. Galectin-3 was correlated with NT-proBNP and the glomerular filtration rate but not with age and s-cTnI. Measured at time of ED arrival, galectin-3 showed good discriminatory capacity for 30-day mortality (AUC ROC: 0.732; 95% CI 0.512–0.953; p?=?0.041) but not for 1-year mortality (0.521; 0.408–0.633; p?=?0.722). Patients with galectin-3 concentrations?>42?μg/L had an OR?=?7.67(95%CI?=?1.57-37.53; p?=?0.012) for 30-day mortality. Conversely, NT-proBNP only showed predictive capacity for 1-year mortality (0.642; 0.537–0.748; p?=?0.014). Patients with NT-proBNP concentrations?>5400?ng/L had an OR?=?4.34 (95%CI?=?1.93-9.77; p?<?0.001) for 1-year mortality. These increased short- (galectin-3) and long-term (NT-proBNP) risks remained significant after adjustment for age or renal function. s-cTnI failed in both short- and long term death prediction. No biomarker predicted the short-term composite endpoint.

Conclusion: These results suggest that galectin-3 could help to monitor the risk of short-term mortality in unselected patients with AHF attended in the ED.     

Endothelin-1 Up-Regulates p115RhoGEF in Embryonic Rat Cardiomyocytes During the Hypertrophic Response

In cardiomyocytes, certain extracellular stimuli that activate heterotrimeric G protein-coupled receptors (GPCRs) can induce hypertrophy by regulating gene expression and increasing protein synthesis. We investigated if rat embryonic cardiomyocytes (H9c2) underwent variations in the expression levels and subcellular distribution of key components of GPCR-activated signaling pathways during endothelin-1 (ET-1)-induced hypertrophic response. A significant increase of p115RhoGEF protein level was evident in ET-1-treated cells. Real-time quantitative PCR showed RhoGEF mRNA levels were significantly increased. Inhibition of the Rho-associated kinase (ROCK) caused a significant decrease of p115RhoGEF protein in the nuclear fraction, whereas an inhibitor of PKC induced a redistribution of the protein between membrane/organelle and nuclear fractions. The ROCK inhibitor also decreased H9c2 cell hypertrophic response. These results indicate that ROCK and its downstream target molecules, which are involved in inducing the hypertrophic response, are also implicated in signaling the up-regulation of the p115RhoGEF protein.     

The high-conductance channels of yeast mitochondrial outer membranes: A planar bilayer study

The high-conductance channels present in the outer membranes of wild-type and porin-less yeast mitochondria have been characterized electrophysiologically after incorporation in planar bilayer membranes. The most prominent activity was ascribed to a voltage-dependent, substaterich, cationic channel which generally inactivated at potentials positive in thecis compartment, in agreement with the observations from patch-clamp experiments on porin-less mitoplasts. This channel has been identified as the so-called peptide-sensitive channel (PSC). We also observed similar channels displaying either no inactivation, or inactivation at both positive and negative potentials. These latter properties match those already described for mammalian and yeast PSC, respectively. These different behaviors are tentatively explained as arising from the presence, or lack of, peptides bound to the PSC. Very high conductances, apparently due to cooperative gating, were frequently displayed. In wild-type membranes, activity ascribable to the porin was also observed.The first two authors contributed equally to the work described in this paper.     

Polyamines, storage substances and abscisic acid-like inhibitors during dormancy and very early activation of Helianthus tuberosus tuber tissues

Abstract Dormancy and break of dormancy of tubers of Helianthus tuberosus L. (Jerusalem artichoke) have been investigated in regard to the possibility that polyamines can control these processes. Polyamines were detected by the method of direct dansylation and abscisic acid was bioassayed using wheat coleoptile growth test. Arginine and glutamine, which are the main store nitrogenous organic compounds of Helianthus tuberosus tuber, decrease during the last phase of dormancy as well as abscisic acid; moreover the corresponding increase in polyamines (putrescine, spermidine and spermine) seems to be strictly related to the break of dormancy of tuber. The artificial break of dormancy induced by 2,4-dichlorophenoxyacetic acid stimulates a great increase in polyamines, just evident within 15 min after activation, and a corresponding decrease in arginine and glutamine. The levels of polyamines, at 1 h of activation are sufficient to stimulate protein synthesis in vitro.     

Invasive crayfish in Europe: the impact of Procambarus clarkii on the littoral community of a Mediterranean lake

1. Despite the growing number of non‐indigenous crayfish species introduced worldwide, little scientific attention has been given to their effects on the recipient communities. Here, we quantified the impact of adult red swamp crayfish (Procambarus clarkii) on key components of the littoral community of a mesotrophic lake in central Italy. We used two densities of crayfish plus a no‐crayfish control, and two complementary methods –in situ enclosures and a laboratory study. 2. Both experiments showed that P. clarkii strongly affects the community even at a low density (4 m⁻²), although a high crayfish density (8 m⁻²) showed a more pronounced impact in a shorter time. 3. In enclosures, P. clarkii quickly consumed the pond snail Haitia acuta, notwithstanding its anti‐predator behaviour, but not the mosquitofish Gambusia affinis. The biomass of the hydrophytes Nymphoides peltata and Potamogeton spp. was strongly reduced by crayfish grazing, coupled with their non‐consumptive plant clipping and uprooting, which were particularly intense in the case of Potamogeton crispus. In contrast, Utricularia australis was avoided by P. clarkii, even when other resources were exhausted. 4. The introduction of P. clarkii could reduce biodiversity and increase biotic homogenisation in a short time.