Fulminant septic shock due to community-acquired pneumonia caused by Legionella pneumophila SG1 Olda OLDA ST1. Case report.

Legionellers' desease accounts for 1-8 % of cases of severe community-acquired pneumonia (CAP). Legionella spp. Is the causative organism that can result in respiratory failure, multi-organ dysfunction, sepsis, and death. Therefore, rapid diagnosis and efficient treatment are crucial. We report the clinical and microbiology study of a patient with community-acquired pneumonia caused by Legionella pneumophila, with fatal outcome. After death, the strain causing the infection was identified as Legionella pneumophila serogroup 1, Olda OLDA phenotype and sequence-type 1. This is the first reported case of septic shock and death associated with an isolate of these characteristics.

A simple method for direct mercury analysis in dried blood spots (DBS) samples for human biomonitoring studies.

Human exposure to mercury can have serious health effects, especially in vulnerable groups such as children and fetuses. The use of dried blood spot (DBS) samples to collect capillary blood greatly facilitates sample collection and fieldwork, being a less invasive alternative to blood collection by venipuncture, needing a small volume of sample, and does not require specialized medical staff. Moreover, DBS sampling reduces logistical and financial barriers related to transport and storage of blood samples. We propose here a novel method to analyze total mercury in DBS samples in a Direct Mercury Analyzer (DMA) that allow the control of the volume of the DBS samples. This method has shown good results in terms of precision (<6% error), accuracy (<10% coefficient of variation) and recovery (75-106%). The applicability of the method in human biomonitoring (HBM) was demonstrated in a pilot study involving 41 adults aged 18-65. Mercury concentrations of DBS samples from capillary blood collected by finger prick (real DBS samples) were determined in the DMA and compared with those determined in whole blood (venous blood) by ICP-MS, the method usually used in HBM. The sampling procedure was also validated by comparison of real DBS samples and DBS generated artificially in the laboratory by depositing venous samples in cellulose cards (laboratory DBS). There were no statistically significant differences in the results obtained using both methodologies (DMA: Geometric Mean (confidence interval 95%) = 3.87 (3.12-4.79) µg/L; ICP-MS: Geometric Mean (confidence interval 95%) = 3.46 (2.80-4.27) µg/L). The proposed method is an excellent alternative to be applied in clinical settings as screening methodology for assessing mercury exposure in vulnerable groups, such us pregnant woman, babies and children.

Selecting the best non-invasive matrix to measure mercury exposure in human biomonitoring surveys.

Exposure to mercury, even at low doses, can affect human health, well-being and life quality at a broad scale. Human biomonitoring is the most straightforward approach to measure and quantify mercury exposure in humans. The objective of the present study is to compare and discuss the relationships between Hg levels in the most used matrices, hair, urine and blood, with the aim to ascertain to what extent mercury exposure and internal mercury levels could be predicted by monitoring non-invasive matrices. The study population (n = 527) is a subsample from Spanish BIOAMBIENT. ES study (18-65 y, both sexes), with data of Hg levels in blood, hair, and urine from the same individuals. We found strong inter-matrix Spearman correlations between blood and hair mercury (r2 = 0.84), while the correlations for urine and blood mercury (r2=0.64) and urine and hair mercury (r2=0.65) were weaker. The geometric mean of the ratios between matrices were (GM, 95%CI): Hair/Blood 280 (271-290), Urine/Blood 0.174 (0.163-0.186) and Hair/Urine 2070 (1953-2194) and Urine/Blood 0.135 (0.128-0.144) for urine corrected by creatinine. High individual variation was observed particularly in those ratios involving urine. Considering the wide range of values observed in the ratios, we do not recommend applying them at individual level. The predictive models indicate that hair Hg was a more accurate predictor than urine. The inclusion of urine values did not increase the predictive accuracy, so, we recommend a cautious interpretation of urine mercury levels. Our study presents clear evidence that in a population highly exposed to food-borne mercury, a large portion of urinary mercury primarily emanates from methylmercury demethylation. We conclude that urine, as a non-invasive matrix, can be used as a reliable qualitative biomarker for Hg exposure when hair measurements not are available. For quantitative individual assessments, still blood measurements are to be preferred.

Recognition and Activation of the Plant AKT1 Potassium Channel by the Kinase CIPK23.

Plant growth largely depends on the maintenance of adequate intracellular levels of potassium (K+). The families of 10 Calcineurin B-Like (CBL) calcium sensors and 26 CBL-Interacting Protein Kinases (CIPKs) of Arabidopsis (Arabidopsis thaliana) decode the calcium signals elicited by environmental inputs to regulate different ion channels and transporters involved in the control of K+ fluxes by phosphorylation-dependent and -independent events. However, the detailed molecular mechanisms governing target specificity require investigation. Here, we show that the physical interaction between CIPK23 and the noncanonical ankyrin domain in the cytosolic side of the inward-rectifier K+ channel AKT1 regulates kinase docking and channel activation. Point mutations on this domain specifically alter binding to CIPK23, enhancing or impairing the ability of CIPK23 to regulate channel activity. Our data demonstrate the relevance of this protein-protein interaction that contributes to the formation of a complex between CIPK23/CBL1 and AKT1 in the membrane for the proper regulation of K+ transport.

Deciphering the Inhibition of the Neuronal Calcium Sensor 1 and the Guanine Exchange Factor Ric8a with a Small Phenothiazine Molecule for the Rational Generation of Therapeutic Synapse Function Regulators.

Protein-protein interactions (PPIs) are known to play an essential role between the neuronal calcium sensor 1 (NCS-1) and the guanine exchange factor Ric8a to regulate synapse function, emerging as a druggable interface for synaptopathies such as the fragile X syndrome (FXS). Recently, the phenothiazine FD44 has been identified as an inhibitor of this PPI, decreasing the abnormally high synapse number and enhancing associative learning in a FXS animal model. Here, we have integrated advanced experimental and computational studies to obtain important structural insights into Drosophila NCS-1/FD44 recognition to understand the basis of its affinity and specificity and generate improved PPI regulators. This has allowed the identification of a new small drug-like molecule, IGS-1.76, which efficiently inhibits the human NCS-1/Ric8a complex with improved binding potency. The crystal structure of the Drosophila NCS-1/IGS-1.76 complex demonstrates that the new inhibitor, although chemically different from FD44, shares the same mechanism of action and constitutes a new hit candidate for FXS.

The crystal structure of mammalian inositol 1,3,4,5,6-pentakisphosphate 2-kinase reveals a new zinc-binding site and key features for protein function.

Inositol 1,3,4,5,6-pentakisphosphate 2-kinases (IP5 2-Ks) are part of a family of enzymes in charge of synthesizing inositol hexakisphosphate (IP6) in eukaryotic cells. This protein and its product IP6 present many roles in cells, participating in mRNA export, embryonic development, and apoptosis. We reported previously that the full-length IP5 2-K from Arabidopsis thaliana is a zinc metallo-enzyme, including two separated lobes (the N- and C-lobes). We have also shown conformational changes in IP5 2-K and have identified the residues involved in substrate recognition and catalysis. However, the specific features of mammalian IP5 2-Ks remain unknown. To this end, we report here the first structure for a murine IP5 2-K in complex with ATP/IP5 or IP6 Our structural findings indicated that the general folding in N- and C-lobes is conserved with A. thaliana IP5 2-K. A helical scaffold in the C-lobe constitutes the inositol phosphate-binding site, which, along with the participation of the N-lobe, endows high specificity to this protein. However, we also noted large structural differences between the orthologues from these two eukaryotic kingdoms. These differences include a novel zinc-binding site and regions unique to the mammalian IP5 2-K, as an unexpected basic patch on the protein surface. In conclusion, our findings have uncovered distinct features of a mammalian IP5 2-K and set the stage for investigations into protein-protein or protein-RNA interactions important for IP5 2-K function and activity.

Interference of the complex between NCS-1 and Ric8a with phenothiazines regulates synaptic function and is an approach for fragile X syndrome.

The protein complex formed by the Ca2+ sensor neuronal calcium sensor 1 (NCS-1) and the guanine exchange factor protein Ric8a coregulates synapse number and probability of neurotransmitter release, emerging as a potential therapeutic target for diseases affecting synapses, such as fragile X syndrome (FXS), the most common heritable autism disorder. Using crystallographic data and the virtual screening of a chemical library, we identified a set of heterocyclic small molecules as potential inhibitors of the NCS-1/Ric8a interaction. The aminophenothiazine FD44 interferes with NCS-1/Ric8a binding, and it restores normal synapse number and associative learning in a Drosophila FXS model. The synaptic effects elicited by FD44 feeding are consistent with the genetic manipulation of NCS-1. The crystal structure of NCS-1 bound to FD44 and the structure-function studies performed with structurally close analogs explain the FD44 specificity and the mechanism of inhibition, in which the small molecule stabilizes a mobile C-terminal helix inside a hydrophobic crevice of NCS-1 to impede Ric8a interaction. Our study shows the drugability of the NCS-1/Ric8a interface and uncovers a suitable region in NCS-1 for development of additional drugs of potential use on FXS and related synaptic disorders.

Calcium-dependent oligomerization of CAR proteins at cell membrane modulates ABA signaling.

Regulation of ion transport in plants is essential for cell function. Abiotic stress unbalances cell ion homeostasis, and plants tend to readjust it, regulating membrane transporters and channels. The plant hormone abscisic acid (ABA) and the second messenger Ca(2+) are central in such processes, as they are involved in the regulation of protein kinases and phosphatases that control ion transport activity in response to environmental stimuli. The identification and characterization of the molecular mechanisms underlying the effect of ABA and Ca(2+) signaling pathways on membrane function are central and could provide opportunities for crop improvement. The C2-domain ABA-related (CAR) family of small proteins is involved in the Ca(2+)-dependent recruitment of the pyrabactin resistance 1/PYR1-like (PYR/PYL) ABA receptors to the membrane. However, to fully understand CAR function, it is necessary to define a molecular mechanism that integrates Ca(2+) sensing, membrane interaction, and the recognition of the PYR/PYL interacting partners. We present structural and biochemical data showing that CARs are peripheral membrane proteins that functionally cluster on the membrane and generate strong positive membrane curvature in a Ca(2+)-dependent manner. These features represent a mechanism for the generation, stabilization, and/or specific recognition of membrane discontinuities. Such structures may act as signaling platforms involved in the recruitment of PYR/PYL receptors and other signaling components involved in cell responses to stress.

Structural basis of the regulatory mechanism of the plant CIPK family of protein kinases controlling ion homeostasis and abiotic stress.

Plant cells have developed specific protective molecular machinery against environmental stresses. The family of CBL-interacting protein kinases (CIPK) and their interacting activators, the calcium sensors calcineurin B-like (CBLs), work together to decode calcium signals elicited by stress situations. The molecular basis of biological activation of CIPKs relies on the calcium-dependent interaction of a self-inhibitory NAF motif with a particular CBL, the phosphorylation of the activation loop by upstream kinases, and the subsequent phosphorylation of the CBL by the CIPK. We present the crystal structures of the NAF-truncated and pseudophosphorylated kinase domains of CIPK23 and CIPK24/SOS2. In addition, we provide biochemical data showing that although CIPK23 is intrinsically inactive and requires an external stimulation, CIPK24/SOS2 displays basal activity. This data correlates well with the observed conformation of the respective activation loops: Although the loop of CIPK23 is folded into a well-ordered structure that blocks the active site access to substrates, the loop of CIPK24/SOS2 protrudes out of the active site and allows catalysis. These structures together with biochemical and biophysical data show that CIPK kinase activity necessarily requires the coordinated releases of the activation loop from the active site and of the NAF motif from the nucleotide-binding site. Taken all together, we postulate the basis for a conserved calcium-dependent NAF-mediated regulation of CIPKs and a variable regulation by upstream kinases.

The consensus-based approach for gene/enzyme replacement therapies and crystallization strategies: the case of human alanine-glyoxylate aminotransferase.

Protein stability is a fundamental issue in biomedical and biotechnological applications of proteins. Among these applications, gene- and enzyme-replacement strategies are promising approaches to treat inherited diseases that may benefit from protein engineering techniques, even though these beneficial effects have been largely unexplored. In the present study we apply a sequence-alignment statistics procedure (consensus-based approach) to improve the activity and stability of the human AGT (alanine-glyoxylate aminotransferase) protein, an enzyme which causes PH1 (primary hyperoxaluria type I) upon mutation. By combining only five consensus mutations, we obtain a variant (AGT-RHEAM) with largely enhanced in vitro thermal and kinetic stability, increased activity, and with no side effects on foldability and peroxisomal targeting in mammalian cells. The structure of AGT-RHEAM reveals changes at the dimer interface and improved electrostatic interactions responsible for increased kinetic stability. Consensus-based variants maintained the overall protein fold, crystallized more easily and improved the expression as soluble proteins in two different systems [AGT and CIPK24 (CBL-interacting serine/threonine-protein kinase) SOS2 (salt-overly-sensitive 2)]. Thus the consensus-based approach also emerges as a simple and generic strategy to increase the crystallization success for hard-to-get protein targets as well as to enhance protein stability and function for biomedical applications.

Preliminary crystallographic analysis of the ankyrin-repeat domain of Arabidopsis thaliana AKT1: identification of the domain boundaries for protein crystallization.

The Arabidopsis thaliana K(+) transporter 1 (AKT1) participates in the maintenance of an adequate cell potassium (K(+)) concentration. The CBL-interacting protein kinase 23 (CIPK23) activates AKT1 for K(+) uptake under low-K(+) conditions. This process is mediated by the interaction between the cytosolic ankyrin-repeat (AR) domain of AKT1 and the kinase domain of CIPK23. However, the precise boundaries of the AR domain and the residues responsible for the interaction are still unknown. Here, the optimization procedure to obtain an AR domain construct suitable for crystallization and the preliminary crystallographic analysis of the obtained crystals are reported. The crystals belonged to space group P21212, with unit-cell parameters a = 34.83, b = 65.89, c = 85.44 Å, and diffracted to 1.98 Šresolution.

Gravitational and magnetic field variations synergize to cause subtle variations in the global transcriptional state of Arabidopsis in vitro callus cultures.

BACKGROUND: Biological systems respond to changes in both the Earth's magnetic and gravitational fields, but as experiments in space are expensive and infrequent, Earth-based simulation techniques are required. A high gradient magnetic field can be used to levitate biological material, thereby simulating microgravity and can also create environments with a reduced or an enhanced level of gravity (g), although special attention should be paid to the possible effects of the magnetic field (B) itself. RESULTS: Using diamagnetic levitation, we exposed Arabidopsis thaliana in vitro callus cultures to five environments with different levels of effective gravity and magnetic field strengths. The environments included levitation, i.e. simulated µg* (close to 0 g* at B = 10.1 T), intermediate g* (0.1 g* at B = 14.7 T) and enhanced gravity levels (1.9 g* at B = 14.7 T and 2 g* at B = 10.1 T) plus an internal 1 g* control (B = 16.5 T). The asterisk denotes the presence of the background magnetic field, as opposed to the effective gravity environments in the absence of an applied magnetic field, created using a Random Position Machine (simulated µg) and a Large Diameter Centrifuge (2 g).Microarray analysis indicates that changes in the overall gene expression of cultured cells exposed to these unusual environments barely reach significance using an FDR algorithm. However, it was found that gravitational and magnetic fields produce synergistic variations in the steady state of the transcriptional profile of plants. Transcriptomic results confirm that high gradient magnetic fields (i.e. to create µg* and 2 g* conditions) have a significant effect, mainly on structural, abiotic stress genes and secondary metabolism genes, but these subtle gravitational effects are only observable using clustering methodologies. CONCLUSIONS: A detailed microarray dataset analysis, based on clustering of similarly expressed genes (GEDI software), can detect underlying global-scale responses, which cannot be detected by means of individual gene expression techniques using raw or corrected p values (FDR). A subtle, but consistent, genome-scale response to hypogravity environments was found, which was opposite to the response in a hypergravity environment.

Blockade of nicotinic receptors of bovine adrenal chromaffin cells by nanomolar concentrations of atropine.

Nanomolar concentrations of atropine have been considered up to now to be selective for blockade of muscarinic receptors for acetylcholine. A collateral finding indicated to us that these low concentrations of atropine could also target the neuronal nicotinic receptors. We report here a detailed study on this novel property of atropine. Catecholamine release, measured on-line with amperometry in chromaffin cells stimulated with acetylcholine pulses was blocked by atropine in a competitive manner. To corroborate a direct action of atropine on nicotinic receptors, we have employed N,N-dimethyl-N'-phenyl-piperazinium (DMPP), a pure nicotinic receptor agonist; atropine blocked its secretory responses with an IC50 of 2.04 nM. Nicotinic currents, recorded with the whole cell configuration of the patch-clamp technique were blocked by atropine in a concentration-dependent manner (IC50 of 11 nM), also showing a competitive nature. Nicotinic receptor currents in oocytes expressing bovine alpha7 and alpha3beta4 nicotinic receptors were blocked by atropine with an IC50 of 11.2 and 46.8 nM, respectively. Atropine (30 nM) also decreased the increment of the cytosolic calcium concentrations after stimulation with 30 microM DMPP in bovine chromaffin cells. However, action potentials evoked by DMPP were not modified by atropine. Our results demonstrate that nicotinic currents and their downstream consequences (i.e. cytosolic calcium elevations and catecholamine release) were blocked by nanomolar concentrations of atropine; although the blockade was partial, it must be considered when using atropine to study cholinergic neurotransmission, particularly at synapses where both nicotinic and muscarinic receptors are present i.e., the adrenal medulla and autonomic ganglia.

Activation and blockade by choline of bovine alpha7 and alpha3beta4 nicotinic receptors expressed in oocytes.

Choline, the precursor and the metabolite of acetylcholine, is reputed as a selective alpha7 nicotinic receptor agonist. In this study, however, we have seen that choline exerted a dual effect on bovine nicotinic receptors expressed in Xenopus oocytes. On the one hand, choline behaved as a weak full agonist on bovine alpha7-mediated inward currents, with an EC50 of 0.43 mM. On the other, choline blocked bovine alpha3beta4 currents, with an IC50 of 0.97 mM. The blockade by choline was fast (tau(on), 0.36 s), fully reversible (tau(off), 1.23 s), exhibited voltage-dependence (60% blockade at -100 mV and 30% blockade at -40 mV), and was of a non-competitive nature, suggesting an open-channel type of alpha3beta4 receptor blockade. Thus, choline by activating alpha7 receptors and/or blocking alpha3beta4 receptors might play a physiological role in the control of neurotransmission at cholinergic synapses where alpha7 and alpha3beta4 receptor are expressed.