Functional and structural asymmetry suggest a unifying principle for catalysis in membrane-bound pyrophosphatases.

Membrane-bound pyrophosphatases (M-PPases) are homodimeric primary ion pumps that couple the transport of Na+- and/or H+ across membranes to the hydrolysis of pyrophosphate. Their role in the virulence of protist pathogens like Plasmodium falciparum makes them an intriguing target for structural and functional studies. Here, we show the first structure of a K+-independent M-PPase, asymmetric and time-dependent substrate binding in time-resolved structures of a K+-dependent M-PPase and demonstrate pumping-before-hydrolysis by electrometric studies. We suggest how key residues in helix 12, 13, and the exit channel loops affect ion selectivity and K+-activation due to a complex interplay of residues that are involved in subunit-subunit communication. Our findings not only explain ion selectivity in M-PPases but also why they display half-of-the-sites reactivity. Based on this, we propose, for the first time, a unified model for ion-pumping, hydrolysis, and energy coupling in all M-PPases, including those that pump both Na+ and H+.

Unexpected structures formed by the kinase RET C634R mutant extracellular domain suggest potential oncogenic mechanisms in MEN2A.

The RET receptor tyrosine kinase plays a pivotal role in cell survival, proliferation, and differentiation, and its abnormal activation leads to cancers through receptor fusions or point mutations. Mutations that disrupt the disulfide network in the extracellular domain (ECD) of RET drive multiple endocrine neoplasia type 2A (MEN2A), a hereditary syndrome associated with the development of thyroid cancers. However, structural details of how specific mutations affect RET are unclear. Here, we present the first structural insights into the ECD of the RET(C634R) mutant, the most common mutation in MEN2A. Using electron microscopy, we demonstrate that the C634R mutation causes ligand-independent dimerization of the RET ECD, revealing an unusual tail-to-tail conformation that is distinct from the ligand-induced signaling dimer of WT RET. Additionally, we show that the RETC634R ECD dimer can form complexes with at least two of the canonical RET ligands and that these complexes form very different structures than WT RET ECD upon ligand binding. In conclusion, this structural analysis of cysteine-mutant RET ECD suggests a potential key mechanism of cancer induction in MEN2A, both in the absence and presence of its native ligands, and may offer new targets for therapeutic intervention.

PTCHD1 Binds Cholesterol but Not Sonic Hedgehog, Suggesting a Distinct Cellular Function.

Deleterious mutations in the X-linked Patched domain-containing 1 (PTCHD1) gene may account for up to 1% of autism cases. Despite this, the PTCHD1 protein remains poorly understood. Structural similarities to Patched family proteins point to a role in sterol transport, but this hypothesis has not been verified experimentally. Additionally, PTCHD1 has been suggested to be involved in Hedgehog signalling, but thus far, the experimental results have been conflicting. To enable a variety of biochemical and structural experiments, we developed a method for expressing PTCHD1 in Spodoptera frugiperda cells, solubilising it in glycol-diosgenin, and purifying it to homogeneity. In vitro and in silico experiments show that PTCHD1 function is not interchangeable with Patched 1 (PTCH1) in canonical Hedgehog signalling, since it does not repress Smoothened in Ptch1-/- mouse embryonic fibroblasts and does not bind Sonic Hedgehog. However, we found that PTCHD1 binds cholesterol similarly to PTCH1. Furthermore, we identified 13 PTCHD1-specific protein interactors through co-immunoprecipitation and demonstrated a link to cell stress responses and RNA stress granule formation. Thus, our results support the notion that despite structural similarities to other Patched family proteins, PTCHD1 may have a distinct cellular function.

Evolutionary journey and characterisation of a novel pan-gene associated with beer strains of Saccharomyces cerevisiae.

The sequencing of over a thousand Saccharomyces cerevisiae genomes revealed a complex pangenome. Over one third of the discovered genes are not present in the S. cerevisiae core genome but instead are often restricted to a subset of yeast isolates and thus may be important for adaptation to specific environmental niches. We refer to these genes as "pan-genes," being part of the pangenome but not the core genome. Here, we describe the evolutionary journey and characterisation of a novel pan-gene, originally named hypothetical (HYPO) open-reading frame. Phylogenetic analysis reveals that HYPO has been predominantly retained in S. cerevisiae strains associated with brewing but has been repeatedly lost in most other fungal species during evolution. There is also evidence that HYPO was horizontally transferred at least once, from S. cerevisiae to Saccharomyces paradoxus. The phylogenetic analysis of HYPO exemplifies the complexity and intricacy of evolutionary trajectories of genes within the S. cerevisiae pangenome. To examine possible functions for Hypo, we overexpressed a HYPO-GFP fusion protein in both S. cerevisiae and Saccharomyces pastorianus. The protein localised to the plasma membrane where it accumulated initially in distinct foci. Time-lapse fluorescent imaging revealed that when cells are grown in wort, Hypo-gfp fluorescence spreads throughout the membrane during cell growth. The overexpression of Hypo-gfp in S. cerevisiae or S. pastorianus strains did not significantly alter cell growth in medium-containing glucose, maltose, maltotriose, or wort at different concentrations.

Conformationally Preorganized Diastereomeric Norbornane-Based Maltosides for Membrane Protein Study: Implications of Detergent Kink for Micellar Properties.

Detergents are essential tools for functional and structural studies of membrane proteins. However, conventional detergents are limited in their scope and utility, particularly for eukaryotic membrane proteins. Thus, there are major efforts to develop new amphipathic agents with enhanced properties. Here, a novel class of diastereomeric agents with a preorganized conformation, designated norbornane-based maltosides (NBMs), were prepared and evaluated for their ability to solubilize and stabilize membrane proteins. Representative NBMs displayed enhanced behaviors compared to n-dodecyl-ß-d-maltoside (DDM) for all membrane proteins tested. Efficacy of the individual NBMs varied depending on the overall detergent shape and alkyl chain length. Specifically, NBMs with no kink in the lipophilic region conferred greater stability to the proteins than NBMs with a kink. In addition, long alkyl chain NBMs were generally better at stabilizing membrane proteins than short alkyl chain agents. Furthermore, use of one well-behaving NBM enabled us to attain a marked stabilization and clear visualization of a challenging membrane protein complex using electron microscopy. Thus, this study not only describes novel maltoside detergents with enhanced protein-stabilizing properties but also suggests that overall detergent geometry has an important role in determining membrane protein stability. Notably, this is the first systematic study on the effect of detergent kinking on micellar properties and associated membrane protein stability.

Resorcinarene-Based Facial Glycosides: Implication of Detergent Flexibility on Membrane-Protein Stability.

As a membrane-mimetic system, detergent micelles are popularly used to extract membrane proteins from lipid environments and to maintain their solubility and stability in an aqueous medium. However, many membrane proteins encapsulated in conventional detergents tend to undergo structural degradation during extraction and purification, thus necessitating the development of new agents with enhanced properties. In the current study, two classes of new amphiphiles are introduced, resorcinarene-based glucoside and maltoside amphiphiles (designated RGAs and RMAs, respectively), for which the alkyl chains are facially segregated from the carbohydrate head groups. Of these facial amphiphiles, two RGAs (RGA-C11 and RGA-C13) conferred markedly enhanced stability to four tested membrane proteins compared to a gold-standard conventional detergent. The relatively high water solubility and micellar stability of the RGAs compared to the RMAs, along with their generally favourable behaviours for membrane protein stabilisation described here, are likely to be, at least in part, a result of the high conformational flexibility of these glucosides. This study suggests that flexibility could be an important factor in determining the suitability of new detergents for membrane protein studies.

New penta-saccharide-bearing tripod amphiphiles for membrane protein structure studies.

Integral membrane proteins either alone or as complexes carry out a range of key cellular functions. Detergents are indispensable tools in the isolation of membrane proteins from biological membranes for downstream studies. Although a large number of techniques and tools, including a wide variety of detergents, are available, purification and structural characterization of many membrane proteins remain challenging. In the current study, a new class of tripod amphiphiles bearing two different penta-saccharide head groups, designated TPSs, were developed and evaluated for their ability to extract and stabilize a range of diverse membrane proteins. Variations in the structures of the detergent head and tail groups allowed us to prepare three sets of the novel agents with distinctive structures. Some TPSs (TPS-A8 and TPS-E7) were efficient at extracting two proteins in a functional state while others (TPS-E8 and TPS-E10L) conferred marked stability to all membrane proteins (and membrane protein complexes) tested here compared to a conventional detergent. Use of TPS-E10L led to clear visualization of a receptor-Gs complex using electron microscopy, indicating profound potential in membrane protein research.

Mesitylene-Cored Glucoside Amphiphiles (MGAs) for Membrane Protein Studies: Importance of Alkyl Chain Density in Detergent Efficacy.

Detergents serve as useful tools for membrane protein structural and functional studies. Their amphipathic nature allows detergents to associate with the hydrophobic regions of membrane proteins whilst maintaining the proteins in aqueous solution. However, widely used conventional detergents are limited in their ability to maintain the structural integrity of membrane proteins and thus there are major efforts underway to develop novel agents with improved properties. We prepared mesitylene-cored glucoside amphiphiles (MGAs) with three alkyl chains and compared these agents with previously developed xylene-linked maltoside agents (XMAs) with two alkyl chains and a conventional detergent (DDM). When these agents were evaluated for four membrane proteins including a G protein-coupled receptor (GPCR), some agents such as MGA-C13 and MGA-C14 resulted in markedly enhanced stability of membrane proteins compared to both DDM and the XMAs. This favourable behaviour is due likely to the increased hydrophobic density provided by the extra alkyl chain. Thus, this study not only describes new glucoside agents with potential for membrane protein research, but also introduces a new detergent design principle for future development.

Investigation of protein secretion and secretion stress in Ashbya gossypii.

BACKGROUND: Ashbya gossypii is a filamentous Saccharomycete used for the industrial production of riboflavin that has been recently explored as a host system for recombinant protein production. To gain insight into the protein secretory pathway of this biotechnologically relevant fungus, we undertook genome-wide analyses to explore its secretome and its transcriptional responses to protein secretion stress. RESULTS: A computational pipeline was used to predict the inventory of proteins putatively secreted by A. gossypii via the general secretory pathway. The proteins actually secreted by this fungus into the supernatants of submerged cultures in minimal and rich medium were mapped by two-dimensional gel electrophoresis, revealing that most of the A. gossypii secreted proteins have an isoelectric point between 4 and 6, and a molecular mass above 25 kDa. These analyses together indicated that 1-4% of A. gossypii proteins are likely to be secreted, of which less than 33% are putative hydrolases. Furthermore, transcriptomic analyses carried out in A. gossypii cells under recombinant protein secretion conditions and dithiothreitol-induced secretion stress unexpectedly revealed that a conventional unfolded protein response (UPR) was not activated in any of the conditions, as the expression levels of several well-known UPR target genes (e.g. IRE1, KAR2, HAC1 and PDI1 homologs) remained unaffected. However, several other genes involved in protein unfolding, endoplasmatic reticulum-associated degradation, proteolysis, vesicle trafficking, vacuolar protein sorting, secretion and mRNA degradation were up-regulated by dithiothreitol-induced secretion stress. Conversely, the transcription of several genes encoding secretory proteins, such as components of the glycosylation pathway, was severely repressed by dithiothreitol CONCLUSIONS: This study provides the first insights into the secretion stress response of A. gossypii, as well as a basic understanding of its protein secretion potential, which is more similar to that of yeast than to that of other filamentous fungi. Contrary to what has been widely described for yeast and fungi, a conventional UPR was not observed in A. gossypii, but alternative protein quality control mechanisms enabled it to cope with secretion stress. These data will help provide strategies for improving heterologous protein secretion in A. gossypii.

Ethical decision making in intensive care units: a burnout risk factor? Results from a multicentre study conducted with physicians and nurses.

BACKGROUND: Ethical decision making in intensive care is a demanding task. The need to proceed to ethical decision is considered to be a stress factor that may lead to burnout. The aim of this study is to explore the ethical problems that may increase burnout levels among physicians and nurses working in Portuguese intensive care units (ICUs). A quantitative, multicentre, correlational study was conducted among 300 professionals. RESULTS: The most crucial ethical decisions made by professionals working in ICU were related to communication, withholding or withdrawing treatments and terminal sedation. A positive relation was found between ethical decision making and burnout in nurses, namely, between burnout and the need to withdraw treatments (p=0.032), to withhold treatments (p=0.002) and to proceed to terminal sedation (p=0.005). This did not apply to physicians. Emotional exhaustion was the burnout subdimension most affected by the ethical decision. The nurses' lack of involvement in ethical decision making was identified as a risk factor. Nevertheless, in comparison with nurses (6%), it was the physicians (34%) who more keenly felt the need to proceed to ethical decisions in ICU. CONCLUSIONS: Ethical problems were reported at different levels by physicians and nurses. The type of ethical decisions made by nurses working in Portuguese ICUs had an impact on burnout levels. This did not apply to physicians. This study highlights the need for education in the field of ethics in ICUs and the need to foster inter-disciplinary discussion so as to encourage ethical team deliberation in order to prevent burnout.

Differences in compliance with Surviving Sepsis Campaign recommendations according to hospital entrance time: day versus night.

INTRODUCTION: Higher compliance with Surviving Sepsis Campaign (SSC) recommendations has been associated with lower mortality. The authors evaluate differences in compliance with SSC 6-hour bundle according to hospital entrance time (day versus night) and its impact on hospital mortality. METHODS: Prospective cohort study of all patients with community-acquired severe sepsis admitted to the intensive care unit of a large university tertiary care hospital, over 3.5 years with a follow-up until hospital discharge. Time to compliance with each recommendation of the SSC 6-hour bundle was calculated according to hospital entrance period: day (08:30 to 20:30) versus night (20:30 to 08:30). For the same periods, clinical staff composition and the number of patients attending the emergency department (ED) was also recorded. RESULTS: In this period 300 consecutive patients were included. Compliance rate was (night vs. day): serum lactate measurement 57% vs. 49% (P = 0.171), blood cultures drawn 59% vs. 37% (P < 0.001), antibiotics administration in the first 3 hours 33% vs. 18% (P = 0.003), central venous pressure >8 mmHg 45% vs. 29% (P = 0.021), and central venous oxygen saturation (SvcO2) >70%, 7% vs. 2% (P = 0.082); fluids were administered in all patients with hypotension in both periods and vasopressors were administered in patients with hypotension not responsive to fluids in 100% vs. 99%. Time to get specific actions done was also different (night vs. day): serum lactate measurement (4.5 vs. 7 h, P = 0.018), blood cultures drawn (4 vs. 8 h, P < 0.001), antibiotic administration (5 vs. 8 h, P < 0.001), central venous pressure (8 vs. 11 h, P = 0.01), and SvcO2 monitoring (2.5 vs. 11 h, P = 0.222). The composition of the nursing team was the same around the clock; the medical team was reduced at night with a higher proportion of less differentiated doctors. The number of patients attending the Emergency Department was lower overnight. Hospital mortality rate was 34% in patients entering in the night period vs. 40% in those entering during the day (P = 0.281). CONCLUSION: Compliance with SSC recommendations was higher at night. A possible explanation might be the increased nurse to patient ratio in that period. Adjustment of the clinical team composition to the patients' demand is needed to increase compliance and improve prognosis.

Burnout in intensive care units - a consideration of the possible prevalence and frequency of new risk factors: a descriptive correlational multicentre study.

BACKGROUND: The provision of Intensive Care (IC) can lead to a health care provider's physical, psychological and emotional exhaustion, which may develop into burnout. We notice the absence of specific studies regarding this syndrome in Portuguese Intensive Care Units (ICUs). Our main objective is to study the incidence and risk factors of burnout in Portuguese ICUs. METHODS: A self-fulfilment questionnaire containing 3 items: (i) socio-demographic data of the study population; (ii) experiences in the workplace; (iii) Maslach Burnout Inventory (MBI) - was applied to evaluate the influence of distinct factors on the prevalence of burnout among physicians and nurses working in ICUs. RESULTS: Three hundred professionals (82 physicians and 218 nurses) from ten ICUs were included in the study, out of a total of 445 who were eligible. There was a high rate of burnout among professionals working in Portuguese ICUs, with 31% having a high level of burnout. However, when burnout levels among nurses and physicians were compared, no significant difference was found. Using multivariate analysis, we identified gender as being a risk factor, where female status increases the risk of burnout. In addition, higher levels of burnout were associated with conflicts and ethical decision making regarding withdrawing treatments. Having a temporary work contract was also identified as a risk factor. Conversely, working for another service of the same health care institution acts as a protective factor. CONCLUSIONS: A high rate of burnout was identified among professionals working in Portuguese ICUs. This study highlights some new risk factors for burnout (ethical decision making, temporary work contracts), and also protective ones (maintaining activity in other settings outside the ICU) that were not previously reported. Preventive and interventive programmes to avoid and reduce burnout syndrome are of paramount importance in the future organization of ICUs and should take the above results into account.

Additional risk factors for infection by multidrug-resistant pathogens in healthcare-associated infection: a large cohort study.

BACKGROUND: There is a lack of consensus regarding the definition of risk factors for healthcare-associated infection (HCAI). The purpose of this study was to identify additional risk factors for HCAI, which are not included in the current definition of HCAI, associated with infection by multidrug-resistant (MDR) pathogens, in all hospitalized infected patients from the community. METHODS: This 1-year prospective cohort study included all patients with infection admitted to a large, tertiary care, university hospital. Risk factors not included in the HCAI definition, and independently associated with MDR pathogen infection, namely MDR Gram-negative (MDR-GN) and ESKAPE microorganisms (vancomycin-resistant Enterococcus faecium, methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella species, carbapenem-hydrolyzing Klebsiella pneumonia and MDR Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species), were identified by logistic regression among patients admitted from the community (either with community-acquired or HCAI). RESULTS: There were 1035 patients with infection, 718 from the community. Of these, 439 (61%) had microbiologic documentation; 123 were MDR (28%). Among MDR: 104 (85%) had MDR-GN and 41 (33%) had an ESKAPE infection. Independent risk factors associated with MDR and MDR-GN infection were: age (adjusted odds ratio (OR) = 1.7 and 1.5, p = 0.001 and p = 0.009, respectively), and hospitalization in the previous year (between 4 and 12 months previously) (adjusted OR = 2.0 and 1,7, p = 0.008 and p = 0.048, respectively). Infection by pathogens from the ESKAPE group was independently associated with previous antibiotic therapy (adjusted OR = 7.2, p < 0.001) and a Karnofsky index <70 (adjusted OR = 3.7, p = 0.003). Patients with infection by MDR, MDR-GN and pathogens from the ESKAPE group had significantly higher rates of inadequate antibiotic therapy than those without (46% vs 7%, 44% vs 10%, 61% vs 15%, respectively, p < 0.001). CONCLUSIONS: This study suggests that the inclusion of additional risk factors in the current definition of HCAI for MDR pathogen infection, namely age >60 years, Karnofsky index <70, hospitalization in the previous year, and previous antibiotic therapy, may be clinically beneficial for early diagnosis, which may decrease the rate of inadequate antibiotic therapy among these patients.

Nutritional requirements and strain heterogeneity in Ashbya gossypii.

Colony radial growth rates and specific growth rates of three related Ashbya gossypii strains ATCC10895, IMI31268, MUCL29450 and an unrelated strain, CBS109.26, were measured on various carbon and nitrogen sources at pH 4.5 and pH 6.5 to elucidate physiological growth requirements and strain differences. All strains grew on yeast extract or ammonium as nitrogen sources, but not on nitrate. Substantial growth at pH 4.5 was observed only on complex medium. D-Glucose, glycerol and starch were utilised as carbon sources. Ethanol was produced during growth on glycerol. Conversion of xylose into xylitol demonstrates that the xylose reductase is active. Phenotypic differences between related strains were greater than expected. We demonstrate that A. gossypii utilizes ammonium as sole nitrogen source at pH 6.5, facilitating further physiological studies using chemically defined media in the future.

Impact of age in critically Ill infected patients: a post-hoc analysis of the INFAUCI study.

PURPOSE: Older patients are the fastest expanding subgroup of intensive care units (ICU) and are particularly susceptible to bacterial infections and sepsis. The aim of this study was to address the epidemiology and the main determinants of outcome of infection in old and very old patients admitted to ICU. METHODS: We performed a post hoc analysis of all infected patients admitted to ICU enrolled in a 1-year prospective, observational, multipurpose study. Patients aged < 65, 65-74 and ≥ 75 years were compared. RESULTS: Of the 1652 patients included, 50% were older than 65 years. There were no significant differences between young, old and very old patients in either ICU, hospital length of stay, or nosocomial infection. All-cause mortality was significantly higher in participants aged ≥ 75. Increased Gram-negative microorganisms' isolates occurred in > 65 years (25% versus 31%; p = 0.034). Multidrug-resistant (MDR) microorganisms were directly associated to inappropriate empiric antibiotic therapy (OR 4.73; 95% CI 2.99-7.47) and inversely associated with community-acquired infection (OR 0.39; 95% CI 0.19-0.83). Age (65-74 years: OR 1.10; 95% CI 0.64-1.90 and ≥ 75 years: OR 1.52; 95% CI 0.89-2.59) and sepsis severity (sepsis: OR 0.67; 95% CI 0.18-2.46; severe sepsis: OR 1.17; 95% CI 0.40-3.44; septic shock: OR 0.77; 95% CI 0.27-2.24) were not associated to MDR bacteria. CONCLUSION: Patients > 65 years accounted for 50% of infected patients admitted to an ICU. ICU and hospital length of stay, and nosocomial infection did not increase with age. Age did predispose to increased risk for infection by Gram-negatives. These findings may optimize strategies for infection management in older patients.

Exploration of Pyrazolo[1,5-a]pyrimidines as Membrane-Bound Pyrophosphatase Inhibitors.

Inhibition of membrane-bound pyrophosphatase (mPPase) with small molecules offer a new approach in the fight against pathogenic protozoan parasites. mPPases are absent in humans, but essential for many protists as they couple pyrophosphate hydrolysis to the active transport of protons or sodium ions across acidocalcisomal membranes. So far, only few nonphosphorus inhibitors have been reported. Here, we explore the chemical space around previous hits using a combination of screening and synthetic medicinal chemistry, identifying compounds with low micromolar inhibitory activities in the Thermotoga maritima mPPase test system. We furthermore provide early structure-activity relationships around a new scaffold having a pyrazolo[1,5-a]pyrimidine core. The most promising pyrazolo[1,5-a]pyrimidine congener was further investigated and found to inhibit Plasmodium falciparum mPPase in membranes as well as the growth of P. falciparum in an ex vivo survival assay.

Reducing mortality in severe sepsis with the implementation of a core 6-hour bundle: results from the Portuguese community-acquired sepsis study (SACiUCI study).

INTRODUCTION: To evaluate the impact of compliance with a core version of the Surviving Sepsis Campaign 6-hour bundle on 28 days mortality. METHODS: Cohort, multi-centre, prospective study on community-acquired sepsis (CAS). RESULTS: Seventeen intensive care units (ICU) entered the study. Over a one year period, 4,142 patients were enrolled in the study. Of the 897 (24%) admitted with CAS, 778 (87%) had severe sepsis or septic shock on ICU admission. In the first six hours of hospital admission: (1) 62% had serum lactate measured; (2) 69% fluids administered; (3) 77% specimens collected for microbiology before antibiotic administration; (4) 48% blood cultures obtained; (5) 52% antibiotics administered within the first hour of the diagnosis; (6) vasopressors were given in 78%; (7) 56% had central venous measurement (CVP) measurement; (8) 17% had a central venous oxygen saturation (ScvO2) measurement; (9) dobutamine was administered in 52%. Compliance with all actions 1 to 6 (core bundle) was associated with an odds ratio (OR) of 0.44 [95% confidence interval (CI) = 0.24-0.80] in severe sepsis and 0.49 (95% CI = 0.25-0.95) in septic shock, for 28 days mortality. This corresponded to a number needed to treat of 6 patients to save one life. CONCLUSIONS: Compliance with this core bundle was associated with a significant reduction in the 28 days mortality. Urgent action should be taken in order to ensure that early sepsis diagnosis is followed by full completion of this "core bundle" followed by activation of expertise help in severe sepsis.

Expression of Trichoderma reesei cellulases CBHI and EGI in Ashbya gossypii.

To explore the potential of Ashbya gossypii as a host for the expression of recombinant proteins and to assess whether protein secretion would be more similar to the closely related Saccharomyces cerevisiae or to other filamentous fungi, endoglucanase I (EGI) and cellobiohydrolase I (CBHI) from the fungus Trichoderma reesei were successfully expressed in A. gossypii from plasmids containing the two micron sequences from S. cerevisiae, under the S. cerevisiae PGK1 promoter. The native signal sequences of EGI and CBHI were able to direct the secretion of EGI and CBHI into the culture medium in A. gossypii. Although CBHI activity was not detected using 4-methylumbelliferyl-beta-D: -lactoside as substrate, the protein was detected by Western blot using monoclonal antibodies. EGI activity was detectable, the specific activity being comparable to that produced by a similar EGI producing S. cerevisiae construct. More EGI was secreted than CBHI, or more active protein was produced. Partial characterization of CBHI and EGI expressed in A. gossypii revealed overglycosylation when compared with the native T. reesei proteins, but the glycosylation was less extensive than on cellulases expressed in S. cerevisiae.

Expression and purification of the extracellular domain of wild-type humanRET and the dimeric oncogenic mutant C634R.

The receptor tyrosine kinase RET is essential in a variety of cellular processes. RET gain-of-function is strongly associated with several cancers, notably multiple endocrine neoplasia type 2A (MEN 2A), while RET loss-of-function causes Hirschsprung's disease and Parkinson's disease. To investigate the activation mechanism of RET as well as to enable drug development, over-expressed recombinant protein is needed for in vitro functional and structural studies. By comparing insect and mammalian cells expression of the RET extracellular domain (RETECD), we showed that the expression yields of RETECD using both systems were comparable, but mammalian cells produced monomeric functional RETECD, whereas RETECD expressed in insect cells was non-functional and multimeric. This was most likely due to incorrect disulfide formation. By fusing an Fc tag to the C-terminus of RETECD, we were able to produce, in HEK293T cells, dimeric oncogenic RETECD (C634R) for the first time. The protein remained dimeric even after cleavage of the tag via the cysteine disulfide, as in full-length RET in the context of MEN 2A and related pathologies. Our work thus provides valuable tools for functional and structural studies of the RET signaling system and its oncogenic activation mechanisms.

Influence of vasopressor agent in septic shock mortality. Results from the Portuguese Community-Acquired Sepsis Study (SACiUCI study).

OBJECTIVE: Guidelines for the adrenergic support of septic shock are controversial. In patients with community-acquired septic shock, we assessed the impact of the choice of vasopressor support on mortality. DESIGN: Cohort, multiple center, observational study. SETTING: Seventeen Portuguese intensive care units (ICUs). PATIENTS: All adult patients admitted to a participating ICU between December 2004 and November 2005. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were followed up during the first five ICU days, the day of discharge or death, and hospital outcome. Eight hundred ninety-seven consecutive patients with community-acquired sepsis (median age, 63 years; 577 men; and hospital mortality, 38%) were studied. Of the 458 patients with septic shock, 73% received norepinephrine and 50.5% dopamine. The norepinephrine group had a higher hospital mortality (52% vs. 38.5%, p = 0.002). A Kaplan-Meier survival curve showed diminished 28-day survival in the norepinephrine group (log-rank = 22.6, p < 0.001). A Cox proportional hazard analysis revealed that the administration of norepinephrine was associated with an increased risk of death (adjusted hazard ratio, 2.501; 95% confidence interval, 1.413-4.425; p = 0.002). In a multivariate analysis with ICU mortality as the dependent factor, Simplified Acute Physiology Score II and norepinephrine administration were independent risk factors for ICU mortality in patients with septic shock. CONCLUSIONS: In patients with community-acquired septic shock, our data suggest that norepinephrine administration could be associated with worse outcome.