Gram-negative bacteria have an outer membrane that serves as a barrier to noxious agents in the environment. This protective function is dependent on lipopolysaccharide, a large glycolipid located in ...the outer leaflet of the outer membrane. Lipopolysaccharide is synthesized at the cytoplasmic membrane and must be transported to the cell surface. To understand this transport process, we reconstituted membrane-to-membrane movement of lipopolysaccharide by incorporating purified inner and outer membrane transport complexes into separate proteoliposomes. Transport involved stable association between the inner and outer membrane proteoliposomes. Our results support a model in which lipopolysaccharide molecules are pushed one after the other in a PEZ dispenser-like manner across a protein bridge that connects the inner and outer membranes.
Biopsy-confirmed liver fibrosis is a prognostic factor for patients with nonalcoholic fatty liver disease (NAFLD). We performed a systematic review to quantify the prognostic value of fibrosis stage ...in patients with NAFLD and the subgroup of patients with nonalcoholic steatohepatitis (NASH) and to assess the evidence that change in fibrosis stage is a surrogate endpoint.
We searched the MEDLINE, Embase, Cochrane Library, and trial registry databases through August 2018 for prospective or retrospective cohort studies of liver-related clinical events and outcomes in adults with NAFLD or NASH. We collected data on mortality (all cause and liver related) and morbidity (cirrhosis, liver cancer, and all liver-related events) by stage of fibrosis, determined by biopsy, for patients with NAFLD or NASH. Using fibrosis stage 0 as a reference population, we calculated fibrosis stage-specific relative risk (RR) and 95% confidence interval (CI) values for mortality and morbidities. We performed fixed-effect and random-effect model meta-analyses. Metaregression was used to examine associations among study design (prospective vs retrospective cohort), overall risk of bias (medium or high), and mean duration of follow-up (in years).
Our meta-analysis included 13 studies, comprising 4428 patients with NAFLD; 2875 of these were reported to have NASH. Compared with no fibrosis (stage 0), unadjusted risk increased with increasing stage of fibrosis (stage 0 vs 4): all-cause mortality RR, 3.42 (95% CI, 2.63–4.46); liver-related mortality RR, 11.13 (95% CI, 4.15–29.84); liver transplant RR, 5.42 (95% CI, 1.05–27.89); and liver-related events RR, 12.78 (95% CI, 6.85–23.85). The magnitude of RR did not differ significantly after adjustment for confounders, including age or sex in the subgroup of NAFLD patients with NASH. Three studies examined the effects of increasing fibrosis on quality of life had inconsistent findings.
In a systematic review and meta-analysis, we found biopsy-confirmed fibrosis to be associated with risk of mortality and liver-related morbidity in patients with NAFLD, with and without adjustment for confounding factors and in patients with reported NASH. Further studies are needed to assess the association between fibrosis stage and patient quality of life and establish that change in liver fibrosis stage is a valid endpoint for use in clinical trials.
COPI‐coated vesicles mediate transport between Golgi stacks and retrograde transport from the Golgi to the endoplasmic reticulum. The COPI coat exists as a stable heptameric complex in the cytosol ...termed coatomer and is recruited en bloc to the membrane for vesicle formation. Recruitment of COPI onto membranes is mediated by the Arf family of small GTPases, which, in their GTP‐bound state, bind both membrane and coatomer. Arf GTPases also influence cargo selection, vesicle scission and vesicle uncoating. Guanine nucleotide exchange factors (GEFs) and GTPase‐activating proteins (GAPs) regulate nucleotide binding by Arf GTPases. To understand the mechanism of COPI‐coated vesicle trafficking, it is necessary to characterize the interplay between coatomer and Arf GTPases and their effectors. It is also necessary to understand interactions between coatomer and cargo, cargo adaptors/receptors and tethers facilitating binding to the target membrane. Here, we summarize current knowledge of COPI coat protein structure; we describe how structural and biochemical studies contributed to this knowledge; we review mechanistic insights into COPI vesicle biogenesis and disassembly; and we discuss the potential to answer open questions in the field.
COPI‐coated vesicles mediate transport within the Golgi and retrograde transport from the Golgi to the endoplasmic reticulum. This review discusses the assembly and disassembly of COPI‐coated vesicles with an emphasis on the structure of the COPI coat components and regulatory factors including coatomer, Arf GTPases, and ArfGAPs and ArfGEFs. We highlight recent developments and open questions in the field.
Gram-negative bacteria are surrounded by an inner cytoplasmic membrane and by an outer membrane, which serves as a protective barrier to limit entry of many antibiotics. The distinctive properties of ...the outer membrane are due to the presence of lipopolysaccharide
. This large glycolipid, which contains numerous sugars, is made in the cytoplasm; a complex of proteins forms a membrane-to-membrane bridge that mediates transport of lipopolysaccharide from the inner membrane to the cell surface
. The inner-membrane components of the protein bridge comprise an ATP-binding cassette transporter that powers transport, but how this transporter ensures unidirectional lipopolysaccharide movement across the bridge to the outer membrane is unknown
. Here we describe two crystal structures of a five-component inner-membrane complex that contains all the proteins required to extract lipopolysaccharide from the membrane and pass it to the protein bridge. Analysis of these structures, combined with biochemical and genetic experiments, identifies the path of lipopolysaccharide entry into the cavity of the transporter and up to the bridge. We also identify a protein gate that must open to allow movement of substrate from the cavity onto the bridge. Lipopolysaccharide entry into the cavity is ATP-independent, but ATP is required for lipopolysaccharide movement past the gate and onto the bridge. Our findings explain how the inner-membrane transport complex controls efficient unidirectional transport of lipopolysaccharide against its concentration gradient.
We sought to assess the extent to which pain relief in chronic back and leg pain (CBLP) following spinal cord stimulation (SCS) is influenced by patient‐related factors, including pain location, and ...technology factors. A number of electronic databases were searched with citation searching of included papers and recent systematic reviews. All study designs were included. The primary outcome was pain relief following SCS, we also sought pain score (pre‐ and post‐SCS). Multiple predictive factors were examined: location of pain, history of back surgery, initial level of pain, litigation/worker's compensation, age, gender, duration of pain, duration of follow‐up, publication year, continent of data collection, study design, quality score, method of SCS lead implant, and type of SCS lead. Between‐study association in predictive factors and pain relief were assessed by meta‐regression. Seventy‐four studies (N = 3,025 patients with CBLP) met the inclusion criteria; 63 reported data to allow inclusion in a quantitative analysis. Evidence of substantial statistical heterogeneity (P < 0.0001) in level of pain relief following SCS was noted. The mean level of pain relief across studies was 58% (95% CI: 53% to 64%, random effects) at an average follow‐up of 24 months. Multivariable meta‐regression analysis showed no predictive patient or technology factors. SCS was effective in reducing pain irrespective of the location of CBLP. This review supports SCS as an effective pain relieving treatment for CBLP with predominant leg pain with or without a prior history of back surgery. Randomized controlled trials need to confirm the effectiveness and cost‐effectiveness of SCS in the CLBP population with predominant low back pain.
Addition of trastuzumab to first-line chemotherapy improves overall survival in patients with HER2-positive metastatic gastric cancer. We assessed the safety and activity of pembrolizumab in ...combination with trastuzumab and chemotherapy in first-line HER2-positive metastatic oesophagogastric (gastric, oesophageal, or gastroesophageal junction) cancer.
This study was an investigator-initiated, open-label, non-randomised, single-arm, single centre, phase 2 trial in patients aged 18 years or older with HER2-positive metastatic oesophagogastric cancer. Eligible patients had measurable or evaluable non-measurable disease, Eastern Cooperative Oncology Group performance status of 0, 1, or 2, and left ventricular ejection fraction of at least 53%. Patients were eligible to receive an initial induction cycle of 200 mg flat dose of intravenous pembrolizumab and 8 mg/kg loading dose of intravenous trastuzumab. For subsequent cycles, patients received 130 mg/m2 of intravenous oxaliplatin or 80 mg/m2 of cisplatin on day 1, 850 mg/m2 of oral capecitabine twice a day for 2 weeks followed by 1 week off (or intravenous 5-fluorouracil, 800 mg/m2 per day on days 1–5), and a 200 mg flat dose of intravenous pembrolizumab, and 6 mg/kg of trastuzumab, administered on day 1 of each 3-week cycle. The primary endpoint was 6-month progression-free survival, defined as the proportion of patients alive and free of progression at 6 months, assessed in patients who received at least one dose of trastuzumab and pembrolizumab. The regimen would be considered worthy of further investigation if 26 or more of 37 patients were progression-free at 6 months. This trial is registered with ClinicalTrials.gov, NCT02954536, and is ongoing, but closed to enrolment.
Between Nov 11, 2016, and Jan 23, 2019, 37 patients were enrolled. At the time of data cutoff on Aug 6, 2019, median follow-up among survivors was 13·0 months (IQR 11·7–23·5). The primary endpoint was achieved; 26 (70%; 95% CI 54–83) of 37 patients were progression-free at 6 months. The most common treatment-related adverse event of any grade was neuropathy, which was reported in 36 (97%) of 37 patients. The most common grade 3 or 4 adverse events were lymphocytopenia (seven 19% patients with grade 3 and two 5% with grade 4), grade 3 decreased electrolytes (six 16% patients), and grade 3 anaemia (four 11% patients). Serious adverse events occurred in two patients patients (both grade 3 nephritis leading to treatment discontinuation). Four patients discontinued pembrolizumab because of immune-related adverse events. There were no treatment-related deaths.
Pembrolizumab can be safely combined with trastuzumab and chemotherapy and has promising activity in HER2-positive metastatic oesophagogastric cancer. A randomised phase 3 clinical trial assessing the efficacy and safety of pembrolizumab versus placebo in combination with trastuzumab and chemotherapy in first-line HER2-positive metastatic oesophagogastric cancer is underway.
Merck & Co.
Terpene biosynthesis in marine sponge animals Wilson, Kayla; de Rond, Tristan; Burkhardt, Immo ...
Proceedings of the National Academy of Sciences - PNAS,
02/2023, Letnik:
120, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Sea sponges are the largest marine source of small-molecule natural products described to date. Sponge-derived molecules, such as the chemotherapeutic eribulin, the calcium-channel blocker manoalide, ...and antimalarial compound kalihinol A, are renowned for their impressive medicinal, chemical, and biological properties. Sponges contain microbiomes that control the production of many natural products isolated from these marine invertebrates. In fact, all genomic studies to date investigating the metabolic origins of sponge-derived small molecules concluded that microbes-not the sponge animal host-are the biosynthetic producers. However, early cell-sorting studies suggested the sponge animal host may play a role particularly in the production of terpenoid molecules. To investigate the genetic underpinnings of sponge terpenoid biosynthesis, we sequenced the metagenome and transcriptome of an isonitrile sesquiterpenoid-containing sponge of the order Bubarida. Using bioinformatic searches and biochemical validation, we identified a group of type I terpene synthases (TSs) from this sponge and multiple other species, the first of this enzyme class characterized from the sponge holobiome. The Bubarida TS-associated contigs consist of intron-containing genes homologous to sponge genes and feature GC percentage and coverage consistent with other eukaryotic sequences. We identified and characterized TS homologs from five different sponge species isolated from geographically distant locations, thereby suggesting a broad distribution amongst sponges. This work sheds light on the role of sponges in secondary metabolite production and speaks to the possibility that other sponge-specific molecules originate from the animal host.
The survival of Gram-negative bacteria depends on assembly of the asymmetric outer membrane, which creates a barrier that prevents entry of toxic molecules including antibiotics. The outer leaflet of ...the outer membrane is composed of lipopolysaccharide, which is made at the inner membrane and pushed across a protein bridge that spans the inner and outer membranes. We have developed a fluorescent assay to follow lipopolysaccharide (LPS) transport across a bridge linking proteoliposomes that mimic the inner and outer membranes. We show that LPS is delivered to the leaflet of the outer membrane proteoliposome that corresponds to the outer leaflet of the membrane in a cell. Transport stops long before substrates at the inner membrane are exhausted. Using mutants of the transport machinery, we find that the final amount of LPS delivered into the membrane depends on the affinity of the outer membrane translocon for LPS. Furthermore, ATP hydrolysis depends on delivery of LPS into the outer membrane. Therefore, the transport process is regulated by the outer membrane translocon causing ATP hydrolysis in the inner membrane proteoliposome to stop. Negative feedback from the outer membrane to the inner membrane provides a mechanism for long distance control over LPS transport.
Background
Cardiovascular disease is the most common cause of death globally. Traditionally, centre‐based cardiac rehabilitation programmes are offered to individuals after cardiac events to aid ...recovery and prevent further cardiac illness. Home‐based cardiac rehabilitation programmes have been introduced in an attempt to widen access and participation. This is an update of a review previously published in 2009 and 2015.
Objectives
To compare the effect of home‐based and supervised centre‐based cardiac rehabilitation on mortality and morbidity, exercise‐capacity, health‐related quality of life, and modifiable cardiac risk factors in patients with heart disease.
Search methods
We updated searches from the previous Cochrane Review by searching the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid), Embase (Ovid), PsycINFO (Ovid) and CINAHL (EBSCO) on 21 September 2016. We also searched two clinical trials registers as well as previous systematic reviews and reference lists of included studies. No language restrictions were applied.
Selection criteria
We included randomised controlled trials, including parallel group, cross‐over or quasi‐randomised designs) that compared centre‐based cardiac rehabilitation (e.g. hospital, gymnasium, sports centre) with home‐based programmes in adults with myocardial infarction, angina, heart failure or who had undergone revascularisation.
Data collection and analysis
Two review authors independently screened all identified references for inclusion based on pre‐defined inclusion criteria. Disagreements were resolved through discussion or by involving a third review author. Two authors independently extracted outcome data and study characteristics and assessed risk of bias. Quality of evidence was assessed using GRADE principles and a Summary of findings table was created.
Main results
We included six new studies (624 participants) for this update, which now includes a total of 23 trials that randomised a total of 2890 participants undergoing cardiac rehabilitation. Participants had an acute myocardial infarction, revascularisation or heart failure. A number of studies provided insufficient detail to enable assessment of potential risk of bias, in particular, details of generation and concealment of random allocation sequencing and blinding of outcome assessment were poorly reported.
No evidence of a difference was seen between home‐ and centre‐based cardiac rehabilitation in clinical primary outcomes up to 12 months of follow up: total mortality (relative risk (RR) = 1.19, 95% CI 0.65 to 2.16; participants = 1505; studies = 11/comparisons = 13; very low quality evidence), exercise capacity (standardised mean difference (SMD) = ‐0.13, 95% CI ‐0.28 to 0.02; participants = 2255; studies = 22/comparisons = 26; low quality evidence), or health‐related quality of life up to 24 months (not estimable). Trials were generally of short duration, with only three studies reporting outcomes beyond 12 months (exercise capacity: SMD 0.11, 95% CI ‐0.01 to 0.23; participants = 1074; studies = 3; moderate quality evidence). However, there was evidence of marginally higher levels of programme completion (RR 1.04, 95% CI 1.00 to 1.08; participants = 2615; studies = 22/comparisons = 26; low quality evidence) by home‐based participants.
Authors' conclusions
This update supports previous conclusions that home‐ and centre‐based forms of cardiac rehabilitation seem to be similarly effective in improving clinical and health‐related quality of life outcomes in patients after myocardial infarction or revascularisation, or with heart failure. This finding supports the continued expansion of evidence‐based, home‐based cardiac rehabilitation programmes. The choice of participating in a more traditional and supervised centre‐based programme or a home‐based programme may reflect local availability and consider the preference of the individual patient. Further data are needed to determine whether the effects of home‐ and centre‐based cardiac rehabilitation reported in the included short‐term trials can be confirmed in the longer term and need to consider adequately powered non‐inferiority or equivalence study designs.
Summary
Purpose: Given the high burden of epilepsy on both health‐related quality of life (HRQoL) and costs, identification of factors that are predictive of either reduced HRQoL or increased ...expenditure is central to the better future targeting and optimization of existing and emerging interventions and management strategies for epilepsy.
Methods: Searches of Medline, Embase, and Cochrane Library (up to July 2010) to identify studies examining the association between demographic, psychosocial, and condition‐related factors and HRQoL, resource utilization or costs in adults with epilepsy. For each study, predictor factor associations were summarized on the basis of statistical significance and direction; the results were then combined across studies.
Key Findings: Ninety‐three HRQoL and 16 resource utilization/cost studies were included. Increases in seizure frequency, seizure severity, level of depression, and level of anxiety and presence of comorbidity were strongly associated with reduced HRQoL. The majority of studies were cross‐sectional in design and had an overall methodologic quality that was judged to be “moderate” for HRQoL studies and “poor” for health care resource or costs studies. In the 53 multivariate studies, age, gender, marital status, type of seizure, age at diagnosis, and duration of epilepsy did not appear to be associated with HRQoL, whereas the predictive influence of educational and employment status, number of antiepileptic drugs (AEDs) and AED side effects was unclear. The association between predictive factors and HRQoL appeared to be consistent across individuals whether refractory or seizures controlled or managed by AEDs. There were insufficient multivariate studies (five) to reliably comment on the predictors of resource utilization or cost in epilepsy.
Significance: In addition to seizure control, effective epilepsy management requires the early detection of those most at risk of psychological dysfunction and comorbidity, and the targeting of appropriate interventions. There is need for more rigorous studies with appropriate multivariate statistical methods that prospectively investigate the predictors of HRQoL, resource utilization, and costs in epilepsy.
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