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164 result(s) for "Liddle, John"
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Emerging and Potential Trends in Public Management: An Age of Austerity
Challenging some of the established practices of public policy and administration, which have been called into question by the financial and banking crises of 2008, this title investigates public sector management and the public managers acting in the interests of civil society to get to the heart of best practice.
Structural and mechanistic basis of differentiated inhibitors of the acute pancreatitis target kynurenine-3-monooxygenase
Kynurenine-3-monooxygenase (KMO) is a key FAD-dependent enzyme of tryptophan metabolism. In animal models, KMO inhibition has shown benefit in neurodegenerative diseases such as Huntington’s and Alzheimer’s. Most recently it has been identified as a target for acute pancreatitis multiple organ dysfunction syndrome (AP-MODS); a devastating inflammatory condition with a mortality rate in excess of 20%. Here we report and dissect the molecular mechanism of action of three classes of KMO inhibitors with differentiated binding modes and kinetics. Two novel inhibitor classes trap the catalytic flavin in a previously unobserved tilting conformation. This correlates with picomolar affinities, increased residence times and an absence of the peroxide production seen with previous substrate site inhibitors. These structural and mechanistic insights culminated in GSK065(C1) and GSK366(C2), molecules suitable for preclinical evaluation. Moreover, revising the repertoire of flavin dynamics in this enzyme class offers exciting new opportunities for inhibitor design. Kynurenine-3-monooxygenase (KMO) is an emerging clinical target for treatment of neurodegenerative diseases and acute pancreatitis. Here, the authors report potent inhibitors that bind KMO in an unexpected conformation, offering structural and mechanistic insights for future drug discovery ventures.
Increased levels of 3-hydroxykynurenine parallel disease severity in human acute pancreatitis
Inhibition of kynurenine 3-monooxygenase (KMO) protects against multiple organ dysfunction (MODS) in experimental acute pancreatitis (AP). We aimed to precisely define the kynurenine pathway activation in relation to AP and AP-MODS in humans, by carrying out a prospective observational study of all persons presenting with a potential diagnosis of AP for 90 days. We sampled peripheral venous blood at 0, 3, 6, 12, 24, 48, 72 and 168 hours post-recruitment. We measured tryptophan metabolite concentrations and analysed these in the context of clinical data and disease severity indices, cytokine profiles and C-reactive protein (CRP) concentrations. 79 individuals were recruited (median age: 59.6 years; 47 males, 59.5%). 57 met the revised Atlanta definition of AP: 25 had mild, 23 moderate, and 9 severe AP. Plasma 3-hydroxykynurenine concentrations correlated with contemporaneous APACHE II scores (R 2  = 0.273; Spearman rho = 0.581; P < 0.001) and CRP (R 2  = 0.132; Spearman rho = 0.455, P < 0.001). Temporal profiling showed early tryptophan depletion and contemporaneous 3-hydroxykynurenine elevation. Furthermore, plasma concentrations of 3-hydroxykynurenine paralleled systemic inflammation and AP severity. These findings support the rationale for investigating early intervention with a KMO inhibitor, with the aim of reducing the incidence and severity of AP-associated organ dysfunction.
Mechanism for antigenic peptide selection by endoplasmic reticulum aminopeptidase 1
Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an intracellular enzyme that optimizes the peptide cargo of major histocompatibility class I (MHC-I) molecules and regulates adaptive immunity. It has unusual substrate selectivity for length and sequence, resulting in poorly understood effects on the cellular immunopeptidome. To understand substrate selection by ERAP1, we solved 2 crystal structures of the enzyme with bound transition-state pseudopeptide analogs at 1.68 Å and 1.72 Å. Both peptides have their N terminus bound at the active site and extend away along a large internal cavity, interacting with shallow pockets that can influence selectivity. The longer peptide is disordered through the central region of the cavity and has its C terminus bound in an allosteric pocket of domain IV that features a carboxypeptidase-like structural motif. These structures, along with enzymatic and computational analyses, explain how ERAP1 can select peptides based on length while retaining the broad sequence-specificity necessary for its biological function.
A selective jumonji H3K27 demethylase inhibitor modulates the proinflammatory macrophage response
A structure-guided small-molecule and chemoproteomics approach uncovers a catalytic site inhibitor selective for the jumonji subfamily of H3K27me3 demethylases; the inhibitor decreases lipopolysaccharide-induced proinflammatory cytokine production by human primary macrophages. JMJ demethylase inhibitors and inflammation Jumonji (JMJ) family histone demethylases have become recognized as key regulators of transcription, although the importance of their enzymatic activity - as opposed to their structural role - has been unclear. JMJD3 demethylases are specific for histone H3 trimethylated at Lys27 (H3K27me3) and are involved in the inflammatory response, as well as other physiological functions. Here, a structure-guided small-molecule and chemoproteomics approach is used to discover a catalytic-site inhibitor selective for the H3K27me3-specific JMJ subfamily. The inhibitor reduces lipopolysaccharide-induced pro-inflammatory cytokine production in human primary macrophages. This study demonstrates the importance of JMJ demethylase activity and suggests that small-molecule inhibitors of JMJ enzymes could have therapeutic applications. The jumonji (JMJ) family of histone demethylases are Fe 2+ - and α-ketoglutarate-dependent oxygenases that are essential components of regulatory transcriptional chromatin complexes 1 , 2 , 3 , 4 . These enzymes demethylate lysine residues in histones in a methylation-state and sequence-specific context 5 . Considerable effort has been devoted to gaining a mechanistic understanding of the roles of histone lysine demethylases in eukaryotic transcription, genome integrity and epigenetic inheritance 2 , 4 , 6 , as well as in development, physiology and disease 3 , 7 . However, because of the absence of any selective inhibitors, the relevance of the demethylase activity of JMJ enzymes in regulating cellular responses remains poorly understood. Here we present a structure-guided small-molecule and chemoproteomics approach to elucidating the functional role of the H3K27me3-specific demethylase subfamily (KDM6 subfamily members JMJD3 and UTX) 8 . The liganded structures of human and mouse JMJD3 provide novel insight into the specificity determinants for cofactor, substrate and inhibitor recognition by the KDM6 subfamily of demethylases. We exploited these structural features to generate the first small-molecule catalytic site inhibitor that is selective for the H3K27me3-specific JMJ subfamily. We demonstrate that this inhibitor binds in a novel manner and reduces lipopolysaccharide-induced proinflammatory cytokine production by human primary macrophages, a process that depends on both JMJD3 and UTX. Our results resolve the ambiguity associated with the catalytic function of H3K27-specific JMJs in regulating disease-relevant inflammatory responses and provide encouragement for designing small-molecule inhibitors to allow selective pharmacological intervention across the JMJ family.
Inhibition of PAD4 activity is sufficient to disrupt mouse and human NET formation
Inhibitors of the PAD4 enzyme that bind the inactive enzyme link this protein deiminase and the resultant arginine-to-citrulline modification to formation of neutrophil extracellular traps, highly decondensed chromatin structures with both host-defense and pathological roles. PAD4 has been strongly implicated in the pathogenesis of autoimmune, cardiovascular and oncological diseases through clinical genetics and gene disruption in mice. New selective PAD4 inhibitors binding a calcium-deficient form of the PAD4 enzyme have validated the critical enzymatic role of human and mouse PAD4 in both histone citrullination and neutrophil extracellular trap formation for, to our knowledge, the first time. The therapeutic potential of PAD4 inhibitors can now be explored.
Kynurenine-3-monooxygenase inhibition prevents multiple organ failure in rodent models of acute pancreatitis
Blocking the enzyme KMO with a small molecule reduces the levels of toxic tryptophan metabolites and reduces multiple extrapancreatic organ failure in a rat model of acute pancreatitis. Acute pancreatitis (AP) is a common and devastating inflammatory condition of the pancreas that is considered to be a paradigm of sterile inflammation leading to systemic multiple organ dysfunction syndrome (MODS) and death 1 , 2 . Acute mortality from AP-MODS exceeds 20% (ref. 3 ), and the lifespans of those who survive the initial episode are typically shorter than those of the general population 4 . There are no specific therapies available to protect individuals from AP-MODS. Here we show that kynurenine-3-monooxygenase (KMO), a key enzyme of tryptophan metabolism 5 , is central to the pathogenesis of AP-MODS. We created a mouse strain that is deficient for Kmo (encoding KMO) and that has a robust biochemical phenotype that protects against extrapancreatic tissue injury to the lung, kidney and liver in experimental AP-MODS. A medicinal chemistry strategy based on modifications of the kynurenine substrate led to the discovery of the oxazolidinone GSK180 as a potent and specific inhibitor of KMO. The binding mode of the inhibitor in the active site was confirmed by X-ray co-crystallography at 3.2 Å resolution. Treatment with GSK180 resulted in rapid changes in the levels of kynurenine pathway metabolites in vivo , and it afforded therapeutic protection against MODS in a rat model of AP. Our findings establish KMO inhibition as a novel therapeutic strategy in the treatment of AP-MODS, and they open up a new area for drug discovery in critical illness.
European Public Leadership in Crisis?
This volume questions the changing dynamics of public leadership across different European settings. Chapters highlight emergent discussions on the strengths and weaknesses of current knowledge. Authors investigate the tensions between Anglo-American and economic focused models of leadership that may challenge received wisdom.
Development of a small molecule that corrects misfolding and increases secretion of Z α1‐antitrypsin
Severe α 1 ‐antitrypsin deficiency results from the Z allele (Glu342Lys) that causes the accumulation of homopolymers of mutant α 1 ‐antitrypsin within the endoplasmic reticulum of hepatocytes in association with liver disease. We have used a DNA‐encoded chemical library to undertake a high‐throughput screen to identify small molecules that bind to, and stabilise Z α 1 ‐antitrypsin. The lead compound blocks Z α 1 ‐antitrypsin polymerisation in vitro , reduces intracellular polymerisation and increases the secretion of Z α 1 ‐antitrypsin threefold in an iPSC model of disease. Crystallographic and biophysical analyses demonstrate that GSK716 and related molecules bind to a cryptic binding pocket, negate the local effects of the Z mutation and stabilise the bound state against progression along the polymerisation pathway. Oral dosing of transgenic mice at 100 mg/kg three times a day for 20 days increased the secretion of Z α 1 ‐antitrypsin into the plasma by sevenfold. There was no observable clearance of hepatic inclusions with respect to controls over the same time period. This study provides proof of principle that “mutation ameliorating” small molecules can block the aberrant polymerisation that underlies Z α 1 ‐antitrypsin deficiency. Synopsis A chemistry campaign has developed a small molecule that stabilises the severe Z deficiency mutant of α1‐antitrypsin. The lead compound binds to a cryptic pocket and blocks the conformational change and pathological polymerisation that underlie α1‐antitrypsin deficiency. A small molecule has been developed that blocks the pathological polymerisation of the Z mutant of α1‐antitrypsin. Crystallography shows that it binds to a cryptic site and negates the local effects of the Z mutation. The lead compound has good selectivity in off‐target screening. The lead compound completely blocks polymerisation and increases the secretion of Z α1‐antitrypsin 3 fold in a cell model of disease and 7 fold in a transgenic mouse model of disease. There was no effect on hepatic inclusions following 20 days of treatment. Graphical Abstract A chemistry campaign has developed a small molecule that stabilises the severe Z deficiency mutant of α1‐antitrypsin. The lead compound binds to a cryptic pocket and blocks the conformational change and pathological polymerisation that underlie α1‐antitrypsin deficiency.
Looking for Consensus?: Civil Society, Social Movements and Crises for Public Management
This volume reflects on the global dimension of the 2008 banking and financial crisis and point to a bigger and deeper crisis of authority and legitimacy for public managers. The chapters examine key conceptual and theoretical ideas in contemporary international public management.