GLP-1 receptor agonists for Parkinson's disease (Review)

Background Parkinson's disease (PD) is a progressive disorder characterised by both motor and non-motor problems. Glucagon-like peptide-1 (GLP-1) receptor agonists, licensed fortreatment oftype 2 diabetes, work by stimulating GLP-1 receptors in the pancreas, which triggers the release of insulin. GLP-1 receptors have been found in the brain. Insulin signalling in the brain plays a key role in neuronal metabolism and repair and in synaptic eEicacy, but insulin signalling is desensitised in the brain of people with PD. Researchers are exploring the neuroprotective effects of GLP-1 receptor agonists in neurodegenerative disorders such as PD. Objectives To evaluate the eEectiveness and safety of GLP-1 receptor agonists for Parkinson's disease. Search methods We searched the Cochrane Movement Disorders Group trials register; the Cochrane Central Register of Controlled Trials (CENTRAL), in the Cochrane Library; and Ovid MEDLINE and Embase. We also searched clinical trials registries, and we handsearched conference abstracts. The most recent search was run on 25 June 2020. Selection criteria We included randomised controlled trials (RCTs) of adults with PD that compared GLP-1 receptor agonists with conventional PD treatment, placebo, or no treatment. Data collection and analysis Two reviewauthors independently assessed studies forinclusion, extracted data, and assessed risk of bias.We rated the quality of evidence using GRADE. We resolved discrepancies between the two data extractors by consultation with a third review author. Main results Through our searches, we retrieved 99 unique records, of which two met ourinclusion criteria. One double-blind study of exenatide versus placebo randomised 62 participants, who self-administered exenatide or placebo for 48 weeks and were followed up at 60 weeks after a 12-week washout. One single-blind study of exenatide versus no additional treatment randomised 45 participants; participants in the intervention group self-administered exenatide for 12 months, and all participants were followed up at 14 months and 24 months following absence of exenatide for 2 months and 12 months, respectively. These trials had low risk of bias, except risk of performance bias was high for Aviles-Olmos 2013. Exenatide versus placebo Primary outcomes We found low-certainty evidence suggesting that exenatide improves motor impairment as assessed by the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III in the oE-medication state (mean difference (MD) -3.10, 95% confidence interval (CI) -6.11 to -0.09). The diEerence in scores was slightly greater when scores were adjusted for baseline severity of the condition (as reported by study authors) (MD -3.5, 95% CI -6.7 to -0.3), exceeding the minimum clinically important difference (MCID). We found low-certainty evidence suggesting that exenatide has little or no eEect on health-related quality of life (HRQoL) as assessed by the Parkinson's Disease Questionnaire (PDQ)-39 Summary Index (SI) (MD -1.80, 95% CI -6.95 to 3.35), the EuroQol scale measuring health status in five dimensions (EQ5D) (MD 0.07, 95% CI -0.03 to 0.16), or the EQ5D visual analogue scale (VAS) (MD 5.00, 95% CI -3.42 to 13.42). Eight serious adverse events (SAEs) were recorded, but all were considered unrelated to the intervention. Low-certainty evidence suggests that exenatide has little or no effect on weight loss (risk ratio (RR) 1.25, 95% CI 0.89 to 1.76). Exenatide versus no treatment Primary outcomes at 14 months We found very low-certainty evidence suggesting that exenatide improves motor impairment as assessed by MDS-UPDRS Part III off medication (MD -4.50, 95% CI -8.64 to -0.36), exceeding the MCID. We are uncertain whether exenatide improves HRQoL as assessed by the PDQ-39 SI (MD 3.50, 95% CI -2.75 to 9.75; very low-quality evidence). We found very low-certainty evidence suggesting that exenatide has little or no eEect on the number of SAEs (RR 1.60, 95% 0.40 to 6.32). We found very low-certainty evidence suggesting that exenatide may lead to weight loss (MD -2.40 kg, 95% CI -4.56 to -0.24). Primary outcomes at 24 months We found evidence as reported by study authors to suggest that exenatide improves motor impairment as measured by MDS-UPDRS Part III off medication (MD 5.6 points, 95% CI 2.2 to 9.0). Exenatide may not improve HRQoL as assessed by the PDQ-39 SI (P = 0.682) and may not result in weight loss (MD 0.1 kg, 95% CI 3.0 to 2.8). Authors' conclusions Low- or very low-certainty evidence suggests that exenatide may improve motor impairment for people with PD. The difference in motor impairment observed between groups may persistfor some time following cessation of exenatide. This raises the possibility that exenatide may have a disease-modifying eEect. SAEs were unlikely to be related to treatment. The eEectiveness of exenatide for improving HRQoL, non-motor outcomes, ADLs, and psychological outcomes is unclear. Ongoing studies are assessing other GLP-1 receptor agonists

The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle

We have prepared and studied a family of cyanobiphenyl dimers with varying linking groups with a view to exploring how molecular structure dictates the stability of the nematic and twist-bend nematic mesophases. Using molecular modelling and 1D (1)H NOESY NMR spectroscopy, we determine the angle between the two aromatic core units for each dimer and find a strong dependency of the stability of both the nematic and twist-bend mesophases upon this angle, thereby satisfying earlier theoretical models

Structural and biochemical characterization of the exopolysaccharide deacetylase Agd3 required for Aspergillus fumigatus biofilm formation

The exopolysaccharide galactosaminogalactan (GAG) is an important virulence factor of the fungal pathogen Aspergillus fumigatus. Deletion of a gene encoding a putative deacetylase, Agd3, leads to defects in GAG deacetylation, biofilm formation, and virulence. Here, we show that Agd3 deacetylates GAG in a metal-dependent manner, and is the founding member of carbohydrate esterase family CE18. The active site is formed by four catalytic motifs that are essential for activity. The structure of Agd3 includes an elongated substrate-binding cleft formed by a carbohydrate binding module (CBM) that is the founding member of CBM family 87. Agd3 homologues are encoded in previously unidentified putative bacterial exopolysaccharide biosynthetic operons and in other fungal genomes. The exopolysaccharide galactosaminogalactan (GAG) is an important virulence factor of the fungal pathogen Aspergillus fumigatus. Here, the authors study an A. fumigatus enzyme that deacetylates GAG in a metal-dependent manner and constitutes a founding member of a new carbohydrate esterase family.Bio-organic Synthesi

Structural Basis for GTP-Dependent Dimerization of Hydrogenase Maturation Factor HypB

Maturation of [NiFe]-hydrogenase requires the insertion of iron, cyanide and carbon monoxide, followed by nickel, to the catalytic core of the enzyme. Hydrogenase maturation factor HypB is a metal-binding GTPase that is essential for the nickel delivery to the hydrogenase. Here we report the crystal structure of Archeoglobus fulgidus HypB (AfHypB) in apo-form. We showed that AfHypB recognizes guanine nucleotide using Asp-194 on the G5 loop despite having a non-canonical NKxA G4-motif. Structural comparison with the GTPγS-bound Methanocaldococcus jannaschii HypB identifies conformational changes in the switch I region, which bring an invariant Asp-72 to form an intermolecular salt-bridge with another invariant residue Lys-148 upon GTP binding. Substitution of K148A abolished GTP-dependent dimerization of AfHypB, but had no significant effect on the guanine nucleotide binding and on the intrinsic GTPase activity. In vivo complementation study in Escherichia coli showed that the invariant lysine residue is required for in vivo maturation of hydrogenase. Taken together, our results suggest that GTP-dependent dimerization of HypB is essential for hydrogenase maturation. It is likely that a nickel ion is loaded to an extra metal binding site at the dimeric interface of GTP-bound HypB and transferred to the hydrogenase upon GTP hydrolysis

Active Site Conformational Dynamics in Human Uridine Phosphorylase 1

Uridine phosphorylase (UPP) is a central enzyme in the pyrimidine salvage pathway, catalyzing the reversible phosphorolysis of uridine to uracil and ribose-1-phosphate. Human UPP activity has been a focus of cancer research due to its role in activating fluoropyrimidine nucleoside chemotherapeutic agents such as 5-fluorouracil (5-FU) and capecitabine. Additionally, specific molecular inhibitors of this enzyme have been found to raise endogenous uridine concentrations, which can produce a cytoprotective effect on normal tissues exposed to these drugs. Here we report the structure of hUPP1 bound to 5-FU at 2.3 Å resolution. Analysis of this structure reveals new insights as to the conformational motions the enzyme undergoes in the course of substrate binding and catalysis. The dimeric enzyme is capable of a large hinge motion between its two domains, facilitating ligand exchange and explaining observed cooperativity between the two active sites in binding phosphate-bearing substrates. Further, a loop toward the back end of the uracil binding pocket is shown to flexibly adjust to the varying chemistry of different compounds through an “induced-fit” association mechanism that was not observed in earlier hUPP1 structures. The details surrounding these dynamic aspects of hUPP1 structure and function provide unexplored avenues to develop novel inhibitors of this protein with improved specificity and increased affinity. Given the recent emergence of new roles for uridine as a neuron protective compound in ischemia and degenerative diseases, such as Alzheimer's and Parkinson's, inhibitors of hUPP1 with greater efficacy, which are able to boost cellular uridine levels without adverse side-effects, may have a wide range of therapeutic applications

5-Formylcytosine alters the structure of the DNA double helix.

The modified base 5-formylcytosine (5fC) was recently identified in mammalian DNA and might be considered to be the 'seventh' base of the genome. This nucleotide has been implicated in active demethylation mediated by the base excision repair enzyme thymine DNA glycosylase. Genomics and proteomics studies have suggested an additional role for 5fC in transcription regulation through chromatin remodeling. Here we propose that 5fC might affect these processes through its effect on DNA conformation. Biophysical and structural analysis revealed that 5fC alters the structure of the DNA double helix and leads to a conformation unique among known DNA structures including those comprising other cytosine modifications. The 1.4-Å-resolution X-ray crystal structure of a DNA dodecamer comprising three 5fCpG sites shows how 5fC changes the geometry of the grooves and base pairs associated with the modified base, leading to helical underwinding.E.-A.R. is supported as a Herchel Smith Fellow. The Balasubramanian laboratory is supported by a Senior Investigator Award from the Wellcome Trust (099232/Z/12/Z to S.B.), and it also receives core funding from Cancer Research UK (C9681/A11961 to S.B.). D.Y.C. is supported by the Crystallographic X-ray Facility (CXF) at the Department of Biochemistry, University of Cambridge, and B.F.L. is supported by the Wellcome Trust (076846/Z/05/A to B.F.L.). We thank the staff of Soleil and Diamond Light Source for use of facilities. We thank C. Calladine for stimulating discussions.This is the accepted manuscript for a paper published in Nature Structural & Molecular Biology 22, 44–49 (2015) doi: 10.1038/nsmb.293

Novel sialic acid derivatives lock open the 150-loop of an influenza A virus group-1 sialidase

Influenza virus sialidase has an essential role in the virus' life cycle. Two distinct groups of influenza A virus sialidases have been established, that differ in the flexibility of the '150-loop', providing a more open active site in the apo form of the group-1 compared to group-2 enzymes. In this study we show, through a multidisciplinary approach, that novel sialic acid-based derivatives can exploit this structural difference and selectively inhibit the activity of group-1 sialidases. We also demonstrate that group-1 sialidases from drug-resistant mutant influenza viruses are sensitive to these designed compounds. Moreover, we have determined, by protein X-ray crystallography, that these inhibitors lock open the group-1 sialidase flexible 150-loop, in agreement with our molecular modelling prediction. This is the first direct proof that compounds may be developed to selectively target the pandemic A/H1N1, avian A/H5N1 and other group-1 sialidase-containing viruses, based on an open 150-loop conformation of the enzyme

Structural and electronic determinants of lytic polysaccharide monooxygenase reactivity on polysaccharide substrates

Lytic polysaccharide monooxygenases (LPMOs) are industrially important copper-dependent enzymes that oxidatively cleave polysaccharides. Here we present a functional and structural characterization of two closely related AA9-family LPMOs from Lentinus similis (LsAA9A) and Collariella virescens (CvAA9A). LsAA9A and CvAA9A cleave a range of polysaccharides, including cellulose, xyloglucan, mixed-linkage glucan and glucomannan. LsAA9A additionally cleaves isolated xylan substrates. The structures of CvAA9A and of LsAA9A bound to cellulosic and non-cellulosic oligosaccharides provide insight into the molecular determinants of their specificity. Spectroscopic measurements reveal differences in copper co-ordination upon the binding of xylan and glucans. LsAA9A activity is less sensitive to the reducing agent potential when cleaving xylan, suggesting that distinct catalytic mechanisms exist for xylan and glucan cleavage. Overall, these data show that AA9 LPMOs can display different apparent substrate specificities dependent upon both productive protein–carbohydrate interactions across a binding surface and also electronic considerations at the copper active site