Pegan SD

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Full name : Pegan Scott D

First name : Scott D

Mail : Department of Pharmaceutical and Biomedical Sciences, University of California, Riverside

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Country : USA

Email : scott.pegan@ucr.edu

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References (7)

Title : Structural and Biochemical Insights into the Inhibition of Human Acetylcholinesterase by G-Series Nerve Agents and Subsequent Reactivation by HI-6 - McGuire_2021_Chem.Res.Toxicol_34_804
Author(s) : McGuire JR , Bester SM , Guelta MA , Cheung J , Langley C , Winemiller MD , Bae SY , Funk V , Myslinski JM , Pegan SD , Height JJ
Ref : Chemical Research in Toxicology , 34 :804 , 2021
Abstract : The recent use of organophosphate nerve agents in Syria, Malaysia, Russia, and the United Kingdom has reinforced the potential threat of their intentional release. These agents act through their ability to inhibit human acetylcholinesterase (hAChE; E.C. 3.1.1.7), an enzyme vital for survival. The toxicity of hAChE inhibition via G-series nerve agents has been demonstrated to vary widely depending on the G-agent used. To gain insight into this issue, the structures of hAChE inhibited by tabun, sarin, cyclosarin, soman, and GP were obtained along with the inhibition kinetics for these agents. Through this information, the role of hAChE active site plasticity in agent selectivity is revealed. With reports indicating that the efficacy of reactivators can vary based on the nerve agent inhibiting hAChE, human recombinatorially expressed hAChE was utilized to define these variations for HI-6 among various G-agents. To identify the structural underpinnings of this phenomenon, the structures of tabun, sarin, and soman-inhibited hAChE in complex with HI-6 were determined. This revealed how the presence of G-agent adducts impacts reactivator access and placement within the active site. These insights will contribute toward a path of next-generation reactivators and an improved understanding of the innate issues with the current reactivators.
ESTHER : McGuire_2021_Chem.Res.Toxicol_34_804
PubMedSearch : McGuire_2021_Chem.Res.Toxicol_34_804
PubMedID: 33538594
Gene_locus related to this paper: human-ACHE

Title : ISG15: It's Complicated - Dzimianski_2019_J.Mol.Biol_431_4203
Author(s) : Dzimianski JV , Scholte FEM , Bergeron E , Pegan SD
Ref : Journal of Molecular Biology , 431 :4203 , 2019
Abstract : Interferon-stimulated gene product 15 (ISG15) is a key component of host responses to microbial infection. Despite having been known for four decades, grasping the functions and features of ISG15 has been a slow and elusive process. Substantial work over the past two decades has greatly enhanced this understanding, revealing the complex and variable nature of this protein. This has unveiled multiple mechanisms of action that are only now beginning to be understood. In addition, it has uncovered diversity not only between how ISG15 affects different pathogens but also between the function and structure of ISG15 itself between different host species. Here we review the complexity of ISG15 within the context of viral infection, focusing primarily on its antiviral function and the mechanisms viruses employ to thwart its effects. We highlight what is known regarding the impact of ISG15 sequence and structural diversity on these interactions and discuss the aspects presenting the next frontier toward elucidating a more complete picture of ISG15 function.
ESTHER : Dzimianski_2019_J.Mol.Biol_431_4203
PubMedSearch : Dzimianski_2019_J.Mol.Biol_431_4203
PubMedID: 30890331

Title : The structural and biochemical impacts of monomerizing human acetylcholinesterase - Bester_2019_Protein.Sci_28_1106
Author(s) : Bester SM , Adipietro KA , Funk VL , Myslinski JM , Keul ND , Cheung J , Wilder PT , Wood ZA , Weber DJ , Height JJ , Pegan SD
Ref : Protein Science , 28 :1106 , 2019
Abstract : Serving a critical role in neurotransmission, human acetylcholinesterase (hAChE) is the target of organophosphate nerve agents. Hence, there is an active interest in studying the mechanism of inhibition and recovery of enzymatic activity, which could lead to better countermeasures against nerve agents. As hAChE is found in different oligomeric assemblies, certain approaches to studying it have been problematic. Herein, we examine the biochemical and structural impact of monomerizing hAChE by using two mutations: L380R/F535K. The activities of monomeric hAChE L380R/F535K and dimeric hAChE were determined to be comparable utilizing a modified Ellman's assay. To investigate the influence of subunit-subunit interactions on the structure of hAChE, a 2.1 A X-ray crystallographic structure was determined. Apart from minor shifts along the dimer interface, the overall structure of the hAChE L380R/F535K mutant is similar to that of dimeric hAChE. To probe whether the plasticity of the active site was overtly impacted by monomerizing hAChE, the kinetic constants of (PR/S ) - VX (ethyl({2-[bis(propan-2-yl)amino]ethyl}sulfanyl)(methyl)phosphinate) inhibition and subsequent rescue of hAChE L380R/F535K activity with HI-6 (1-(2'-hydroxyiminomethyl-1'-pyridinium)-3-(4'-carbamoyl-1-pyridinium)) were determined and found to be comparable to those of dimeric hAChE. Thus, hAChE L380R/F535K could be used as a substitute for dimeric hAChE when experimentally probing the ability of the hAChE active site to accommodate future nerve agent threats or judge the ability of new therapeutics to access the active site.
ESTHER : Bester_2019_Protein.Sci_28_1106
PubMedSearch : Bester_2019_Protein.Sci_28_1106
PubMedID: 30993792
Gene_locus related to this paper: human-ACHE

Title : Synthesis and Molecular Properties of Nerve Agent Reactivator HLo-7 Dimethanesulfonate - Hsu_2019_ACS.Med.Chem.Lett_10_761
Author(s) : Hsu FL , Bae SY , McGuire J , Anderson DR , Bester SM , Height JJ , Pegan SD , Walz AJ
Ref : ACS Med Chem Lett , 10 :761 , 2019
Abstract : The threat of a deliberate release of chemical nerve agents has underscored the need to continually improve field effective treatments for these types of poisonings. The oxime containing HLo-7 is a potential second-generation therapeutic reactivator. A synthetic process for HLo-7 is detailed with improvements to the DIBAL reduction and ion exchange steps. HLo-7 was visualized for the first time within the active site of human acetylcholinesterase and its relative ex vivo potency confirmed against various nerve agents using a phrenic nerve hemidiaphragm assay.
ESTHER : Hsu_2019_ACS.Med.Chem.Lett_10_761
PubMedSearch : Hsu_2019_ACS.Med.Chem.Lett_10_761
PubMedID: 31097996
Gene_locus related to this paper: human-ACHE

Title : Structural Insights of Stereospecific Inhibition of Human Acetylcholinesterase by VX and Subsequent Reactivation by HI-6 - Bester_2018_Chem.Res.Toxicol_31_1405
Author(s) : Bester SM , Guelta MA , Cheung J , Winemiller MD , Bae SY , Myslinski J , Pegan SD , Height JJ
Ref : Chemical Research in Toxicology , 31 :1405 , 2018
Abstract : Over 50 years ago, the toxicity of irreversible organophosphate inhibitors targeting human acetylcholinesterase (hAChE) was observed to be stereospecific. The therapeutic reversal of hAChE inhibition by reactivators has also been shown to depend on the stereochemistry of the inhibitor. To gain clarity on the mechanism of stereospecific inhibition, the X-ray crystallographic structures of hAChE inhibited by a racemic mixture of VX (P R/S) and its enantiomers were obtained. Beyond identifying hAChE structural features that lend themselves to stereospecific inhibition, structures of the reactivator HI-6 bound to hAChE inhibited by VX enantiomers of varying toxicity, or in its uninhibited state, were obtained. Comparison of hAChE in these pre-reactivation and post-reactivation states along with enzymatic data reveals the potential influence of unproductive reactivator poses on the efficacy of these types of therapeutics. The recognition of structural features related to hAChE's stereospecificity toward VX shed light on the molecular influences of toxicity and their effect on reactivators. In addition to providing a better understanding of the innate issues with current reactivators, an avenue for improvement of reactivators is envisioned.
ESTHER : Bester_2018_Chem.Res.Toxicol_31_1405
PubMedSearch : Bester_2018_Chem.Res.Toxicol_31_1405
PubMedID: 30462502
Gene_locus related to this paper: human-ACHE

Title : Engineering the Organophosphorus Acid Anhydrolase Enzyme for Increased Catalytic Efficiency and Broadened Stereospecificity on Russian VX - Daczkowski_2015_Biochemistry_54_6423
Author(s) : Daczkowski CM , Pegan SD , Harvey SP
Ref : Biochemistry , 54 :6423 , 2015
Abstract : The enzyme organophosphorus acid anhydrolase (OPAA), from Alteromonas sp. JD6.5, has been shown to rapidly catalyze the hydrolysis of a number of toxic organophosphorus compounds, including several G-type chemical nerve agents. The enzyme was cloned into Escherichia coli and can be produced up to approximately 50% of cellular protein. There have been no previous reports of OPAA activity on VR {Russian VX, O-isobutyl S-[2-(diethylamino)ethyl] methylphosphonothioate}, and our studies reported here show that wild-type OPAA has poor catalytic efficacy toward VR. However, via application of a structurally aided protein engineering approach, significant improvements in catalytic efficiency were realized via optimization of the small pocket within the OPAA's substrate-binding site. This optimization involved alterations at only three amino acid sites resulting in a 30-fold increase in catalytic efficiency toward racemic VR, with a strong stereospecificity toward the P(+) enantiomer. X-ray structures of this mutant as well as one of its predecessors provide potential structural rationales for their effect on the OPAA active site. Additionally, a fourth mutation at a site near the small pocket was found to relax the stereospecificity of the OPAA enzyme. Thus, it allows the altered enzyme to effectively process both VR enantiomers and should be a useful genetic background in which to seek further improvements in OPAA VR activity.
ESTHER : Daczkowski_2015_Biochemistry_54_6423
PubMedSearch : Daczkowski_2015_Biochemistry_54_6423
PubMedID: 26418828

Title : Development and validation of a yeast high-throughput screen for inhibitors of Abeta oligomerization - Park_2011_Dis.Model.Mech_4_822
Author(s) : Park SK , Pegan SD , Mesecar AD , Jungbauer LM , LaDu MJ , Liebman SW
Ref : Dis Model Mech , 4 :822 , 2011
Abstract : Recent reports point to small soluble oligomers, rather than insoluble fibrils, of amyloid beta (Abeta), as the primary toxic species in Alzheimer's disease. Previously, we developed a low-throughput assay in yeast that is capable of detecting small Abeta(42) oligomer formation. Specifically, Abeta(42) fused to the functional release factor domain of yeast translational termination factor, Sup35p, formed sodium dodecyl sulfate (SDS)-stable low-n oligomers in living yeast, which impaired release factor activity. As a result, the assay for oligomer formation uses yeast growth to indicate restored release factor activity and presumably reduced oligomer formation. We now describe our translation of this assay into a high-throughput screen (HTS) for anti-oligomeric compounds. By doing so, we also identified two presumptive anti-oligomeric compounds from a sub-library of 12,800 drug-like small molecules. Subsequent biochemical analysis confirmed their anti-oligomeric activity, suggesting that this form of HTS is an efficient, sensitive and cost-effective approach to identify new inhibitors of Abeta(42) oligomerization.
ESTHER : Park_2011_Dis.Model.Mech_4_822
PubMedSearch : Park_2011_Dis.Model.Mech_4_822
PubMedID: 21810907