title: Discovery of an inhibitor of Z-alpha1 antitrypsin polymerization.
abstract: Polymerization of the Z variant alpha-1-antitrypsin (Z-α1AT) results in the most common and severe form of α1AT deficiency (α1ATD), a debilitating genetic disorder whose clinical manifestations range from asymptomatic to fatal liver and/or lung disease. As the altered conformation of Z-α1AT and its attendant aggregation are responsible for pathogenesis, the polymerization process per se has become a major target for the development of therapeutics. Based on the ability of Z-α1AT to aggregate by recruiting the reactive center loop (RCL) of another Z-α1AT into its s4A cavity, we developed a high-throughput screening assay that uses a modified 6-mer peptide mimicking the RCL to screen for inhibitors of Z-α1AT polymer growth. A subset of compounds from the Library of Pharmacologically Active Compounds (LOPAC) with molecular weights ranging from 300 to 700 Da, was used to evaluate the assay's capabilities. The inhibitor S-(4-nitrobenzyl)-6-thioguanosine was identified as a lead compound and its ability to prevent Z-α1AT polymerization confirmed by secondary assays. To further investigate the binding location of S-(4-nitrobenzyl)-6-thioguanosine, an in silico strategy was pursued and the intermediate α1AT M* state modeled to allow molecular docking simulations and explore various potential binding sites. Docking results predict that S-(4-nitrobenzyl)-6-thioguanosine can bind at the s4A cavity and at the edge of β-sheet A. The former binding site would directly block RCL insertion whereas the latter site would prevent β-sheet A from expanding between s3A/s5A, and thus indirectly impede RCL insertion. Altogether, our investigations have revealed a novel compound that inhibits the formation of Z-α1AT polymers, as well as in vitro and in silico strategies for identifying and characterizing additional blocking molecules of Z-α1AT polymerization.
authors.affiliation: Department of Medicine, University of Tennessee Health Science Center-Graduate School of Medicine, Knoxville, Tennessee, United States of America; UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Valerie
authors.initials: V
authors.lastname: Berthelier
authors.affiliation: UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee, United States of America; UT-ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America.
authors.forename: Jason Brett
authors.initials: JB
authors.lastname: Harris
authors.affiliation: Department of Medicine, University of Tennessee Health Science Center-Graduate School of Medicine, Knoxville, Tennessee, United States of America; UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Kasey Noel
authors.initials: KN
authors.lastname: Estenson
authors.affiliation: UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee, United States of America; Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America; UT-ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America.
authors.forename: Jerome
authors.initials: J
authors.lastname: Baudry
mesh_terms: D001665:Binding Sites; D055808:Drug Discovery; D006151:Guanosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D057166:High-Throughput Screening Assays; D006801:Humans; D020128:Inhibitory Concentration 50; D008958:Models, Molecular; D015394:Molecular Structure; D066263:Protein Aggregation, Pathological / Q000188:drug therapy / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization / Q000187:drug effects*; D054852:Small Molecule Libraries; D013872:Thionucleosides / Q000737:chemistry / Q000494:pharmacology; D000515:alpha 1-Antitrypsin / Q000737:chemistry* / Q000235:genetics; D019896:alpha 1-Antitrypsin Deficiency / Q000188:drug therapy / Q000235:genetics
chemical_list: D054852:Small Molecule Libraries; D013872:Thionucleosides; D000515:alpha 1-Antitrypsin; D006151:Guanosine; C005783:6-thioguanosine