title: A High-Throughput Enzyme-Coupled Assay for SAMHD1 dNTPase.
abstract: Sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1) is a recently discovered enzyme that plays a central role in nucleotide metabolism and innate immunity. SAMHD1 has deoxyribonucleoside triphosphate (dNTP) triphosphohydrolase activity that depletes the dNTP substrates required for DNA synthesis in cells. The involvement of SAMHD1 in biological processes as varied as viral restriction, endogenous retroelement control, cancer, and modulation of anticancer/antiviral nucleoside drug efficacy makes it a valuable target for the development of small-molecule inhibitors. We report a high-throughput colorimetric assay for SAMHD1 dNTP hydrolase activity that takes advantage of Escherichia coli inorganic pyrophosphatase to convert PPPi to 3 Pi. The assay was validated by screening a library of 2653 clinically used compounds. Fifteen primary hits were obtained (0.57% hit rate); 80% of these were confirmed in a direct secondary assay for dNTP hydrolysis. The zinc salt of the antibiotic cephalosporin C was a potent inhibitor of SAMHD1 with an IC50 of 1.1 ± 0.1 µM, and this inhibition was largely attributable to the presence of zinc. The assay also screened a targeted library of nucleosides and their analogs, revealing that the antiviral drug acycloguanosine (acyclovir) is an inhibitor possessing excellent properties for future fragment-based drug development efforts.
authors.affiliation: Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Kyle J
authors.initials: KJ
authors.lastname: Seamon
authors.affiliation: Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA jstivers@jhmi.edu.
authors.forename: James T
authors.initials: JT
authors.lastname: Stivers
mesh_terms: D004305:Dose-Response Relationship, Drug; D055808:Drug Discovery; D004789:Enzyme Activation / Q000187:drug effects; D057075:Enzyme Assays; D004791:Enzyme Inhibitors; D057166:High-Throughput Screening Assays; D006801:Humans; D020128:Inhibitory Concentration 50; D020559:Monomeric GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011755:Pyrophosphatases / Q000378:metabolism; D015203:Reproducibility of Results; D000076106:SAM Domain and HD Domain-Containing Protein 1; D054852:Small Molecule Libraries
chemical_list: D004791:Enzyme Inhibitors; D054852:Small Molecule Libraries; D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; D011755:Pyrophosphatases; D020559:Monomeric GTP-Binding Proteins
keywords: high-throughput screening; innate immunity; nucleotide metabolism; viral restriction