Substrates and Inhibitors of SAMHD1

• Authors: Joseph A. Hollenbaugh, Emory University; Jadd Shelton, Emory University; Sijia Tao, Emory University; Sheida Amiralaei, Emory University; Peng Liu, Emory University; Xiao Lu, Emory University; Russell W. Goetze, Emory University; Longhu Zhou, Emory University; James Nettles, Emory University; Raymond Schinazi, Emory University; Baek Kim, Emory University
• Journal Title: PLoS ONE
• Volume: Volume 12, Number 1
• Publisher: Public Library of Science | 2017-01-03, Pages e0169052-e0169052
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pone.0169052
• Subjects: Chemistry, Pharmaceutical; Health Sciences, Pharmacology
• Keywords: Science & Technology; Multidisciplinary Sciences; Hydrolysis; Nucleosides; Thin-layer chromatography; High performance liquid chromatography; Arabinose; Nucleotides; Biochemical analysis; Cancer treatment

Abstract

SAMHD1 hydrolyzes 2′-deoxynucleoside-5′-triphosphates (dNTPs) into 2′-deoxynucleosides and inorganic triphosphate products. In this paper, we evaluated the impact of 2′ sugar moiety substitution for different nucleotides on being substrates for SAMHD1 and mechanisms of actions for the results. We found that dNTPs ((2′R)-2′-H) are only permissive in the catalytic site of SAMHD1 due to L150 exclusion of (2′R)-2′-F and (2′R)-2′-OH nucleotides. However, arabinose ((2′S)-2′-OH) nucleoside-5′-triphosphates analogs are permissive to bind in the catalytic site and be hydrolyzed by SAMHD1. Moreover, when the (2′S)-2′ sugar moiety is increased to a (2′S)-2′-methyl as with the SMDU-TP analog, we detect inhibition of SAMHD1's dNTPase activity. Our computational modeling suggests that (2′S)-2′-methyl sugar moiety clashing with the Y374 of SAMHD1. We speculate that SMDU-TP mechanism of action requires that the analog first docks in the catalytic pocket of SAMHD1 but prevents the A351-V378 helix conformational change from being completed, which is needed before hydrolysis can occur. Collectively we have identified stereoselective 2′ substitutions that reveal nucleotide substrate specificity for SAMHD1, and a novel inhibitory mechanism for the dNTPase activity of SAMHD1. Importantly, our data is beneficial for understanding if FDA-approved antiviral and anticancer nucleosides are hydrolyzed by SAMHD1 in vivo.