Reaction hijacking inhibition of Plasmodium falciparum asparagine tRNA synthetase.

Published in: Research square Journal; Preprint 2023

DOI: 10.21203/rs.3.rs-3198291/v1

Authors: Xie, Stanley C ; Wang, Yinuo; Morton, Craig J ; Metcalfe, Riley D; Dogovski, Con; Pasaje, Charisse Flerida A ; Dunn, Elyse; Luth, Madeline R; Kumpornsin, Krittikorn; Istvan, Eva S ; Park, Joon Sung ; Fairhurst, Kate J; Ketprasit, Nutpakal ; Yeo, Tomas ; Yildirim, Okan; Bhebhe, Mathamsanqa N; Klug, Dana M; Rutledge, Peter J ; Godoy, Luiz C; Dey, Sumanta; De Souza, Mariana Laureano; Siqueira-Neto, Jair L; Du, Yawei; Puhalovich, Tanya; Amini, Mona; Shami, Gerry ; Loesbanluechai, Duangkamon; Nie, Shuai; Williamson, Nicholas ; Jana, Gouranga P (TCGLS Member); Maity, Bikash C (TCGLS Member); Thomson, Patrick ; Foley, Thomas; Tan, Derek S ; Niles, Jacquin C ; Han, Byung Woo ; Goldberg, Daniel E ; Burrows, Jeremy ; Fidock, David A ; Lee, Marcus C S; Winzeler, Elizabeth A; Griffin, Michael D W ; Todd, Matthew H ; Tilley, Leann

Abstract: Malaria poses an enormous threat to human health. With ever increasing resistance to currently deployed drugs, breakthrough compounds with novel mechanisms of action are urgently needed. Here, we explore pyrimidine-based sulfonamides as a new low molecular weight inhibitor class with drug-like physical parameters and a synthetically accessible scaffold. We show that the exemplar, OSM-S-106, has potent activity against parasite cultures, low mammalian cell toxicity and low propensity for resistance development. In vitro evolution of resistance using a slow ramp-up approach pointed to the Plasmodium falciparum cytoplasmic asparaginyl tRNA synthetase (PfAsnRS) as the target, consistent with our finding that OSM-S-106 inhibits protein translation and activates the amino acid starvation response. Targeted mass spectrometry confirms that OSM-S-106 is a pro-inhibitor and that inhibition of PfAsnRS occurs via enzyme-mediated production of an Asn-OSM-S-106 adduct. Human AsnRS is much less susceptible to this reaction hijacking mechanism. X-ray crystallographic studies of human AsnRS in complex with inhibitor adducts and docking of pro-inhibitors into a model of Asn-tRNA-bound PfAsnRS provide insights into the structure activity relationship and the selectivity mechanism.