The antimalarial drug target PfATP4 and effects of its inhibition at the intersection of life and death in Plasmodium falciparum

Aarti Atmaram Ramanathan

doi:10.17918/00000872

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The antimalarial drug target PfATP4 and effects of its inhibition at the intersection of life and death in Plasmodium falciparum

Dissertation

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The antimalarial drug target PfATP4 and effects of its inhibition at the intersection of life and death in Plasmodium falciparum

Aarti Atmaram Ramanathan

Doctor of Philosophy (Ph.D.), Drexel University

Apr 2020

DOI:

https://doi.org/10.17918/00000872

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Abstract

Oligomerization

Plasmodium falciparum

Antimalarials

Malaria

Microbiology

Plasmodium falciparum P-type Na⁺ /H⁺ ATPase (PfATP4) is a novel antimalarial drug target that is crucial for maintaining low [Na⁺]_i in malaria parasites during the intraerythrocytic cycle. Drugs targeting PfATP4 cause disruption of Na⁺ homeostasis within the parasite, a consequence that leads to parasite death and rapid in vivo clearance. Here we showed that PfATP4 exists as a large complex. Immuno-pulldown and proteomic analyses revealed that PfATP4 assembles co-translationally into homo-oligomeric complexes. PfATP4 forms a distinct class within P-type ATPases having fewer transmembrane (TM) helices compared to their orthologues. We hypothesized that reduced TM helices might necessitate oligomerization for its function. We predicted pi-pi interactions between aromatic amino acids in the last helix to be critical for oligomerization. By using merodiploid parasite lines expressing wildtype or mutant PfATP4 genes at an ectopic locus, in which endogenous copy is conditionally expressed, we showed that, unlike the wildtype, parasites expressing mutant PfATP4 were unable to oligomerize and complement the knockdown of endogenous PfATP4 causing parasite demise. To understand signaling events that lead to parasite demise upon Na⁺ homeostasis disruption, we carried out phosphoproteomic analysis of parasites treated with PfATP4-active drugs. This revealed massive dephosphorylation of parasite proteins upon drug treatment. One of the most significant modifications was of A TP-dependent phosphofructokinase (PfPFK). Further, analyses reveal enrichment in pathways related to cell cycle progression such as DNA replication, repair, microtubule-organization, chromosome segregation and mRNA metabolism. Having previously shown that PfATP4-active drugs trigger premature schizogony, these data lead us to propose a metabolic-collapse to be a physiological requisite preceding schizogony.

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Title: The antimalarial drug target PfATP4 and effects of its inhibition at the intersection of life and death in Plasmodium falciparum
Creators: Aarti Atmaram Ramanathan
Contributors: Akhil B. Vaidya (Advisor)
Awarding Institution: Drexel University
Degree Awarded: Doctor of Philosophy (Ph.D.)
Publisher: Drexel University; Philadelphia, Pennsylvania
Number of pages: 202 pages
Resource Type: Dissertation
Language: English
Academic Unit: Microbiology and Immunology; College of Medicine; Drexel University
Other Identifier: 991016814282304721

The antimalarial drug target PfATP4 and effects of its inhibition at the intersection of life and death in Plasmodium falciparum

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