Functional characterization of three putative serpentine receptor proteins SR10, SR12 and 7 helix 2 important for the proliferation of asexual and sexual blood stages of the human malaria parasite Plasmodium falciparum

Njila Tchoufack, Emilie Joëlle; Pradel, Gabriele (Thesis advisor); Huber, Michael (Thesis advisor); van Dongen, Joost Thomas (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021

Abstract

Serpentine receptors (SRs) are components of the cell integral membrane proteins that can bind to a wide range of ligands. SRs are well known to mediate the communication within a cell and its external environment. Many SRs bind to the heterotrimeric G protein in an activation dependent manner; therefore, they are referred to as G-protein-coupled receptors. Although the putative SRs were identified in the genome of the malaria parasite P. falciparum; the agent responsible for the deadliest form of malaria, most of the functions of these proteins are still unknown.The present work aim was to functionally characterize putative serpentine receptors of P.falciparum named PfSR10, PfSR12 and Pf7 helix 2. The expression and localization of these three proteins of interest were investigated immunochemically using reverse transcription polymerase chain reaction and generated polyclonal mouse antisera directed against the three proteins. Additionally, parasite lines expressing PfSR10 tagged with hemagglutinin were generated. To determine the potential role of the three proteins in P. falciparum, their genes were disrupted using reverse genetic knock-out and the selective linked integration targeted gene disruption system. The knock-out parasite lines were then used for phenotypic characterization of the asexual and sexual development of the parasites in vitro.The combined data show that the three putative SRs studied during this work are localized intracellularly in vesicles. PfSR10 and PfSR12 were expressed in both asexual and sexual blood-stage parasites while Pf7 helix 2 was expressed in gametocytes only. Additionally, co-immunoprecipitation assays demonstrated that PfSR10 interacts with the endoplasmic reticulum calcium-binding protein PfERC. The loss of PfSR0 showed a defect in the asexual blood-stage and gametocyte development. Additionally, the loss of PfSR10 revealed a defect in the synthesis of the sexual stage-specific proteins PfCCps in mature gametocytes. The loss of Pf7 helix 2 demonstrated a defect in mature gametocytes development.This dissertation is the first research on the characterization of PfSR10, PfSR12 and Pf7 helix2. Putative SRs characterized during this dissertation could contribute to characterize other PfSRs proteins and are a promising candidate for the development of novel antimalarial drugs.