Title : Identification of novel P. falciparum Kelch13 (PfK13) interacting partners via coimmunoprecipitation (co-IP)
Malaria remains a global health issue affecting half of the world's population. The current treatment regimen which includes artemisinin and other combination therapies is being threatened with the rapid emergence of resistance. P. falciparum under drug pressure has revealed insights into mechanisms of resistance most commonly used antimalarials, such as Chloroquine, Amodiaquine, Piperaquine, DHFR inhibitors etc. There are currently no alternative drugs available to replace Artemisinin should render it obsolete. ART resistance has been shown to be mediated by the Plasmodium Kelch13 (PfK13) protein. Pf kelch 13 gene is situated in chromosome 13 and associated with ART resistance, owing to the association of majority of mutations at the kelch BTB/POZ & propeller domain. The present study recombinantly expressed the PfK13-p (BTB/POZ & propeller domain) and ge nerated anti-PfK13-p antibodies for cellular localization and co-immunoprecipitation (co-I P) assays and mass spectroscopy was performed to identify the PfK13 interacting partners. Unique coimmunoprecipitated proteins were identified barring few proteins overlapping with previous studies- Protein disulfide isomerase, heat shock proteins, merozoite surface protei n 1 (MSP1), L-lactate dehydrogenase, elongation factor 1-alpha. The unique hits of the s tudy were- falcilysin, enolase, phosphoethanolamine N-methyltransferase, glideosome-asso ciated protein 50, fructose-bisphosphate aldolase, adenylate kinase, peptidyl-prolyl cis-tra ns isomerase, thioredoxin-related protein, putative, 20 kDa chaperonin, ornithine aminotra nsferase, rhoptry-associated protein 1. The identified proteins were categorized into protein folding, protein binding/invasion, cellular metabolism and mobility functions. Further, bioinformatics proteins identified by the STRING database represent the PfK13 protein and the respective potential interactors or performing shared functions are shown in network. The minimum interaction score was set to medium confidence level (0.400) and no more than 10 interactors were selected. PGK (Phosphoglycerate kinase) and Q7KQL9 (Fructosebiphosphate aldolase) are the two predicted proteins, which have been identified via co-IP assays. In other experiment, strong binding affinities of PfK13-p and two coimmunoprecipitated proteins- Heat Shock Protein 70 and PfFBAP (6.6 and 7.6 µM, respectively) were observed using surface plasmon resonance (SPR). Using anti-PfK13-p antibodies, the endogenous PfK13 protein was observed to colocalization with a cytosolic marker- PfAspRS (aspartyl transfer-RNA synthetase). Together, this work identified unique interacting partners of endogenous PfK13 protein, which might have crucial implications in the PfK13 protein network and its role in mediating ART resistance.
Keywords: Malaria, Artemisinin, P. falciparum, Kelch 13 protein, protein-protein interactions
Audience take away:
1. A fuller understanding of the resistance mechanism will underpin the efforts to develop alternative antimalarial strategies.
2. A better understanding of the mechanisms of the action, and resistance to artemisinins is now emerging; this may help us to understand why resistance is currently limited in geographic spread and results in only partial loss of efficacy.
3. These insights should also support efforts to prolong the lifespan of this class of drugs and to discover new drugs with related mechanisms of action.
4. Systematic identification of interacting proteins partners of pfK13 could help us to understanding the networking with other protein partners.