Analysis of P-glycoprotein expression in purified parasite plasma membrane and food vacuole from Plasmodium falciparum

Abstract

A P-glycoprotein homologue (Pgh1) is believed to play a role in modulating levels of chloroquine resistance in Plasmodium falciparum. To study the role of Pgh1 in the mechanism of chloroquine (CQ) resistance, antisera were raised against this protein. There was no direct association between the level of Pgh1 expression and chloroquine sensitivity. We also failed to detect phosphorylation of Pgh1 in the food vacuole (FV), suggesting that other mechanisms regulate the chloroquine-resistant (CQR) phenotype. Therefore, high levels of expression of Pgh1 or phosphorylation of this protein in the FV could not account for CQ sensitivity. In addition, the lack of inhibition of CQ accumulation by anti-Pgh1 antibodies suggests that Pgh1 is not involved as a CQ transporter in the plasma membrane of P. falciparum. Furthermore, resistance reversers do not appear to act at the plasma membrane level.

Plasmodium knowlesi as a model system for characterising Plasmodium vivax drug resistance candidate genes

“…This could be a cleavage product, perhaps between the two 6-transmembrane domain channels, based on the observed size. A similar sized secondary product for PfMDR1 was also observed by Elandaloussi and colleagues [75] in P. falciparum extracts, and by van Es and colleagues [76] while overexpressing PfMDR1 in CHO cells, suggesting that the two MDR1 homologues may be proteolytically cleaved in a similar way.…”

“…Although these three proteins have never been functionally studied in P. vivax , their P. falciparum homologues have been extensively investigated. PfMDR1 is known to localise to the food vacuole membrane [75, 77] and PfDHFR is a cytoplasmic enzyme [78]. PfDHPS has never been localised, although both cytosolic and mitochondrial localisation have been described for Arabidopsis thaliana homologues [79].…”