Genetic variations in human ATP2B4 gene alter Plasmodium falciparum in vitro growth in RBCs from Gambian adults

Abstract

AbstractBackgroundPolymorphisms inATP2B4coding for PMCA4b, the primary regulator of erythrocyte calcium concentration, have been shown by GWAS and cross-sectional studies to protect against severe malaria but the mechanism remains unknown.MethodsUsing a recall-by-genotype design, we investigated the impact of a common haplotype variant inATP2B4using in vitro assays that model erythrocyte stage malaria pathogenesis. Ninety-six donors representing homozygotes (carriers of the minor alleles, T/T (variant), heterozygote T/C and wildtype C/C (ancestral)) carriers of the tagging SNP rs1541252 were selected from a cohort of over 12,000 participants in the Keneba Biobank.ResultsRed blood cells (RBCs) from homozygotes showed reduced PMCA4b protein expression (mean fluorescence intensities (MFI = 2428 ± 124, 3544 ± 159 and 4261 ± 283], for homozygotes, heterozygotes and wildtypes respectively, p < 0.0001) and slower rates of calcium expulsion (calcium t½ ± SD = 4.7 ± 0.5, 1.8 ± 0.3 and 1.9 ± 0.4 min, p < 0.0001). Growth of aPlasmodium falciparumlaboratory strain (FCR3) and two Gambian field isolates was decreased in RBCs from homozygotes compared to heterozygotes and wildtypes (p < 0.01). Genotype group did not affect parasite adhesion in vitro orvar-gene expression in malaria-infected RBCs. Parasite growth was inhibited by a known inhibitor of PMCA4b, aurintricarboxylic acid (IC50 = 122uM CI: 110–134) confirming its sensitivity to calcium channel blockade.ConclusionThe data support the hypothesis that thisATP2B4genotype, common in The Gambia and other malaria-endemic areas, protects against severe malaria through the suppression of parasitaemia during an infection. Reduction in parasite density plays a pivotal role in disease outcome by minimizing all aspects of malaria pathogenesis. Follow up studies are needed to further elucidate the mechanism of protection and to determine if thisATP2B4genotype carries a fitness cost or increases susceptibility to other human disease.