Multiple essential functions of Plasmodium falciparum actin-1 during malaria blood-stage development

Abstract

BackgroundThe phylum Apicomplexa includes intracellular parasites causing immense global disease burden, the deadliest of them being the human malaria parasite Plasmodium falciparum, which invades and replicates within erythrocytes. The cytoskeletal protein actin is well conserved within apicomplexans but divergent from mammalian actins, and was primarily reported to function during host cell invasion. However, novel invasion mechanisms have been described for several apicomplexans, and specific functions of the acto-myosin system are being reinvestigated. Of the two actin genes in P. falciparum, actin-1 (pfact1) is ubiquitously expressed in all life-cycle stages and is thought to be required for erythrocyte invasion, although its functions during parasite development are unknown, and definitive in vivo characterisation during invasion is lacking.ResultsHere we have used a conditional Cre-lox system to investigate the functions of PfACT1 during P. falciparum blood-stage development and host cell invasion. We demonstrate that PfACT1 is crucially required for segregation of the plastid-like organelle, the apicoplast, and for efficient daughter cell separation during the final stages of cytokinesis. Surprisingly, we observe that egress from the host cell is not an actin-dependent process. Finally, we show that parasites lacking PfACT1 are capable of microneme secretion, attachment and formation of a junction with the erythrocyte, but are incapable of host cell invasion.ConclusionsThis study provides important mechanistic insights into the definitive essential functions of PfACT1 in P. falciparum, which are not only of biological interest, but owing to functional divergence from mammalian actins, could also form the basis for the development of novel therapeutics against apicomplexans.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-017-0406-2) contains supplementary material, which is available to authorized users.

Formin-2 drives intracellular polymerisation of actin filaments enabling correct segregation of apicoplasts in Plasmodium falciparum and Toxoplasma gondii

“…In 220 order to determine the localisation of F-actin during apicoplast segregation we used deconvolution 221 microscopy on fixed parasites stained with the apicoplast marker CPN60, which revealed a close 222 apposition of apicoplasts with F-actin structures (Fig 3F DMSO). Upon disruption of PfACT1, a defect 223 in apicoplast segregation was apparent (Fig 3F RAP) recapitulating the phenotype observed 224 previously (Das, Lemgruber et al 2017). Super-resolution microscopy confirmed that actin filaments 225 labelled by CB-EME are closely placed next to migrating apicoplasts ( Fig S1, lower panel).…”

“…2A lower panel), but the multilobed structures of the parasite were 189 not disrupted (Video V6). The F-actin stabilising drug jasplakinolide also disrupted these filopodia-190 like extensions and resulted in formation of thick filaments ( Fig 4A lower panel We previously found that apicoplast inheritance depends on PfACT1 (Das, Lemgruber et al 2017). In 220 order to determine the localisation of F-actin during apicoplast segregation we used deconvolution 221 microscopy on fixed parasites stained with the apicoplast marker CPN60, which revealed a close 222 apposition of apicoplasts with F-actin structures (Fig 3F DMSO).…”

“…S2B, C)into a 212 conditional mutant of PfACT1 (loxPACT1) (Das, Lemgruber et al 2017) (Fig 3A). Upon activation of 213 DiCre with rapamycin, the pfact1 locus is excised together with loss of PfACT1 protein within 35h 214(Das, Lemgruber et al 2017). Upon disruption of pfact1 in 1h-old ring stages, CB-EME(Fig.…”

Apicomplexan F-actin is required for efficient nuclear entry during host cell invasion

“…While T. gondii is a relevant model to address general questions in apicomplexan biology, we previously observed differences in the role of F-actin during the asexual life cycles of T. gondii and P. falciparum, the causative agent of human malaria. For instance, in case of P. falciparum, invasion is dependent on parasite F-actin (Das, Lemgruber et al, 2017), while in the case of T. gondii residual invasion can be observed. To analyse the role of F-actin during merozoite invasion, we expressed CB-Halo and Cb-EmeraldFP in P. falciparum and validated their efficiency to analyse F-actin localisation and dynamics in this parasite (Stortz et al, BioRXiv2019).…”

Avaliação do papel do receptor imune inato dectina-1 e antígenos solúveis de neospora caninum no tratamento da malária cerebral murina

“…Nas regiões tropicais e subtropicais existem muitas áreas endêmicas, com alta porcentagem de indivíduos infectados em relação às demais áreas (WHITE et al, 2014;RECHT et al, 2017 proporção em que cada uma das duas espécies infecta humanos depende da região geográfica, bem como da susceptibilidade da população (DAS et al, 2017;HOWES et al, 2011). Na África, existe uma predominância de indivíduos negativos para a molécula CD 234 -Cluster of Differentiation 234, também conhecida como Duffy antigen ou antígeno Fy.…”