Life Cycle-Dependent Cytoskeletal Modifications in Plasmodium falciparum Infected Erythrocytes

Shi, Hui; Liu, Zhuo; Li, Ang; Yin, Jing; Chong, Adrian; Tan, Kevin S. W.; Zhang, Yong; Lim, Chwee Teck

doi:10.1371/journal.pone.0061170

Cited by 69 publications

(98 citation statements)

References 35 publications

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“…In uninfected RBCs, the average spectrin length is 51 ± 9 nm (Fig. 2B), in agreement with previous reports (10,18). In trophozoites and stage III gametocytes, a significant increase in spectrin length was observed (61 ± 14 and 62 ± 8 nm, respectively; P < 0.0001) (Fig.…”

Section: Disruption Of the Gametocyte Microtubule Network Does Notsupporting

confidence: 92%

“…Atomic force microscopy (AFM) has revealed reorganization and expansion of the spectrin network of the host cell membrane (10,11), while cryo-electron tomography suggests that this reorganization occurs as a result of mining of the actin junctions in order to generate actin filaments that connect parasite-derived organelles known as Maurer's clefts to the knobs (12). A parasiteencoded protein called the Knob-Associated Histidine-Rich Protein (KAHRP) is thought to be a major contributor to RBC rigidification (8,13).…”

Section: Significancementioning

confidence: 99%

“…To assess changes to the nanostructure of the RBC membrane, we imaged the skeletal meshwork at the cytoplasmic surface (10,17). Uninfected RBCs or RBCs infected with trophozoites or stage III or V gametocytes were adhered to glass coverslips.…”

Section: Disruption Of the Gametocyte Microtubule Network Does Notmentioning

confidence: 99%

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Reversible host cell remodeling underpins deformability changes in malaria parasite sexual blood stages

Dearnley

Chu

Zhang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

101

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The sexual blood stage of the human malaria parasite Plasmodium falciparum undergoes remarkable biophysical changes as it prepares for transmission to mosquitoes. During maturation, midstage gametocytes show low deformability and sequester in the bone marrow and spleen cords, thus avoiding clearance during passage through splenic sinuses. Mature gametocytes exhibit increased deformability and reappear in the peripheral circulation, allowing uptake by mosquitoes. Here we define the reversible changes in erythrocyte membrane organization that underpin this biomechanical transformation. Atomic force microscopy reveals that the length of the spectrin crossmembers and the size of the skeletal meshwork increase in developing gametocytes, then decrease in mature-stage gametocytes. These changes are accompanied by relocation of actin from the erythrocyte membrane to the Maurer's clefts. Fluorescence recovery after photobleaching reveals reversible changes in the level of coupling between the membrane skeleton and the plasma membrane. Treatment of midstage gametocytes with cytochalasin D decreases the vertical coupling and increases their filterability. A computationally efficient coarse-grained model of the erythrocyte membrane reveals that restructuring and constraining the spectrin meshwork can fully account for the observed changes in deformability.gametocyte | deformability | spectrin/actin skeleton | AFM | molecular dynamics simulation T he most virulent of the human malaria parasites, Plasmodium falciparum causes ∼440,000 deaths annually (1). Pathology is associated with asexual multiplication within red blood cells (RBCs). The trophozoite (growing) and schizont (dividing) stages (∼24-48 h after invasion) sequester in deep tissue using adhesive proteins presented on platform-like structures called "knobs" at the infected RBC surface. Cytoadhesion enables the parasite to avoid passage through the splenic sinuses and thus mechanical clearance from the circulation. Unfortunately, complications associated with sequestration of infected RBCs in the brain are responsible for much of the malaria-related mortality and morbidity.After a period of asexual cycling, a proportion of blood-stage parasites commit to sexual development (gametocytogenesis). The intraerythrocytic gametocyte develops through five distinct stages (I-V) over a period of 10-12 d, eventually adopting the characteristic crescent (falciform) shape that gives P. falciparum its name. Elongation is driven by assembly of a sheath of microtubules, attached to an inner membrane complex, underneath the parasite plasma membrane. From stage II to IV, gametocytes disappear from the circulation (2, 3); however, the mechanism of sequestration is not well understood. Upon maturation, the microtubule cytoskeleton is disassembled, and stage V gametocytes re-enter the circulation (2, 3). Ingestion of mature gametocytes by an Anopheles mosquito triggers release from the RBCs, followed by sexual recombination in the insect gut, and eventual transmission.

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Section: Disruption Of the Gametocyte Microtubule Network Does Notsupporting

confidence: 92%

Section: Significancementioning

confidence: 99%

See 1 more Smart Citation

Reversible host cell remodeling underpins deformability changes in malaria parasite sexual blood stages

Dearnley

Chu

Zhang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

101

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“…50 Spectrin tetramers are capable of stretching to 194 nm in length, 51 which would allow for knob intercalation into the cytoskeleton mesh without further modification. It has been reported that the red cell cytoskeleton is gradually dismantled as the intracellular parasite develops, 42,52,53 and it is possible that some cytoskeletal connections are broken during knob formation. However, in this study, which used highly synchronized, mature schizont preparations, no differences in cytoskeletal structure outside of the knobs were observed between uninfected erythrocyte skeletons and those from mature schizonts.…”

Section: Discussionmentioning

confidence: 99%

A spiral scaffold underlies cytoadherent knobs in Plasmodium falciparum–infected erythrocytes

Watermeyer

Hale

Hackett

et al. 2016

Blood

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Key Points• Plasmodium falciparumgenerated cytoadherent knobs on infected erythrocytes contain a spiral framework linked to the red cell cytoskeleton.• The findings suggest a structural basis for transmission of shear forces in adhesion of infected cells.Much of the virulence of Plasmodium falciparum malaria is caused by cytoadherence of infected erythrocytes, which promotes parasite survival by preventing clearance in the spleen. Adherence is mediated by membrane protrusions known as knobs, whose formation depends on the parasite-derived, knob-associated histidine-rich protein (KAHRP). Knobs are required for cytoadherence under flow conditions, and they contain both KAHRP and the parasite-derived erythrocyte membrane protein PfEMP1. Using electron tomography, we have examined the 3-dimensional structure of knobs in detergent-insoluble skeletons of P falciparum 3D7 schizonts. We describe a highly organized knob skeleton composed of a spiral structure coated by an electron-dense layer underlying the knob membrane. This knob skeleton is connected by multiple links to the erythrocyte cytoskeleton. We used immuno-electron microscopy (EM) to locate KAHRP in these structures. The arrangement of membrane proteins in the knobs, visualized by high-resolution freeze-fracture scanning EM, is distinct from that in the surrounding erythrocyte membrane, with a structure at the apex that likely represents the adhesion site. Thus, erythrocyte knobs in P falciparum infection contain a highly organized skeleton structure underlying a specialized region of membrane. We propose that the spiral and dense coat organize the cytoadherence structures in the knob, and anchor them into the erythrocyte cytoskeleton. The high density of knobs and their extensive mechanical linkage suggest an explanation for the rigidification of the cytoskeleton in infected cells, and for the transmission to the cytoskeleton of shear forces experienced by adhering cells. (Blood. 2016;127(3):343-351) IntroductionPlasmodium falciparum malaria remains one of the leading causes of child deaths globally, with the majority of cases occurring in subSaharan Africa and Southeast Asia. Although chemopreventive and vector control initiatives led to an estimated 42% reduction in mortality rates between 2000 and 2012, the emergence of artemisinin resistance highlights the importance of continued efforts to understand and interfere with the biology of the parasite. 1Of the 5 Plasmodium species capable of infecting humans, P falciparum and P vivax are the most prevalent, with P falciparum causing 90% of malaria-related deaths. P falciparum-infected erythrocytes become cytoadherent, causing erythrocyte sequestration in the microvasculature and avoiding clearance of infected cells by the spleen.2 Much of the virulence of P falciparum malaria has been attributed to this cytoadherence, which impedes blood circulation and results in severe syndromes such as cerebral or placental malaria. 2-4The dominant ligand mediating cytoadherence is PfEMP1, a major variable erythrocyte...

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“…It was shown by atomic force microscopy that the spectrin network is denser and sparser in knobby and nonknobby regions, respectively, and that the spectrin length increases during the replicative cycle (25). Using multiscale modeling, it has been argued that the vertical linking between the knobs and the spectrin network strongly changes the mechanics of the host cell (26).…”

Section: Introductionmentioning

confidence: 99%

Rolling Adhesion of Schizont Stage Malaria-Infected Red Blood Cells in Shear Flow

Dasanna

Lansche

Lanzer

et al. 2017

Biophysical Journal

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To avoid clearance by the spleen, red blood cells infected with the human malaria parasite Plasmodium falciparum (iRBCs) adhere to the vascular endothelium through adhesive protrusions called ''knobs'' that the parasite induces on the surface of the host cell. However, the detailed relation between the developing knob structure and the resulting movement in shear flow is not known. Using flow chamber experiments on endothelial monolayers and tracking of the parasite inside the infected host cell, we find that trophozoites (intermediate-stage iRBCs) tend to flip due to their biconcave shape, whereas schizonts (late-stage iRBCs) tend to roll due to their almost spherical shape. We then use adhesive dynamics simulations for spherical cells to predict the effects of knob density and receptor multiplicity per knob on rolling adhesion of schizonts. We find that rolling adhesion requires a homogeneous coverage of the cell surface by knobs and that rolling adhesion becomes more stable and slower for higher knob density. Our experimental data suggest that schizonts are at the border between transient and stable rolling adhesion. They also allow us to establish an estimate for the molecular parameters for schizont adhesion to the vascular endothelium and to predict bond dynamics in the contact region.

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Life Cycle-Dependent Cytoskeletal Modifications in Plasmodium falciparum Infected Erythrocytes

Cited by 69 publications

References 35 publications

Reversible host cell remodeling underpins deformability changes in malaria parasite sexual blood stages

Reversible host cell remodeling underpins deformability changes in malaria parasite sexual blood stages

A spiral scaffold underlies cytoadherent knobs in Plasmodium falciparum–infected erythrocytes

Rolling Adhesion of Schizont Stage Malaria-Infected Red Blood Cells in Shear Flow

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