Essential Role of the PfRh5/PfRipr/CyRPA Complex during Plasmodium falciparum Invasion of Erythrocytes

Abstract

Plasmodium falciparum parasites in the merozoite stage invade human erythrocytes and cause malaria. Invasion requires multiple interactions between merozoite ligands and erythrocyte receptors. P. falciparum reticulocyte binding homolog 5 (PfRh5) forms a complex with the PfRh5-interacting protein (PfRipr) and Cysteine-rich protective antigen (CyRPA) and binds erythrocytes via the host receptor basigin. However, the specific role that PfRipr and CyRPA play during invasion is unclear. Using P. falciparum lines conditionally expressing PfRipr and CyRPA, we show that loss of PfRipr or CyRPA function blocks growth due to the inability of merozoites to invade erythrocytes. Super-resolution microscopy revealed that PfRipr, CyRPA, and PfRh5 colocalize at the junction between merozoites and erythrocytes during invasion. PfRipr, CyRPA, and PfRipr/CyRPA/PfRh5-basigin complex is required for triggering the Ca(2+) release and establishing the tight junction. Together, these results establish that the PfRh5/PfRipr/CyRPA complex is essential in the sequential molecular events leading to parasite invasion of human erythrocytes.

Plasmodium falciparum ligand binding to erythrocytes induce alterations in deformability essential for invasion

“…To determine if FTY720 decreased the ability of merozoites to deform the erythrocyte during invasion, schizonts were purified and added to erythrocytes stained with Bodipy TR Ceramide, a viable membrane dye that allows invasion (Volz et al, 2016). Live imaging of merozoites in the process of interaction with an erythrocyte showed that, in the presence of FTY720, the parasite was able to contact and attach, but could not invade (Figure 4F and G, Videos 1 and 2).…”

“…During the initial steps of the invasion, the merozoite intermittently contacts the erythrocyte until it attaches and initiates internalization. Attachment and internalization involve a series of dramatic changes that include deformation of the erythrocyte (Figure 1A) and calcium (Ca 2+ ) influx after which a tight junction is formed and invasion mediated using force generated by the parasite actomyosin motor (Weiss et al, 2015; Volz et al, 2016). The mechanical alterations of the erythrocyte that occur during merozoite invasion have been described using video-microscopy (Weiss et al, 2015; Gilson et al, 2009).…”

“…The mechanical alterations of the erythrocyte that occur during merozoite invasion have been described using video-microscopy (Weiss et al, 2015; Gilson et al, 2009). Merozoite invasion involves the interaction of multiple parasite ligands with specific erythrocyte receptors that include merozoite surface proteins (MSPs) (Hodder et al, 2012), erythrocyte binding antigens (EBAs) (Adams et al, 2001) and reticulocyte binding-like homologs (PfRhs) (Rayner et al, 2000; Triglia et al, 2001; Hayton et al, 2008; Baum et al, 2009), and the functional requirement of these during specific steps of the invasion has been defined (Weiss et al, 2015; Volz et al, 2016). This includes binding of the merozoite surface protein Duffy Binding-Like 1 and 2 (MSPDBL1 and 2) with unknown receptors (Hodder et al, 2010), EBA-175 with glycophorin A (GPA) (Orlandi et al, 1992), EBA-140 (also known as BAEBL) with glycophorin C (GPC) (Maier et al, 2003), PfRh4 with Complement Receptor 1 (CR1) (Tham et al, 2010) and PfRh5 with basigin (Crosnier et al, 2011).…”

Gliding motility powers invasion and egress in Apicomplexa

“…The binding of EBA-175 to glycophorin A mediates marked deformability of the RBC membrane, which is required for invasion 117 . At the tip of the merozoite, the binding of RH5 to basigin triggers calcium release 170 and the formation of the moving junction that supports the motility-dependent host cell invasion of the parasite. The underlined proteins are transmembrane proteins inserted in the plasma membrane.…”

Human vaccination against RH5 induces neutralizing antimalarial antibodies that inhibit RH5 invasion complex interactions

“…CyRPA, however, can bind Ripr and likely recruits this molecule to the complex leading to its one-way release from P113, either by proteolytic cleavage of RH5Nt or mutually exclusive binding of P113 and Ripr. The function of the RH5-CyRPA-Ripr complex has been linked to pore formation between the merozoite and the RBC, allowing for the movement of Ca 2+ into the host cell and alterations in RBC cytoskeleton architecture, prior to establishment of the tight junction (30,31).…”