Structure of the PfRCR complex which bridges the malaria parasite and erythrocyte during invasion

Abstract

The symptoms of malaria occur during the blood stage of infection, when parasites invade and replicate within human erythrocytes. The five-component PfPCRCR complex, containing PfRH5, PfCyRPA, PfRIPR, PfCSS and PfPTRAMP, is essential for erythrocyte invasion by the deadliest human malaria parasite, Plasmodium falciparum. Invasion can be prevented by antibodies or nanobodies against each of these five conserved proteins, making them the leading blood stage malaria vaccine candidates. However, little is known about the molecular mechanism by which PfPCRCR functions during invasion. Here we present the structure of the PfRCR complex, containing PfRH5, PfCyRPA and PfRIPR, determined by cryogenic-electron microscopy. This reveals that PfRIPR consists of an ordered multi-domain core flexibly linked to an elongated tail. We test the hypothesis that PfRH5 opens to insert into the membrane, but instead show that a rigid, disulphide-locked PfRH5 can mediate efficient erythrocyte invasion. Finally, we show that the elongated tail of PfRIPR, which is the target of growth-neutralising antibodies, binds to the PfCSS-PfPTRAMP complex on the parasite membrane. Therefore, a modular PfRIPR is linked to the merozoite membrane through an elongated tail, while its structured core presents PfCyRPA and PfRH5 to interact with erythrocyte receptors. This provides novel insight into the mechanism of erythrocyte invasion and opens the way to new approaches in rational vaccine design.

Basigin mediation ofPlasmodium falciparumred blood cell invasion does not require its interaction with monocarboxylate transporter 1

“…PfRh5 and PfRipr have been proposed to insert into the membrane following conformational changes upon binding to basigin, facilitating formation of a pore that enables invading merozoites to inject components into the erythrocyte cytoplasm [23]. However the viability of this mechanism has recently been challenged, with locking disulphide bonds introduced into PfRh5 that prevent such necessary conformational changes failing to inhibit invasion [27].…”

Preclinical Development of a Stabilized RH5 Virus-Like Particle Vaccine that Induces Improved Anti-Malarial Antibodies

“…However, the identification of the reticulocyte-binding protein homolog 5 (RH5) 10 has renewed vigor in the P. falciparum blood-stage vaccine field over the last decade 8 . RH5 is an essential, highly conserved and antibody-susceptible antigen, delivered to the parasite surface in a pentameric protein complex [11][12][13] where it binds to host basigin/CD147 14 . This receptor-ligand interaction is critical for parasite invasion 15 , underlies the human host tropism of P. falciparum 16 , and vaccination of Aotus monkeys with RH5 conferred significant in vivo protection against a stringent blood-stage P. falciparum challenge 17 .…”

Rational structure-guided design of a blood stage malaria vaccine immunogen presenting a single epitope from PfRH5

“…The most promising candidates for a blood-stage malaria vaccine are components of the PfPCRCR complex, consisting of PfRH5, PfCyRPA, PfRIPR, PfCSS and PfPTRAMP (5,6). Each of these is essential for erythrocyte invasion (5)(6)(7)(8) and the complex has recently been shown to bridge the merozoite and erythrocyte membranes (5,6).…”

“…The most promising candidates for a blood-stage malaria vaccine are components of the PfPCRCR complex, consisting of PfRH5, PfCyRPA, PfRIPR, PfCSS and PfPTRAMP (5,6). Each of these is essential for erythrocyte invasion (5)(6)(7)(8) and the complex has recently been shown to bridge the merozoite and erythrocyte membranes (5,6). PfRH5 is the best understood component of PfPCRCR and interacts with human membrane protein complexes containing the erythrocyte receptor basigin (9)(10)(11).…”