Pfcerli2, a duplicated gene in the malaria parasitePlasmodium falciparumessential for invasion of erythrocytes as revealed by phylogenetic and cell biological analysis

Abstract

Merozoite invasion of host red blood cells (RBCs) is essential for survival of the human malaria parasite Plasmodium falciparum. Proteins involved with RBC binding and invasion are secreted from dual-club shaped organelles at the apical tip of the merozoite called the rhoptries. Here we characterise P. falciparum Cytosolically Exposed Rhoptry Leaflet Interacting protein 2 (PfCERLI2), as a rhoptry bulb protein that is essential for merozoite invasion. Phylogenetic analyses show that cerli2 arose through an ancestral gene duplication of cerli1, a related cytosolically exposed rhoptry bulb protein. We show that PfCERLI2 is essential for blood-stage growth and localises to the cytosolic face of the rhoptry bulb. Inducible knockdown of PfCERLI2 led to an inhibition of merozoite invasion after tight junction formation. PfCERLI2 knockdown was associated with inhibition of rhoptry antigen processing and a significant elongation of the rhoptries, suggesting that the inability of merozoites to invade is caused by aberrant rhoptry function due to PfCERLI2 deficiency. These findings identify PfCERLI2 as a protein that has key roles in rhoptry biology during merozoite invasion.

Expansion microsopy reveals Plasmodium falciparum blood-stage parasites undergo anaphase with a chromatin bridge in the absence of mini-chromosome maintenance complex binding protein

“…Despite this, NHS ester staining appeared denser around the likely position of the microtubule organizing center (MTOC) prior to segmentation (Figure 1a). Additionally, NHS ester staining appeared denser at the apical tip of merozoites in segmented schizonts, reminiscent of staining previously observed for the doublebulbous rhoptries [36,37] (Figure 1a). Despite its unclear staining in unexpanded parasites, U-ExM parasites stained with NHS ester allowed the clear and striking identification of many intracellular structures.…”

Unraveling the Elusive Rhoptry Exocytic Mechanism of Apicomplexa

“…The past 3 years have seen spectacular progress in our understanding of rhoptry secretion in the apicomplexan model Toxoplasma and, to some extent, in P. falciparum, at both molecular and structural levels [45,68,[72][73][74]77]. These recent studies strongly suggest that Toxoplasma rhoptries do not directly contact the PPM but instead do so via an AV tightly connected to a rosette of eight IMPs embedded in the PPM.…”

“…In a parallel study, P. falciparum RASP2, named P. falciparum cytosolically exposed rhoptry leaflet interacting protein 1 (PfCERLI1), was also shown to be essential for rhoptry secretion and invasion, although characterized as a rhoptry-bulb protein [73]. Its homolog, PfCERLI2, appears to be required for rhoptry protein processing and the formation of morphologically wild-type rhoptries, and is consequently important for parasite invasion [74]. In Toxoplasma, degenerate Ca 2+ lipid-binding-like (C2) and pleckstrin homology-like (PH) domains in TgRASP2 bind specifically to phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ), and this is crucial for rhoptry secretion [72].…”

“…With the new knowledge that rhoptries directly contact the AV [45], RASP2 might rather function at the rhoptry-AV interface. Further work is required to support this model, particularly because of conflicting results regarding the locations and functions of PfCERLI proteins [73,74]. The C2 domains in Toxoplasma and Plasmodium RASP2 are In Toxoplasma, TgFer2, TgNd9, and TgNdP1 are all found in undefined punctate structures throughout the cytosol of the parasites, with TgFer2 being also associated with the IMC and rhoptries in intra-and extracellular tachyzoites, respectively, while TgNd6 and TgNdP2 show, in addition to this dispersed pattern, a distinct accumulation at the apical end of the parasite [45,68].…”