| The invasion of malaria merozoites into erythrocytes is an essential part of blood-stage infections. The invasion process is mediated by specific molecular interactions between specific parasite ligands and erythrocyte receptors. The Plasmodium vivax Duffy Binding Protein (DBP) and P. falciparum Erythrocyte Binding Antigen-175 (EBA-175) are two such parasite molecules involved in this invasion process and belong to the erythrocyte binding-like (ebl) gene family. While successful P. vivax merozoite invasion requires the interaction of DBP with its erythrocyte receptor, P. falciparum is known to have alternate invasion pathways. The aim of my research is to advance the understanding of the molecular mechanisms underlying P. falciparum merozoite invasion into the erythrocyte focusing on the members of a growing ebl family.; I have partially characterized P. falciparum maebl and identified it as a unique member of the ebl family. maebl appears to be ubiquitous among Plasmodium species with an ancient origin predating speciation. P. falciparum maebl is highly conserved with its orthologues in P. yoelii and P. berghei, but distinct from other Plasmodium ebl. Importantly, MAEBL is chimeric with putative ligand cysteine-rich domains similar to the Apical Membrane Antigen-1, and a consensus carboxyl cysteine-rich domain similar to the ebl. MAEBL localized with known rhoptry proteins and on the merozoite surface and not with microneme proteins including EBA-175. MAEBL products appear as proteolytically processed fragments in P. falciparum parasites. Consistent with the ebl, maebl is a single copy gene with consensus ebl exon/intron boundaries. Similarly, preliminary data indicates the M2 ligand domain binds erythrocytes.; The P. falciparum ebl family currently consists of six members due to the identification of baebl, jesebl , pebl from sequence data obtained from the P. falciparum genome project and ebl-1 from previous studies. I partially characterized each of these ebls and used quantitative real-time RT-PCR 5′ nuclease assays (TaqMan®) for the first time on malaria parasites to analyze erythrocytic stage-specific ebl gene expression. Using temperature-synchronized parasites in this novel assay, I determined ebl gene transcription to be tightly controlled and stage-specific. My analysis demonstrated that TaqMan® assays are a sensitive, quantitative, and high-throughput method for analyzing Plasmodium transcripts. |
