The Ins and Outs of Plasmodium Rhoptries, Focusing on the Cytosolic Side

Parasites of the genus Plasmodium cause human and animal malaria, leading to significant health and economic impacts. A key aspect of the complex life cycle of Plasmodium parasites is the invasion of the parasite into its host cell, which is mediated by secretory organelles. The largest of these organelles, the rhoptry, undergoes rapid and profound physiological changes when it secretes its contents during merozoite and sporozoite invasion of the host erythrocyte and hepatocyte, respectively. Here we discuss recent advancements in our understanding of the dynamic rhoptry biology during the parasite's invasive stages, with a focus on the roles of cytosolically exposed rhoptry-interacting proteins (C-RIPs). We explore potential similarities between the molecular mechanisms driving merozoite and sporozoite rhoptry function. Plasmodium parasites secrete proteins from their rhoptries during host cell invasion.Rhoptries undergo significant physiological changes during invasion, and these differ significantly between the rhoptries of merozoites and sporozoites.Rhoptry secretion requires fusion between rhoptry pairs and between the rhoptries and parasite plasma membrane.Proteins on the cytosolic face of the rhoptries likely coordinate many of the poorly explored aspects of rhoptry biology, including rhoptry biogenesis, morphology, and secretion.