Essential function of alveolin PfIMC1g in the Plasmodium falciparum asexual blood stage

The cytoskeleton of Plasmodium parasites is essential for replication, motility, and infectivity. Plasmodium falciparum leverages a family of cytoskeletal proteins known as alveolins to meet these diverse needs. The functional role of individual alveolins in Plasmodium blood stages, however, remains unexplored. Here, we demonstrate that the alveolin PfIMC1g (PF3D7_0525800) is essential for P. falciparum asexual replication. Unlike alveolins studied in mosquito stages, PfIMC1g does not play an important role in determining cell shape. PfIMC1g-deficient parasites exhibit only minor defects during segmentation, with most merozoites being indistinguishable from wild type by super-resolution fluorescence microscopy, ultrastructure expansion microscopy, and electron microscopy. In the current study, we demonstrate that the absence of PfIMC1g leads to parasite death shortly after merozoite internalization into red blood cells (RBCs). PfIMC1g-deficient parasites egress and enter new RBCs but fail to develop into rings and die. We hypothesize that the primary role of PfIMC1g is to maintain structural integrity, protecting parasites from incurring damage during the process of internalization. Along with the dispensability of PfIMC1g for merozoite cell shape, we report new findings about the architecture of Plasmodium alveolins including the localization of PfIMC1e and 1f to the basal complex.