The Molecular Basis of Erythrocyte Invasion by Malaria Parasites Alan F. Cowman, Christopher J. Tonkin, Wai-Hong Tham, Manoj T. Duraisingh  Cell Host & Microbe  Volume 22, Issue 2, Pages 232-245 (August 2017) DOI: 10.1016/j.chom.2017.07.003 Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 1 The Life Cycle of P. falciparum in the Human Host and the Anopheles Mosquito Vector The Plasmodium-infected mosquito injects sporozoites into the host and these migrate to the liver, where they pass through Kupffer cells and invade hepatocytes within which they develop to liver merozoites. Liver merozoites are released into the bloodstream where they invade erythrocytes. They develop through ring, trophozoite, and schizont stages replicating to produce from 16–32 merozoites that are released at egress. The free merozoite invades new erythrocytes to continue the asexual blood-stage life cycle. Some intraerythrocytic stages develop into male or female microgametocyte and macrogametocytes, the sexual forms of the parasite. These are taken up by the mosquito during feeding and develop into gametes in the insect gut and fuse to form zygotes. The zygote develops to form an invasive ookinete, which traverses the midgut and transforms into an oocyst, from which sporozoites are released that migrate to the salivary glands for injection into a human host during the next blood meal. Cell Host & Microbe 2017 22, 232-245DOI: (10.1016/j.chom.2017.07.003) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 2 Structure of the Merozoite and Steps in its Interaction with the Host Erythrocyte (A) The subcellular structure of a P. falciparum merozoite showing the microneme and rhoptry organelles at the apical end. (B) Merozoite invasion of erythrocytes. Invasion involves an initial attachment, which may involve MSPs or directly with EBAs and PfRh proteins. Apical reorientation likely involves membrane wrapping so that the apical end is adjacent to the erythrocyte, allowing tight attachment. Evidence suggests that a pore is formed between the merozoite and erythrocyte that is mediated either directly or indirectly by the PfRh5/PfRipr/CyRPA complex. This is associated with movement of the RON complex on the host membrane. A tight junction is formed involving high-affinity ligand-receptor interactions between AMA1 on the merozoite surface and RON2 inserted in the erythrocyte membrane. This tight junction then moves from the apical to posterior pole powered by the parasite's actinomyosin motor. The surface coat is shed at the moving junction by a serine protease, or “sheddase.” Upon reaching the posterior pole, the adhesive proteins at the junction are also proteolytically removed by a resident protease, most likely a rhomboid, in a process that facilitates resealing of the membrane. By this process the parasite does not actually penetrate the membrane, but invades in a manner that creates a parasitophorous vacuole. Cell Host & Microbe 2017 22, 232-245DOI: (10.1016/j.chom.2017.07.003) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 3 Parasite Ligand-Receptor Interactions and Events Associated with the Actomyosin Motor (A) Erythrocyte receptor and parasite ligand interactions involved in merozoite invasion for P. falciparum, P. vivax, and P. knowlesi. (B) A model for the merozoite motor and associated proteins based mainly on evidence from T. gondii tachyzoites. The adhesin complex is linked to actin through the glideosome associated protein (GAC). The MyoA neck region is stabilized through the essential light chain (ELC) and linked to the glideosome associated protein 45 (GAP45). GAP45 spans the inner membrane complex (IMC) and the plasma membrane and is associated with GAP40 and GAP50 in the IMC. Short actin filaments are depolymerized by cofilin to G-actin. Activity of the glideosome is regulated at the apical end of the zoite where the actin nucleating protein formin1 is localized. GAC is held in check by the apical lysine methyl transferase (AKMT) at the apical end. G-actin is polymerized into F-actin via profilin. Adhesins are released from micronemes and phosphatidic acid produced during signaling events. Cell Host & Microbe 2017 22, 232-245DOI: (10.1016/j.chom.2017.07.003) Copyright © 2017 Elsevier Inc. Terms and Conditions