Toxoplasma gondii HOOK-FTS-HIP Complex is Critical for Secretory Organelle Discharge during Motility, Invasion, and Egress. 2023

David J Dubois, and Sylia Chehade, and Jean-Baptiste Marq, and Kannan Venugopal, and Bohumil Maco, and Albert Tell I Puig, and Dominique Soldati-Favre, and Sabrina Marion
Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland.

Members of the Apicomplexa phylum possess specialized secretory organelles that discharge, apically and in a timely regulated manner, key factors implicated in parasite motility, host cell invasion, egress and subversion of host cellular functions. The mechanisms regulating trafficking and apical docking of these secretory organelles are only partially elucidated. Here, we characterized two conserved endosomal trafficking regulators known to promote vesicle transport and/or fusion, HOOK and Fused Toes (FTS), in the context of organelle discharge in Toxoplasma gondii. TgHOOK and TgFTS form a complex with a coccidian-specific partner, named HOOK interacting partner (HIP). TgHOOK displays an apically enriched vesicular pattern and concentrates at the parasite apical tip where it colocalizes with TgFTS and TgHIP. Functional investigations revealed that TgHOOK is dispensable but fitness conferring. The protein regulates the apical positioning and secretion of micronemes and contributes to egress, motility, host cell attachment, and invasion. Conditional depletion of TgFTS or TgHIP impacted on the same processes but led to more severe phenotypes. This study provides evidence of endosomal trafficking regulators involved in the apical exocytosis of micronemes and possibly as a consequence or directly on the discharge of the rhoptries. IMPORTANCE Toxoplasma gondii affects between 30 and 80% of the human population, poses a life-threatening risk to immunocompromised individuals, and is a cause of abortion and birth defects following congenital transmission. T. gondii belongs to the phylum of Apicomplexa characterized by a set of unique apical secretory organelles called the micronemes and rhoptries. Upon host cell recognition, this obligatory intracellular parasite secretes specific effectors contained in micronemes and rhoptries to promote parasite invasion of host cells and subsequent persistence. Here, we identified novel T. gondii endosomal trafficking regulators and demonstrated that they regulate microneme organelle apical positioning and exocytosis, thereby strongly contributing to host cell invasion and parasite virulence.

UI MeSH Term Description Entries
D010351 Patient Discharge The administrative process of discharging the patient, alive or dead, from hospitals or other health facilities. Discharge Planning,Discharge Plannings,Discharge, Patient,Discharges, Patient,Patient Discharges,Planning, Discharge,Plannings, Discharge
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001692 Biological Transport The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments. Transport, Biological,Biologic Transport,Transport, Biologic
D014122 Toxoplasma A genus of protozoa parasitic to birds and mammals. T. gondii is one of the most common infectious pathogenic animal parasites of man. Toxoplasma gondii,Toxoplasma gondius,Toxoplasmas,gondius, Toxoplasma
D014774 Virulence The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its VIRULENCE FACTORS. Pathogenicity
D015388 Organelles Specific particles of membrane-bound organized living substances present in eukaryotic cells, such as the MITOCHONDRIA; the GOLGI APPARATUS; ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES. Organelle
D015800 Protozoan Proteins Proteins found in any species of protozoan. Proteins, Protozoan

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