Structural insights into an atypical secretory pathway kinase crucial for Toxoplasma gondii invasion

Gaëlle Lentini,Jonas Grossmann,Rouaa Ben Chaabene,Matteo Lunghi,Bohumil Maco,Rémy Visentin,Budhaditya Mukherjee,Dominique Soldati-Favre,Oscar Vadas,Ved Mehta,Chandra Ramakrishnan,Adrian B Hehl,Volodymyr M Korkhov

doi:10.1038/s41467-021-24083-y

Abstract

Active host cell invasion by the obligate intracellular apicomplexan parasites relies on the formation of a moving junction, which connects parasite and host cell plasma membranes during entry. Invading Toxoplasma gondii tachyzoites secrete their rhoptry content and insert a complex of RON proteins on the cytoplasmic side of the host cell membrane providing an anchor to which the parasite tethers. Here we show that a rhoptry-resident kinase RON13 is a key virulence factor that plays a crucial role in host cell entry. Cryo-EM, kinase assays, phosphoproteomics and cellular analyses reveal that RON13 is a secretory pathway kinase of atypical structure that phosphorylates rhoptry proteins including the components of the RON complex. Ultimately, RON13 kinase activity controls host cell invasion by anchoring the moving junction at the parasite-host cell interface.

Highlights

Active host cell invasion by the obligate intracellular apicomplexan parasites relies on the formation of a moving junction, which connects parasite and host cell plasma membranes during entry
The rhoptry neck proteins (RONs) complex is inserted in the host plasma membrane (PM) and binds to the microneme protein AMA1 on the parasite surface, forming a multiprotein complex that contributes to the formation of the moving junction (MJ)[3,4]
Focused ion beam scanning electron microscopy (FIB-SEM) analysis confirmed that the rhoptry necks are morphologically aberrant and do not extend to the apical tip of the parasite (Fig. 1b, Supplementary Fig. 1b, and Supplementary Movies 1 and 2)

Summary

Introduction

Active host cell invasion by the obligate intracellular apicomplexan parasites relies on the formation of a moving junction, which connects parasite and host cell plasma membranes during entry. Invading Toxoplasma gondii tachyzoites secrete their rhoptry content and insert a complex of RON proteins on the cytoplasmic side of the host cell membrane providing an anchor to which the parasite tethers. Rhoptries inject proteins across the host cell plasma membrane (PM)[1], some acting as receptors during host cell invasion and others as effectors to subvert host cellular functions[2]. These club-shaped organelles contain rhoptry bulb proteins (ROPs) in the enlarged base that are segregated from rhoptry neck proteins (RONs) at the thin neck connected to the apical tip of the parasite. RON13 kinase activity stabilizes the RON complex at the MJ to ensure successful invasion

Methods

Results

Conclusion