Clustering of host N-glycans licenses Toxoplasma rhoptry discharge

Area of Science:

• Cell biology
• Parasitology
• Molecular biology

Background:

• Apicomplexan parasites, like Toxoplasma gondii, invade host cells by discharging contents from specialized organelles (rhoptries).
• This invasion requires prior host cell recognition and binding mediated by proteins from micronemes.
• The specific host-parasite interactions governing rhoptry discharge remain largely uncharacterized.

Purpose of the Study:

• To identify host factors essential for rhoptry discharge during Toxoplasma gondii invasion.
• To elucidate the molecular mechanisms underlying host-parasite interactions at the invasion interface.

Main Methods:

• Conducted a host-cell directed, genome-wide screen to identify host genes required for Toxoplasma gondii rhoptry discharge.
• Investigated the role of identified host pathways (N-glycosylation, cholesterol biosynthesis) in the invasion process.
• Characterized the function of the trimeric microneme complex (MIC1/4/6) in mediating host-parasite interactions.

Main Results:

• The screen revealed that host N-glycosylation and cholesterol biosynthesis pathways are critical for normal rhoptry discharge.
• The MIC1/4/6 complex binds host N-glycans, clustering host proteins in a process dependent on plasma membrane cholesterol.
• Depletion of host cholesterol or competition with exogenous glycans inhibits this clustering and rhoptry discharge.

Conclusions:

• Host N-glycosylation and cholesterol are essential for apicomplexan parasite invasion.
• The MIC1/4/6 complex acts as a molecular bridge, linking host glycan structures and membrane cholesterol to facilitate invasion.
• This study reveals a novel step in Toxoplasma invasion, highlighting host membrane preparation mediated by parasite proteins.