The invasion pore induced by Toxoplasma gondii

Area of Science:

• Parasitology
• Cell Biology
• Biophysics

Background:

• Obligate intracellular parasites like Toxoplasma gondii invade host cells for survival.
• Toxoplasma gondii injects essential invasion proteins into host cells upon contact.

Purpose of the Study:

• To investigate the biophysical mechanisms of host cell invasion by Toxoplasma gondii.
• To characterize the transient changes in host cell membrane conductance during parasite invasion.

Main Methods:

• Utilized high-resolution electrophysiological recordings (sub-200 ms) of host cells exposed to Toxoplasma gondii.
• Applied time-series analysis to a large dataset of parasite-induced membrane conductance transients.
• Investigated the role of the RON2 protein in invasion and conductance changes using depleted parasites.

Main Results:

• Detected a transient increase in host membrane conductance preceding Toxoplasma gondii invasion.
• Parasites lacking RON2 induced conductance transients but failed to invade, indicating RON2 is not directly structural.
• Revealed multiple quantal conductance steps within the transient, suggesting pore formation and modulation.
• Identified conductance step sizes similar to the EXP2 protein translocon, proposing the term 'invasion pore'.

Conclusions:

• The invasion of host cells by Toxoplasma gondii involves a transient, quantal conductance pathway, termed the 'invasion pore'.
• The protein translocon EXP2 is a potential component of this invasion pore.
• RON2 plays a role in the invasion process but not in the direct formation or gating of the conductance pathway.