Actin filament polymerization regulates gliding motility by apicomplexan parasites

Area of Science:

• Parasitology
• Cell Biology
• Biophysics

Background:

• Host cell entry by Toxoplasma gondii is crucial for infection.
• Parasite actin is predominantly monomeric, with limited understanding of filament dynamics.
• The role of actin filaments in parasite motility remains paradoxical.

Purpose of the Study:

• To investigate the role of actin filaments in Toxoplasma gondii motility.
• To understand how actin filament dynamics influence parasite gliding and host cell invasion.

Main Methods:

• Utilized rapid-freeze electron microscopy to visualize actin filaments.
• Employed jasplakinolide (JAS) to stabilize actin filaments in live and fixed parasites.
• Monitored actin distribution using yellow fluorescent protein (YFP)-actin.
• Assessed parasite motility and directionality via videomicroscopy.

Main Results:

• Actin filaments form beneath the plasma membrane during parasite gliding.
• Jasplakinolide (JAS) treatment led to filament redistribution and spiral patterns.
• JAS treatment increased gliding speed threefold, indicating actin filaments are rate-limiting.
• JAS also caused abnormal motility, including reversed direction and disrupted cell entry.

Conclusions:

• Precisely controlled actin filament polymerization is essential for parasite gliding motility.
• Actin filament dynamics dictate the timing, duration, and directionality of movement in Apicomplexa.
• Targeting actin dynamics offers potential strategies for controlling parasite infections.