Coupling Polar Adhesion with Traction, Spring and Torque Forces Allows High Speed Helical Migration of the Protozoan Parasite Toxoplasma .

Among the eukaryotic cells that navigate through fully developed metazoan tissues, protozoans from the Apicomplexa phylum have evolved motile developmental stages that move much faster than the fastest crawling cells owing to a peculiar substrate-dependent type of motility, known as gliding. Best-studied models are the sporozoite and the tachyzoite polarized cells for which motility is vital to achieve their developmental programs in the metazoan hosts. The gliding machinery is shared between the two stages and functionally characterized. Localized beneath the cell surface, it includes actin filaments with unconventional myosin motors housed within a multi-member glideosome unit, and apically secreted transmembrane adhesins. In contrast, less is known on the force mechanisms powering cell movement. Pioneered biophysical studies on the sporozoite and phenotypic analysis of tachyzoite actin-related mutants have added complexity to the general view that force production for parasite forward movement directly results from the myosin-driven rearward motion of the actin-coupled adhesion sites. Here, we have interrogated how forces and substrate adhesion-deadhesion cycles operate and coordinate to allow the typical left-handed helical gliding mode of the tachyzoite in 3D conditions. By combining quantitative traction force and reflection interference microscopy with micropatterning and expansion microscopy we unveil at the millisecond and nanometer scales the integration of a critical apical anchoring adhesion with specific traction and spring-like forces. We propose that the acto-myoA motor directs the traction force which allows transient energy storage by the microtubule cytoskeleton and therefore sets the thrust force required for tachyzoite vital gliding capacity.