A function of profilin in force generation during malaria parasite motility independent of actin binding

Abstract

During transmission of malaria-causing parasites from mosquito to mammal, Plasmodium sporozoites migrate at high speed within the skin to access the bloodstream and infect the liver. This unusual gliding motility is based on retrograde flow of membrane proteins and highly dynamic actin filaments that provide short tracks for a myosin motor. Using laser tweezers and parasite mutants, we previously suggested that actin filaments form macromolecular complexes with plasma-membrane spanning adhesins to generate force during migration. Mutations in the actin-binding region of profilin, a near ubiquitous actin-binding protein, revealed that loss of actin binding also correlates with loss of force production and motility. Here we show that different mutations in profilin, not affecting actin binding in vitro, still generate lower force during Plasmodium sporozoite migration. Lower force generation inversely correlates with increased retrograde flow suggesting that, like in mammalian cells, the slow-down of flow to generate force is the key underlying principle governing Plasmodium gliding motility.

The multiple functions of actin in apicomplexan parasites

“…In divergence from classical profilins, apicomplexan profilins contain an additional β-hairpin loop, which is critically required for actin monomer binding, and a single point mutation in this loop region eliminates a hydrogen-bond, thereby abrogating fast motility seen in P. berghei sporozoites (Moreau et al, 2017). Recently, the same group produced mutations in another acidic loop in profilin, which did not affect actin polymerisation in vitro and yet affected gliding motility of P. berghei sporozoites, indicating that additional factors beyond actin polymerisation are at play during motility and invasion of apicomplexan parasites (Moreau et al, 2020). TgProfilin is critical for the completion of the lytic life cycle as depletion of TgProfilin rendered parasites defective in gliding motility, invasion and host cell egress (Plattner et al, 2008).…”

Phosphorylation of myosin A regulatesPlasmodiumsporozoite motility and is essential for efficient malaria transmission

“…After calibration, we repeatedly observed that around 70% of wt sporozoites were able to pull a bead out of the trap at 30 pN of force. This percentage was observed at a force of 70 pN in the previous setup (Quadt et al, 2016;Moreau et al, 2017Moreau et al, , 2020. Currently we do not know the source of this difference and as the previous setup was dismantled, we unfortunately cannot compare them sideby-side.…”

“…Parasite motility results from a complex interplay between adhesion and force generation. Yet, force generation of sporozoites has so far only been investigated in parasites lacking either surface receptors or actin-binding proteins without a direct function in force generation (Münter et al, 2009;Hegge et al, 2012;Quadt et al, 2016;Moreau et al, 2017Moreau et al, , 2020. Intriguingly, force generation of sporozoites was found to be lower in mutant parasites that show similar migratory capacity or speeds as wt.…”

Characterization of a profilin-like protein from Fasciola hepatica

“…Profilins are characterized by having three major biochemical functions (Krishnan & Moens, 2009;Moreau et al, 2017Moreau et al, , 2020; firstly, profilins bind to and sequester actin monomers, therefore affecting how actin filaments polymerize. Secondly, profilins have an affinity for proline-rich domains contained within their interacting ligands and lastly, they have an affinity for phosphatidylinositol lipids that dissociate the actin:profilin complexes.…”