Ultrastructural and functional analysis of extra-axonemal structures in trichomonads

Abstract

Trichomonas vaginalis and Tritrichomonas foetus are extracellular flagellated parasites that inhabit humans and other mammals, respectively. In addition to motility, flagella act in a variety of biological processes in different cell types; and extra-axonemal structures (EASs) has been described as fibrillar structures that provide mechanical support and act as metabolic, homeostatic and sensory platforms in many organisms. Here, we identified the presence of EASs forming prominent flagellar swellings in T. vaginalis and T. foetus and we observed that their formation was associated with the parasites adhesion on the host cells, fibronectin, and precationized surfaces; and parasite:parasite interaction. A high number of rosettes, clusters of intramembrane particles that has been proposed as sensorial structures, and microvesicles protruding from the membrane were observed in the EASs. The protein VPS32, a member of the ESCRT-III complex crucial for diverse membrane remodeling events, the pinching off and release of microvesicles, was found in the surface as well as in microvesicles protruding from EASs. Moreover, we demonstrated that overexpression of VPS32 protein induce EAS formation and increase parasite motility in semi-solid medium. These results provide valuable data about the role of the flagellar EASs in the cell-to-cell communication and pathogenesis of these extracellular parasites.

Structures of Native Doublet Microtubules fromTrichomonas vaginalisReveal Parasite-Specific Proteins as Potential Drug Targets

“…As observed in low-resolution thin-section TEM studies 12 , the locomotive flagella originate from cytosolic basal bodies, and extend into the flagellar membrane with decorations along the microtubule filaments that stabilize the tubules and facilitate intraflagellar transport.…”

“…As observed in low-resolution, thin-section transmission electron microscopy (TEM) studies 13 , the locomotive flagella originate from cytosolic basal bodies, and extend into the flagellar membrane with decorations along the microtubule filaments that stabilize the tubules and facilitate intraflagellar transport. The flagellar core, or axoneme, conforms to the canonical "9+2" axonemal arrangement wherein a central pair of singlet microtubules (MTs) is connected via radial spokes to nine surrounding doublet-microtubules (DMTs) which transduce force through the flagella (Fig.…”

“…The flagellar core, or axoneme, conforms to the canonical "9+2" axonemal arrangement wherein a central pair of singlet microtubules (MTs) is connected via radial spokes to nine surrounding doublet-microtubules (DMTs) which transduce force through the flagella (Fig. 1) 13,14 . Studies in other organisms revealed DMTs are coated with different combinations of microtubule inner and outer proteins (MIPs and MOPs) that facilitate assembly, stability, and function (Fig.…”