Myosin‐Like Protein (M_R 175,000) In Gregarina Blaberae

Abstract

A myosin-like protein (M(r) 175,000) was detected in the parasitic protozoan Gregarina blaberae, by both immunofluorescence and immunoblotting of one- and two-dimensional electrophoresis gels using anti-myosin antibodies. This protein was present in the trophozoite ghost but not in the cytoplasmic extract, nor in extract from the sexual stage, suggesting a protein-stage-dependent expression. The protein tightly bound to the cortical membranes was insoluble at low ionic strength, or in detergent solutions, but could be extracted from Gregarina ghosts by 6 M urea in high ionic strength solution (0.5 M NaCl) and in the presence of reducing agents (20 mM DTT). The protein was localized by indirect immunofluorescence in the cortex of the epimerite, in the fibrillar disc (the so-called septum) separating the proto- and the deutomerite segments, in the contractile ring or sphincter at the top of the protomerite, and as longitudinal lines underlying the G. blaberae epicyte folds. The presence of both actin-like and myosin-like proteins would be consistent with a role in gliding and other cell motility processes of this parasite.

The enigma of eugregarine epicytic folds: where gliding motility originates?

“…Although the localisation of actin seems to be more diffuse in gregarines, myosin seems to be organised in longitudinal rows corresponding to epicytic folds similar to observations in G. blaberae [54]. The micrographs obtained with the anti-myosin antibody (smooth and skeletal, the whole antiserum from Sigma-Aldrich, Czech Republic) showed similar localization of myosin as obtained by Heintzelman with specific antibodies directed against the myosins A, B and F [20,27].…”

Sophisticated Adaptations of Gregarina cuneata (Apicomplexa) Feeding Stages for Epicellular Parasitism

“…Therefore, Lucarotti [11] speculated about hypothetical reattachment of Leidyana trophozoites to younger cells after abandoning senescing cells, facilitated by a retractable epimerite and eugregarine gliding motility. The presence of contractile elements in the area of the epimerite [20], [21] and protomerite top [30], [31] serves as a more convincing argument in favour of the structural dynamics of these cell regions and epimerite retraction theory [8], [11]. Similarly, actin-like filaments demonstrated in the mucron of lecudinid eugregarine are considered to facilitate its adhesion to the host cell [20], [32].…”

“…There are two contradictory hypotheses on gregarine detachment from host tissue at the end of the trophozoite stage. One of them describes trophozoite detachment via epimerite retraction, self-regulated by the vegetative stage [8], while the other is based on gradual epimerite constriction facilitated by the supposed contractility of an osmiophilic ring surrounding the base of the epimerite and acting as a sphincter during the separation of the epimerite from the rest of the gregarine body [9], [10], [20], [21], [22]. All of these questions raised by conflicting data must be satisfactorily answered to clarify the parasitic strategies of gregarines and to better understand the evolutionary history of the phylum Apicomplexa.…”

Motility in blastogregarines (Apicomplexa): Native and drug-induced organisation of Siedleckia nematoides cytoskeletal elements

“…nematoides , some eugregarines and protococcidian Eleutheroschizon duboscqi , the phalloidin labelling revealed the presence of F-actin, even without the application of filament-stabilising probes [3, 46, 47, 62]. The research on involvement of actin- and myosin-like proteins in gregarine cell motility has been restricted to representatives of the genus Gregarina [3, 4, 12, 15, 16, 21]. The gregarine movement is often attributed to the F-actin cytoskeleton that is assumed to exist in the form of a myocyte (= outer layer of longitudinal and inner layer of circular myonemes) underlying the pellicle [12, 24, 25, 30, 32, 34] and to the ectoplasmic network [63], e.g.…”