Gregarinasina

Gregarines
Scientific classification
Kingdom:	Protista
Phylum:	Apicomplexa
Class:	Conoidasida
Subclass:	Gregarinasina
Orders
Archigregarinorida Eugregarinorida Neogregarinorida

The gregarines are a group of Apicomplexan protozoa, classified as the Gregarinasina or Gregarinea.

The gregarines are able to move and change direction along a surface through gliding motility without the use of cilia, flagella, or lamellipodia [Walker et al., 1979]. This is accomplished through the use of an actin and myosin complex [Heintzelman, 2004]. The complexes require an actin cytoskeleton to perform their gliding motions [Mitchison and Cramer, 1996]. In the proposed ‘capping’ model, an uncharacterized protein complex moves rearward, moving the parasites forward [Sibley et al., 1998].

The large (roughly half a millimeter) parasites inhabit the intestines of a large number of invertebrates. They are not found in humans. However, Gregarinasina is closely related to both Toxoplasma and Plasmodium, which cause toxoplasmosis and malaria, respectively. Both protists use protein complexes similar to those that are formed by the gregarines for gliding motility and to invade target cells [Sibley et al., 1998; Menard, 2001; Meissner et al, 2002]. This makes them an excellent model for studying gliding motility with the goal of creating toxoplasmosis and malaria treatment options.

Bibliography

• Heintzelman, M B. 2004. Actin and Myosin in Gregarina polymorpha. Cell Motil Cytoskeleton 58:83-95.
• Menard, R. 2001. Gliding Motility and Cell Invasion by Apicomplexa: Insights from the Plasmodium sporozoite. Cell. Microbiol 3: 63-73.
• Meissner, M, Schluter, D and Soldati, D. 2002. Role of Toxoplasma Gondii Myosin a in Powering Parasite Gliding and Host Cell Invasion. Science 298: 837-841.
• Mitchison, T.J., and Cramer, L.P. 1996. Actin-based cell motility and cell locomotion. Cell 84: 371–379
• Sibley, L.D., Hakansson, S, Carruthers, V. B. 1998. Gliding motility: An efficient mechanism for cell penetration Curr. Biol. 8, 12.
• Walker, M M., C Mackenzie, S P Bainbridge, and C Orme. 1979. A Study of the Structure and Gliding Movement of Gregarina garnhami. J Protozool 26: 566-574.