The enigma of eugregarine epicytic folds: Where gliding motility originates?
|Druh||Článek v odborném periodiku|
|Časopis / Zdroj||Frontiers in Zoology|
|Fakulta / Pracoviště MU|
|Klíčová slova||Actin; Cytochalasin D; Epicyte; Epicytic folds; Eugregarine; Glideosome; Gliding motility; Jasplakinolide; Mucus; Myosin; Pellicle|
|Popis||Gregarines (Conoidasida, Gregarinasina) are a heterogeneous group that parasitize invertebrates and urochordates, and are thought to be an early branching lineage of Apicomplexa. As characteristic of apicomplexan zoites, gregarines are covered by a complicated pellicle, consisting of the plasma membrane and the closely apposed inner membrane complex, associated with cytoskeletal elements. The cell cortex of eugregarines, the epicyte, is more complicated than that of other apicomplexans, as it forms various superficial structures. The epicyte of the eugregarines, Gregarina cuneata, G. polymorpha and G. steini, analysed in the present study is organised in longitudinal folds covering the entire cell. In mature trophozoites and gamonts, each epicytic fold exhibits similar ectoplasmic structures and is built up from the plasma membrane, inner membrane complex, 12-nm filaments, rippled dense structures and basal lamina. In addition, rib-like myonemes and an ectoplasmic network are frequently observed. Under experimental conditions, eugregarines showed varied speeds and paths of simple linear gliding. In all three species, actin and myosin were associated with the pellicle, and this actomyosin complex appeared to be restricted to the lateral parts of the epicytic folds. Treatment of living gamonts with jasplakinolide and cytochalasin D confirmed that actin actively participates in gregarine gliding. Contributions to gliding of specific subcellular components are discussed. Cell motility in gregarines and other apicomplexans share features in common, i.e. a three-layered pellicle, an actomyosin complex, and the polymerisation of actin during gliding. Although the general architecture and supramolecular organisation of the pellicle is not correlated with gliding rates of eugregarines, an increase in cytoplasmic mucus concentration is correlated. Data suggest that gregarines utilize several mechanisms of motility and that this is influenced by environmental conditions.|