Detection and localization of actin inToxoplasma gondii

Abstract

The immunological cross-reactivity of the protein from whole-cell extracts of Toxoplasma gondii with antisera against actins from chicken-gizzard smooth muscle and from Ascaris body-wall muscle was demonstrated by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis (SDS-PAGE) and immunofluorescence studies. A protein of about 42 kDa, with the same mobility as that of rabbit smooth-muscle actin in SDS-PAGE showed cross-reactivity with anti-actin antisera on the electroblotted nitrocellulose sheet. Indirect fluorescent antibody staining of the parasites clearly showed that actin localized strongly in the anterior third of the organism in both extra- and intrahost cellular stages. From both a biochemical as well as structural point of view, the results obtained in the present experiments might explain the locomotive features of the parasite such as twirling and sliding, with most of the activity at the anterior end.

Actin in the parasiteToxoplasma gondii is encoded by a single copy gene,ACT1 and exists primarily in a globular form

“…Our results differ from previous reports that suggested actin was primarily concentrated at the apical end of the parasite [Cintra and DeSousa, 1985;Endo et al, 1988;Yasuda et al, 1988]. While there are several possible explanations for these differences, they are unlikely to result from differences in fixation conditions as we have observed similar circumferential actin staining in aldehyde, methanol of acetone-treated parasites (Dobrowolski and Sibley unpublished).…”

“…By indirect immunofluorescence, actin was reported to be primarily concentrated in the anterior one-third of the tachyzoite and in a diffuse staining pattern throughout the cytoplasm [Cintra and De Souza, 1985;Endo et al, 1988]. Immunoelectron microscopy (EM) staining with heterologous antisera localized actin at the apical end of the parasite in the conoid and associated with subpellicular microtubules .…”

Toxoplasma gondii Tissue Cyst: Cyst Wall Incorporation Activity and Matrix Cytoskeleton Proteins Paving the Way to Nutrient Acquisition

“…By indirect immunofluorescence, actin has been reported to be primarily concentrated in the anterior third of the tachyzoite and in a diffuse staining pattern throughout the cytoplasm [40,41], our immunofluorescence for Toxoplasma gondii Tissue Cyst: Cyst Wall Incorporation Activity and Matrix Cytoskeleton... http://dx.doi.org/10.5772/intechopen.68202 actin in the bradyzoite stage revealing the same staining pattern. We also considered that the strong fluorescence staining along the cyst wall could be a false positive and may be caused by adsorptions of the antibody.…”

Lytic Cycle ofToxoplasma gondii

“…Although microfilaments have not been observed in this organism (27), actin has been detected in the conoid, preconoidal rings, and subpellicular microtubules by immunoelectron microscopy (183). Immunofluorescence of intracellular tachyzoites demonstrates that actin resides predominantly in the anterior portion of 75% of extracellular parasites (the remaining 25% demonstrated staining throughout the cell) (50).…”