Presence and localization of vinculin in Giardia.

A requisite element of pathogenicity in Giardia infections is the parasites' ability to adhere to the intestinal epithelial brush border. The presence of vinculin in Giardia was studied because this protein is known to link the cytoskeleton to the plasma membrane and is localized at adhesion foci in many cell-cell and cell-substrate contact sites. Actin, alpha-actinin, and vinculin were identified in Giardia by western blot analysis. Giardia trophozoites attached to glass substrates were examined by interference reflection microscopy (IRM) and immunofluorescence. The IRM defined the lateral crest, bare area, and overlap region of the ventral disk, as well as the ventrolateral flange and lateral shields as close contact areas between parasite and substrate. These close contact regions were then correlated with immunofluorescence localization of actin, alpha-actinin, and vinculin. Actin was seen in the lateral crest, while alpha-actinin was observed in the ventral disc periphery and lateral shields. Vinculin was viewed at the bare and overlap areas of the ventral disc and portions of the lateral crest, as well as the ventrolateral flange and lateral shields. The correspondence of close contact sites with vinculin localization suggests a role for vinculin in Giardia attachment and adherence.