IMMUNOELECTRON MICROSCOPY OF GIARDIA-LAMBLIA CYTOSKELETON USING ANTIBODY TO ACETYLATED ALPHA-TUBULIN

Giardia lamblia trophozoites contain acetylated alpha-tubulin but lack detectable levels of tyrosinolated alpha-tubulin, as demonstrated in immunoblots with monoclonal antibodies specific for these tubulin form s. By immunofluorescence microscopy, acetylated alpha-tubulin is local ized in axonemes, median bodies and in the adhesive disk. Post-embeddm ent immunogold labeling of thin sections of cells was used to evaluate acetylation at the level of individual microtubules by electron micro scopy. Cells were fixed with glutaraldehyde and embedded in the acryli c resin LR Gold. Results indicate all microtubules in adhesive disk, a xonemes, basal bodies, funis and the median bodies contain acetylated alpha-tubulin. Unlike immunofluorescence labeling, all microtubules of the adhesive disk and the funis could be gold labeled. No nonspecific labeling of the cytoplasm or of structures other than microtubules wa s observed. Acetylated microtubules in G. lamblia do not appear to be a subset of microtubules and acetylation appears uniform along the ent ire length of individual microtubules. Acetylation and the tyrosinolat ion state of microtubules in Giardia are discussed in the context of m icrotubule stability and crosslinked features of the cytoskeleton.