Freeze-fracture localization of filipin-cholesterol complexes in the plasma membrane of Trypanosoma cruzi.

The polyene antibiotic filipin was used as a probe for the detection of cholesterol on the P and E faces of the cell body and the flagellar membranes of epimastigotes of Trypanosoma cruzi. When glutaraldehyde-fixed cells were treated with filipin the filipin-cholesterol complexes were homogenously distributed throughout the parasite's plasma membrane. In some cells, mainly on their P faces, such complexes were arranged linearly forming parallel bands with a distance between the bands similar to that existent between the subpellicular microtubules that are attached to the plasma membrane. Filipin-cholesterol complexes were more abundant in the flagellar membrane than in the membrane that enclosed the cell body. No filipin-cholesterol complexes were seen in the membrane of intracellular organelles. Treatment of living epimastigotes with filipin-induced aggregation of cholesterol and intramembranous particles.