Uptake of [3H]-gangliosides by an intestinal protozoan, Giardia lamblia

Because of their limited lipid synthesis ability it has been postulated that Giardia lamblia trophozoites depend on lipid remodeling reactions, to generate parasite-specific phospho and glycolipids. We have shown earlier that exogenous bile acids and lipid molecules are taken up by Giardia through active transport and by other mechanisms. Another report suggests that lipoprotein-like receptors may be present in this parasite that are involved in lipid endocytosis. In the present investigation, we asked whether and by what mechanism exogenous gangliosides can be taken up by Giardia. We found that ganglioside uptake was dependent, on time and concentration, but was not temperature- or carrier-dependent. Gangliosides encapsulated into liposomes were taken up much more effectively than non-encapsulated gangliosides. These results are consistent with a passive uptake process, facilitated by membrane fusion with lipid carriers, but not dependent on a catalytic carrier mechanism. This observation may have some therapeutic implications.