Synthesis of Gb3 Glycosphingolipids with Labeled Head Groups: Distribution in Phase-Separated Giant Unilamellar Vesicles

The receptor lipid Gb(3) is responsible for the specific internalization of Shiga toxin (STx) into cells. The head group of Gb(3) defines the specificity of STx binding, and the backbone with different fatty acids is expected to influence its localization within membranes impacting membrane organization and protein internalization. To investigate this influence, a set of Gb(3) glycosphingolipids labeled with a BODIPY fluorophore attached to the head group was synthesized. C-24 fatty acids, saturated, unsaturated, alpha-hydroxylated derivatives, and a combination thereof, were attached to the sphingosine backbone. The synthetic Gb(3) glycosphingolipids were reconstituted into coexisting liquid-ordered (l(o))/liquid-disordered (l(d)) giant unilamellar vesicles (GUVs), and STx binding was verified by fluorescence microscopy. Gb(3) with the C-24:0 fatty acid partitioned mostly in the l(o) phase, while the unsaturated C-24:1 fatty acid distributes more into the l(d) phase. The alpha-hydroxylation does not influence its partitioning.