Biophysical Society Conference | Tahoe 2024

Molecular Biophysics of Membranes

Tuesday Speaker Abstracts

SYNTHESIS OF A GM1 STRUCTURAL LIBRARY REVEALS DISTINCT MEMBRANE BEHAVIOR BASED ON CERAMIDE STRUCTURE Stefanie Schnieder 1 ; Michael Anderson 1 ; Wayne Lencer 1 ; 1 Boston Children's Hospital, Harvard Medical School, GI and Nutrition, Boston, MA, USA Each cell exhibits a diversity of ceramide acyl chain structures in their sphingolipids, which likely influence the sphingolipid’s membrane behavior, endocytic trafficking, and intracellular distributions. How cells discern among the different ceramides remains unknown. To address mechanism, we synthesized a library of GM1 glycosphingolipids with naturally varied acyl chain structures and quantitatively assessed their membrane behavior. Using superresolution microscopy and single particle tracking we found a motif within the acyl chain, the C14* motif – a stretch of at least 14 saturated hydrocarbons extending from the C1 at the water-bilayer interface – that dictates incorporation into membrane nanodomains. This motif allows for lysosomal sorting by exclusion from endosome sorting tubules. Intracellular sorting by the C14* motif is cholesterol and nanodomain dependent. Perturbations of the C14* motif by unsaturation enables GM1 entry into endosomal sorting tubules of the recycling, retrograde and transcytotic pathways. These GM1 species cannot assemble into membrane nanodomains. Unsaturation occurring beyond the C14* motif (in very long unsaturated acyl chains) rescued lysosomal sorting, interaction with cholesterol and nanodomain incorporation. These results define a structural motif underlying the membrane organization and trafficking of sphingolipids and implicate cholesterol-sphingolipid nanodomain formation in endocytic sorting mechanisms.

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