Gangliosides Modulate the Secretion of Extracellular Vesicles and Their Misfolded Protein Cargo

Gangliosides are glycosphingolipids that play an integral role in cell signaling and provide neuroprotection. While present on extracellular vesicles (EVs) - key mediators of intercellular communication - their role in EV biogenesis remains unclear. Here, we identify gangliosides, both endogenously synthesized and exogenously administered, as key modulators of EV biogenesis, with the specific composition of their glycan headgroup and the presence or absence of sialic acid and N-acetyl-D-galactosamine residues dictating whether they promote or inhibit EV biogenesis. We show that GM1 and other complex gangliosides enhance EV secretion, while disruption of ganglioside synthesis impairs it. GM1 supplementation restores EV secretion in Huntingtons disease (HD) fibroblasts and HD cell models that have lower than normal levels of gangliosides, and in cells with a genetic block of ganglioside synthesis that models rare early-onset neurodegenerative diseases. Notably, GM1 also enhances EV-mediated secretion of pathogenic misfolded proteins, including mutant huntingtin (mHTT), -synuclein and tau, reducing intracellular burden and providing mechanistic insight into the mHTT-lowering effects of GM1 treatments in HD models. Our findings shed light on the neuroprotective roles of gangliosides and highlight their potential for therapeutic exploitation in misfolded protein disorders.