Sim, V. | Search bioRxiv

bioRxiv2025

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.

cell biology↗

bioRxiv2023

Fibronectin: a natural barrier against prion infection

A distinctive signature of the prion diseases is the accumulation of the pathogenic isoform of the prion protein, PrPSc, in the central nervous system of prion-affected humans and animals. PrPSc is also found in peripheral tissues, raising concerns about the potential transmission of pathogenic prions through human food supplies and posing a significant risk to public health. Although muscle tissues are considered to contain levels of low prion infectivity, it has been shown that myotubes in culture efficiently propagate PrPSc. Given the high consumption of muscle tissue, it is important to understand what factors could influence the establishment of a prion infection in muscle tissue. Here we used in vitro myotube cultures, differentiated from the C2C12 myoblast cell line (dC2C12), to identify factors affecting prion replication. A range of experimental conditions revealed that PrPSc is tightly associated with proteins found in the systemic extracellular matrix (ECM), mostly fibronectin (FN). The interaction of PrPSc with FN decreased prion infectivity, as determined by standard scrapie cell assay. Interestingly, the prion-resistant reserve cells in dC2C12 cultures displayed a FN-rich ECM while the prion-susceptible myotubes expressed FN at a low level. In agreement with the in vitro results, immunohistopathological analyses of tissues from sheep infected with natural scrapie demonstrated a prion susceptibility phenotype linked to an extracellular matrix with undetectable levels of FN. Conversely, PrPSc deposits were not observed in tissues expressing FN. These data indicate that extracellular FN may act as a natural barrier against prion replication and that the extracellular matrix composition may be a crucial feature determining prion tropism in different tissues. Author summaryPrion diseases are complex fatal neurodegenerative disorders caused by a misfolded form of the cellular protein PrPC (PrPSc). Due to the potential zoonotic transmission of these disorders through animal-based food intake, it is crucial to identify the tissues in which PrPSc can accumulate and what might influence its tropism. Animal muscle (or meat) and related food products are highly consumed, raising concern of the involvement of muscle cells in prion replication. Muscle tissue from prion-affected animals contains low levels of infectivity and PrPSc is mostly associated with nerve structures rather than myofibers, whereas C2C12 myotubes, a muscle-derived cell type, efficiently replicate prions in vitro and generate high levels of infectivity compared with other cell cultures. We demonstrate a fibronectin-mediated interference with prion infection in differentiated C2C12 cultures that correlates with the findings in tissues from naturally scrapie-infected animals. Our results suggest that extracellular matrix composition, specifically regarding the presence of fibronectin, might determine prion tropism and dissemination.

biochemistry↗