Biology subjects

McNamara, E.

Publications and source records attributed to McNamara, E..

3 recordsLinked to original sources

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↗

bioRxiv2022

Dynamic regulation of inter-organelle communication by ubiquitylation controls skeletal muscle development and disease onset

Ubiquitin-proteasome system (UPS) dysfunction is associated with the pathology of a wide range of human diseases including myopathies and muscular atrophy. However, the mechanistic understanding of specific components on the regulation of protein turnover during development and disease progression in skeletal muscle is unclear. Mutations in KLHL40, an E3 ubiquitin ligase cullin3 (CUL3) substrate-specific adapter protein result in a severe form of congenital nemaline myopathy, but the events that initiate the pathology and the mechanism through which it becomes pervasive, remains poorly understood. To characterize the KLHL40-regulated ubiquitin modified proteome during skeletal muscle development and disease onset, we used global, quantitative mass spectrometry-based ubiquitylome and global proteome analyses of klhl40 mutant zebrafish during disease progression. Global proteomics during skeletal muscle development revealed extensive remodeling of functional modules linked with sarcomere formation, energy and biosynthetic metabolic processes and vesicle trafficking. Combined analysis of klh40 mutant muscle proteome and ubiquitylome identified thin filament proteins, metabolic enzymes and ER-Golgi vesicle trafficking pathway proteins regulated by ubiquitylation during muscle development. Our studies identified a role for KLHL40 as a negative regulator of ER-Golgi anterograde trafficking through ubiquitin-mediated protein degradation of secretion associated Ras related GTPase1a (Sar1a). In KLHL40 deficient muscle, defects in ER exit site vesicle formation alter Golgi compartment and downstream transport of extracellular cargo proteins, resulting in structural and functional abnormalities. Our work reveals that the muscle proteome is dynamically fine-tuned by ubiquitylation to regulate skeletal muscle development and uncovers new disease mechanisms for therapeutic development in patients. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/501000v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1950696org.highwire.dtl.DTLVardef@e37313org.highwire.dtl.DTLVardef@9804a6org.highwire.dtl.DTLVardef@59527f_HPS_FORMAT_FIGEXP M_FIG C_FIG

genetics↗

bioRxiv2020

Tau conformers in FTLD-MAPT undergo liquid-liquid phase separation and perturb the nuclear envelope

Recent studies show that a single MAPT gene mutation can promote alternative tau misfolding pathways engendering divergent forms of frontotemporal dementia and that under conditions of molecular crowding, the repertoire of tau forms can include liquid-liquid phase separation (LLPS). We show here that following pathogenic seeding, tau condenses on the nuclear envelope (NE) and disrupts nuclear-cytoplasmic transport (NCT). Interestingly, NE fluorescent tau signals and small fluorescent inclusions behaved as demixed liquid droplets in living cells. Thioflavin S-positive intracellular aggregates were prevalent in tau-derived inclusions with a size bigger than 3 m2, indicating that a threshold of critical mass in the liquid state condensation may drive liquid-solid phase transitions. Our findings indicate that tau undergoing LLPS is more toxic amongst a spectrum of alternative conformers; LLPS droplets on the NE that disrupt NCT serve to trigger cell death and can act as nurseries for fibrillar structures abundantly detected in end-stage disease.

neuroscience↗