Actin-nucleation promoting factor N-WASP influences alpha-synuclein condensates and pathology

Abnormal intraneuronal accumulation of soluble and insoluble alpha-synuclein (alpha-Syn) is one of the main pathological hallmarks of synucleinopathies, such as Parkinson’s disease (PD). It has been well- documented that the reversible liquid-liquid phase separation of alpha-Syn can modulate synaptic vesicle condensates at the presynaptic terminals. However, alpha-Syn can also form liquid-like droplets that may convert into amyloid-enriched hydrogels or fibrillar polymorphs under stressful conditions. To advance our understanding on the mechanisms underlying alpha-Syn phase transition, we employed a series of unbiased proteomic analyses and found that actin and actin regulators are part of the alpha-Syn interactome. We focused on Neural Wiskott-Aldrich syndrome protein (N-WASP) because of its association with a rare early-onset familial form of PD. In cultured cells, we demonstrate that N-WASP undergoes phase separation and can be recruited to synapsin-1 liquid-like droplets, whereas it is excluded from alpha-Syn/synapsin-1 condensates. Consistently, we provide evidence that wsp-1/WASL loss of function (lof) alters the number and dynamics of alpha-Syn inclusions in the nematode Caenorhabditis elegans. Together, our findings indicate that N-WASP expression may create permissive conditions that promote alpha-Syn condensates and their potentially deleterious conversion into toxic species.