Rescuing dopaminergic dysfunction through E3-ubiquitin ligase modulation in endophilin-A mutants

Dopaminergic neuron functions rely on active synaptic vesicle dynamics and proteostasis. Deficientendocytosis due to lack of endophilins-A, key endocytic adaptors, alters the expression of genesassociated with ataxia, Parkinson's disease and protein homeostasis. Fbxo32, a E3-ubiquitin ligaserequired for muscle atrophy but also expressed in the brain, was shown to be up-regulated inendophilin mutants. Hence, we aimed to investigate the dopaminergic system alterations in theendophilins-A murine model, and explore the effects of Fbxo32 genetic modifications on dopaminedegeneration in this mammalian system.Immunohistochemistry targeting typical dopaminergic markers revealed distinctive alterations in thedopaminergic system of endophilin-A1KO-A2HT-A3KO mice, characterized by an increase ofdysmorphic clusters expressing dopamine transporter (DAT) and tyrosine hydroxylase (TH) in thestriatum. To elucidate the role of Fbxo32 in this phenotype, we crossed endophilin-A1KO-A2HT-A3KOmice with Fbxo32-HT mice, resulting in a quadruple mutant (endophilin-A1KO-A2HT-A3KO/FBXO32-HT). Intriguingly, modulation of Fbxo32 in endophilin-A1KO-A2HT-A3KO mice rescued dopaminergicdeficiencies, as evidenced by immunohistochemistry and behavioral data to be discussed during thesymposium. Further, Western blot analysis of striatum extracts from endophilin-A1KO-A2HT-A3KO/FBXO32-HT mice revealed a restoration of increased ubiquitination observed in endophilin-A1KO-A2HT-A3KO mice.In sum, the alteration of Fbxo32 in endophilin-A mutants rescues dopaminergic pathology andaltered proteostasis. These findings suggest new potential treatment strategies for Parkinson'sdisease, emphasizing the key role of endophilins-A in the dopaminergic neuron function andintegrity.