ALPHA-SYNUCLEIN PHOSPHORYLATION DIRECTS TRAFFICKING OF THE V-SNARE SYNAPTOBREVIN-2

Alpha-synuclein has been extensively studied for its role in Parkinson's disease, however its native function remains unclear. Several lines of evidence suggest it modulates presynaptic function. As many presynaptic proteins have their functions regulated by phosphorylation, we sought to determine whether alpha-synuclein, a known phosphoprotein, might similarly have phospho-dependent roles. Using phospho-proteomics we identified two residues in alpha-synuclein, Ser42 and Thr81, that undergo activity-dependent phosphorylation. We used a phospho-mimetic approach and a battery of pHluorin assays we show that ablating phosphorylation at Thr81 alters the subcellular distribution of synaptobrevin-2, a crucial fusogenic vesicular SNARE protein and known binding partner of LPH-synuclein. Ablating phosphorylation of LPH-synuclein at Thr81 specifically accelerated endocytic retrieval of synaptobrevin-2 during stimulation without impacting global endocytosis, evoked exocytosis, or the size of the recycling pool. Conversely, mimicking phosphorylation at Thr81 augmented post-stimulation retrieval of synaptobrevin-2. This suggests that via phosphorylation at Thr81, alpha-synuclein has an important role in modulating endocytic retrieval of synaptobrevin-2. Since synaptobrevin-2 has a key role in synaptic vesicle exocytosis, we hypothesize that this novel function of alpha-synuclein is crucial for sustaining neurotransmission and may be a contributing disease mechanism in alpha-synuclein pathologies.