ITSN1 and Parkinson disease: ITSN1 encodes a multidomain scaffold protein that orchestrates protein-protein interactions during clathrin-mediated endocytosis and synaptic vesicle recycling.36 Notably, several other PD risk genes function in synaptic vesicle trafficking, including SNCA, LRRK2, DNAJC6, SYNJ1, VPS35, and SH3GL2.