siRNA-mediated knockdown (KD) of a modulator for autophagosome formation, ATG5, BECN1, or FIP200 inhibited autophagic flux and secretion, causing accumulation of Triton X-100-insoluble α-synuclein (α-syn), which is an aggregate-prone protein responsible for neuronal loss in Parkinson’s disease. The gene discussed is ATG5; the disease is Parkinson disease.