Disruption of the OPTN-TBK1 axis impairs autophagosome formation in prion disease

Prion diseases are chronic, transmissible, and neurodegenerative disorders that affect both humans and other mammals. Mitophagy is essential for maintaining mitochondrial homeostasis and normal neuronal function. Our previous research show that the PINK1-Parkin-dependent mitophagy pathway is impaired in the PrP^106-126 induced prion disease model, yet the underlying downstream mechanisms remain elusive. We report that impaired phosphorylation of ubiquitin at Ser65 diminishes OPTN recruitment to mitochondria, thereby influence mitochondrial translocation of TBK1 and ATG9A, consequently suppresses TBK1 autophosphorylation that depends on the OPTN-ATG9A interaction. As a result, reduction of OPTN phosphorylation dependent on TBK1 inhibits autophagosome formation and ultimately leads to defective mitophagy. Importantly, overexpression of OPTN rescued the mitophagy impairment induced by PrP^106-126 and partially restoring mitochondrial morphology and function. Our findings identify OPTN as a critical node, proposing its therapeutic targeting as a strategy to counteract prion disease progression.