Roughly 10% of all cases of Parkinson’s disease occur comparatively early in life (onset <55 years) and can be linked to mutations in ~15 PARK genes. The E3 ubiquitin ligase Parkin, and the ubiquitin kinase PINK1 are amongst the most prevalent mutated genes. Cell biological studies in the past decade have linked PINK1 and Parkin to mitophagy, a cellular process responsible for the removal of damaged mitochondria by autophagy.
My lab has gained insights into mitophagy via mechanistic structural and biochemical studies, and we have illuminated the phospho-ubiquitin-driven activation process of the autoinhibited E3 ligase Parkin and the mechanism of its antagonist, the mitochondrial deubiquitinase USP30. We have recently extended our studies to PINK1, the ubiquitin kinase. PINK1 stabilisation is considered the most upstream process in mitophagy, but available structural snapshots of PINK1 from diverse insects have so far failed to explain how it becomes an active ubiquitin kinase.
We have now followed the PINK1 activation process in molecular detail, using X-ray crystallography and cryo-EM. Our data illuminate how PINK1 is active in its unphosphorylated state and dimerises with another PINK1 molecule to perform trans-autophosphorylation. Upon phosphorylation, a conformational change and disorder-order transitions in the kinase N-lobe lead to formation of the ubiquitin binding domain, and dissolves the dimer to generate a monomeric ubiquitin kinase. We further reveal how PINK1 activity and dimerization is be regulated by phosphorylation and oxidation.