Mutations in PINK1 and PARKIN cause recessive, early-onset Parkinson's disease (PD). Together, these two proteins orchestrate a protective mitophagic response that ensures the safe disposal of damaged mitochondria. The kinase PINK1 phosphorylates ubiquitin (Ub) at the conserved residue S65, in addition to modifying the E3 ubiquitin ligase Parkin. The structural and functional consequences of Ub phosphorylation (pS65-Ub) have already been suggested from in vitro experiments, but its (patho-)physiological significance remains unknown. We have generated novel antibodies and assessed pS65-Ub signals in vitro and in cells, including primary neurons, under endogenous conditions. pS65-Ub is dependent on PINK1 kinase activity as confirmed in patient fibroblasts and postmortem brain samples harboring pathogenic mutations. We show that pS65-Ub is reversible and barely detectable under basal conditions, but rapidly induced upon mitochondrial stress in cells and amplified in the presence of functional Parkin. pS65-Ub accumulates in human brain during aging and disease in the form of cytoplasmic granules that partially overlap with mitochondrial, lysosomal, and total Ub markers. Additional studies are now warranted to further elucidate pS65-Ub functions and fully explore its potential for biomarker or therapeutic development. Synopsis In this study, two newly generated antibodies are used to detect endogenous phospho-ubiquitin in cells and human brain samples. pS65-Ub is shown to be reversible, respond to mitochondrial stress and accumulate during aging and in Parkinson's disease (PD). pS65-Ub is amplified by the concerted action of PINK1 kinase and Parkin E3 ubiquitin ligase in response to mitochondrial stress. pS65-Ub specifically labels severely damaged mitochondria destined for degradation. pS65-Ub is a novel biomarker of mitochondrial quality control and could also serve as a potential therapeutic target for PD. In this study, two newly generated antibodies are used to detect endogenous phospho-ubiquitin in cells and human brain samples. pS65-Ub is shown to be reversible, respond to mitochondrial stress and accumulate during aging and in Parkinson's disease.
- early-onset Parkinson's disease
- phosphorylated ubiquitin
ASJC Scopus subject areas
- Molecular Biology