Pink1 Parkinson mutations, the Cdc37/Hsp90 chaperones and Parkin all influence the maturation or subcellular distribution of Pink1

Abstract

Mutations in the ubiquitously expressed gene PTEN-induced kinase 1 (Pink1) cause autosomal recessive Parkinson's disease. Pink1 encodes a putative serine/threonine kinase with an N-terminal mitochondrial targeting sequence. The mechanism that leads to selective degeneration of dopaminergic neurons via Pink1 mutations is unknown. A full-length pre-protein (66 kDa) and an N-terminally truncated mature form (55 kDa) have been described in human brain. Here, we report that the endogenous 66 kDa and 55 kDa Pink1 forms in cultured cells are not exclusive to mitochondria but also occur in cytosolic and microsome-rich fractions. Pink1 66 kDa is the predominant isoform in cultured cells. Using unbiased analyses of immunoisolated Pink1 complexes by mass spectrometry, co-immunoprecipitation and Hsp90 inhibitor studies, we identify Pink1 as a novel Cdc37/Hsp90 client kinase. This chaperone system influences both the subcellular distribution and the 66/55 kDa protein ratio of Pink1. PD-causing Pink1 mutations decrease whereas Parkin expression increases the Pink1 66/55 kDa protein ratio, biochemically linking Pink1 and Parkin and highlighting the potential relevance of this ratio for PD pathogenesis. Finally, we document the influence of Parkin on Pink1 subcellular distribution, providing further evidence for a common pathogenic pathway in recessive PD.