Autosomal dominant mutations in leucine-rich repeat kinase 2 ( LRRK2 ) are associated with Parkinson's disease (PD). Most pathogenic LRRK2 mutations result in amino-acid substitutions in the central ROC-COR-Kinase triple domain and affect enzymatic functions of the protein. However, there are several variants in LRRK2 , including the risk factor G2385R, that impact PD pathogenesis by unknown mechanisms. Previously, we have shown that G2385R LRRK2 has decreased kinase activity in vitro and altered affinity to LRRK2 interactors. Specifically, we found an increased binding to the chaperone Hsp90 that is known to stabilize LRRK2, suggesting that G2385R may have structural effects on LRRK2. In this study, we further explored the effects of G2385R on LRRK2 in cells. We found that G2385R LRRK2 has lower steady state intracellular protein levels compared to wild type LRRK2 due to increased protein turnover of the mutant protein. Mechanistically, this is a consequence of a higher affinity of G2385R compared to the wild type protein for two proteins involved in proteasomal degradation, Hsc70 and CHIP. Overexpression of CHIP decreased intracellular protein levels of both G2385R mutant and wild type LRRK2 while siRNA CHIP knock-down had the opposite effect. We suggest that the G2385R substitution tilts the equilibrium between re-folding and proteasomal degradation towards intracellular degradation. The observation of lower steady state protein levels may explain why G2385R is a risk factor rather than a penetrant variant for inherited PD.
- Parkinson's disease
- protein stability
- ©2017 The Author(s)
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