Papkovskaia, TD; (2013) Leucine Rich Repeat Kinase 2 in the pathogenesis of Parkinson's disease. Doctoral thesis , UCL (University College London).

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Abstract

The Leucine Rich Repeat kinase 2 (LRRK2) G2019S mutation is the most common genetic cause of Parkinons's disease (PD) which is clinically and pathologically indistinguishable from idiopathic PD. The effects of the G2019S mutation were explored in primary fibroblasts and SHSY5Y cells expressing wild type or G2019S LRRK2. LRRK2 was predominantly in the cytosol and small vesicular fraction of lymphoblasts and SHSY5Y cells with some localized to the mitochondria in overexpressing cells. While we could detect LRRK2 in various mouse and marmoset brain regions LRRK2 protein levels were higher in fibroblast and lymphoblast cultures. LRRK2 cellular distribution, mRNA and protein expression were not affected by the mutation. Mitochondrial abnormalities are a common feature in PD. To determine whether mitochondrial function is compromised in mutant cells, a detailed bioenergetic assessment was carried out on both G2019S cell models. An increase in basal and oligomycin inhibited respiration rates, reduced mitochondrial membrane potential and cellular ATP levels was observed for G2019S fibroblasts with similar changes observed in the neuroblastoma G2019S model. Respiratory rates and membrane potential were restored with LRRK2 kinase inhibition. Our data is consistent with reversable uncoupling of oxidative phosphorylation. Investigating transcriptional levels of mitochondrial uncoupling proteins (UCP) identified a G2019S dependent increase in UCP2 and 4 in fibroblasts and SHSY5Y cells. Upstream of this transcriptional event, an interaction between LRRK2 and the negative regulator of PGC1α expression, HDAC5 was investigated for both the wild type and G2019S protein. We have identified a role for endogenous LRRK2 in regulating mitochondrial bioenergetics with a kinase dependent gain of function for the G2019S mutation consistent with partial uncoupling of oxidative phosphorylation. LRRK2 G2019S enhanced the HDAC5 association which may be responsible for increased PGC1α expression and the downstream UCP transcription linked with the observed mitochondrial phenotype.

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