Morrison, Rebecca; (2024) The effects of LRRK2 mutations on macrophage function in Parkinson's disease. Doctoral thesis (Ph.D), UCL (University College London).

Text Rebecca Morrison - 20191361 - PhD thesis.pdf - Other Access restricted to UCL open access staff until 1 October 2025. Download (12MB)

Abstract

LRRK2 is commonly mutated in Parkinson’s disease and has cell type-specific mechanisms of activation and function. LRRK2 is expressed by immune cells, and while there is evidence of an inflammatory component to PD, the activity of LRRK2 pathogenic mutations in immune cells is not well characterised. In macrophages, LRRK2 is associated with lysosomes and is activated following lysosomal damage. However, the functional outcomes of clinically relevant pathogenic mutations in macrophages are unknown. Here, using primary mouse and patient-derived iPSC derived macrophage (iPSDM) models of LRRK2-G2019S, I defined the substrates of LRRK2 after lysosomal damage. A phosphoproteomics-based comparison between wild-type macrophages and macrophages lacking LRRK2 kinase activity revealed a subset of Rab GTPases, common to those identified in previous studies, as LRRK2 kinase substrates in macrophages. Comparison of LRRK2-G2019S and wild-type macrophages demonstrated a remarkably similar level of Rab GTPase phosphorylation at baseline and after lysosomal damage. Only two Rab phosphorylations differed after lysosomal damage in LRRK2-G2019S macrophages: phosphorylated Rab12 was increased, while phosphorylated Rab35 was decreased compared to wild-type cells. Live cell snapshot imaging revealed a deficit in the repair of lysosomal damage in LRRK2-G2019S macrophages. However, lysosomal repair via the endosomal sorting complex required for transport (ESCRT) machinery was not dependent on LRRK2 kinase activity in mouse primary macrophages. Functionally, LRRK2-G2019S macrophages showed more cell death and increased markers of apoptosis after lysosomal membrane damage. This increase in lysosomal damage-induced cell death was recapitulated in iPSDM from patients carrying the G2019S mutation, but not in isogenic control iPSDM. Altogether, this work defines the signaling downstream of G2019S in macrophages and identifies susceptibility to cell death after lysosomal damage as an important phenotype of this mutation.

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