Regulation of LRRK2 in lysosomal stress response

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The pathophysiological basis of selective neurodegeneration in Parkinson's disease remains controversial. Recent genetic and biochemical analyses have uncovered aberrant LRRK2 kinase activity as a salient feature of late-onset Parkinson's disease (PD) of both familial and idiopathic origin. Familial LRRK2 mutations are generally associated with elevated kinase activity. Identifying the pathophysiological processes that regulate LRRK2 kinase could provide a critical window to understand the pathogenesis unique to PD. LRRK2 is recruited and activated at enlarged lysosomes induced by lysosome stressors, chloroquine (CO) and LLOMe. We hypothesize that LRRK2 recruitment to the stressed lysosome is part of the lysosome stress response that acts to return lysosome to the basal states. LRRK2 association with stressed lysosomes is typically transient Remarkably, the LRRK2 association with stressed lysosomes becomes dramatically enhanced in PD-associated Vps35-D620N mutant cells. This finding suggests that LRRK2 becomes excessively activated by the lysosomal stress in Vps35-D620N cells. Thus, stress-induced LRRK2-lysosome association and activation are tightly regulated, and this regulation is disrupted by a mutation that causes familial PD. A small focused chemical inhibitor screen for additional regulators of LRRK2-lysosome association identified PKD. PKD, similar to LRRK2, is activated by lysosomal stresses, while its inactivation led to aberrant LRRK2-lysosome association and activation. This proposal aims to identify the molecular entity that recruits LRRK2 to stressed lysosomes and characterize the role of PKD-signaling pathway in LRRK2 activation and pathogenic toxicity. This proposal's completion could provide a biochemical mechanism underlying pathogenic LRRK2 activation, identify PKD as a novel regulator of LRRK2, and ascertain lysosomal stress as a pathophysiological trigger to late-onset PD