Abstract
Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with late-onset, autosomal-dominant, familial Parkinson's disease (PD) and also contribute to sporadic disease. The LRRK2 gene encodes a large protein with multiple domains, including functional Roc GTPase and protein kinase domains. Mutations in LRRK2 most likely cause disease through a toxic gain-of-function mechanism. The expression of human LRRK2 variants in cultured primary neurons induces toxicity that is dependent on intact GTP binding or kinase activities. However, the mechanism(s) underlying LRRK2-induced neuronal toxicity is poorly understood, and the contribution of GTPase and/or kinase activity to LRRK2 pathobiology is not well defined. To explore the pathobiology of LRRK2, we have developed a model of LRRK2 cytotoxicity in the baker's yeast Saccharomyces cerevisiae. Protein domain analysis in this model reveals that expression of GTPase domain-containing fragments of human LRRK2 are toxic. LRRK2 toxicity in yeast can be modulated by altering GTPase activity and is closely associated with defects in endocytic vesicular trafficking and autophagy. These truncated LRRK2 variants induce similar toxicity in both yeast and primary neuronal models and cause similar vesicular defects in yeast as full-length LRRK2 causes in primary neurons. The toxicity induced by truncated LRRK2 variants in yeast acts through a mechanism distinct from toxicity induced by human α-synuclein. A genome-wide genetic screen identified modifiers of LRRK2-induced toxicity in yeast including components of vesicular trafficking pathways, which can also modulate the trafficking defects caused by expression of truncated LRRK2 variants. Our results provide insight into the basic pathobiology of LRRK2 and suggest that the GTPase domain may contribute to the toxicity of LRRK2. These findings may guide future therapeutic strategies aimed at attenuating LRRK2-mediated neurodegeneration.
Highlights
Parkinson’s disease (PD (OMIM #168600)) is a common neurodegenerative movement disorder that is characterized by muscular rigidity, bradykinesia, resting tremor and postural instability [1,2]
We employ yeast cells to provide insight into the pathobiology of human leucine-rich repeat kinase 2 (LRRK2), a protein that is associated with autosomal dominant PD
Expression of LRRK2 fragments containing the GTPase domain markedly reduces the viability of yeast cells relative to other protein domains of LRRK2
Summary
Parkinson’s disease (PD (OMIM #168600)) is a common neurodegenerative movement disorder that is characterized by muscular rigidity, bradykinesia, resting tremor and postural instability [1,2]. Typically a sporadic disease, mutations in the leucinerich repeat kinase 2 (LRRK2, PARK8, OMIM #607060, GenBank #AY792511) gene have been identified as a cause of late-onset, autosomal dominant familial PD that is clinically and neurochemically indistinguishable from sporadic PD [3,4,5,6,7]. Mutations in LRRK2 are the most common cause of familial and sporadic PD identified to date [9]. The LRRK2 gene encodes a large protein of 2527 amino acids that contains multiple domains. GTP binding markedly enhances the kinase activity of LRRK2 and is an essential requirement for kinase activity [14,15,21,22]. Disease-associated mutations located throughout the LRRK2 protein have been shown to variably alter GTP binding, GTP hydrolysis or Author Summary
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