Dopaminergic Neurodegeneration Induced by Parkinson's Disease-Linked G2019S LRRK2 is Dependent on Kinase and GTPase Activity
AO_SCPLOWBSTRACTC_SCPLOWMutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset, autosomal dominant familial Parkinsons disease (PD) and represent the most common known cause of PD. LRRK2 can function as both a protein kinase and GTPase and PD-linked mutations are known to influence both of these enzymatic activities. While PD-linked LRRK2 mutations can commonly induce neuronal damage and toxicity in cellular models, the mechanisms underlying these pathogenic effects remain uncertain. Rodent models based upon familial LRRK2 mutations often lack the hallmark features of PD and robust neurodegenerative phenotypes in general. Here, we develop a robust pre-clinical model of PD in adult rats induced by the brain delivery of recombinant adenoviral vectors with neuronal-specific expression of full-length human LRRK2 harboring the most common G2019S mutation. In this model, G2019S LRRK2 induces the robust degeneration of substantia nigra dopaminergic neurons, a pathological hallmark of PD. Introduction of a stable kinase-inactive mutation or in-diet dosing with the selective kinase inhibitor, PF-360, attenuates neurodegeneration induced by G2019S LRRK2. Neuroprotection provided by pharmacological kinase inhibition is mediated by an unusual mechanism involving the selective and robust destabilization of human LRRK2 protein in the rat brain relative to endogenous LRRK2. Our study further demonstrates that dopaminergic neurodegeneration induced by G2019S LRRK2 critically requires normal GTPase activity. The introduction of hypothesis-testing mutations that increase GTP hydrolysis or impair GTP binding activity provide neuroprotection against G2019S LRRK2 via distinct mechanisms. Taken together, our data demonstrate that G2019S LRRK2 induces neurodegeneration in vivo via a mechanism that is dependent on kinase and GTPase activity. Our study provides a robust rodent model of LRRK2-linked PD and nominates kinase inhibition and modulation of GTPase activity as promising disease-modifying therapeutic targets.