Dopaminergic neurodegeneration induced by Parkinson's disease-linked G2019S LRRK2 is dependent on kinase and GTPase activity

Significance

Parkinson’s disease (PD)-linked familial mutations in LRRK2 impact its enzymatic activity by commonly increasing kinase activity, either directly within the kinase domain or indirectly via the GTPase domain by impairing GTP hydrolysis. Familial LRRK2 mutations also commonly promote neuronal toxicity in cultured cells, and for the common G2019S mutation, these effects are kinase dependent. The mechanisms underlying familial LRRK2 mutations in animal models are uncertain, due to the general lack of robust phenotypes. Our study demonstrates important roles for kinase and GTPase activities in mediating the neurodegenerative effects of G2019S LRRK2 in rodents, highlighting both as promising therapeutic targets for PD.

Abstract

Mutations in leucine-rich repeat kinase 2 ( LRRK2) are the most common cause of late-onset, autosomal-dominant familial Parkinson’s disease (PD). LRRK2 functions as both a kinase and GTPase, and PD-linked mutations are known to influence both enzymatic activities. While PD-linked LRRK2 mutations can commonly induce neuronal damage in culture models, the mechanisms underlying these pathogenic effects remain uncertain. Rodent models containing familial LRRK2 mutations often lack robust PD-like neurodegenerative phenotypes. Here, we develop a robust preclinical model of PD in adult rats induced by the brain delivery of recombinant adenoviral vectors with neuronal-specific expression of 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 administration of 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 robust destabilization of human LRRK2 protein in the brain relative to endogenous LRRK2. Our study further demonstrates that G2019S LRRK2-induced dopaminergic neurodegeneration critically requires normal GTPase activity, as hypothesis-testing mutations that increase GTP hydrolysis or impair GTP-binding activity provide neuroprotection although 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 preclinical model of LRRK2-linked PD and nominates kinase inhibition and modulation of GTPase activity as promising disease-modifying therapeutic targets.