Biochemical evidence suggests that aberrant GTPase and kinase activities are linked to disease causing mutations in LRRK2, and may be at the basis of neuronal toxicity and pathogenesis of PD. Recently we have found several inhibitors of LRRK2 kinase activity that provide protection against LRRK2 toxicity in cell culture. We propose to test the efficacy of these inhibitors in preventing the dopaminergic neurodegeneration and motor dysfunction in the LRRK2 Drosophila model.
The fly, Drosophila melanogaster, is an excellent organism to model neuronal degenerative diseases and has been used to study mechanism in models of PD. The LRRK2 gene is highly conserved across species and Drosophila has a single orthologue of the human LRRK2 (CG5483). Since mutations in LRRK2 result in autosomal dominant disease that typically are gain-of-function diseases transgenic animals traditionally provide the best models. LRRK2 transgenic flies recapitulate several key features of human parkinsonism including motor dysfunction and loss of dopaminergic neurons. These flies will be treated with new inhibitors of LRRK2 and their parkinsonian features will be evaluated to determine if these drugs can provide relief from the symptoms and perhaps rescue the dopaminergic neuronal death.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
These studies will test the efficacy of new LRRK2 inhibitors in preventing the dopaminergic neurodegeneration and motor dysfunction in the LRRK2 Drosophila model. We will learn if inhibition of LRRK2 can prevent loss of function and if so, further development of these drugs will be initiated to produce agents useful in the human clinical setting.
In test tube and cell culture models inhibition of LRRK2 and its disease-causing mutants is protective. We anticipate that inhibition of LRRK2 in the transgenic fly model will protect dopamine neurons from cell death and preserve motor function. If these studies are successful in the future we will conduct a time course to determine when the drugs can be given and still provide efficacy and we will begin to explore additional drugs.
We investigated the efficacy of potential LRRK2 inhibitors identified previously in our chemical library screen to prevent dopaminergic neurodegeneration and motor dysfunction in the LRRK2 Drosophila model. We found that two compounds significantly increased fly survival and improved locomotor activity in flies expressing the most common PD-linked mutant, G2O19S-LRRK2.These compounds also partially rescued the mutant G2019S-LRRK2-induced dopaminergic neuron degeneration in fly brains and reduced the autophosphorylation of mutant G2O19S-LRRK2 in fly brain homogenates. In contrast, the inactive compound had no effect on fly survival, locomotor activity, autophosphorylation or dopaminergic neuron degeneration induced by G2019S-LRRK2 expression. These data indicate that inhibition of LRRK2 can provide protection against the pathologic actions of the PD associated mutation G2019S-LRRK2.