Investigating the Genetic Interaction of dLRRK/LRRK2 with the Visual System and the Stability of LRRK2 Protein in a Drosophila model of Parkinson’s Disease

The G2019S mutation within the kinase domain of Leucine-rich repat kinase 2 (LRRK2) is the most common reported and studied cause of familial Parkinson’s Disease (PD). LRRK2 has been associated with many cellular pathways, but its exact role is still to be elucidated. Using Drosophila as a model for PD, the role of the protein is examined. In this project, we found that dLRRK loss-of-function (dLRRKLOF) flies had an age- dependent visual deficit that was rescued with the expression of the native gene (dLRRK) in non-neuronal cells (fat body and pigment cells) bolstering the suggestion of protein’s ability to transport cell-cell. Furthermore, placing mutations of different eye colour genes encoding proteins normally involved in vesicle trafficking in the dLRRKLOF background caused a loss of viability in combination which suggests a role for dLRRK in regulating pigment granules specifically and in the lysosomal pathway in general. In a gain-of-function approach, young flies expressing LRRK2-G2019S in dopaminergic (DA) neurons and pigment cells demonstrated an aberrant electroretinogram (ERG) indicating a failure in their ability to adapt to light. This was partially complemented by anatomical assessment where expressing LRRK2-G2019S in pigment cell caused flies to have larger deep pseudopupil (DPP) than the controls indicating defective eye function. Finally, mutations in LRRK2 are thought to potentially affect the stability of the protein in fly model as well as in cells. We used two kinase inhibitors (vitamin B12 and MLi-2) with different mode of actions to test their effect on LRRK2 stability. We showed that these two inhibitors might variably affect LRRK2 stability dependent on the mutation on the protein.