Identification of candidate substrates of the leucine rich repeat kinase 2 by mass spectrometry-based phosphoproteomics

Abstract

Mutations in the kinase domain of the leucine rich repeat kinase (LRRK2) have been implicated in heritable forms of Parkinson’s disease (PD). Specifically, a glycine to serine mutation (G2019S) has demonstrated hyperactive autophosphorylation, neuronal toxicity, and locomotor deficits in the fruit fly Drosophila melanogaster— all of which are related to its pathogenicity in PD. My dissertation focuses on identifying novel substrates of LRRK2 through analysis of proteome-wide changes in protein abundance as well as identifying changes in phosphorylation of proteins in vitro and in the in vivo fruit fly model. Using mass spectrometry, I provide quantitative information on thousands of proteins and phosphorylation sites. In vitro kinase assays on peptides derived from fly heads or a neuroblastoma cell line provide evidence for direct substrates of LRRK2, while the in vivo experiment in flies expressing LRRK2 identifies both direct and indirect phosphorylation substrates of the kinase. Herein, I present evidence for novel, LRRK2-mediated phosphorylation sites in the Drosophila melanogaster and the neuroblastoma models of PD. I also show changes in protein expression upon expression of human LRRK2 in the fly model.