Objective/Rationale:
Mutations in the LRRK2 gene are a common cause of familial and sporadic Parkinson’s disease. The LRRK2 protein can function as a kinase in vitro and certain familial mutations may enhance this kinase activity. As yet, however, bona fide substrates of LRRK2 kinase activity have not been identified. This project aims to identify and validate novel protein phosphorylation substrates for LRRK2 in vivo using pre-clinical models with altered LRRK2 expression.
Project Description:
We propose to identify novel protein substrates of LRRK2-mediated phosphorylation by proteomic profiling of tissue from LRRK2 transgenic mice. We have generated transgenic mice with inducible expression of human wild-type or G2019S mutant LRRK2 protein. Two-dimensional differential gel electrophoresis (2D-DIGE) and phosphorylation-specific staining techniques, together with phospho-specific antibody microarrays, will be employed to comprehensively profile protein phosphorylation in brain tissue from young and aged LRRK2 transgenic mice compared with non-transgenic control mice. Proteins with altered phosphorylation in the transgenic mice will be identified by mass spectrometry. LRRK2 phospho-substrates will be further validated using phospho-specific substrate antibodies in i) various LRRK2 transgenic and viral rodent models, and ii) human Parkinson’s disease patients with or without LRRK2 mutations.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
We do not yet understand how mutations in LRRK2 lead to the degeneration of neurons in Parkinson’s disease. While LRRK2 may function as a kinase, we do not yet know the identity of LRRK2 phosphorylation substrates and whether LRRK2 mutations alter their phosphorylation. The identification of LRRK2 substrates is critical for understanding the pathogenic effects of familial mutations, they may constitute novel biomarkers of disease, and they may provide novel therapeutic targets for treating disease.
Anticipated Outcome:
This project will identify proteins that are differentially phosphorylated in brain tissue due to LRRK2 expression and/or familial mutations from various LRRK2 transgenic pre-clinical models and human Parkinson’s disease patients. We hope to understand whether or not LRRK2 functions as a kinase in vivo, and if so how familial mutations influence protein phosphorylation. Ultimately, we aim to clarify how the kinase activity of LRRK2 may contribute to neuronal degeneration in Parkinson’s disease.