Detection of Post-Translationally Modified Proteins as a Biomarker panel for Parkinson’s Disease
To date, research aimed at identifying biomarkers for Parkinson’s Disease (PD) has, for the most part, focused on measuring the levels of all isoforms of a given protein such as alpha-synuclein or DJ-1 in serum or CSF. These biomarkers, have not had the clinical sensitivity and specificity necessary to be used as indicators of disease. Recent evidence suggests that specific post-translational modifications such as phosphorylation and ubiquitination are key to the pathophysiology of PD. Most of these post-translationally modified proteins have not yet been measured in serum because their concentrations are below the limit of detection of conventional ELISAs. We hypothesize that the detection of post-translationally modified proteins will be critical to PD biomarker development for disease diagnosis and monitoring. We employ newly developed technology from our laboratory, which is 100-1000 times more sensitive than traditional ELISA to detect these PTM-isoforms. This new technology, Single Molecule Arrays (Simoa), is a digital ELISA that counts individual molecules in solution. In this NINDS-funded project, we have developed 11 Simoa assays specific for both post-translationally modified and total proteins relevant to PD. To the best of our knowledge, these assays are currently the most sensitive assays ever created for these proteins and post-translationally modified proteins. We now plan to multiplex these assays and use them to measure these post-translationally modified proteins in the serum healthy controls and PD patients in order to assess the sensitivity and specificity of this biomarker panel. As an exploratory measure, we will also use this biomarker panel to test the serum of patients with Essential Tremor, patients with Multiple System Atrophy and patients with Progressive Supranuclear Palsy, in order to determine the specificity of our assay panel for PD rather than for movement disorders in general.