Detection of Post-Translationally Modified Proteins in Cerebrospinal Fluid 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 cerebrospinal fluid 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 as well as for the creation of effective companion diagnostics for novel medications. 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 12 Simoa assays specific for both post-translationally modified and total proteins relevant to PD and can measure each of these proteins in the cerebrospinal fluid of healthy controls. To the best of our knowledge, these assays are currently the most sensitive assays ever created for both the proteins and post-translationally modified proteins. We have now multiplexed many of our assays and will use them to measure key targets in the cerebrospinal fluid of 100 healthy controls and 100 patients with PD in order to assess the sensitivity and specificity of this biomarker panel.