Dataset Information

Identification of novel cerebrospinal fluid biomarkers for parkinsonism using a proteomics approach

ABSTRACT: The aim of our study was to investigate cerebrospinal fluid (CSF) tryptic peptide profiles as potential diagnostic biomarkers for the discrimination of parkinsonian disorders. CSF samples were collected from individuals with parkinsonism, who had an uncertain diagnosis at the time of inclusion and who were followed for up to 12 years in a longitudinal study. We performed shotgun proteomics to identify tryptic peptides in CSF of Parkinson’s disease (PD, n=10), multiple system atrophy patients (MSA, n=5) and non-neurological controls (n=10). We validated tryptic peptides with differential levels between PD and MSA using a newly developed selected reaction monitoring (SRM) assay in CSF of PD (n=46), atypical parkinsonism patients (AP; MSA, n=17; Progressive supranuclear palsy; n=8) and non-neurological controls (n=39). We identified 191 tryptic peptides that differed significantly between PD and MSA, of which 34 met our criteria for SRM development. For 14/34 peptides we confirmed differences between PD and AP. These tryptic peptides discriminated PD from AP with moderate-to-high accuracy. Random forest modelling including tryptic peptides plus either clinical assessments or other CSF parameters (neurofilament light chain, phosphorylated tau protein) and age improved the discrimination of PD vs. AP. Our results show that discovery of tryptic peptides by untargeted and subsequent validation by targeted proteomics is a suitable strategy to identify novel potential CSF biomarkers for PD versus AP. Furthermore, the tryptic peptides, and corresponding proteins, that we identified as differential biomarkers may increase our current knowledge about the disease-specific pathophysiological mechanisms of parkinsonism.

INSTRUMENT(S): maXis

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cerebrospinal Fluid

DISEASE(S): Parkinsonism

SUBMITTER: Hans Wessels

LAB HEAD: Alain J. van Gool

PROVIDER: PXD028842 | Pride | 2022-02-16

REPOSITORIES: pride

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Identification of cerebrospinal fluid biomarkers for parkinsonism using a proteomics approach.

Marques Tainá M TM van Rumund Anouke A Kersten Iris I Bruinsma Ilona B IB Wessels Hans J C T HJCT Gloerich Jolein J Kaffa Charlotte C Esselink Rianne A J RAJ Bloem Bastiaan R BR Kuiperij H Bea HB Verbeek Marcel M MM

NPJ Parkinson's disease 20211130 1

The aim of our study was to investigate cerebrospinal fluid (CSF) tryptic peptide profiles as potential diagnostic biomarkers for the discrimination of parkinsonian disorders. CSF samples were collected from individuals with parkinsonism, who had an uncertain diagnosis at the time of inclusion and who were followed for up to 12 years in a longitudinal study. We performed shotgun proteomics to identify tryptic peptides in CSF of Parkinson's disease (PD, n = 10), multiple system atrophy patients ( ...[more]

PMID: 34848724

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Project description:Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder caused by dopaminergic neuronal deaths. For a proper treatment of PD, biomarkers that would enable us to monitor disease progression or responses to a disease-modifying agent, or that can be used as a presymptomatic marker are critical. In addition, a biomarker that could be used to distinguish between the various diseases that manifest with PD-like symptoms would greatly enhance patient care and management of future clinical trials. Previous research indicates that c-Abl is overactive in PD patients resulting in an increased phosphorylation of the tyrosine 39 residue of alpha-synuclein (a-syn) (pY39 a-syn) and eventually dopaminergic neuronal death via a-syn aggregation. For this reason, monitoring pY39 a-syn will enable us to diagnose presymptomatic PD, monitoring disease progression and monitoring the response disease-modifying agents. We hypothesized that this increased phosphorylation on Y39 of a-syn (pY39 a-syn) will be reflected in the cerebrospinal fluid (CSF) of PD patients and monitoring pY39 a-syn level in CSF will enable us to monitor pY39 a-syn level in the brain. Mass spectrometry has been widely used for the detection of phosphorylated peptides using parallel reaction monitoring (PRM) and we utilized the PRM mass spectrometry for the detection of pY39 a-syn. However, pY39 a-syn was not detected even after immunoprecipitation of a-syn, phosphopeptide enrichment or phosphotyrosine peptide enrichment from a practical volume. For this reason, we have developed a two-step enrichment method in which pY39 a-syn was first enriched with an anti-phosphotyrosine antibody followed by a further enrichment of phosphopeptides with titanium oxide (TiO2) beads to remove non-phosphopeptides. Accurate quantification was obtained by including a synthetic pY39 a-syn peptide labeled with heavy lysine that was added before an enzyme digestion. To detect pY39 α-syn peptide in CSF lower than 10 femtomolar concentration, experimental parameters were optimized. Comparison of pY39 a-syn to total a-syn in CSF from PD patients and controls reveals that pY39 a-syn levels are significantly elevated in the CSF of PD patient versus controls. This optimized two-step enrichment PRM detection method may be of value as a biomarker to monitor c-Abl activation in PD patients for future diagnostic studies as well as a pharmacodynamic marker for c-Abl therapeutic trials in PD. Furthermore, this developed method can be applicable to quantifying other phosphotyrosine peptides with low abundance in biological samples.

Project description:s synapse degeneration is an early event in Alzheimer’s disease (AD) pathophysiology, a biofluid marker of synapse loss in living patients could be a surrogate marker of disease prognosis and therefore would be an excellent addition to the AD biomarker arsenal. With direct access to the brain interstitial fluid, the cerebrospinal fluid (CSF) is a potential source of synapse-derived proteins that could be potential biomarkers of underlying synapse degeneration. The aim of this study was to identify, verify and evaluate a set of synaptic proteins as surrogate CSF markers of underlying synapse loss in AD patients. In the Discovery Stage, we combined high-throughput shotgun proteomics of the CSF with an exhaustive search of the literature and public databases for proteomic studies of the CSF and synapse. A thorough characterization of the synaptic component of the CSF identified 210 synaptic proteins that are detectable in human CSF. We selected an initial panel of 22 candidate biomarkers for evaluation. In the Verification Stage, 12 proteins were discarded due to poor detection by targeted mass spectrometry (Selected Reaction Monitoring, SRM). We confirmed the expression of the remaining 10 proteins either directly at (Calsynytenin-1, GluR2, GluR4, Neurexins 2A and 3A, Neuroligin-2, Syntaxin-1B, Thy-1 and Vamp-2), or surrounding (Tenascin-R), the human synapse using Array Tomography microscopy and biochemical fractionation methods. We quantified the synaptic panel by SRM in CSF samples from 2 independent clinical cohorts of cognitively normal controls and all clinical stages of AD (n=140). A set of the panel proteins demonstrated a non-linear profile distinct to that of existing biomarkers whereby the CSF levels were decreased at the earliest preclinical stage of AD, reflecting reduced synaptic density in these asymptomatic individuals and elevated at later symptomatic stages when neurodegeneration is widespread. In conclusion, we have identified a set of novel synapse-specific proteins that could have clinical value for assessing disease progression in individuals at-risk for AD and potentially in other neurological disorders characterized by early synapse loss.

			Action	DRS
	AnalysesToSamplesTable.xlsx	Xlsx
	ProteinIDdata.zip	Other
	Sample10_raw.zip	Other
	Sample11_raw.zip	Other
	Sample12_raw.zip	Other