Cerebrospinal Fluid Peptides as Potential Parkinson Disease Biomarkers: A Staged Pipeline for Discovery and Validation*

Abstract

a Finding robust biomarkers for Parkinson disease (PD) is currently hampered by inherent technical limitations associated with imaging or antibody-based protein assays.To circumvent the challenges, we adapted a staged pipeline, starting from our previous proteomic profiling followed by high-throughput targeted mass spectrometry (MS), to identify peptides in human cerebrospinal fluid (CSF) for PD diagnosis and disease severity correlation. In this multicenter study consisting of training and validation sets, a total of 178 subjects were randomly selected from a retrospective cohort, matching age and sex between PD patients, healthy controls, and neurological controls with Alzheimer disease (AD). From ϳ14,000 unique peptides displaying differences between PD and healthy control in proteomic investigations, 126 peptides were selected based on relevance and observability in CSF using bioinformatic analysis and MS screening, and then quantified by highly accurate and sensitive selected reaction monitoring (SRM) in the CSF of 30 PD patients versus 30 healthy controls (training set), followed by diagnostic (receiver operating characteristics) and disease severity correlation analyses. The most promising candidates were further tested in an independent cohort of 40 PD patients, 38 AD patients, and 40 healthy controls (validation set). A panel of five peptides (derived from SPP1, LRP1, CSF1R, EPHA4, and TIMP1) was identified to provide an area under curve (AUC) of 0.873 (sensitivity ‫؍‬ 76.7%, specificity ‫؍‬ 80.0%) for PD versus healthy controls in the training set. The performance was essentially confirmed in the validation set (AUC ‫؍‬ 0.853, sensitivity ‫؍‬ 82.5%, specificity ‫؍‬ 82.5%). Additionally, this panel could also differentiate the PD and AD groups (AUC ‫؍‬ 0.990, sensitivity ‫؍‬ 95.0%, specificity ‫؍‬ 97.4%). Furthermore, a combination of two peptides belonging to proteins TIMP1 and APLP1 significantly correlated with disease severity as determined by the Unified Parkinson's Disease Rating Scale motor scores in both the training (r ‫؍‬ 0.381, p ‫؍‬ 0.038)j and the validation (r ‫؍‬ 0.339, p ‫؍‬ 0.032) sets. The novel panel of CSF peptides, if validated in independent co-

Proteomic profiling in MPTP monkey model for early Parkinson disease biomarker discovery

“…For example, HYOU, LSAMP, N1CAM, and SEMA4D have been identified and validated in the plasma of PD patients using glycopeptide enrichment and selected reaction monitoring MS assay [59]. In addition, LRP1 when combined with a 5-peptide model has been found to perform well in differentiating patients with PD and healthy controls [60]. …”

Insight of brain degenerative protein modifications in the pathology of neurodegeneration and dementia by proteomic profiling

“…However, a more promising approach might be the development of complex panels of multiple biomarkers that can provide a more detailed picture of pathological events occurring in the brain. Indeed, in a recent study of human CSF samples, Shi et al used a targeted approach to develop a biomarker profile capable of distinguishing patients with PD and AD by detecting dysregulated levels of macrophage colony-stimulating factor 1 receptor, osteopontin (SPP1), pro-low-density lipoprotein receptor-related protein 1, ephrin type-A receptor 4, and metalloproteinase inhibitor 1 [190]. …”

Direct interaction of receptor tyrosine kinases, EphA4 and PDGFRβ, plays an important role in the proliferation of neural stem cells

“…Bidirectional signaling possesses many functions, including neural stem cell maintenance and plasticity regulation in the proliferation zone of adult brain, 6,7 neuron migration, 8 axon guidance, 9 angiogenesis, 10 bone homeostasis, 11 embryonic patterning, 12 tumorgenesis, [13][14][15][16][17][18] insulin secretion, 19 and so on. EphA4 expression is very high in the brain, and recently, EphA4 has been proposed to be implicated in Alzheimer's disease (AD), 20,21 Parkinson's disease (PD), 22,23 amyotrophic lateral sclerosis (ALS), 24 and other neurodegenerative diseases. Hence, EphA4 may have functions for protecting neuron loss and reversing the aging cells.…”