Neuropeptide Y (NPY) in cerebrospinal fluid from patients with Huntington's Disease: increased NPY levels and differential degradation of the NPY1-30 fragment
Wagner L1,2,3, Björkqvist M4,5, Hult Lundh S5, Wolf R6,2, Börgel A2,7, Schlenzig D2, Ludwig HH5, Rahfeld JU2, Leavitt B7, Demuth HU2, Petersén Å4 and von Hörsten S8.
Journal of Neurochemistry 137(5): 820-37 (2016)
1Deutschsprachige Selbsthilfegruppe für Alkaptonurie (DSAKU) e.V, Stuttgart, Germany.
2probiodrug AG, Halle (Saale, Germany.
3Department of Experimental Therapy, Franz-Penzoldt-Center, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
4Brain Disease Biomarker Unit, Department of Experimental Medical Science, Wallenberg Neuroscience Centre, Lund University, Lund, Sweden.
5Translational Neuroendocrine Research Unit, Lund University, Lund, Sweden.
6Center for Clinical Chemistry, Microbiology and Transfusion, Klinikum St. Georg GmbH, Leipzig, Germany.
7Institute of Molecular Biology (IMB), Johannes Gutenberg-University Mainz, Mainz, Germany.
8Fraunhofer-Institute for cell therapy and immunology, Department of Drug Design and Target Validation, Halle (Saale), Germany.
Huntington's disease (HD) is an inherited and fatal polyglutamine neurodegenerative disorder caused by an expansion of the CAG triplet repeat coding region within the HD gene. Progressive dysfunction and loss of striatal GABAergic medium spiny neurons (MSNs) may account for some of the characteristic symptoms in HD patients. Interestingly, in HD, MSNs expressing neuropeptide Y (NPY) are spared and their numbers is even up-regulated in HD patients. In line with this, we report here on increased immuno-linked NPY (IL-NPY) levels in human cerebrospinal fluid (hCSF) from HD patients. As this antibody-based detection of NPY may provide false positive differences due to the antibody-based detections of only fragments of NPY, the initial finding was validated by investigating the proteolytic stability of NPY in hCSF using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and selective inhibitors. A comparison between resulting NPY-fragments and detailed epitope analysis verified significant differences of IL-NPY1-36/3-36 and NPY1-30 levels between HD patients and control subjects. Ex vivo degradomics analysis demonstrated that NPY is initially degraded to NPY1-30 by cathepsin D (CTSD) in both HD patients and control subjects. Yet, NPY1-30 is then further differentially hydrolyzed by thimet oligopeptidase (TOP) in HD patients and by neprilysin (NEP) in control subjects. Furthermore, altered hCSF TOP-inhibitor Dynorphin A1-13 (Dyn-A1-13 ) and TOP-substrate Dyn-A1-8 levels indicate an impaired Dyn-A-TOP network in HD patients. Thus, we conclude that elevated IL-NPY-levels in conjunction with TOP- / NEP-activity/protein as well as Dyn-A1-13 -protein levels may serve as a potential biomarker in human CSF of HD. This article is protected by copyright. All rights reserved.