Loss of Corticostriatal Mu-Opioid Receptors in α-Synuclein Transgenic Mouse Brains

Ultrastructural, neurochemical, and molecular alterations within the striatum are associated with the onset and progression of Parkinson's disease (PD). In PD, the dopamine-containing neurons in the substantia nigra pars compacta (SNc) degenerate and reduce dopamine-containing innervations to the striatum. The loss of striatal dopamine is associated with enhanced corticostriatal glutamatergic plasticity at the early stages of PD. However, with disease progression, the glutamatergic corticostriatal white matter tracts (WMTs) also degenerate. We analyzed the levels of Mu opioid receptors (MORs) in the corticostriatal WMTs, as a function of α-Synuclein (α-Syn) toxicity in transgenic mouse brains. Our data show an age-dependent loss of MOR expression levels in the striatum and specifically, within the caudal striatal WMTs in α-Syn tg mouse brains. The loss of MOR expression is associated with degeneration of the myelinated axons that are localized within the corticostriatal WMTs. In brains affected with late stages of PD, we detect evidence confirming the degeneration of myelinated axons within the corticostriatal WMTs. We conclude that loss of corticostriatal MOR expression is associated with degeneration of corticostriatal WMT in α-Syn tg mice, modeling PD

Velusetrag rescues GI dysfunction, gut inflammation and dysbiosis in a mouse model of Parkinson's disease

: In patients with Parkinson's disease (PD), constipation is common, and it appears in a prodromal stage before the hallmark motor symptoms. The present study aimed to investigate whether Velusetrag, a selective 5‑HT4 receptor agonist, may be a suitable candidate to improve intestinal motility in a mouse model of PD. Five months old PrP human A53T alpha-synuclein transgenic (Tg) mice, which display severe constipation along with decreased colonic cholinergic transmission already at 3 months, were treated daily with the drug for 4 weeks. Velusetrag treatment reduced constipation by significantly stimulating both the longitudinal and circular-driven contractions and improved inflammation by reducing the level of serum and colonic IL1β and TNF-α and by decreasing the number of GFAP-positive glia cells in the colon of treated mice. No significant downregulation of the 5-HT4 receptor was observed but instead Velusetrag seemed to improve axonal degeneration in Tgs as shown by an increase in NF-H and VAChT staining. Ultimately, Velusetrag restored a well-balanced intestinal microbial composition comparable to non-Tg mice. Based on these promising data, we are confident that Velusetrag is potentially eligible for clinical studies to treat constipation in PD patients

Alpha-synuclein/synapsin III pathological interplay boosts the motor response to methylphenidate

: Loss of dopaminergic nigrostriatal neurons and fibrillary α-synuclein (α-syn) aggregation in Lewy bodies (LB) characterize Parkinson's disease (PD). We recently found that Synapsin III (Syn III), a phosphoprotein regulating dopamine (DA) release with α-syn, is another key component of LB fibrils in the brain of PD patients and acts as a crucial mediator of α-syn aggregation and toxicity. Methylphenidate (MPH), a monoamine reuptake inhibitor (MRI) efficiently counteracting freezing of gait in advanced PD patients, can bind α-syn and controls α-syn-mediated DA overflow and presynaptic compartmentalization. Interestingly, MPH results also efficient for the treatment of attention deficits and hyperactivity disorder (ADHD), a neurodevelopmental psychiatric syndrome associated with Syn III and α-syn polymorphisms and constituting a risk factor for the development of LB disorders. Here, we studied α-syn/Syn III co-deposition and longitudinal changes of α-syn, Syn III and DA transporter (DAT) striatal levels in nigrostriatal neurons of a PD model, the human C-terminally truncated (1-120) α-syn transgenic (SYN120 tg) mouse, in comparison with C57BL/6J wild type (wt) and C57BL/6JOlaHsd α-syn null littermates. Then, we analyzed the locomotor response of these animals to an acute administration of MPH (d-threo) and other MRIs: cocaine, that we previously found to stimulate Syn III-reliant DA release in the absence of α-syn, or the selective DAT blocker GBR-12935, along aging. Finally, we assessed whether these drugs modulate α-syn/Syn III interaction by fluorescence resonance energy transfer (FRET) and performed in silico studies engendering a heuristic model of the α-syn conformations stabilized upon MPH binding. We found that only MPH was able to over-stimulate a Syn III-dependent/DAT-independent locomotor activity in the aged SYN120 tg mice showing α-syn/Syn III co-aggregates. MPH enhanced full length (fl) α-syn/Syn III and even more (1-120) α-syn/Syn III interaction in cells exhibiting α-syn/Syn III inclusions. Moreover, in silico studies confirmed that MPH may reduce α-syn fibrillation by stabilizing a protein conformation with increased lipid binding predisposition. Our observations indicate that the motor-stimulating effect of MPH can be positively fostered in the presence of α-syn/Syn III co-aggregation. This evidence holds significant implications for PD and ADHD therapeutic management

Analysis in vitro of the neuroprotective action of recombinant human TAT-parkin and parkin over-expression in the 6-hydroxydopamine model of Parkinson's disease

Parkinson's disease is a chronic progressive neurodegenerative movement disorder characterized by a profound and selective loss of nigrostriatal dopaminergic neurons. A major hurdle in the development of neuroprotective therapies is due to limited understanding of disease processes leading to the death of neurons. The etiology of dopaminergic neuronal demise in Parkinson's disease is elusive, but a combination of genetic and environmental factors seems to play a critical role. Mutations in parkin are known to be the predominant cause of autosomal recessive, early-onset parkinsonism. Parkin is an E3 ubiquitin ligase, an essential component of the ubiquitin-proteasomal system, and its over-expression is neuroprotective in several cellular models of apoptosis. Cell-penetrating peptides, e.g. linked to the transactivator of transcription (TAT) provide an attractive delivery system across biological membranes. In the first part of the study, we describe the construction, purification, and characterization of a TAT-parkin fusion protein, and its neuroprotective activity in an in vitro model of Parkinson's disease. Western blot and immunocytochemical analyses showed TAT-parkin to transduce PC12 pheocromocytoma cells and Chinese hamster ovary cells and to localize in the nucleus, cytoplasm, and mitochondria. Moreover, TAT-parkin exhibited ubiquitination activity in vitro. Importantly, TAT-parkin at nanomolar concentrations protected nerve growth factor-differentiated PC12 cells against the dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA), but only if present in the culture medium before, during, and after treatment with 6-OHDA. Based on these results, the second part of the study was designed to assess the pro-survival action of parkin using a system in which parkin is over-expressed. To accomplish this, stable PC12 cells transfectants were established with plasmids carrying either human wild-type (WT) parkin, or the human R42P mutation (parkinR42P). Non-transfected PC12 cells were used as control. Clones were screened for the expression of human parkin gene by Reverse Transcription-Polymerase Chain Reaction and Western blotting. The selected clones and un-transfected PC12 cells were treated with 50 and 75 μM 6-OHDA for different times. Cell-viability decreased in a time-dependent manner in both clonal and control cells, but the PC12 parkinR42P expressing clone and un-trasfected cells showed a statistically significant reduction in cell viability already from 2 h. In contrast, in the PC12 parkin (WT) expressing clone cell viability was significantly reduced only from 12 h. As abnormalities in the ubiquitin-proteasome system and in the autophagy-lysosome pathway are thought to be involved in the etiopathogenesis of Parkinson's disease, we treated the above cells with either a specific proteasome inhibitor (MG132) or the macroautophagy inhibitor 3-methyladenine (3-MA) for further 16 h. Improved survival was again evident in PC12 parkin (WT) expressing cells. This latter also showed an increase in the amount of ubiquitinated proteins and in the basal level of autophagy activation. Nevertheless, co-administration of the proteasome and autophagy inhibitors, neutralized the protective effect of PC12 parkin (WT) expression. Over-expression of WT parkin thus appears able to protect cells from oxidative stress by 6-OHDA and from the neurotoxicity of proteasome or macroautophagy inhibitors, and confirmed that the R42P amino-acid substitution affects parkin physiological action. Taken together, our data suggest that parkin, either as a recombinant TAT-fusion protein or when over-expressed is strongly neuroprotective, preventing dopaminergic PC12 cell death under various stress conditions. Parkin may thus represent a potential new therapeutic target in Parkinson's disease. Moreover, these findings support also the view that protein transduction strategies are well suited for intracellular translocation of proteins and, in particular, point to the application of designing fusion proteins with a protein transduction domain for potential therapeutic benefit, including Parkinson's disease.La Malattia di Parkinson (Parkinson’s disease, PD), descritta per la prima volta nel 1817 da James Parkinson, è la più importante affezione del sistema extrapiramidale, le cui principali caratteristiche patologiche sono la progressiva e selettiva perdita di neuroni dopaminergici nella substantia nigra pars compacta, la conseguente diminuzione dei livelli striatali di dopamina e la presenza, nei neuroni dopaminergici nigrali sopravvissuti, di inclusioni citoplasmatiche, denominate Corpi di Lewy, che contengono soprattutto aggregati di α-sinucleina e parkina. La PD è sempre sporadica, eccetto alcuni rari casi associati a mutazioni geniche e che sono responsabili di forme di PD ad insorgenza precoce. A queste forme appartengono: - forme della PD autosomiche dominanti, dovute a due mutazioni nel gene che codifica per l'α-sinucleina e una mutazione nel gene che codifica per la parte C-terminale dell’Ubiquitina idrolasi L1 (UCHL1); - forme autosomiche recessive, dovute a mutazioni nel gene che codifica per la parkina, che portano alla maggior parte dei casi di PD familiare e giovanile sporadico e che si caratterizzano per la mancanza dei Corpi di Lewy. Forme autosomiche recessive della PD sono inoltre dovute a mutazioni nel gene che codifica per DJ-1 e PINK1. Studi sulle forme ereditarie della PD si stanno concentrando verso un’ipotesi comune, cioè che l’accumulo normale e anormale di proteine intracellulari (mutate, disassemblate o danneggiate) ed il malfunzionamento del sistema ubiquitina-proteasoma possa condurre alla morte dei neuroni dopaminergici nigrali. In particolare, lo stress ossidativo generato dallo scompenso delle funzioni mitocondriali e dal metabolismo della dopamina potrebbe promuovere la formazione di proteine mal-ripiegate come risultato di modifiche post-traslazionali, specialmente a carico della α-sinucleina e della parkina. La parkina è una E3-ubiquitina ligasi coinvolta nei processi di degradazione di proteine danneggiate o mal ripiegate mediante l’interazione con il complesso proteasomico. La perdita di questa funzione da parte della parkina, conseguente a mutazioni (per esempio la mutazione puntiforme Arg42Pro (R42P)) o a stress ossidativo, sembra costituire il meccanismo patogenetico del PD giovanile, portando ad un accumulo delle proteine e alla disregolazione del metabolismo della dopamina. In questo contesto è rilevante notare che recenti studi, sia in vitro che in vivo, hanno attribuito un probabile ruolo protettivo alla parkina nella sopravvivenza dei neuroni dopaminergici nigrali, aprendo così interessanti prospettive per lo studio e lo sviluppo di strategie terapeutiche innovative della PD, basate sulla neuroprotezione endogena. Alla luce di queste ultime evidenze, il progetto di ricerca ha avuto lo scopo di indagare il potenziale effetto neuroprotettivo della parkina nella risposta cellulare allo stress ossidativo indotto dalla tossina dopaminergica 6-idrossi-dopamina (6-OHDA). Tale obbiettivo è stato perseguito avvalendoci di due approcci sperimentali: 1. produzione, purificazione e caratterizzazione di una proteina TAT-parkina umana da Escherichia coli e valutazione della potenziale capacità protettiva mediante somministrazione esogena della stessa. 2. sovra-espressione della parkina wild-type (WT) umana e valutazione del possibile effetto protettivo mediante confronto con cellule di controllo e con cellule sovra-esprimenti la forma mutata R42P (parkina R42P). Il modello in vitro utilizzato è costituito da cellule surrenali adrenergiche PC12, di feocromocitoma di ratto, sia indifferenziate, sia indotte a sviluppare tratti fenotipici che caratterizzano i neuroni dopaminergici in seguito all’esposizione al fattore di crescita nervoso. Nella prima parte dello studio è stata clonata ed espressa, attraverso l’uso di sistemi d’espressione in procarioti, una proteina parkina umana. Tale proteina è stata fusa, nella porzione ammino-terminale, con una coda di 6 istidine (His6) necessaria per la successiva purificazione, seguita dalla sequenza TAT di traslocazione cellulare, derivante dall’immunodeficienza umana (HIV). La sequenza TAT fa parte di una più ampia classe di domini di trasduzione (protein transduction domains (PTD)) che hanno lo scopo di agevolare la diffusione di macromolecole attraverso le membrana cellulari. La proteina di fusione His(6)TAT-parkina è stata espressa in Escherichia coli e purificata secondo la tecnica standard del DNA ricombinante. Le varie fasi di purificazione sono state confermate mediante analisi elettroforetica SDS-PAGE. L’analisi in Western blotting e l’immunocitochimica hanno invece evidenziato come tale proteina sia in grado di entrare nelle cellule attraverso la sequenza TAT, di localizzare preferenzialmente nel nucleo e nel citoplasma, di co-localizzare nei mitocondri; mentre un saggio di ubiquitinazione in vitro ha rivelato la sua attività biologica di ubiquitina E3-ligasi. Questa proteina è stata pertanto testata su cellule PC12 differenziate sottoposte precedentemente a stress ossidativo indotto da 6-OHDA. I risultati ottenuti hanno dimostrato che TAT-parkina umana, a concentrazioni nanomolari, è in grado di proteggere i neuroni simil-dopaminergici purché sia presente prima, durante e dopo il danno indotto da 6-OHDA. Sulla base di questi ultimi risultati e su recenti studi che hanno dimostrato come la sovra-espressione della parkina protegge dalla tossicitù indotta dall'α-sinucleina e in modelli cellulari di apoptosi, nella seconda parte dello studio si è indagata la potenziale proprietà neuroprotettiva della parkina nei confronti dello stress ossidativo, valutando gli effetti dell’aumento dell’espressione della proteina umana (WT) a confronto con la forma patologica mutata R42P. A tale scopo le cellule PC12 sono state transfettate stabilmente con un plasmide d’espressione codificante in parte per la proteina parkina umana (WT) e in parte per la forma umana mutata R42P. Le cellule non transfettate sono state usate come controllo. I cloni sono stati selezionati mediante Reverse Transcription-Polymerase Chain Reaction e Western blotting. I cloni selezionati e le cellule non transfettate sono state trattate con 6-OHDA (50 e 75 μ­M) a tempi differenti. Per entrambe le dosi e per tutte le cellule, è stata osservata una riduzione della vitalità cellulare tempo-dipendente; tuttavia in maniera già significativa a partire dalle 2 ore per le cellule di controllo e per il clone sovra-esprimente la parkina mutata R42P, mentre il clone sovra-esprimente la parkina WT ha mostrato una significativa riduzione della vitalità solo a partire dalle 12 ore. Una successiva analisi in Western blotting ha inoltre evidenziato che questo ultimo clone è caratterizzato da un incremento della quantità di proteine ubiquitinate e da un aumento basale dell’autofagia. Poiché molti studi indicano che un mal funzionamento del sistema proteasoma-ubiquitina e del sistema autofagico sembra essere uno dei meccanismi di induzione e promozione della PD, per verificare se l’effetto protettivo della parkina nei confronti dello stress ossidativo potesse essere mediato da entrambi questi processi, è stato inibito il pathway proteosomico con l’inibitore specifico del proteasoma (MG132), o il pathway autofagico con l’inibitore selettivo del’autofagia, 3-metil-adenina (3-MA). Anche in questo caso è apparsa evidente una maggior capacità di sopravvivenza cellulare nelle cellule sovra-esprimenti la parkina (WT). Tuttavia, la contemporanea somministrazione di entrambi gli inibitori ha determinato una riduzione della vitalità cellulare simile sia per i cloni, sia per le cellule di controllo, annullando pertanto l’effetto protettivo della parkina (WT). Questi ultimi risultati hanno dimostrato l’effetto protettivo della sovra-espressione della parkina sui neuroni simil-dopaminergici in condizioni di danno da stress ossidativo indotto da 6-OHDA. La sovra-espressione della parkina protegge inoltre dalla tossicità indotta da disfunzioni del sistema proteasoma-ubiquitina o del sistema autofagico, confermando infine che la mutazione R42P compromette la funzione fisiologica della proteina. Complessivamente i dati ottenuti confermano che la parkina, sia come proteina TAT-parkina ricombinante, sia quando sovra-espressa, è dotata di una spiccata capacità neuroprotettiva nei confronti di differenti stimoli tossici. La parkina potrebbe quindi rappresentare un possibile target di strategia terapeutica basato sulla neuroprotezione endogena, così come l’applicazione dei domini di trasduzione potrebbero rappresentare un valido strumento di somministrazione di farmaci o sostanze potenzialmente terapeutiche per la cura di molteplici patologie, compresa la PD

Loss of Corticostriatal Mu-Opioid Receptors in α-Synuclein Transgenic Mouse Brains

Ultrastructural, neurochemical, and molecular alterations within the striatum are associated with the onset and progression of Parkinson’s disease (PD). In PD, the dopamine-containing neurons in the substantia nigra pars compacta (SNc) degenerate and reduce dopamine-containing innervations to the striatum. The loss of striatal dopamine is associated with enhanced corticostriatal glutamatergic plasticity at the early stages of PD. However, with disease progression, the glutamatergic corticostriatal white matter tracts (WMTs) also degenerate. We analyzed the levels of Mu opioid receptors (MORs) in the corticostriatal WMTs, as a function of α-Synuclein (α-Syn) toxicity in transgenic mouse brains. Our data show an age-dependent loss of MOR expression levels in the striatum and specifically, within the caudal striatal WMTs in α-Syn tg mouse brains. The loss of MOR expression is associated with degeneration of the myelinated axons that are localized within the corticostriatal WMTs. In brains affected with late stages of PD, we detect evidence confirming the degeneration of myelinated axons within the corticostriatal WMTs. We conclude that loss of corticostriatal MOR expression is associated with degeneration of corticostriatal WMT in α-Syn tg mice, modeling PD

Alpha-Synuclein and Parkinson’s Disease Motor and Non-Motor Symptoms: What Is New?

Although it was discovered about 25 years ago, alpha-synuclein (αS) misfolding and accumulation in neuronal tissues is still recognized as one of the most crucial aspects in Parkinson’s disease (PD) pathology [...

Proteomic study of 6-OHDA-induced neurodegeneration of rat nigrostriatal pathway

Background: The aetiology of Parkinson's disease (PD), an age-related disorder characterized by a progressive degeneration of dopaminergic neurons of the substantia nigra (SN) pars compacta, remains unclear. Current treatments, such as administration of L-DOPA, are only symptomatic and do not stop or delay the progressive loss of neurons. In fact, it has been suggested that the dopamine precursor L-DOPA, increases generation of reactive oxygen species (ROS) leading to further neuronal damage. A similar loss in nigro-striatal dopaminergic neurons is produced on intracerebral administration of the catecholaminergic neurotoxin 6-hydroxydopamine (6-OHDA). In this animal model of PD, termed 'the hemi-parkinsonian rat', unilateral injection of 6-OHDA into the nigro-striatal pathway results in extensive loss of dopaminergic cells in the ipsolateral SN. In an attempt to identify some of the proteins that are involved in dopaminergic neuronal death, we used the proteomic methods to analyze this animal model of PD. Methods: Five hemiparkinsonian rats were obtained by intranigral stereotaxic injection of 6-OHDA. The right 6-OHDA-lesioned substantia nigra and striatum tissues along with the left, unlesioned controlateral tissues, were excised and homogenized, using urea-based buffer, to extract the tissues protein. The separation of the protein mixtures and the visualization of the protein patterns obtained were performed using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Protein profiles of control and treated tissues were compare by the PDQuest 2D-gel analysis software (BIO-Rad Lab., Hercules, CA, USA). The protein spots showing differential expression were analysed by matrix assisted laser desorption/ionizing time of flight (MALDI-TOF) mass spectrometry. Results: The brain protein extraction and solubilization protocol was validated obtaining a satisfactory protein profile. In comparison to the normal rats, emiparkinsonian animals exhibited a different expression in alpha-enolase and beta-actin in substantia nigra and striatum, respectively. Conclusion: The proteomic study of rats unilateral injection of 6-OHDA into the nigro-striatal tissues allowed us to identify two proteins, alpha-enolase and beta-actin, showing increased levels in the 6-OHDA-lesioned brain tissues compared to control. Previous studies described the same proteins as oxidized and proteins in Alzheimer's disease (AD) brain. Our preliminary data could mirror those results pointing out a common mechanism of neurodegenerative diseases

A proteomic approach in the study of an animal model of Parkinson's disease

BACKGROUND: The aetiology of Parkinson's disease (PD), an age-related disorder characterized by a progressive degeneration of dopaminergic neurons of the substantia nigra (SN) pars compacta, remains unclear. Current treatments, such as administration of L-DOPA, are only symptomatic and do not stop or delay the progressive loss of neurons. In fact, it has been suggested that the dopamine precursor L-DOPA, increases generation of reactive oxygen species (ROS) leading to further neuronal damage. A similar loss in nigrostriatal dopaminergic neurons is produced on intracerebral administration of the catecholaminergic neurotoxin 6-hydroxydopamine (6-OHDA). In an animal model of PD, termed 'the hemiparkinsonian rat', unilateral injection of 6-OHDA into the nigrostriatal pathway results in extensive loss of dopaminergic cells in the ipsolateral SN. In an attempt to identify some of the proteins that are involved in dopaminergic neuronal death, we used the proteomic methods to analyze this animal model of PD. METHODS: Five hemiparkinsonian rats were obtained by intranigral stereotaxic injection of 6-OHDA. The right 6-OHDA-lesioned substantia nigra and striatum tissues along with the left, unlesioned controlateral tissues, were excised and homogenized, using urea-based buffer, to extract the tissues protein. The separation of the protein mixtures and the visualization of the protein patterns obtained were performed using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Protein profiles of control and treated tissues were compare by the PDQuest 2D-gel analysis software (BIO-Rad laboratory). The protein spots showing differential expression were analysed by matrix assisted laser desorption/ionizing time of flight (MALDI-TOF) mass spectrometry. RESULTS: The brain protein extraction and solubilization protocol was validated obtaining a satisfactory protein profile. In comparison to the normal rats, hemiparkinsonian animals exhibited a different expression in alpha-enolase and beta-actin in substantia nigra and striatum, respectively. CONCLUSION: The proteomic study of 6-OHDA-induced lesions in the nigrostriatial pathway allowed us to identify two proteins, alpha-enolase and beta-actin, showing increased levels in the 6-OHDA-lesioned brain tissues compared to control. Previous studies described the same proteins as oxidized and proteins in Alzheimer's disease (AD) brain. Our preliminary data could mirror those results pointing out a common mechanism of neurodegenerative diseases

From α-synuclein to synaptic dysfunctions: new insights into the pathophysiology of Parkinson's disease

Alpha-synuclein is a natively unfolded protein playing a key role in the regulation of several neuronal synaptic functions in physiological and pathological conditions. Many studies, over the past years, have shown that it is actively involved in PD pathophysiology. Alpha-synuclein is integrated in a complex network of neuronal processes through the interaction with cytosolic and synaptic proteins. Hence, it is not the sole α-synuclein pathology but its effects on diverse protein partners and specific cellular pathways in the membrane and/or cytosolic districts such as endoplasmic reticulum/Golgi, axonal and synaptic compartments of dopaminergic neurons, that may cause the onset of neuronal cell dysfunction and degeneration which are among the key pathological features of the PD brain. Here we summarize a series of experimental data supporting that α-synuclein aggregation may induce dysfunction and degeneration of synapses via these multiple mechanisms. Taken together, these data add new insights into the complex mechanisms underlying synaptic derangement in PD and other α-synucleinopathies. This article is part of a Special Issue entitled: Brain Integration

α‐Synuclein in blood cells differentiates Parkinson’s disease from healthy controls

Objective: To determine whether blood cells expressed α-Syn can differentiate Parkinson's disease (PD) from healthy controls (HC). Methods: The concentrations of α-Syn were determined in samples of blood cell pellets using a quantitative Lipid-ELISA assay. In addition, the levels of total protein, hemoglobin, iron and H-ferritin were determined. The study includes samples from the Biofind cohort (n = 46 PD and 45 HC) and results were validated with an additional cohort (n = 35 PD and 28 HC). Results: A composite biomarker consisting of the concentrations of total α-Syn, proteinase-K resistant (PKres ) α-Syn and phospho-Serine 129 α-Syn (PSer 129), is designed based on the analysis of the discovery BioFIND cohort. This composite biomarker differentiates a PD subgroup, presenting motor symptoms without dementia from a HC group, with a convincing accuracy, represented by an AUC = 0.81 (95% CI, 0.71 to 0.92). Closely similar results were obtained for the validation cohort, that is, AUC = 0.81, (95% CI, 0.70 to 0.94). Interpretation: Our results demonstrate the potential usefulness of blood cells expressed α-Syn as a biomarker for PD