Mannose 6-Phosphate Receptor Is Reduced in -Synuclein Overexpressing Models of Parkinsons Disease

Increasing evidence points to defects in autophagy as a common denominator in most neurodegenerative conditions. Progressive functional decline in the autophagy-lysosomal pathway (ALP) occurs with age, and the consequent impairment in protein processing capacity has been associated with a higher risk of neurodegeneration. Defects in cathepsin D (CD) processing and α-synuclein degradation causing its accumulation in lysosomes are particularly relevant for the development of Parkinson's disease (PD). However, the mechanism by which alterations in CD maturation and α-synuclein degradation leads to autophagy defects in PD neurons is still uncertain. Here we demonstrate that MPR300 shuttling between endosomes and the trans Golgi network is altered in α-synuclein overexpressing neurons. Consequently, CD is not correctly trafficked to lysosomes and cannot be processed to generate its mature active form, leading to a reduced CD-mediated α-synuclein degradation and α-synuclein accumulation in neurons. MPR300 is downregulated in brain from α-synuclein overexpressing animal models and in PD patients with early diagnosis. These data indicate MPR300 as crucial player in the autophagy-lysosomal dysfunctions reported in PD and pinpoint MRP300 as a potential biomarker for PD

LRRK2 and Lipid Pathways: Implications for Parkinson’s Disease

Genetic alterations in the LRRK2 gene, encoding leucine-rich repeat kinase 2, are a common risk factor for Parkinson’s disease. How LRRK2 alterations lead to cell pathology is an area of ongoing investigation, however, multiple lines of evidence suggest a role for LRRK2 in lipid pathways. It is increasingly recognized that in addition to being energy reservoirs and structural entities, some lipids, including neural lipids, participate in signaling cascades. Early investigations revealed that LRRK2 localized to membranous and vesicular structures, suggesting an interaction of LRRK2 and lipids or lipid-associated proteins. LRRK2 substrates from the Rab GTPase family play a critical role in vesicle trafficking, lipid metabolism and lipid storage, all processes which rely on lipid dynamics. In addition, LRRK2 is associated with the phosphorylation and activity of enzymes that catabolize plasma membrane and lysosomal lipids. Furthermore, LRRK2 knockout studies have revealed that blood, brain and urine exhibit lipid level changes, including alterations to sterols, sphingolipids and phospholipids, respectively. In human LRRK2 mutation carriers, changes to sterols, sphingolipids, phospholipids, fatty acyls and glycerolipids are reported in multiple tissues. This review summarizes the evidence regarding associations between LRRK2 and lipids, and the functional consequences of LRRK2-associated lipid changes are discussed

Increased peripheral inflammation in asymptomatic leucine-rich repeat kinase 2 mutation carriers

Background: We aimed to determine if peripheral or central inflammatory cytokines are altered in healthy subjects carrying a leucine-rich repeat kinase 2 (LRRK2) G2019S mutation, and thus genetically at risk of Parkinson's disease (PD). We also aimed to identify differences in inflammatory cytokines between LRRK2 G2019S-associated and idiopathic PD once the disease manifests. Methods: Participants were genetically screened and phenotyped, and biological samples were collected and stored by the Michael J. Fox Foundation LRRK2 Cohort Consortium. Serum samples and matching clinical data were obtained from 71 asymptomatic LRRK2 G2019S mutation carriers (CSF n = 25), 75 neurologically normal controls (CSF n = 22), 75 idiopathic PD patients (CSF n = 29), and 76 PD patients with a LRRK2 G2019S mutation (CSF n = 20). Inflammatory cytokines were measured using multiplex enzyme-linked immunosorbent assays. Results: Serum levels of interleukin 1 beta could discriminate asymptomatic LRRK2 G2019S mutation carriers from controls, with a high inflammatory subgroup of carriers identified. This subgroup was significantly higher in a number of PD-implicated pro-inflammatory cytokines. Once PD had manifest, LRRK2 G2019S patients were discriminated from idiopathic PD by higher serum platelet-derived growth factor, and higher CSF vascular endothelial growth factor and interleukin 8. Conclusions: The results suggest that peripheral inflammation is higher in a percentage of subjects carrying the LRRK2 G2019S mutation. Replication and longitudinal follow-up is required to determine whether the increased peripheral cytokines can predict clinical PD. Importantly, these biological changes were observed prior to the clinical manifestations thought to herald PD.9 page(s

Measurement of LRRK2 and Ser910/935 phosphorylated LRRK2 in peripheral blood mononuclear cells from idiopathic Parkinson's disease patients

A significant number of autosomal dominantly inherited Parkinson's disease (PD) cases are due to mutations in the leucine-rich repeat kinase 2 (LRRK2) gene. In cells, these pathogenic mutations have a number of differing effects on LRRK2 enzymatic activity and protein stability. In particular, five of the six described pathogenic LRRK2 mutations ablate the constitutive phosphorylation of LRRK2 on Ser910 and Ser935, two residues required for binding of LRRK2 to 14-3-3 proteins. This suggests a potential pathogenic role for these residues. However, LRRK2 kinase inhibitors, which have shown early promise as neuroprotective agents, also ablate the phosphorylation of Ser910 and Ser935. Additionally, LRRK2 is phosphorylated on Ser910 and Ser935 following activation of the inflammatory toll-like receptor pathway and inflammatory cytokines are often increased in PD patients. Whether LRRK2 protein or phosphorylation is altered in idiopathic PD is unknown. We therefore measured LRRK2 protein and its phosporylation in peripheral blood mononuclear cells (PBMCs) from 33 idiopathic Parkinson's disease patients and 27 age-matched controls. We found no significant difference in total LRRK2 protein levels in PBMCs from PD patients compared to controls. Furthermore, total LRRK2 protein expression was not effected by age, disease duration, disease severity or levodopa medication. The amount of phosphorylation on LRRK2 at both Ser910 and Ser935 correlated highly with total LRRK2 levels and was also unchanged in PD patients. Therefore, changes in LRRK2 Ser910/Ser935 phosphorylation in PBMCs are unlikely to contribute to idiopathic Parkinson's disease or be of utility as a disease biomarker. However, the invariance of Ser910 and Ser935 phosphorylation in PD PBMC's suggests that these residues could be used as pharmacodynamic biomarkers for the effectiveness of LRRK2 kinase inhibitors in patients.8 page(s

Evaluation of plasma levels of NFL, GFAP, UCHL1 and tau as Parkinson's disease biomarkers using multiplexed single molecule counting

Abstract Objective biomarkers for Parkinson’s Disease (PD) could aid early and specific diagnosis, effective monitoring of disease progression, and improved design and interpretation of clinical trials. Although alpha-synuclein remains a biomarker candidate of interest, the multifactorial and heterogenous nature of PD highlights the need for a PD biomarker panel. Ideal biomarker candidates include markers that are detectable in easily accessible samples, (ideally blood) and that reflect the underlying pathological process of PD. In the present study, we explored the diagnostic and prognostic PD biomarker potential of the SIMOA neurology 4-plex-A biomarker panel, which included neurofilament light (NFL), glial fibrillary acid protein (GFAP), tau and ubiquitin C-terminal hydrolase L1 (UCHL-1). We initially performed a serum vs plasma comparative study to determine the most suitable blood-based matrix for the measurement of these proteins in a multiplexed assay. The levels of NFL and GFAP in plasma and serum were highly correlated (Spearman rho-0.923, p  0.05). The neurology 4-plex-A panel, along with plasma alpha-synuclein was then assessed in a cross-sectional cohort of 29 PD patients and 30 controls. Plasma NFL levels positively correlated with both GFAP and alpha-synuclein levels (rho = 0.721, p  0.05). As disease state biomarkers, motor severity (MDS-UPDRS III) correlated with increased NFL (rho = 0.646, p  0.05). In conclusion, plasma was determined to be most suitable blood-based matrix for multiplexing the neurology 4-plex-A panel. Given their correlation with motor features of PD, NFL and GFAP appear to be promising disease state biomarker candidates and further longitudinal validation of these two proteins as blood-based biomarkers for PD progression is warranted

Unlocking the secrets of LRRK2 function with selective kinase inhibitors

Leucine rich repeat kinase 2 is currently considered a potential therapeutic target for the treatment of Parkinsons disease. A number of pathological mutations, all of which lie in the dual catalytic domains of LRRK2, segregate with Parkinsons disease in an autosomal dominant fashion. The most common mutation, G2019S, results in an increase in the kinase activity of LRRK2 and much work has therefore gone into the development of potent and specific inhibitors of LRRK2 kinase activity. A number of LRRK2 kinase inhibitors have now been employed in the search for the physiological function of LRRK2 and the targets of LRRK2 kinase activity