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Proteomic mapping of differentially vulnerable pre-synaptic populations identifies regulators of neuronal stability in vivo.

ABSTRACT: Synapses are an early pathological target in many neurodegenerative diseases ranging from well-known adult onset conditions such as Alzheimer and Parkinson disease to neurodegenerative conditions of childhood such as spinal muscular atrophy (SMA) and neuronal ceroid lipofuscinosis (NCLs). However, the reasons why synapses are particularly vulnerable to such a broad range of neurodegeneration inducing stimuli remains unknown. To identify molecular modulators of synaptic stability and degeneration, we have used the Cln3 -/- mouse model of a juvenile form of NCL. We profiled and compared the molecular composition of anatomically-distinct, differentially-affected pre-synaptic populations from the Cln3 -/- mouse brain using proteomics followed by bioinformatic analyses. Identified protein candidates were then tested using a Drosophila CLN3 model to study their ability to modify the CLN3-neurodegenerative phenotype in vivo. We identified differential perturbations in a range of molecular cascades correlating with synaptic vulnerability, including valine catabolism and rho signalling pathways. Genetic and pharmacological targeting of key 'hub' proteins in such pathways was sufficient to modulate phenotypic presentation in a Drosophila CLN3 model. We propose that such a workflow provides a target rich method for the identification of novel disease regulators which could be applicable to the study of other conditions where appropriate models exist.

SUBMITTER: Llavero Hurtado M

PROVIDER: S-EPMC5622084 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Proteomic mapping of differentially vulnerable pre-synaptic populations identifies regulators of neuronal stability in vivo.

Llavero Hurtado Maica M Fuller Heidi R HR Wong Andrew M S AMS Eaton Samantha L SL Gillingwater Thomas H TH Pennetta Giuseppa G Cooper Jonathan D JD Wishart Thomas M TM

Scientific reports 20170929 1

Synapses are an early pathological target in many neurodegenerative diseases ranging from well-known adult onset conditions such as Alzheimer and Parkinson disease to neurodegenerative conditions of childhood such as spinal muscular atrophy (SMA) and neuronal ceroid lipofuscinosis (NCLs). However, the reasons why synapses are particularly vulnerable to such a broad range of neurodegeneration inducing stimuli remains unknown. To identify molecular modulators of synaptic stability and degeneration ...[more]

PMID: 28963550

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Project description:Neurons are highly polarized cells consisting of three distinct functional domains: the cell body (and associated dendrites), the axon and the synapse. Previously, it was believed that the clinical phenotypes of neurodegenerative diseases were caused by the loss of entire neurons, however it has recently become apparent that these neuronal sub-compartments can degenerate independently, with synapses being particularly vulnerable to a broad range of stimuli. Whilst the properties governing the differential degenerative mechanisms remain unknown, mitochondria consistently appear in the literature, suggesting these somewhat promiscuous organelles may play a role in affecting synaptic stability. Synaptic and non-synaptic mitochondrial subpools are known to have different enzymatic properties (first demonstrated by Lai et al., 1977). However, the molecular basis underpinning these alterations, and their effects on morphology, has not been well documented.The current study has employed electron microscopy, label-free proteomics and in silico analyses to characterize the morphological and biochemical properties of discrete sub-populations of mitochondria. The physiological relevance of these findings was confirmed in-vivo using a molecular genetic approach at the Drosophila neuromuscular junction.Here, we demonstrate that mitochondria at the synaptic terminal are indeed morphologically different to non-synaptic mitochondria, in both rodents and human patients. Furthermore, generation of proteomic profiles reveals distinct molecular fingerprints - highlighting that the properties of complex I may represent an important specialisation of synaptic mitochondria. Evidence also suggests that at least 30% of the mitochondrial enzymatic activity differences previously reported can be accounted for by protein abundance. Finally, we demonstrate that the molecular differences between discrete mitochondrial sub-populations are capable of selectively influencing synaptic morphology in-vivo. We offer several novel mitochondrial candidates that have the propensity to significantly alter the synaptic architecture in-vivo.Our study demonstrates discrete proteomic profiles exist dependent upon mitochondrial subcellular localization and selective alteration of intrinsic mitochondrial proteins alters synaptic morphology in-vivo.

Project description:Degeneration of synaptic and axonal compartments of neurons is an early event contributing to the pathogenesis of many neurodegenerative diseases, but the underlying molecular mechanisms remain unclear. Here, we demonstrate the effectiveness of a novel "top-down" approach for identifying proteins and functional pathways regulating neurodegeneration in distal compartments of neurons. A series of comparative quantitative proteomic screens on synapse-enriched fractions isolated from the mouse brain following injury identified dynamic perturbations occurring within the proteome during both initiation and onset phases of degeneration. In silico analyses highlighted significant clustering of proteins contributing to functional pathways regulating synaptic transmission and neurite development. Molecular markers of degeneration were conserved in injury and disease, with comparable responses observed in synapse-enriched fractions isolated from mouse models of Huntington's disease (HD) and spinocerebellar ataxia type 5. An initial screen targeting thirteen degeneration-associated proteins using mutant Drosophila lines revealed six potential regulators of synaptic and axonal degeneration in vivo. Mutations in CALB2, ROCK2, DNAJC5/CSP, and HIBCH partially delayed injury-induced neurodegeneration. Conversely, mutations in DNAJC6 and ALDHA1 led to spontaneous degeneration of distal axons and synapses. A more detailed genetic analysis of DNAJC5/CSP mutants confirmed that loss of DNAJC5/CSP was neuroprotective, robustly delaying degeneration in axonal and synaptic compartments. Our study has identified conserved molecular responses occurring within synapse-enriched fractions of the mouse brain during the early stages of neurodegeneration, focused on functional networks modulating synaptic transmission and incorporating molecular chaperones, cytoskeletal modifiers, and calcium-binding proteins. We propose that the proteins and functional pathways identified in the current study represent attractive targets for developing therapeutics aimed at modulating synaptic and axonal stability and neurodegeneration in vivo.

Project description:ObjectiveNational data suggest drivers who are younger, older, and have lower socioeconomic status (SES) have heightened crash-related injury rates. Ensuring vulnerable drivers are in the safest vehicles they can afford is a promising approach to reducing crash injuries in these groups. However, we do not know the extent to which these drivers are disproportionately driving less safe vehicles. Our objective was to obtain population-based estimates of the prevalence of important vehicle safety criteria among a statewide population of drivers.MethodsWe analyzed data from the NJ Safety and Health Outcomes warehouse, which includes all licensing and crash data from 2010-2017. We borrowed the quasi-induced exposure method's fundamental assumption-that non-responsible drivers in clean (i.e., only one responsible driver) multi-vehicle crashes are reasonably representative of drivers on the road-to estimate statewide prevalence of drivers' vehicle characteristics across four driver age groups (17-20; 21-24; 25-64, and ≥65) and quintiles of census tract median household income (n = 983,372). We used NHTSA's Product Information Catalog and Vehicle Listing platform (vPIC) to decode the VIN of each crash-involved vehicle to obtain model year, presence of electronic stability control (ESC), vehicle type, engine horsepower, and presence of front, side, and curtain air bags.ResultsThe youngest and oldest drivers were more likely than middle-aged drivers to drive vehicles that were older, did not have ESC, and were not equipped with side airbags. Additionally, across all age groups drivers of higher SES were in newer and safer vehicles compared with those of lower SES. For example, young drivers living in lowest-income census tracts drove vehicles that were on average almost twice as old as young drivers living in highest-income tracts (median [IQR]: 11 years [6-14] vs. 6 years [3-11]).ConclusionsVehicle safety is an important component of seminal road safety philosophies that aim to reduce crash fatalities. However, driver groups that are overrepresented in fatal crashes-young drivers, older drivers, and those of lower SES-are also driving the less safe vehicles. Ensuring drivers are in the safest car they can afford should be further explored as an approach to reduce crash-related injuries among vulnerable populations.

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Proteomic mapping of differentially vulnerable pre-synaptic populations identifies regulators of neuronal stability in vivo.

Publications

Proteomic mapping of differentially vulnerable pre-synaptic populations identifies regulators of neuronal stability in vivo.

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