Integrating molecular, histopathological, neuroimaging and clinical neuroscience data with NeuroPM-box

Understanding and treating heterogeneous brain disorders requires specialized techniques spanning genetics, proteomics, and neuroimaging. Designed to meet this need, NeuroPM-box is a user-friendly, open-access, multi-tool cross-platform software capable of characterizing multiscale and multifactorial neuropathological mechanisms. Using advanced analytical modeling for molecular, histopathological, brain-imaging and/or clinical evaluations, this framework has multiple applications, validated here with synthetic (N > 2900), in-vivo (N = 911) and post-mortem (N = 736) neurodegenerative data, and including the ability to characterize: (i) the series of sequential states (genetic, histopathological, imaging or clinical alterations) covering decades of disease progression, (ii) concurrent intra-brain spreading of pathological factors (e.g., amyloid, tau and alpha-synuclein proteins), (iii) synergistic interactions between multiple biological factors (e.g., toxic tau effects on brain atrophy), and (iv) biologically-defined patient stratification based on disease heterogeneity and/or therapeutic needs. This freely available toolbox (neuropm-lab.com/neuropm-box.html) could contribute significantly to a better understanding of complex brain processes and accelerating the implementation of Precision Medicine in Neurology.

Preanalytical Stability of CSF Total and Oligomeric Alpha-Synuclein

Background: The role of cerebrospinal fluid (CSF) alpha-synuclein as a potential biomarker has been challenged mainly due to variable preanalytical measures between laboratories. To evaluate the impact of the preanalytical factors contributing to such variability, the different subforms of alpha-synuclein need to be studied individually.Method: We investigated the effect of exposing CSF samples to several preanalytical sources of variability: (1) different polypropylene (PP) storage tubes; (2) use of non-ionic detergents; (3) multiple tube transfers; (4) multiple freeze-thaw cycles; and (5) delayed storage. CSF oligomeric- and total-alpha-synuclein levels were estimated using our in-house sandwich-based enzyme-linked immunosorbent assays.Results: Siliconized tubes provided the optimal preservation of CSF alpha-synuclein proteins among other tested polypropylene tubes. The use of tween-20 detergent significantly improved the recovery of oligomeric-alpha-synuclein, while multiple freeze-thaw cycles significantly lowered oligomeric-alpha-synuclein in CSF. Interestingly, oligomeric-alpha-synuclein levels remained relatively stable over multiple tube transfers and upon delayed storage.Conclusion: Our study showed for the first-time distinct impact of preanalytical factors on the different forms of CSF alpha-synuclein. These findings highlight the need for special considerations for the different forms of alpha-synuclein during CSF samples’ collection and processing.

Coevolution study of tau and a-synuclein suggests a connection between their normal interaction in neurons and the Parkinson's disease-associated mutation A53T

Alpha-synuclein lies at the center of Parkinson’s disease etiology, and polymorphisms in the gene for the microtubule-associated protein tau are risk factors for getting the disease. Tau and a-synuclein interact in vitro, and a-synuclein can also compete with tau binding to microtubules. To test whether these interactions might be part of their natural biological functions, a correlated mutation analysis was performed between tau and a-synuclein, looking for evidence of coevolution. For comparison, analyses were also performed between tau and b- and g-synuclein. In addition, analyses were performed between tau and the synuclein proteins and the neuronal tubulin proteins. Potential correlated mutations were detected between tau and a-synuclein, one involving an a-synuclein residue known to interact with tau in vitro, Asn122, and others involving the Parkinson’s disease-associated mutation A53T. No significant correlated mutations were seen between tau and b- and g-synuclein. Tau showed potential correlated mutations with the neuron-specific bIII-tubulin protein, encoded by the TUBB3 gene. No convincing correlated mutations were seen between the synuclein and tubulin proteins, with the possible exception of b-synuclein with bIVa-tubulin, encoded by the TUBB4A gene. While the correlated mutations between tau and a-synuclein suggest the two proteins have coevolved, additional study will be needed to confirm that their interaction is part of their normal biological function in cells.

The Lipid-Chaperon Hypothesis: A Common Molecular Mechanism of Membrane Disruption by Intrinsically Disordered Proteins

<p>Increasing number of human diseases have been shown to be linked to aggregation and amyloid formation by intrinsically disordered proteins (IDPs). Amylin, amyloid-β, and α-synuclein are, indeed, involved in type-II diabetes, Alzheimer’s, and Parkinson’s, respectively. Despite the correlation of the toxicity of these proteins at early aggregation stages with membrane damage, the molecular events underlying the process is quite complex to understand. In this study, we demonstrate the crucial role of free lipids in the formation of lipid-protein complex, which enables an easy membrane insertion for amylin, amyloid-β, and α-synuclein. Experimental results from a variety of biophysical methods and molecular dynamics results reveal this common molecular pathway in membrane poration is shared by amyloidogenic (amylin, amyloid-β, and α-synuclein) and non-amyloidogenic (rat IAPP, β-synuclein) proteins. Based on these results, we propose a “lipid-chaperone” hypothesis as a unifying framework for protein-membrane poration.<b></b></p>

The Lipid-Chaperon Hypothesis: A Common Molecular Mechanism of Membrane Disruption by Intrinsically Disordered Proteins

<p>Increasing number of human diseases have been shown to be linked to aggregation and amyloid formation by intrinsically disordered proteins (IDPs). Amylin, amyloid-β, and α-synuclein are, indeed, involved in type-II diabetes, Alzheimer’s, and Parkinson’s, respectively. Despite the correlation of the toxicity of these proteins at early aggregation stages with membrane damage, the molecular events underlying the process is quite complex to understand. In this study, we demonstrate the crucial role of free lipids in the formation of lipid-protein complex, which enables an easy membrane insertion for amylin, amyloid-β, and α-synuclein. Experimental results from a variety of biophysical methods and molecular dynamics results reveal this common molecular pathway in membrane poration is shared by amyloidogenic (amylin, amyloid-β, and α-synuclein) and non-amyloidogenic (rat IAPP, β-synuclein) proteins. Based on these results, we propose a “lipid-chaperone” hypothesis as a unifying framework for protein-membrane poration.<b></b></p>

Pathological α-synuclein triggers synaptic NMDA receptor dysfunction through altered trafficking

Background α-Synuclein misfolding and aggregation contribute to synaptic dysfunction in synucleinopathies, including Parkinson’s disease. However, the mechanism underlying the effect of α-synuclein on synaptic components remains unclear. Since the N-methyl-D-aspartic acid receptor (NMDAR) plays a key role in glutamate synapse pathophysiology, we here investigated its surface dynamics and functional distribution in neurons exposed to various pathological α-synuclein forms. Methods A combination of single-molecule tracking, immunochemistry, immunoblot and calcium imaging approaches were used to assess the changes in NMDAR membrane dynamics and functions. The NMDAR alterations were evaluated in rat cultured hippocampal networks, in which α-synuclein mutants were overexpressed or exposed to α-synuclein proteins (monomeric/PFF α-synuclein). The surface dynamics of NMDAR subtype was artificially tuned in order to test its instrumental role. Results We observed that mutant α-synuclein (A53T-α-synuclein) restricted NMDAR surface trafficking and impaired synaptic function. In contrast, wild-type α-synuclein did not affect synaptic NMDAR. Further, we found that chronic exposure to α-synuclein preformed fibrils induced molecular dysfunctions that mainly targeted the GluN2B-NMDAR subtype. The deficits of synaptic NMDAR have also been found in A53T transgenic mice α-synuclein. Upon fine-tuning of the surface dynamics of GluN2B-NMDAR, pathological α-synuclein gradually lost its synaptic toxicity. Conclusions Our findings indicate that pathological α-synuclein alters GluN2B-NMDAR synaptic dynamics and organization, which leads to glutamate synapse dysfunction.