Dataset Information

Single cell imaging and quantification of TDP-43 and α-synuclein intercellular propagation.

ABSTRACT: The intercellular spreading of protein assemblies is a major factor in the progression of neurodegenerative disorders. The quantitative study and visualization of cell-to-cell propagation using tagged-proteins is challenging due to the steric effect of relatively large fluorescence tags and the risk of 'false positive' identification when analyzing these rare transmission events. Here, we established a cell culture model to characterize the cell-to-cell transmission of TAR DNA-binding protein and α-synuclein, involved in amyotrophic lateral sclerosis and Parkinson's disease, respectively, using the small nine amino acid influenza hemagglutinin tag. The novel use of single cell resolution imaging flow cytometry allowed the visualization and quantification of all individual transmission events. Cell-level analysis of these events indicated that the degree of transfer is lower than previously reported based on conventional flow cytometry. Furthermore, our analysis can exclude 'false positive' events of cellular overlap and extracellular debris attachment. The results were corroborated by high-resolution confocal microscopy mapping of protein localization.

SUBMITTER: Peled S

PROVIDER: S-EPMC5428807 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Single cell imaging and quantification of TDP-43 and α-synuclein intercellular propagation.

Peled Sivan S Sade Dorin D Bram Yaron Y Porat Ziv Z Kreiser Topaz T Mimouni Michael M Lichtenstein Alexandra A Segal Daniel D Gazit Ehud E

Scientific reports 20170328 1

The intercellular spreading of protein assemblies is a major factor in the progression of neurodegenerative disorders. The quantitative study and visualization of cell-to-cell propagation using tagged-proteins is challenging due to the steric effect of relatively large fluorescence tags and the risk of 'false positive' identification when analyzing these rare transmission events. Here, we established a cell culture model to characterize the cell-to-cell transmission of TAR DNA-binding protein an ...[more]

PMID: 28373710

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Project description:Many neurodegenerative diseases induce high levels of sustained cellular stress and alter a number of cellular processes. To examine how different mutations associated with neurodegenerative disease affect cell stress and signaling, we created live-cell assays for endoplasmic reticulum (ER)-mediated cell stress and second messenger signaling. We first examined neurodegenerative mutations associated with direct ER stress by exploring the effect of rhodopsin mutations on ER stress and Ca2+ signaling. The rhodopsin P23H mutation, the most common mutation in autosomal dominant Retinitis Pigmentosa (RP), produced increased ER stress levels compared to wild type (WT) rhodopsin. Moreover, this increase in cell stress correlated with blunted Ca2+ signaling in a stress-dependent manner. Analysis of single-cell Ca2+ signaling profiles revealed unique Ca2+ signaling responses exist in cells expressing WT or P23H rhodopsin, consistent with the idea that second messenger signaling is affected by cell stress. To explore the use of the ER-stress biosensor in neurodegenerative diseases that may not have a direct effect on ER-mediated cell stress, we examined how various mutants of α-synuclein and TDP-43 affected ER stress. Mutants of both α-synuclein and TDP-43 associated with Parkinson's disease (PD) and Amyotrophic lateral sclerosis (ALS) demonstrated increased ER stress compared to WT proteins. To examine the effect of α-synuclein and TDP-43 mutants on cellular signaling, we created a second live-cell assay to monitor changes in cAMP signaling during expression of various forms of α-synuclein and TDP-43. The increased cell stress caused by expression of the mutant proteins was accompanied by changes in phosphodiesterase activity. Both HEK293T and SH-SY5Y cells expressing these proteins displayed a shift towards increased cAMP degradation rates, likely due to increased phosphodiesterase activity. Together these data illustrate how biosensors for cellular stress and signaling can provide nuanced, new views of neurodegenerative disease processes.

Project description:The pathological hallmark of amyotrophic lateral sclerosis (ALS) is the presence of cytoplasmic inclusions, containing C-terminal fragments of the protein TDP-43. Here, we tested the hypothesis that highly sensitive mass spectrometry with parallel reaction monitoring (MS-PRM) can generate a high-resolution map of pathological TDP-43 peptide ratios to form the basis for quantitation of abnormal C-terminal TDP-43 fragment enrichment. Human cortex and spinal cord, microscopically staged for the presence of p-TDP-43, p-tau, alpha-synuclein, and beta-amyloid pathology, were biochemically fractionated and analyzed by immunoblot and MS for the detection of full-length and truncated (disease-specific) TDP-43 peptides. This informed the synthesis of heavy isotope-labeled peptides for absolute quantification of TDP-43 by MS-PRM across 16 ALS, 8 Parkinson's, 8 Alzheimer's disease, and 8 aged control cases. We confirmed by immunoblot the previously described enrichment of pathological C-terminal fragments in ALS-TDP urea fractions. Subsequent MS analysis resolved specific TDP-43 N- and C-terminal peptides, including a novel N-terminal truncation site-specific peptide. Absolute quantification of peptides by MS-PRM showed an increased C:N-terminal TDP-43 peptide ratio in ALS-TDP brain compared to normal and disease controls. A C:N-terminal ratio >1.5 discriminated ALS from controls with a sensitivity of 100% (CI 79.6-100) and specificity of 100% (CI 68-100), and from Parkinson's and Alzheimer's disease with a sensitivity of 93% (CI 70-100) and specificity of 100% (CI 68-100). N-terminal truncation site-specific peptides were increased in ALS in line with C-terminal fragment enrichment, but were also found in a proportion of Alzheimer cases with normal C:N-terminal ratio but coexistent limbic TDP-43 neuropathological changes. In conclusion this is a novel, sensitive, and specific method to quantify the enrichment of pathological TDP-43 fragments in human brain, which could form the basis for an antibody-free assay. Our methodology has the potential to help clarify if specific pathological TDP-43 peptide signatures are associated with primary or secondary TDP-43 proteinopathies.

Dataset Information

Single cell imaging and quantification of TDP-43 and α-synuclein intercellular propagation.

Publications

Single cell imaging and quantification of TDP-43 and α-synuclein intercellular propagation.

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