Dataset Information

Characterization of TDP-43 RRM2 Partially Folded States and Their Significance to ALS Pathogenesis.

ABSTRACT: The human protein TDP-43 is a major component of the cellular aggregates found in amyotrophic lateral sclerosis and other neurodegenerative diseases. Insoluble cytoplasmic aggregates isolated from the brain of amyotrophic lateral sclerosis and frontotemporal lobar degeneration patients contain ubiquitinated, hyperphosphorylated, and N-terminally truncated TDP-43. Truncated fragments of TDP-43 identified from patient tissues contain part of the second RNA recognition motif (RRM2) and the disordered C-terminus, indicating that both domains can be involved in aggregation and toxicity. Here, we focus on RRM2. Using all-atom replica-averaged metadynamics simulations with NMR chemical shift restraints, we characterized the atomic structure of non-native states of RRM2, sparsely populated under native conditions. These structures reveal the exposure to the solvent of aggregation-prone peptide regions, normally buried in the native state, supporting a role in aggregation for the partially folded states of RRM2.

SUBMITTER: Tavella D

PROVIDER: S-EPMC6224623 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Characterization of TDP-43 RRM2 Partially Folded States and Their Significance to ALS Pathogenesis.

Tavella Davide D Zitzewitz Jill A JA Massi Francesca F

Biophysical journal 20180921 9

The human protein TDP-43 is a major component of the cellular aggregates found in amyotrophic lateral sclerosis and other neurodegenerative diseases. Insoluble cytoplasmic aggregates isolated from the brain of amyotrophic lateral sclerosis and frontotemporal lobar degeneration patients contain ubiquitinated, hyperphosphorylated, and N-terminally truncated TDP-43. Truncated fragments of TDP-43 identified from patient tissues contain part of the second RNA recognition motif (RRM2) and the disorder ...[more]

PMID: 30309612

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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

Characterization of TDP-43 RRM2 Partially Folded States and Their Significance to ALS Pathogenesis.

Publications

Characterization of TDP-43 RRM2 Partially Folded States and Their Significance to ALS Pathogenesis.

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