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Cascella R, Banchelli M, Abolghasem Ghadami S, Ami D, Gagliani MC, Bigi A, Staderini T, Tampellini D, Cortese K, Cecchi C, Natalello A, Adibi H, Matteini P, Chiti F. An in situ and in vitro investigation of cytoplasmic TDP-43 inclusions reveals the absence of a clear amyloid signature. Ann Med 2023; 55:72-88. [PMID: 36495262 PMCID: PMC9746631 DOI: 10.1080/07853890.2022.2148734] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Introduction: Several neurodegenerative conditions are associated with a common histopathology within neurons of the central nervous system, consisting of the deposition of cytoplasmic inclusions of TAR DNA-binding protein 43 (TDP-43). Such inclusions have variably been described as morphologically and molecularly ordered aggregates having amyloid properties, as filaments without the cross-β-structure and dye binding specific for amyloid, or as amorphous aggregates with no defined structure and fibrillar morphology.Aims and Methods: Here we have expressed human full-length TDP-43 in neuroblastoma x spinal cord 34 (NSC-34) cells to investigate the morphological, structural, and tinctorial properties of TDP-43 inclusions in situ. We have used last-generation amyloid diagnostic probes able to cross the cell membrane and detect amyloid in the cytoplasm and have adopted Raman and Fourier transform infrared microspectroscopies to study in situ the secondary structure of the TDP-43 protein in the inclusions. We have then used transmission electron microscopy to study the morphology of the TDP-43 inclusions.Results: The results show the absence of amyloid dye binding, the lack of an enrichment of cross-β structure in the inclusions, and of a fibrillar texture in the round inclusions. The aggregates formed in vitro from the purified protein under conditions in which it is initially native also lack all these characteristics, ruling out a clear amyloid-like signature.Conclusions: These findings indicate a low propensity of TDP-43 to form amyloid fibrils and even non-amyloid filaments, under conditions in which the protein is initially native and undergoes its typical nucleus-to-cell mislocalization. It cannot be excluded that filaments emerge on the long time scale from such inclusions, but the high propensity of the protein to form initially other types of inclusions appear to be an essential characteristic of TDP-43 proteinopathies.KEY MESSAGESCytoplasmic inclusions of TDP-43 formed in NSC-34 cells do not stain with amyloid-diagnostic dyes, are not enriched with cross-β structure, and do not show a fibrillar morphology.TDP-43 assemblies formed in vitro from pure TDP-43 do not have any hallmarks of amyloid.
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Affiliation(s)
- Roberta Cascella
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy
| | - Martina Banchelli
- Institute of Applied Physics "Nello Carrara", National Research Council, Sesto Fiorentino, Italy
| | | | - Diletta Ami
- Department of Biotechnologies and Biosciences, University of Milano-Bicocca, Milan, Italy.,Milan Center of Neuroscience (NeuroMI), Milan, Italy
| | - Maria Cristina Gagliani
- Cellular Electron Microscopy Laboratory, Department of Experimental Medicine, University of Genova, Genoa, Italy
| | - Alessandra Bigi
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy
| | - Tommaso Staderini
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy
| | - Davide Tampellini
- U 1195 INSERM-Université Paris-Saclay, Paris, France.,Institut Professeur Baulieu, Paris, France
| | - Katia Cortese
- Cellular Electron Microscopy Laboratory, Department of Experimental Medicine, University of Genova, Genoa, Italy
| | - Cristina Cecchi
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy
| | - Antonino Natalello
- Department of Biotechnologies and Biosciences, University of Milano-Bicocca, Milan, Italy.,Milan Center of Neuroscience (NeuroMI), Milan, Italy
| | - Hadi Adibi
- Pharmaceutical Sciences Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Paolo Matteini
- Institute of Applied Physics "Nello Carrara", National Research Council, Sesto Fiorentino, Italy
| | - Fabrizio Chiti
- Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy
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Capitini C, Fani G, Vivoli Vega M, Penco A, Canale C, Cabrita LD, Calamai M, Christodoulou J, Relini A, Chiti F. Full-length TDP-43 and its C-terminal domain form filaments in vitro having non-amyloid properties. Amyloid 2021; 28:56-65. [PMID: 33026249 PMCID: PMC7613275 DOI: 10.1080/13506129.2020.1826425] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Accumulation of ubiquitin-positive, tau- and α-synuclein-negative intracellular inclusions of TDP-43 in the central nervous system represents the major hallmark correlated to amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Such inclusions have variably been described as amorphous aggregates or more structured deposits having amyloid properties. Here we have purified full-length TDP-43 (FL TDP-43) and its C-terminal domain (Ct TDP-43) to investigate the morphological, structural and tinctorial features of aggregates formed in vitro by them at pH 7.4 and 37 °C. AFM images indicate that both protein variants show a tendency to form filaments. Moreover, we show that both FL TDP-43 and Ct TDP-43 filaments possess a largely disordered secondary structure, as ascertained by far-UV circular dichroism and Fourier transform infra-red spectroscopy, do not bind Congo red and induce a very weak increase of thioflavin T fluorescence, indicating the absence of a clear amyloid-like signature.
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Affiliation(s)
- Claudia Capitini
- Section of Biochemistry, Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy.,European Laboratory for Non-linear Spectroscopy, Sesto Fiorentino, Italy
| | - Giulia Fani
- Section of Biochemistry, Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
| | - Mirella Vivoli Vega
- Section of Biochemistry, Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
| | - Amanda Penco
- Department of Physics, University of Genoa, Genoa, Italy
| | - Claudio Canale
- Department of Physics, University of Genoa, Genoa, Italy
| | - Lisa D Cabrita
- Institute of Structural and Molecular Biology, UCL and Birkbeck College London, London, UK
| | - Martino Calamai
- European Laboratory for Non-linear Spectroscopy, Sesto Fiorentino, Italy.,National Institute of Optics, National Research Council, Sesto Fiorentino, Italy
| | - John Christodoulou
- Institute of Structural and Molecular Biology, UCL and Birkbeck College London, London, UK
| | | | - Fabrizio Chiti
- Section of Biochemistry, Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
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