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Gomez-Cardona E, Eskandari-Sedighi G, Fahlman R, Westaway D, Julien O. Application of N-Terminal Labeling Methods Provide Novel Insights into Endoproteolysis of the Prion Protein in Vivo. ACS Chem Neurosci 2024; 15:134-146. [PMID: 38095594 PMCID: PMC10768724 DOI: 10.1021/acschemneuro.3c00533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 01/04/2024] Open
Abstract
Alternative α- and β-cleavage events in the cellular prion protein (PrPC) central region generate fragments with distinct biochemical features that affect prion disease pathogenesis, but the assignment of precise cleavage positions has proven challenging. Exploiting mouse transgenic models expressing wild-type (WT) PrPC and an octarepeat region mutant allele (S3) with increased β-fragmentation, cleavage sites were defined using LC-MS/MS in conjunction with N-terminal enzymatic labeling and chemical in-gel acetylation. Our studies profile the net proteolytic repertoire of the adult brain, as deduced from defining hundreds of proteolytic events in other proteins, and position individual cleavage events in PrPC α- and β-target areas imputed from earlier, lower resolution methods; these latter analyses established site heterogeneity, with six cleavage sites positioned in the β-cleavage region of WT PrPC and nine positions for S3 PrPC. Regarding α-cleavage, aside from reported N-termini at His110 and Val111, we identified a total of five shorter fragments in the brain of both mice lines. We infer that aminopeptidase activity in the brain could contribute to the ragged N-termini observed around PrPC's α- and β-cleavage sites, with this work providing a point of departure for further in vivo studies of brain proteases.
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Affiliation(s)
- Erik Gomez-Cardona
- Department
of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Ghazaleh Eskandari-Sedighi
- Department
of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
- Center
for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2M8, Canada
| | - Richard Fahlman
- Department
of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - David Westaway
- Department
of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
- Center
for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2M8, Canada
- Department
of Medicine, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Olivier Julien
- Department
of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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Adulla A, Patel U, Ashok A, Katiyar P, Kaulakis M, Kritikos AE, Pillai S, Lee H, Lindner E, Rhee DJ, Singh N. α-Synuclein modulates fibronectin expression in the trabecular meshwork independent of TGFβ2. Exp Eye Res 2023; 226:109351. [PMID: 36539052 PMCID: PMC10384565 DOI: 10.1016/j.exer.2022.109351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 12/06/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022]
Abstract
α-Synuclein (α-Syn) is implicated in Parkinson's disease (PD), a neuromotor disorder with prominent visual symptoms. The underlying cause of motor dysfunction has been studied extensively, and is attributed to the death of dopaminergic neurons mediated in part by intracellular aggregation of α-Syn. The cause of visual symptoms, however, is less clear. Neuroretinal degeneration due to the presence of aggregated α-Syn has been reported, but the evidence is controversial. Other symptoms including those arising from primary open angle glaucoma (POAG) are believed to be the side-effects of medications prescribed for PD. Here, we explored the alternative hypothesis that dysfunction of α-Syn in the anterior eye alters the interaction between the actin cytoskeleton of trabecular meshwork (TM) cells with the extracellular matrix (ECM), impairing their ability to respond to physiological changes in intraocular pressure (IOP). A similar dysfunction in neurons is responsible for impaired neuritogenesis, a characteristic feature of PD. Using cadaveric human and bovine TM tissue and primary human TM cells as models, we report two main observations: 1) α-Syn is expressed in human and bovine TM cells, and significant amounts of monomeric and oligomeric α-Syn are present in the AH, and 2) primary human TM cells and human and bovine TM tissue endocytose extracellular recombinant monomeric and oligomeric α-Syn via the prion protein (PrPC), and upregulate fibronectin (FN) and α-smooth muscle actin (α-SMA), fibrogenic proteins implicated in POAG. Transforming growth factor β2 (TGFβ2), a fibrogenic cytokine implicated in ∼50% cases of POAG, is also increased, and so is RhoA-associated coiled-coil-containing protein kinase 1 (ROCK-1). However, silencing of α-Syn in primary human TM cells reduces FN, α-SMA, and ROCK-1 in the absence or presence of over-expressed active TGFβ2, suggesting modulation of FN and ROCK-1 independent of, or upstream of TGFβ2. These observations suggest that extracellular α-Syn modulates ECM proteins in the TM independently or via PrPC by activating the RhoA-ROCK pathway. These observations reveal a novel function of α-Syn in the anterior eye, and offer new therapeutic options.
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Affiliation(s)
- Anika Adulla
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Urvi Patel
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ajay Ashok
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Priya Katiyar
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Mare Kaulakis
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Alexander E Kritikos
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Sachin Pillai
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - HyunPin Lee
- Departments of Ophthalmology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ewald Lindner
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036, Graz, Austria
| | - Douglas J Rhee
- Departments of Ophthalmology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Neena Singh
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA.
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