Abstract
The aggregation of α-synuclein is the hallmark of a collective of neurodegenerative disorders known as synucleinopathies. The tendency to aggregate of this protein, the toxicity of its aggregation intermediates and the ability of the cellular protein quality control system to clear these intermediates seems to be regulated, among other factors, by post-translational modifications (PTMs). Among these modifications, we consider herein proteolysis at both the N- and C-terminal regions of α-synuclein as a factor that could modulate disassembly of toxic amyloids by the human disaggregase, a combination of the chaperones Hsc70, DnaJB1 and Apg2. We find that, in contrast to aggregates of the protein lacking the N-terminus, which can be solubilized as efficiently as those of the WT protein, the deletion of the C-terminal domain, either in a recombinant context or as a consequence of calpain treatment, impaired Hsc70-mediated amyloid disassembly. Progressive removal of the negative charges at the C-terminal region induces lateral association of fibrils and type B* oligomers, precluding chaperone action. We propose that truncation-driven aggregate clumping impairs the mechanical action of chaperones, which includes fast protofilament unzipping coupled to depolymerization. Inhibition of the chaperone-mediated clearance of C-truncated species could explain their exacerbated toxicity and higher propensity to deposit found in vivo.
Highlights
Sonicated fibrils were incubated with the chaperone mixture in the presence of ATP and an ATP regeneration system, and the reaction products were fractionated in a density-gradient centrifugation and analyzed by immunoblotting (Figure 1b)
We show that α-syn fibrils lacking the last 30 C-terminal amino acids are not disassembled by this chaperone machinery, whereas those without the N-terminus are solubilized to the WT fibrils by the chaperone mixture, in agreement with recently published data [21]
This behavior was initially explained considering that the C-terminal end of α-syn contains the binding sites for DnaJB1, whose initial interaction with the aggregate promotes productive Hsc70 recruiting to the fibril surface [19,21]
Summary
The tendency to aggregate of this protein, the toxicity of its aggregation intermediates and the ability of the cellular protein quality control system to clear these intermediates seems to be regulated, among other factors, by post-translational modifications (PTMs) Among these modifications, we consider proteolysis at both the N- and C-terminal regions of α-synuclein as a factor that could modulate disassembly of toxic amyloids by the human disaggregase, a combination of the chaperones Hsc, DnaJB1 and Apg. Introduction with regard to jurisdictional claims in α-Synuclein (α-syn) is a presynaptic protein whose biological function remains unclear, it has been implicated in diverse physiological processes including the regulation of synaptic transmission, calcium regulation or mitochondrial homeostasis [1] It represents approximately 1% of the total cytosolic protein in the central nervous system [2] and can be found either soluble, adopting a largely disordered conformation, or membrane-associated, partially folding into an amphipathic α-helix.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
