The Properties of α-Synuclein Secondary Nuclei are Dominated by the Solution Conditions Rather than the Seed Fibril Strain

10.26434/chemrxiv.9757778 ◽

2019 ◽

Author(s):

Alessia Peduzzo ◽

Sara Linse ◽

Alexander Buell

Keyword(s):

Amyloid Fibrils ◽

Lewy Bodies ◽

The Other ◽

Secondary Nucleation ◽

Presynaptic Terminals ◽

Unfolded Protein ◽

Primary Nucleation ◽

Other Hand ◽

Natively Unfolded Protein ◽

Natively Unfolded

α-synuclein (α-syn) is a natively unfolded protein predominantly localized in the presynaptic terminals of neurons. It has been shown that α-syn fibrils are the major component of abnormal neuronal aggregates known as Lewy bodies, the characteristic hallmark of Parkinson’s disease. Amyloid fibrils arise through primary nucleation from monomers, which in the case of α-syn is accelerated by suitable surfaces with an affinity for the protein, followed by the elongation of the nuclei by monomer addition. Secondary nucleation, on the other hand, corresponds to the formation of new fibrils when it is facilitated by pre-existing fibrils. While<br>α-synuclein (α-syn) is a natively unfolded protein predominantly localized in the presynaptic terminals of neurons. It has been shown that α-syn fibrils are the major component of abnormal neuronal aggregates known as Lewy bodies, the characteristic hallmark of Parkinson’s disease. Amyloid fibrils arise through primary nucleation from monomers, which in the case of α-syn is accelerated by suitable surfaces with an affinity for the protein, followed by the elongation of the nuclei by monomer addition. Secondary nucleation, on the other hand, corresponds to the formation of new fibrils when it is facilitated by pre-existing fibrils. While it is well-established that the newly added monomer in the process of fibril elongation adopts the conformation of the monomers in the seed, often called templating, it is still unclear under which conditions fibrils formed through secondary nucleation of monomers on the surface of fibrils copy the structure of the parent. Here we show by biochemical and microscopical methods that the secondary nucleation of α-syn, enabled at mildly acidic pH, leads to fibrils that structurally resemble more closely those formed de novo under the same conditions, rather than the seeds if these are formed under different solution condition. This result has important implications for the mechanistic understanding of the secondary nucleation of amyloid fibrils and its role in the propagation of aggregate pathology in protein misfolding diseases.<br>

Download Full-text

The interplay between lipids and dopamine on α-synuclein oligomerization and membrane binding

Bioscience Reports ◽

10.1042/bsr20130092 ◽

2013 ◽

Vol 33 (5) ◽

Cited By ~ 16

Author(s):

Chi L. L. Pham ◽

Roberto Cappai

Keyword(s):

Lipid Membranes ◽

Amyloid Fibrils ◽

Lipid Membrane ◽

Hydrophobic Interactions ◽

Membrane Integrity ◽

Lipid Vesicles ◽

Helical Conformation ◽

Unfolded Protein ◽

Natively Unfolded Protein ◽

Natively Unfolded

The deposition of α-syn (α-synuclein) as amyloid fibrils and the selective loss of DA (dopamine) containing neurons in the substantia nigra are two key features of PD (Parkinson's disease). α-syn is a natively unfolded protein and adopts an α-helical conformation upon binding to lipid membrane. Oligomeric species of α-syn have been proposed to be the pathogenic species associated with PD because they can bind lipid membranes and disrupt membrane integrity. DA is readily oxidized to generate reactive intermediates and ROS (reactive oxygen species) and in the presence of DA, α-syn form of SDS-resistant soluble oligomers. It is postulated that the formation of the α-syn:DA oligomers involves the cross-linking of DA-melanin with α-syn, via covalent linkage, hydrogen and hydrophobic interactions. We investigate the effect of lipids on DA-induced α-syn oligomerization and studied the ability of α-syn:DA oligomers to interact with lipids vesicles. Our results show that the interaction of α-syn with lipids inhibits the formation of DA-induced α-syn oligomers. Moreover, the α-syn:DA oligomer cannot interact with lipid vesicles or cause membrane permeability. Thus, the formation of α-syn:DA oligomers may alter the actions of α-syn which require membrane association, leading to disruption of its normal cellular function.

Download Full-text

Human full-length Securin is a natively unfolded protein

Protein Science ◽

10.1110/ps.051368005 ◽

2009 ◽

Vol 14 (6) ◽

pp. 1410-1418 ◽

Cited By ~ 39

Author(s):

Nuria Sánchez-Puig ◽

Dmitry B. Veprintsev ◽

Alan R. Fersht

Keyword(s):

Full Length ◽

Unfolded Protein ◽

Natively Unfolded Protein ◽

Natively Unfolded

Download Full-text

Degradation of a Short-lived Glycoprotein from the Lumen of the Endoplasmic Reticulum: The Role of N-linked Glycans and the Unfolded Protein Response

Molecular Biology of the Cell ◽

10.1091/mbc.10.12.4059 ◽

1999 ◽

Vol 10 (12) ◽

pp. 4059-4073 ◽

Cited By ~ 58

Author(s):

Maddalena de Virgilio ◽

Claudia Kitzmüller ◽

Eva Schwaiger ◽

Michael Klein ◽

Gert Kreibich ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Unfolded Protein Response ◽

The Other ◽

Slow Phase ◽

Type I ◽

Unfolded Protein ◽

Other Hand ◽

The Unfolded Protein Response ◽

Protein Response

We are studying endoplasmic reticulum–associated degradation (ERAD) with the use of a truncated variant of the type I ER transmembrane glycoprotein ribophorin I (RI). The mutant protein, RI332, containing only the N-terminal 332 amino acids of the luminal domain of RI, has been shown to interact with calnexin and to be a substrate for the ubiquitin-proteasome pathway. When RI332 was expressed in HeLa cells, it was degraded with biphasic kinetics; an initial, slow phase of ∼45 min was followed by a second phase of threefold accelerated degradation. On the other hand, the kinetics of degradation of a form of RI332 in which the single used N-glycosylation consensus site had been removed (RI332-Thr) was monophasic and rapid, implying a role of the N-linked glycan in the first proteolytic phase. RI332degradation was enhanced when the binding of glycoproteins to calnexin was prevented. Moreover, the truncated glycoprotein interacted with calnexin preferentially during the first proteolytic phase, which strongly suggests that binding of RI332 to the lectin-like protein may result in the slow, initial phase of degradation. Additionally, mannose trimming appears to be required for efficient proteolysis of RI332. After treatment of cells with the inhibitor of N-glycosylation, tunicamycin, destruction of the truncated RI variants was severely inhibited; likewise, in cells preincubated with the calcium ionophore A23187, both RI332 and RI332-Thr were stabilized, despite the presence or absence of the N-linked glycan. On the other hand, both drugs are known to trigger the unfolded protein response (UPR), resulting in the induction of BiP and other ER-resident proteins. Indeed, only in drug-treated cells could an interaction between BiP and RI332 and RI332-Thr be detected. Induction of BiP was also evident after overexpression of murine Ire1, an ER transmembrane kinase known to play a central role in the UPR pathway; at the same time, stabilization of RI332 was observed. Together, these results suggest that binding of the substrate proteins to UPR-induced chaperones affects their half lives.

Download Full-text