Insights into the mechanism of cystatin C oligomer and amyloid formation and its interaction with β-amyloid

Perlenfein, Tyler J.; Mehlhoff, Jacob D.; Murphy, Regina M.

doi:10.1074/jbc.m117.786558

“…It is interesting to note that these stabilized HCC oligomers, which do not readily form fibrillar species, maintain a significant degree of native-like structure. Such maintenance of native-like structure has also been reported for WT HCC oligomeric species formed under non-denaturing conditions [45]. These reported oligomers retain native secondary structure and both papain and legumain enzymatic inhibitory function and appear to be non-domain-swapped species, but unlike our stabilized oligomers, the average size of those species is that of a trimer [45].…”

Section: Discussionsupporting

confidence: 80%

Structural Characterization of Covalently Stabilized Human Cystatin C Oligomers

Chrabąszczewska

¹

,

Sieradzan

²

,

Rodziewicz‐Motowidło

³

et al. 2020

IJMS

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Human cystatin C (HCC), a cysteine-protease inhibitor, exists as a folded monomer under physiological conditions but has the ability to self-assemble via domain swapping into multimeric states, including oligomers with a doughnut-like structure. The structure of the monomeric HCC has been solved by X-ray crystallography, and a covalently linked version of HCC (stab-1 HCC) is able to form stable oligomeric species containing 10–12 monomeric subunits. We have performed molecular modeling, and in conjunction with experimental parameters obtained from atomic force microscopy (AFM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) measurements, we observe that the structures are essentially flat, with a height of about 2 nm, and the distance between the outer edge of the ring and the edge of the central cavity is ~5.1 nm. These dimensions correspond to the height and diameter of one stab-1 HCC subunit and we present a dodecamer model for stabilized cystatin C oligomers using molecular dynamics simulations and experimentally measured parameters. Given that oligomeric species in protein aggregation reactions are often transient and very highly heterogeneous, the structural information presented here on these isolated stab-1 HCC oligomers may be useful to further explore the physiological relevance of different structural species of cystatin C in relation to protein misfolding disease.

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“…Such maintenance of native-like structure has also been reported for WT HCC oligomeric species formed under non-denaturing conditions [45]. These reported oligomers retain native secondary structure and both papain and legumain enzymatic inhibitory function and appear to be non-domain swapped species, but unlike our stabilized oligomers, the average size of those species is that of a trimer [45]. Interestingly, stabilized oligomers from another member of the cystatin superfamily, stefin B (or cystatin B), have been observed and characterised as domain-swapped tetrameric oligomers which are stabilized by a "hand-shake mechanism" [46].…”

Section: Discussionsupporting

confidence: 65%

“…As such, Pro74 is in the cis form (opposed to the trans form normally adopted in the monomer) and this causes domain-swapped dimers to become intertwined. Like the stab-1 HCC oligomers, the reported trimeric non-domain swapped oligomers as well as the stefin B oligomers do not readily proceed to fibril formation of cystatin C [16,41,45,46].…”

Section: Discussionmentioning

confidence: 99%

Structural characterization of covalently stabilized human cystatin C oligomers

Chrabąszczewska

¹

,

Sieradzan

²

,

Rodziewicz‐Motowidło

³

et al. 2019

Preprint

0

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Human cystatin C (HCC), a cysteine-protease inhibitor, exists as a folded monomer under physiological conditions but has the ability to self-assemble via domain swapping into multimeric states, including oligomers with a characteristic doughnut-like structure. The structure of the monomeric HCC has been solved by X-ray crystallography, and a covalently linked version of HCC (stab-1 HCC) is able to form stable oligomeric species containing 10-12 monomeric subunits. We have performed molecular modeling, and in conjunction with experimental parameters obtained from AFM, TEM and SAXS measurements, we observe that the structures are essentially flat, with a height of about 2 nm, and the distance between the outer edge of the ring and the edge of the central cavity is circa 5.1 nm. These dimensions correspond to the height and diameter of one stab-1 HCC subunit and we use these measurements, along with molecular dynamics simulations, to propose a model for a stab-1 HCC dodecamer structure that appears to be the most likely structure. Given that oligomeric species in protein aggregation reactions are often transient and very highly heterogeneous, the structural information presented here on these isolated stab-1 HCC oligomers may provide useful information to further explore the physiological relevance of different structural species of cystatin C in relationship to protein misfolding disease. Statement of SignificanceHere we present a dodecamer model for stabilized cystatin C oligomers using molecular dynamics simulations and experimentally measured parameters. Cystatin C is present in amyloid deposits in patients with sporadic cerebral amyloid angiopathy. Given the diversity of peptides and proteins which can form amyloid fibrils, information about the structure of different species present along the aggregation pathway is vital. As oligomeric species formed during fibril formation are likely to be responsible for cellular toxicity through interactions and disruption of cellular membranes, defining structural attributes of oligomeric species from a diverse range of proteins and peptides is important for gaining insights into their physiological relevance in relationship to protein misfolding diseases.

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“…If the domain-swapped dimer binds A␤ with the same affinity as monomeric CysC but does not inhibit CatB, CysC and CatB would no longer undermine the neuroprotective effects of one another. Additionally, we have observed oligomeric aggregates of CysC in vitro, which are not domain-swapped (18,20). Nonswapped oligomers remain fully active against CatB, but they inhibit A␤ aggregation much more potently than CysC monomers.…”

Section: Modeling Cysc/catb Effect On A␤mentioning

confidence: 79%

A mechanistic model to predict effects of cathepsin B and cystatin C on β-amyloid aggregation and degradation

Perlenfein

¹

,

Murphy

²

2017

Journal of Biological Chemistry

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β-Amyloid (Aβ) aggregation is thought to initiate a cascade of neurodegenerative events in Alzheimer's disease (AD). Much effort is underway to develop strategies to reduce Aβ concentration or inhibit aggregation. Cathepsin B (CatB) proteolytically degrades Aβ into non-aggregating fragments but is potently inhibited by cystatin C (CysC). It has been suggested that decreasing CysC would facilitate Aβ clearance by relieving CatB inhibition. However, CysC binds Aβ and inhibits Aβ aggregation, suggesting that an intervention that increases CysC would prevent Aβ aggregation. Both approaches have been tested in animal models, yielding contradictory results, possibly because of the opposing influences of CysC on Aβ degradation aggregation. Here, we sought to develop a model that quantitatively predicts the effects of CysC and CatB on Aβ aggregation. Aβ aggregation kinetics in the absence of CatB or CysC was measured. The rate constant for Aβ degradation by CatB and the equilibrium constant for binding of CysC to Aβ were determined. We derived a mathematical model that combines material balances and kinetic rate equations. The model accurately predicted Aβ aggregation kinetics at various CatB and CysC concentrations. We derived approximate expressions for the half-times of degradation and aggregation and show that their ratio can be used to estimate, at any given Aβ, CatB, or CysC concentration, whether Aβ aggregation or degradation will result. Our results may be useful for designing experiments and interpreting results from investigations of manipulation of CysC concentration as an AD therapy.

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Insights into the mechanism of cystatin C oligomer and amyloid formation and its interaction with β-amyloid

Cited by 28 publications

References 76 publications

Structural Characterization of Covalently Stabilized Human Cystatin C Oligomers

Structural Characterization of Covalently Stabilized Human Cystatin C Oligomers

Structural characterization of covalently stabilized human cystatin C oligomers

A mechanistic model to predict effects of cathepsin B and cystatin C on β-amyloid aggregation and degradation

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