Comparative calorimetric study of non-amyloidogenic and amyloidogenic variants of the homotetrameric protein transthyretin

Shnyrov, Valery L.; Villar, Enrique; Zhadan, Galina G.; Sanchez-Ruiz, José M.; Quintas, Alexandre; Saraiva, Maria João; Brito, Rui M. M.

doi:10.1016/s0301-4622(00)00199-x

Cited by 50 publications

(44 citation statements)

References 26 publications

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“…Such an effect is reminiscent of that observed for I84S and I84A TTR variants, for which a large conformational change in the region hosting the mutation was induced by the lowering of the pH (32). Although limited, at least at neutral pH, the above described structural perturbations induced in TTR by amyloidogenic mutations possibly represent early events correlated with a destabilization of the TTR structure, in accordance with several lines of evidence indicating that amyloidogenic TTR variants are more prone to denaturation and amyloid aggregation relative to wild-type TTR (22,(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62).…”

Section: Crystal Structures Of Amyloidogenic Ttr Variants At Neutralsupporting

confidence: 84%

Amyloidogenic Potential of Transthyretin Variants

Cendron

Trovato

Seno

et al. 2009

Journal of Biological Chemistry

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Human transthyretin (TTR) is an amyloidogenic protein whose mild amyloidogenicity is enhanced by many point mutations affecting considerably the amyloid disease phenotype. To ascertain whether the high amyloidogenic potential of TTR variants may be explained on the basis of the conformational change hypothesis, an aim of this work was to determine structural alterations for five amyloidogenic TTR variants crystallized under native and/or destabilizing (moderately acidic pH) conditions. While at acidic pH structural changes may be more significant because of a higher local protein flexibility, only limited alterations, possibly representing early events associated with protein destabilization, are generally induced by mutations. This study was also aimed at establishing to what extent wildtype TTR and its amyloidogenic variants are intrinsically prone to ␤-aggregation. We report the results of a computational analysis predicting that wild-type TTR possesses a very high intrinsic ␤-aggregation propensity which is on average not enhanced by amyloidogenic mutations. However, when located in ␤-strands, most of these mutations are predicted to destabilize the native ␤-structure. The analysis also shows that rat and murine TTR have a lower intrinsic ␤-aggregation propensity and a similar native ␤-structure stability compared with human TTR. This result is consistent with the lack of in vitro amyloidogenicity found for both murine and rat TTR. Collectively, the results of this study support the notion that the high amyloidogenic potential of human pathogenic TTR variants is determined by the destabilization of their native structures, rather than by a higher intrinsic ␤-aggregation propensity.Protein misfolding and aggregation are involved in the pathogenesis of particularly relevant human deposition diseases, known as amyloidoses. In such diseases, normally soluble proteins undergo misfolding and become insoluble, causing the extracellular deposition of fibrillar aggregates (for reviews, see Ref. 1, 2). To date, more than 40 distinct human proteins have been associated with amyloidoses. For some of such proteins, including transthyretin (TTR), 4 lysozyme, gelsolin, ApoAI, and ApoAII, fibrinogen A ␣-chain and cystatin C, the amyloidogenic potential is induced, or is enhanced as in the case of TTR (see below), by specific mutations. The most frequent hereditary amyloidoses are caused by the genetic variants of human TTR (2).TTR is a homotetramer of about 55 kDa involved in the transport of thyroxine in the extracellular fluids and in the cotransport of vitamin A, by forming a macromolecular complex with retinol-binding protein, the specific plasma carrier of retinol (3-5). Its three-dimensional structure is known at high resolution (6, 7). The structure is characterized by a large predominance of ␤-strands, and its four monomers are arranged according to a 222 symmetry, where one of the 2-fold symmetry axes of the molecule coincides with a long channel that transverses the entire tetramer and harbors two symmetrical bind...

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Section: Crystal Structures Of Amyloidogenic Ttr Variants At Neutralsupporting

confidence: 84%

Amyloidogenic Potential of Transthyretin Variants

Cendron

Trovato

Seno

et al. 2009

Journal of Biological Chemistry

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“…More recently, micro-calorimetric work [44] and pressure-induced unfolding experiments followed by NMR [45] confirmed in a more quantitative way this earlier view. In fact, the micro-calorimetric studies showed that, at pH 7.0 and relatively high protein concentrations (6.2 µM tetramer) both amyloidogenic and nonamyloidogenic variants of TTR showed very high transition temperatures (T m ) for thermal unfolding.…”

Section: Stability and Conformational Fluctuations Of Tetrameric Ttrsupporting

confidence: 52%

Amyloid Formation by Transthyretin: From Protein Stability to Protein Aggregation

Brito¹,

Damas²,

Saraiva

2003

CMCIEMA

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Abstract:In recent years the issues of protein stability, folding and aggregation have become central in several pathological conditions and in particular in amyloid diseases. Here, we review the recent developments on the molecular mechanisms of amyloid formation by transthyretin (TTR), in particular, in what concerns to protein conformational stability, protein folding and aggregation.Transthyretin has been implicated in pathologies such as senile systemic amyloidosis (SSA), familial amyloid polyneuropathy (FAP) and familial amyloid cardiomyopathy (FAC) which are characterized by extracellular deposition of insoluble amyloid fibrils. SSA is generally a mild disorder and affects predominantly individuals over 80 years of age. In contrast, FAP is an autossomal dominant lethal disease, characterized by peripheral neuropathy, which may affect individuals from their twenties. While in SSA WT-TTR and its fragments are the major constituents of the amyloid fibrils, in FAP and FAC the amyloid fibrils are mostly constituted by variants of TTR. Today, more than 80 amyloidogenic TTR mutations throughout the TTR sequence are known.Transthyretin is a homotetrameric protein found in the plasma and in the cerebral-spinal fluid, it is synthesized in the liver and in the choroid plexus of the brain, it has a total molecular mass of 55kDa and a high percentage of β-sheet. Current views on amyloid fibril formation by TTR state that, depending on the protein variant or solution conditions, the native tetrameric protein might dissociate to non-native or partially unfolded monomeric (or even dimeric) species with a high tendency for ordered aggregation into soluble oligomers which grow into insoluble oligomers and eventually mature amyloid fibrils. Thus, issues such as dissociation thermodynamics and dissociation kinetics of the native tetrameric TTR and thermodynamic stability and conformational fluctuations of the non-native TTR molecular species are essential in determining the amyloidogenic potential of different TTR variants. In addition, several other cellular and tissue factors must be involved in modulating the penetrance and age of onset of amyloid pathologies by TTR.

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“…Additionally, the observed small differences in conformational stability do not agree with the relative amyloidogenic potential of the TTR variants studied (21). Thus, differences in the conformational stability of tetrameric TTR do not seem to justify the amyloidogenic character of some TTR variants.…”

Section: Discussionmentioning

confidence: 70%

“…Recently, we showed by differential scanning calorimetry (DSC) of WT-, V30M-, L55P-, and T119M-TTR that the tetrameric forms of these variants are highly stable to thermal unfolding (21). Additionally, the observed small differences in conformational stability do not agree with the relative amyloidogenic potential of the TTR variants studied (21).…”

Section: Discussionmentioning

confidence: 98%

Tetramer Dissociation and Monomer Partial Unfolding Precedes Protofibril Formation in Amyloidogenic Transthyretin Variants

Quintas

Vaz

Cardoso

et al. 2001

Journal of Biological Chemistry

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293

262

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Amyloid fibril formation and deposition is a common feature of a wide range of fatal diseases including spongiform encephalopathies, Alzheimer's disease, and familial amyloidotic polyneuropathies (FAP), among many others. In certain forms of FAP, the amyloid fibrils are mostly constituted by variants of transthyretin (TTR), a homotetrameric plasma protein. Recently, we showed that transthyretin in solution may undergo dissociation to a non-native monomer, even under close to physiological conditions of temperature, pH, ionic strength, and protein concentration. We also showed that this non-native monomer is a compact structure, does not behave as a molten globule, and may lead to the formation of partially unfolded monomeric species and high molecular mass soluble aggregates (Quintas, A., Saraiva, M. J. M., and Brito, R. M. M. (1999) J. Biol. Chem. 274, 32943-32949). Here, based on aging experiments of tetrameric TTR and chemically induced protein unfolding experiments of the non-native monomeric forms, we show that tetramer dissociation and partial unfolding of the monomer precedes amyloid fibril formation. We also show that TTR variants with the least thermodynamically stable non-native monomer produce the largest amount of partially unfolded monomeric species and soluble aggregates under conditions that are close to physiological. Additionally, the soluble aggregates formed by the amyloidogenic TTR variants showed morphological and thioflavin-T fluorescence properties characteristic of amyloid. These results allowed us to conclude that amyloid fibril formation by some TTR variants might be triggered by tetramer dissociation to a compact non-native monomer with low conformational stability, which originates partially unfolded monomeric species with a high tendency for ordered aggregation into amyloid fibrils. Thus, partial unfolding and conformational fluctuations of molecular species with marginal thermodynamic stability may play a crucial role on amyloid formation in vivo.

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Comparative calorimetric study of non-amyloidogenic and amyloidogenic variants of the homotetrameric protein transthyretin

Cited by 50 publications

References 26 publications

Amyloidogenic Potential of Transthyretin Variants

Amyloidogenic Potential of Transthyretin Variants

Amyloid Formation by Transthyretin: From Protein Stability to Protein Aggregation

Tetramer Dissociation and Monomer Partial Unfolding Precedes Protofibril Formation in Amyloidogenic Transthyretin Variants

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