Biology subjects

Pedretti, R.

Publications and source records attributed to Pedretti, R..

7 recordsLinked to original sources

bioRxiv2024

ATTRv-V30M Type A amyloid fibrils from the heart and nerves exhibit structural homogeneity.

ATTR amyloidosis is a systemic disease characterized by the deposition of amyloid fibrils made of transthyretin, a protein integral to transporting retinol and thyroid hormones. Transthyretin is primarily produced by the liver and circulates in blood as a tetramer. The retinal epithelium also secretes transthyretin, which is secreted to the vitreous humor of the eye. Because of mutations or aging, transthyretin can dissociate into amyloidogenic monomers triggering amyloid fibril formation. The deposition of transthyretin amyloid fibrils in the myocardium and peripheral nerves causes cardiomyopathies and neuropathies, respectively. Using cryo-electron microscopy, here we determined the structures of amyloid fibrils extracted from cardiac and nerve tissues of an ATTRv-V30M patient. We found that fibrils from both tissues share a consistent structural conformation, similar to the previously described structure of cardiac fibrils from an individual with the same genotype, but different from the fibril structure obtained from the vitreous humor. Our study hints to a uniform fibrillar architecture across different tissues within the same individual, only when the source of transthyretin is the liver. Moreover, this study provides the first description of ATTR fibrils from the nerves of a patient and enhances our understanding of the role of deposition site and protein production site in shaping the fibril structure in ATTRv-V30M amyloidosis.

biophysics↗

bioRxiv2024

Detection of ATTR aggregates in plasma of polyneuropathic ATTR-V30M amyloidosis patients

ATTR amyloidosis is caused by the deposition of transthyretin amyloid fibrils in tissues often leading to organ failure and death. The clinical spectrum of this disease is highly diverse and dependent on many factors including the presence or absence of mutations within the transthyretin protein and/or an individuals ancestry. The phenotypic variability of ATTR amyloidosis makes it difficult to diagnose, delaying treatment and worsening patient prognosis. Our lab has recently developed a peptide probe that detects transthyretin aggregates in plasma of ATTR amyloidosis patients with cardiomyopathy but has not been tested in plasma from polyneuropathic patients. Here we evaluate our probe in a cohort of Portuguese patients carrying the ATTR-V30M mutation and having no cardiac phenotype. We found that we could indeed detect aggregates in their plasma, and there appeared to be no relationship between the presence of aggregates and patient age or gender. Our work has broad implications on the pathobiology of ATTR amyloidosis and contribute to the validation of our probe as a novel detection tool for this disease.

biochemistry↗

bioRxiv2024

Amyloid fibril polymorphism in the heart of an ATTR amyloidosis patient with polyneuropathy attributed to the V122Δ variant

ATTR amyloidosis is a phenotypically heterogeneous disease characterized by the pathological deposition of transthyretin in the form of amyloid fibrils into various organs. ATTR amyloidosis may result from mutations in variant (ATTRv) amyloidosis, or aging in wild-type (ATTRwt) amyloidosis. ATTRwt generally manifests as cardiomyopathy, whereas ATTRv may present as polyneuropathy, cardiomyopathy, or mixed, in combination with many other symptoms deriving from multisystem organ involvement. Over 220 different mutational variants of transthyretin have been identified, many of them being linked to specific disease symptoms. Yet, the role of these mutations in explaining differential disease manifestations remains unclear. Using cryo-electron microscopy, here we structurally characterized fibrils from the heart and the liver of an ATTRv patient carrying the V122{Delta} mutation, which is predominantly associated with polyneuropathy. Our results show that these fibrils are polymorphic, presenting as both single and double filaments. Our study alludes to a structural connection contributing to phenotypic variation in ATTR amyloidosis, as polymorphism in ATTR fibrils may manifest in patients with predominantly polyneuropathic phenotypes. SignificanceATTR amyloidosis is a systemic, clinically diverse disease that results in organ failure due to the accumulation of transthyretin amyloid fibrils. ATTR patients present with varied symptoms, yet the root of this phenotypic heterogeneity remains unclear. Previous studies suggest an association between phenotype and fibril structure polymorphism. Here we describe the cryo-electron microscopy structure of variant transthyretin amyloid fibrils associated with a predominantly polyneuropathy phenotype. We have found polymorphism within these fibrils, a phenomenon we have thus far only observed in polyneuropathic associated transthyretin mutations. Our results signify an association between fibril structure and phenotype in ATTR amyloidosis.

molecular biology↗

bioRxiv2024

Structure-based probe reveals the presence of large transthyretin aggregates in plasma of ATTR amyloidosis patients

ATTR amyloidosis is a relentlessly progressive disease caused by the misfolding and systemic accumulation of amyloidogenic transthyretin into amyloid fibrils. These fibrils cause diverse clinical phenotypes, mainly cardiomyopathy and/or polyneuropathy. Little is known about the aggregation of transthyretin during disease development and whether this has implications for diagnosis and treatment. Using the cryogenic electron microscopy structures of mature ATTR fibrils, we developed a peptide probe for fibril detection. With this probe, we have identified previously unknown aggregated transthyretin species in plasma of patients with ATTR amyloidosis. These species are large, non-native, and distinct from monomeric and tetrameric transthyretin. Observations from our study open many questions about the biology of ATTR amyloidosis and reveals a potential diagnostic and therapeutic target.

molecular biology↗

bioRxiv2024

Cryo-EM confirms a common fibril fold in the heart of four patients with ATTRwt amyloidosis

ATTR amyloidosis results from the conversion of transthyretin into amyloid fibrils that deposit in tissues causing organ failure and death. This conversion is facilitated by mutations in ATTRv amyloidosis, or aging in ATTRwt amyloidosis. ATTRv amyloidosis exhibits extreme phenotypic variability, whereas ATTRwt amyloidosis presentation is consistent and predictable. Previously, we found an unprecedented structural variability in cardiac amyloid fibrils from polyneuropathic ATTRv-I84S patients. In contrast, cardiac fibrils from five genotypically-different patients with cardiomyopathy or mixed phenotypes are structurally homogeneous. To understand fibril structures impact on phenotype, it is necessary to study the fibrils from multiple patients sharing genotype and phenotype. Here we show the cryo-electron microscopy structures of fibrils extracted from four cardiomyopathic ATTRwt amyloidosis patients. Our study confirms that they share identical conformations with minimal structural variability, consistent with their homogenous clinical presentation. Our study contributes to the understanding of ATTR amyloidosis biopathology and calls for further studies. One-Sentence Summary: Wild-type cardiac ATTR fibrils are structurally homogeneous.

biophysics↗

bioRxiv2023

O-GlcNAc modification forces the formation of an α-Synuclein amyloid-strain with notably diminished seeding activity and pathology

The process of amyloid fibril formation remains one of the primary targets for developing diagnostics and treatments for several neurodegenerative diseases (NDDs). Amyloid-forming proteins such -Synuclein and Tau, which are implicated in the pathogenesis of Alzheimers and Parkinsons disease, can form different types of fibril structure, or strains, that exhibit distinct structures, toxic properties, seeding activities, and pathology spreading patterns in the brain. Therefore, understanding the molecular and structural determinants contributing to the formation of different amyloid strains or their distinct features could open new avenues for developing disease-specific diagnostics and therapies. In this work, we report that O-GlcNAc modification of -Synuclein monomers results in the formation of amyloid fibril with distinct core structure, as revealed by Cryo-EM, and diminished seeding activity in seeding-based neuronal and rodent models of Parkinsons disease. Although the mechanisms underpinning the seeding neutralization activity of the O-GlcNAc modified fibrils remain unclear, our in vitro mechanistic studies indicate that heat shock proteins interactions with O-GlcNAc fibril inhibit their seeding activity, suggesting that the O-GlcNAc modification may alter the interactome of the -Synuclein fibrils in ways that lead to reduce seeding activity in vivo. Our results show that post-translational modifications, such as O-GlcNAc modification, of -Synuclein are key determinants of -Synuclein amyloid strains and pathogenicity. These findings have significant implications for how we investigate and target amyloids in the brain and could possibly explain the lack of correlation between amyloid burden and neurodegeneration or cognitive decline in some subtypes of NDDs.

biochemistry↗

bioRxiv2022

Structural polymorphism of amyloid fibrils in cardiac ATTR amyloidosis revealed by cryo-electron microscopy

The deposition of amyloidogenic transthyretin (ATTR) in ATTR amyloidosis leads to an unexplained variety of clinical phenotypes, including cardiomyopathy. In brain amyloid conditions, there is an apparent association between the clinical phenotype and the amyloid fibril structure. Here, we question this phenotype-structure association in cardiac amyloidoses by determining the cryo-electron microscopy structures of fibrils extracted from the hearts of seven ATTR amyloidosis patients. We found that, in contrast to brain fibrils, cardiac ATTR fibrils display a structural polymorphism that is not genotype-specific, can co-exist within the same individual, and is independent of the cardiac phenotype. This polymorphism challenges the current paradigm of "one disease equals one fibril fold" proposed in tauopathies and synucleinopathies, and questions whether a similar structural heterogeneity occurs in other amyloidoses. One-Sentence SummaryUnlike brain amyloid fibrils, cardiac ATTR fibrils are polymorphic independent of genotype and even within the same patient.

molecular biology↗