Biology subjects

Broggini, L.

Publications and source records attributed to Broggini, L..

4 recordsLinked to original sources

bioRxiv2025

Exploring light chain cardiotoxicity in AL amyloidosis: Impact on hiPSC-derived Cardiomyocyte Activity

AimsImmunoglobulin light chain (AL) amyloidosis is a protein misfolding disease characterized by the systemic deposition of amyloid fibrils derived from monoclonal light chains (LCs). Cardiac involvement is the major determinant of prognosis and mortality, and beyond fibril accumulation, soluble cardiotoxic LCs play a critical role in disease progression. While current in vivo models like C. elegans and murine systems have demonstrated LC toxicity, they lack human relevance or fail to capture soluble LC-induced cardiotoxicity. This study aimed to characterize the electrophysiological effects of cardiotoxic LCs on a human-relevant model using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Methods and ResultsTwo amyloidogenic cardiotoxic LCs (H3 and H6) from AL patients and one non-cardiotoxic LC (M10) from a multiple myeloma patient were biophysically characterized and tested in hiPSC-CMs at clinically relevant concentrations. Electrophysiological recordings revealed that H3 and H6 significantly reduced spontaneous action potential (AP) firing frequency and maximal upstroke velocity (dV/dt) in hiPSC-CMs, indicating impaired excitability. H6 also shortened AP duration. H3 exposure led to a [~]40% reduction in peak sodium current density and altered inactivation kinetics of the L-type calcium current, without affecting major pacemaker or repolarizing potassium (IKr or IKs) currents. In contrast, M10 had no effect on any measured parameter, validating the models ability to discriminate toxic from non-toxic LCs. ConclusionThis study demonstrates that hiPSC-CMs provide a clinically relevant human model to investigate LC-induced cardiotoxicity. Cardiotoxic LCs exert distinct but converging electrophysiological impairments, including disruption of sodium and L-type calcium currents, contributing to reduced excitability and altered AP morphology. These findings provide mechanistic insights into AL amyloidosis-related cardiac dysfunction and establish a foundation for future therapeutic screening targeting soluble LC toxicity in a human context.

pathology↗

bioRxiv2025

Tau catalyzes amyloid-β aggregation in a fold-dependent manner

Interactions between amyloidogenic proteins are emerging as critical drivers of neurodegenerative diseases, yet the molecular mechanisms remain poorly understood. In Alzheimers disease (AD) and chronic traumatic encephalopathy (CTE), co-deposition of tau and amyloid-{beta} (A{beta}) leads to accelerated disease progression. Here, we investigated the direct interaction between A{beta} and tau, combining in vitro reconstruction, computational modeling, and in vivo models. We show that tau aggregates with AD paired helical filament (PHF) and CTE folds catalyze the primary nucleation of A{beta}42 in a fold-specific manner, through an enzyme-like kinetic with recognition mechanisms. CTE fibrils exhibit the highest catalytic activity, also constraining A{beta}42 polymorphism. PHF and CTE tau fibrils increase A{beta}42 toxicity in SH-SY5Y neuroblastoma cells and transgenic Caenorhabditis elegans. Catalytic heterotypic interactions between amyloidogenic proteins offer new insights into the pathological mechanisms of multiple proteinopathies. The mechanisms described here may guide the structure-based design of new therapeutic agents targeting specific amyloidogenic interactions.

biochemistry↗

bioRxiv2023

Nanobodies counteract the toxicity of an amyloidogenic light chain by stabilizing a partially open dimeric conformation

Light chain amyloidosis (AL) is a systemic disease where fibrillar deposition of misfolded immunoglobulin light chains (LCs) severely affects organ function and results in poor prognosis for patients, especially when heart involvement is severe. Particularly relevant in this context is the cardiotoxicity exerted by still uncharacterized soluble LC species. Here, with the final goal of identifying alternative therapeutic strategies to tackle AL amyloidosis, we produced five llama-derived nanobodies (Nbs) specific against H3, a well-characterized amyloidogenic and cardiotoxic LC from an AL patient with severe cardiac involvement. We found that Nbs are specific and potent agents capable of abolishing H3 soluble toxicity in C. elegans in vivo model. Structural characterization of H3-Nb complexes revealed that the protective effect of Nbs is related to their ability to bind to the H3 VL domain and stabilise an unexpected partially open LC dimer in which the two VL domains no longer interact with each other. Thus, while identifying potent inhibitors of LC soluble toxicity, we also describe the first non-native structure of an amyloidogenic LC that may represent a crucial step in toxicity and aggregation mechanisms.

biophysics↗

bioRxiv2022

Multi-eGO: an in-silico lens to look into protein aggregation kinetics at atomic resolution

Protein aggregation into amyloid fibrils is the archetype of aberrant biomolecular self-assembly processes, with more than 50 diseases associated that are mostly uncurable. Understanding aggregation mechanisms is thus of fundamental importance and goes in parallel with the characterization of the structures of the transient oligomers formed in the process. Oligomers have been proven elusive to high-resolution structural techniques, while the large sizes and long-time scales typical of aggregation processes have limited, so far, the use of computational methods. To surmount these limitations, we introduce here multi-eGO, an atomistic, hybrid structure-based model, which leveraging on the knowledge of monomers conformational dynamics and of fibril structures, can efficiently capture the essential structural and kinetics aspects of protein aggregation. Multi-eGO molecular dynamics simulations can describe the aggregation kinetics of thousands of monomers. The concentration dependence of the simulated kinetics, as well as the structural features of the resulting fibrils, are in qualitative agreement with in vitro experiments on an amyloidogenic peptide of Transthyretin, a protein responsible for one of the most common cardiac amyloidosis. Multi-eGO simulations allow to observe in time and at atomic resolution the formation of primary nuclei in a sea of transient lower order oligomers, to follow their growth and the subsequent secondary nucleation events, till the maturation of multiple fibrils. Multi-eGO, combined with the many experimental techniques deployed to study protein aggregation, can provide the structural basis needed to advance the design of molecules targeting amyloidogenic diseases. Significance StatementAlzheimers and Parkinsons diseases are uncurable pathologies associated to the aberrant aggregation of specific proteins into amyloid fibrils. Understanding the mechanism leading to protein aggregation, by characterizing the structures of the oligomeric species populated in the process, would have a tremendous impact on the design of therapeutic molecules. We propose that a structure-based approach to molecular dynamics simulations can allow following at high resolution the aggregation kinetics of thousands of monomers. Having shown that simulations can describe the aggregation of a Transthyretin amyloidogenic peptide, we demonstrate how their efficiency allows acquiring a wealth of structural information. We foresee that integrating the latter with the many techniques developed to study protein aggregation will support the design of molecules to modulate amyloidogenesis.

biochemistry↗