title: Molecular insights into cell toxicity of a novel familial amyloidogenic variant of β2-microglobulin.
abstract: The first genetic variant of β2 -microglobulin (b2M) associated with a familial form of systemic amyloidosis has been recently described. The mutated protein, carrying a substitution of Asp at position 76 with an Asn (D76N b2M), exhibits a strongly enhanced amyloidogenic tendency to aggregate with respect to the wild-type protein. In this study, we characterized the D76N b2M aggregation path and performed an unprecedented analysis of the biochemical mechanisms underlying aggregate cytotoxicity. We showed that, contrarily to what expected from other amyloid studies, early aggregates of the mutant are not the most toxic species, despite their higher surface hydrophobicity. By modulating ganglioside GM1 content in cell membrane or synthetic lipid bilayers, we confirmed the pivotal role of this lipid as aggregate recruiter favouring their cytotoxicity. We finally observed that the aggregates bind to the cell membrane inducing an alteration of its elasticity (with possible functional unbalance and cytotoxicity) in GM1-enriched domains only, thus establishing a link between aggregate-membrane contact and cell damage.
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche 'Mario Serio', Università degli Studi di Firenze, Firenze, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Leri
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche 'Mario Serio', Università degli Studi di Firenze, Firenze, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bemporad
authors.affiliation: Dipartimento di Nanofisica, Istituto Italiano di Tecnologia, Genova, Italy.
authors.forename: Reinier
authors.initials: R
authors.lastname: Oropesa-Nuñez
authors.affiliation: Dipartimento di Nanofisica, Istituto Italiano di Tecnologia, Genova, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Canale
authors.affiliation: European Laboratory for Non-linear Spectroscopy (LENS), Università degli Studi di Firenze, Sesto Fiorentino, Italy.|National Institute of Optics, Consiglio Nazionale delle Ricerche (CNR), Firenze, Italy.
authors.forename: Martino
authors.initials: M
authors.lastname: Calamai
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Firenze, Firenze, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Nosi
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche 'Mario Serio', Università degli Studi di Firenze, Firenze, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Ramazzotti
authors.affiliation: Dipartimento di Medicina Molecolare, Istituto di Biochimica, Università degli Studi di Pavia, Pavia, Italy.
authors.forename: Sofia
authors.initials: S
authors.lastname: Giorgetti
authors.affiliation: European Laboratory for Non-linear Spectroscopy (LENS), Università degli Studi di Firenze, Sesto Fiorentino, Italy.
authors.forename: Francesco S
authors.initials: FS
authors.lastname: Pavone
authors.affiliation: Dipartimento di Medicina Molecolare, Istituto di Biochimica, Università degli Studi di Pavia, Pavia, Italy.|Wolfson Drug Discovery Unit, Centre for Amyloidosis and Acute Phase Proteins, Division of Medicine, Royal Free Campus University College London, London, UK.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bellotti
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche 'Mario Serio', Università degli Studi di Firenze, Firenze, Italy.|Centro Interuniversitario per lo Studio delle Malattie Neurodegenerative (CIMN), Firenze, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Stefani
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche 'Mario Serio', Università degli Studi di Firenze, Firenze, Italy.|Centro Interuniversitario per lo Studio delle Malattie Neurodegenerative (CIMN), Firenze, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Bucciantini
mesh_terms: D000682:Amyloid / Q000633:toxicity*; D055592:Biophysical Phenomena / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004058:Diffusion; D005677:G(M1) Ganglioside; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism; D018625:Microscopy, Atomic Force; D050505:Mutant Proteins / Q000633:toxicity*; D066329:Protein Aggregates / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D001613:beta 2-Microglobulin / Q000633:toxicity*
chemical_list: D000682:Amyloid; D008051:Lipid Bilayers; D050505:Mutant Proteins; D066329:Protein Aggregates; D017382:Reactive Oxygen Species; D001613:beta 2-Microglobulin; D005677:G(M1) Ganglioside; D002118:Calcium
keywords: GM1 ganglioside; amyloid cytotoxicity; membrane bilayers; protein misfolding; systemic amyloidosis