Interaction with prefibrillar species and amyloid-like fibrils changes the stiffness of lipid bilayers.

Evaluating the toxicity of self-assembled protein states is a key step towards developing effective strategies against amyloidogenic pathologies such as Alzheimer's and Parkinson's diseases. Such analysis is directly connected to quantitatively probing the stability of the cellular membrane upon interaction with different protein states. Using a combination of spectroscopic techniques, morphological observations, and spectral analysis of membrane fluctuations, we identify different destabilisation routes for giant unilamellar vesicles interacting with native-like states, prefibrillar species and amyloid-like fibrils of α-lactalbumin. These effects range from substantially lowering the bending rigidity of the membranes to irreversible structural changes and complete disruption of the lipid bilayers. Our findings clearly indicate how the wide heterogeneity in structures occurring during protein aggregation can result in different destabilisation pathways, acting on different length scales and not limited to enhanced membrane permeability.

[1]  J. Brender,et al.  Amyloid fiber formation and membrane disruption are separate processes localized in two distinct regions of IAPP, the type-2-diabetes-related peptide. , 2008, Journal of the American Chemical Society.

[2]  F. Chiti,et al.  Structural and Dynamics Characteristics of Acylphosphatase from Sulfolobus solfataricus in the Monomeric State and in the Initial Native-like Aggregates* , 2010, The Journal of Biological Chemistry.

[3]  M. Kronman,et al.  INTER- AND INTRAMOLECULAR INTERACTIONS OF ALPHA-LACTALBUMIN. II. AGGREGATION REACTIONS AT ACID PH. , 1964, Biochemistry.

[4]  P. Hough,et al.  High-resolution Atomic Force Microscopy of Soluble Aβ42 Oligomers , 2006 .

[5]  S. Wijmenga,et al.  Probing Solvent Accessibility of Transthyretin Amyloid by Solution NMR Spectroscopy* , 2004, Journal of Biological Chemistry.

[6]  Pietro Cicuta,et al.  Flickering analysis of erythrocyte mechanical properties: dependence on oxygenation level, cell shape, and hydration level. , 2009, Biophysical journal.

[7]  P. Sharma,et al.  Rigid proteins and softening of biological membranes—with application to HIV-induced cell membrane softening , 2016, Scientific Reports.

[8]  M. Bucciantini,et al.  Amyloid Aggregation: Role of Biological Membranes and the Aggregate-Membrane System. , 2014, The journal of physical chemistry letters.

[9]  B. Vestergaard,et al.  Protein/lipid coaggregates are formed during α-synuclein-induced disruption of lipid bilayers. , 2014, Biomacromolecules.

[10]  A. Fink,et al.  Characterization of Oligomeric Intermediates in α-Synuclein Fibrillation: FRET Studies of Y125W/Y133F/Y136F α-Synuclein , 2005 .

[11]  P. Kinnunen,et al.  Membrane effects of lysozyme amyloid fibrils. , 2012, Chemistry and physics of lipids.

[12]  W. Yau,et al.  Fibrillation of β amyloid peptides in the presence of phospholipid bilayers and the consequent membrane disruption. , 2015, Biochimica et biophysica acta.

[13]  Fabrizio Chiti,et al.  A causative link between the structure of aberrant protein oligomers and their toxicity. , 2010, Nature chemical biology.

[14]  I. Bertini,et al.  Fully Metallated S134N Cu,Zn-Superoxide Dismutase Displays Abnormal Mobility and Intermolecular Contacts in Solution* , 2005, Journal of Biological Chemistry.

[15]  D. Tieleman,et al.  Alamethicin in lipid bilayers: combined use of X-ray scattering and MD simulations. , 2009, Biochimica et biophysica acta.

[16]  M. Rinaudo,et al.  Influence of molecular weight and pH on adsorption of chitosan at the surface of large and giant vesicles. , 2008, Biomacromolecules.

[17]  F. Chiti,et al.  Protein misfolded oligomers: experimental approaches, mechanism of formation, and structure-toxicity relationships. , 2012, Chemistry & biology.

[18]  Patrick Walsh,et al.  Differences between amyloid-β aggregation in solution and on the membrane: insights into elucidation of the mechanistic details of Alzheimer's disease. , 2014, Chemical Society reviews.

[19]  V. Uversky,et al.  Conformational Prerequisites for α-Lactalbumin Fibrillation† , 2002 .

[20]  Nicolas L. Fawzi,et al.  Atomic resolution dynamics on the surface of amyloid β protofibrils probed by solution NMR , 2011, Nature.

[21]  P. Cicuta,et al.  Direct measurement of DNA-mediated adhesion between lipid bilayers. , 2015, Physical chemistry chemical physics : PCCP.

[22]  Ayyalusamy Ramamoorthy,et al.  Two-step mechanism of membrane disruption by Aβ through membrane fragmentation and pore formation. , 2012, Biophysical journal.

[23]  V. Uversky,et al.  Structural transformations of oligomeric intermediates in the fibrillation of the immunoglobulin light chain LEN. , 2003, Biochemistry.

[24]  A. Chattopadhyay,et al.  Organization and dynamics of tryptophans in the molten globule state of bovine alpha-lactalbumin utilizing wavelength-selective fluorescence approach: comparisons with native and denatured states. , 2010, Biochemical and biophysical research communications.

[25]  C M Dobson,et al.  Formation of insulin amyloid fibrils followed by FTIR simultaneously with CD and electron microscopy , 2000, Protein science : a publication of the Protein Society.

[26]  N. Voelcker,et al.  Annular alpha-synuclein oligomers are potentially toxic agents in alpha-synucleinopathy. Hypothesis , 2009, Neurotoxicity Research.

[27]  D. Otzen,et al.  Interactions between misfolded protein oligomers and membranes: A central topic in neurodegenerative diseases? , 2015, Biochimica et biophysica acta.

[28]  P. Cicuta,et al.  The role of optical projection in the analysis of membrane fluctuations. , 2015, Soft matter.

[29]  Bente Vestergaard,et al.  Unlocked Concanavalin A Forms Amyloid-like Fibrils from Coagulation of Long-lived “Crinkled” Intermediates , 2013, PloS one.

[30]  J. Nagle,et al.  HIV-1 fusion peptide decreases bending energy and promotes curved fusion intermediates. , 2007, Biophysical journal.

[31]  C. Dobson,et al.  Reversal of protein aggregation provides evidence for multiple aggregated States. , 2005, Journal of molecular biology.

[32]  L. Berliner,et al.  α‐Lactalbumin: structure and function , 2000 .

[33]  E. Masliah,et al.  Mechanisms of Hybrid Oligomer Formation in the Pathogenesis of Combined Alzheimer's and Parkinson's Diseases , 2008, PloS one.

[34]  Jacques Prost,et al.  Refined contour analysis of giant unilamellar vesicles , 2004, The European physical journal. E, Soft matter.