The toxicity of an "artificial" amyloid is related to how it interacts with membranes.

IBGC, UMR 5095, CNRS, Université Bordeaux 2 Victor Segalen, Bordeaux, France.
Prion (Impact Factor: 2.13). 10/2010; 4(4):283-91. DOI:10.4161/pri.4.4.13126
Source: PubMed

ABSTRACT Despite intensive research into how amyloid structures can impair cellular viability, the molecular nature of these toxic species and the cellular mechanisms involved are not clearly defined and may differ from one disease to another. We systematically analyzed, in Saccharomyces cerevisiae, genes that increase the toxicity of an amyloid (M8), previously selected in yeast on the sole basis of its cellular toxicity (and consequently qualified as "artificial"). This genomic screening identified the Vps-C HOPS (homotypic vacuole fusion and protein sorting) complex as a key-player in amyloid toxicity. This finding led us to analyze further the phenotype induced by M8 expression. M8-expressing cells displayed an identical phenotype to vps mutants in terms of endocytosis, vacuolar morphology and salt sensitivity. The direct and specific interaction between M8 and lipids reinforces the role of membrane formation in toxicity due to M8. Together these findings suggest a model in which amyloid toxicity results from membrane fission.

0 0
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: REF (Hevb1) and SRPP (Hevb3) are two major components of Hevea brasiliensis latex, well known for their allergenic properties. They are obviously taking part in the biosynthesis of natural rubber, but their exact function is still unclear. They could be involved in defense/stress mechanisms after tapping or directly acting on the isoprenoid biosynthetic pathway. The structure of these two proteins is still not described. In this work, it was discovered that REF has amyloid properties, contrary to SRPP. We investigated their structure by CD, TEM, ATR-FTIR and WAXS and neatly showed the presence of β-sheet organized aggregates for REF, whereas SRPP mainly fold as a helical protein. Both proteins are highly hydrophobic but differ in their interaction with lipid monolayers used to mimic the monomembrane surrounding the rubber particles. Ellipsometry experiments showed that REF seems to penetrate deeply into the monolayer and SRPP only binds to the lipid surface. These results could therefore clarify the role of these two paralogous proteins in latex production, either in the coagulation of natural rubber or in stress-related responses. To our knowledge, this is the first report of an amyloid formed from a plant protein. This suggests also the presence of functional amyloid in the plant kingdom.
    PLoS ONE 01/2012; 7(10):e48065. · 3.73 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Many studies have pointed out the interaction between amyloids and membranes, and their potential involvement in amyloid toxicity. Previously, we generated a yeast toxic amyloid mutant (M8) from the harmless amyloid protein by changing a few residues of the Prion Forming Domain of HET-s (PFD HET-s(218-289)) and clearly demonstrated the complete different behaviors of the non-toxic Wild Type (WT) and toxic amyloid (called M8) in terms of fiber morphology, aggregation kinetics and secondary structure. In this study, we compared the interaction of both proteins (WT and M8) with membrane models, as liposomes or supported bilayers. We first demonstrated that the toxic protein (M8) induces a significant leakage of liposomes formed with negatively charged lipids and promotes the formation of microdomains inside the lipid bilayer (as potential "amyloid raft"), whereas the non-toxic amyloid (WT) only binds to the membrane without further perturbations. The secondary structure of both amyloids interacting with membrane is preserved, but the anti-symmetric PO(2)(-) vibration is strongly shifted in the presence of M8. Secondly, we established that the presence of membrane models catalyzes the amyloidogenesis of both proteins. Cryo-TEM (cryo-transmission electron microscopy) images show the formation of long HET-s fibers attached to liposomes, whereas a large aggregation of the toxic M8 seems to promote a membrane disruption. This study allows us to conclude that the toxicity of the M8 mutant could be due to its high propensity to interact and disrupt lipid membranes.
    Biochimica et Biophysica Acta 04/2012; 1818(9):2325-34. · 4.66 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The toxicity of amyloids is a subject under intense scrutiny. Many studies link this toxicity to the existence of various intermediate structures prior to the fiber formation and/or their specific interaction with membranes. Membranes can also be a catalyst of amyloidogenesis and the composition or the charge of membrane lipids may be of particular importance. Despite intensive research in the field, such intermediates are not yet fully characterized probably because of the lack of adapted methods for their analyses, and the mechanisms of interaction with the membrane are far to be understood. The purpose of this mini-review is to highlight some in vitro characteristics that seem to be convergent to explain the toxicity observed for some amyloids. Based on a comparison between the behavior of a model non-toxic amyloid (the Prion Forming Domain of HET-s) and its toxic mutant (M8), we could establish that short oligomers and/or fibers assembled in antiparallel β-sheets strongly interact with membrane leading to its disruption. Many recent evidences are in favor of the formation of antiparallel toxic oligomers assembled in β-helices able to form pores. We may also propose a new model of amyloid interaction with membranes by a "raft-like" mode of insertion that could explain important destabilization of membranes and thus amyloid toxicity.
    Biochimie 07/2012; · 3.14 Impact Factor

Full-text (2 Sources)

Available from
Jul 15, 2013