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Updated: Jun 3, 2026
Interactions with and Membrane Permeabilization of Brain Mitochondria by Amyloid Fibrils
Published on: September 28, 2019
Comparative studies of nontoxic and toxic amyloids interacting with membrane models at the air-water interface
Ha Phuong Ta1, Karine Berthelot, Bénédicte Coulary-Salin
1Chimie et Biologie des Membranes et Nano-objets, Université de Bordeaux-CNRS, 2 rue Robert Escarpit, 33607 Pessac, France.
Abstract:
Many in vitro studies have pointed out the interaction between amyloids and membranes, and their potential involvement in amyloid toxicity. In a previous study, we generated a yeast toxic mutant (M8) of the harmless model amyloid protein HET-s((218-289)). In this study, we compared the self-assembling process of the nontoxic wild-type (WT) and toxic (M8) protein at the air-water interface and in interaction with various phospholipid monolayers (DOPE, DOPC, DOPI, DOPS and DOPG). We first demonstrate using ellipsometry measurements and polarization-modulated infrared reflection absorption spectroscopy (PMIRRAS) that the air-water interface promotes and modifies the assembly of WT since an amyloid-like film was instantaneously formed at the interface with an antiparallel β-sheet structuration instead of the parallel β-sheet commonly observed for amyloid fibers generated in solution. The toxic mutant (M8) behaves in a similar manner at the air-water interface or in bulk, with a fast self-assembling and an antiparallel β-sheet organization. The transmission electron microscopy (TEM) images established the fibrillous morphology of the protein films formed at the air-water interface. Second, we demonstrate for the first time that the main driving force between this particular fungus amyloid and membrane interaction is based on electrostatic interactions with negatively charged phospholipids (DOPG, DOPI, DOPS). Interestingly, the toxic mutant (M8) clearly induces perturbations of the negatively charged phospholipid monolayers, leading to a massive surface aggregation, whereas the nontoxic (WT) exhibits a slight effect on the membrane models. This study allows concluding that the toxicity of the M8 mutant could be due to its high propensity to interact with membranes.
Insights
The toxic HET-s amyloid mutant (M8) readily self-assembles at air-water interfaces and interacts strongly with negatively charged membranes, unlike its non-toxic wild-type counterpart. This enhanced membrane interaction likely underlies the M8 mutant's toxicity.
Area of Science:
- Biophysics
- Biochemistry
- Materials Science
Background:
- Amyloid proteins are implicated in toxicity through interactions with cell membranes.
- A previously generated toxic yeast mutant (M8) of the HET-s((218-289)) amyloid protein provides a model for studying toxicity mechanisms.
Purpose of the Study:
- To compare the self-assembly and membrane interaction properties of non-toxic wild-type (WT) HET-s((218-289)) and its toxic M8 mutant.
- To investigate the role of electrostatic interactions in amyloid-membrane binding.
- To elucidate the structural and dynamic differences contributing to M8-induced toxicity.
Main Methods:
- Ellipsometry and polarization-modulated infrared reflection absorption spectroscopy (PMIRRAS) to analyze protein assembly at the air-water interface.
- Transmission electron microscopy (TEM) to determine the morphology of assembled protein films.
- Studies of protein interaction with various phospholipid monolayers (DOPE, DOPC, DOPI, DOPS, DOPG) to assess membrane binding.
Main Results:
- The air-water interface promotes WT HET-s assembly into amyloid-like films with antiparallel β-sheet structures.
- The toxic M8 mutant self-assembles rapidly with antiparallel β-sheet organization, similar to WT at the interface and in bulk.
- Amyloid-membrane interactions are primarily driven by electrostatic forces with negatively charged phospholipids (DOPG, DOPI, DOPS).
- The toxic M8 mutant causes significant perturbations and aggregation in negatively charged phospholipid monolayers, while WT has a minimal effect.
Conclusions:
- The air-water interface influences HET-s amyloid assembly, inducing antiparallel β-sheet structures.
- Electrostatic interactions are key drivers of HET-s amyloid binding to negatively charged membranes.
- The M8 mutant's pronounced interaction with and perturbation of negatively charged membranes likely explains its toxicity.
