Induction of Negative Curvature as a Mechanism of Cell Toxicity by Amyloidogenic Peptides: The Case of Islet Amyloid Polypeptide

Abstract

The death of insulin-producing β-cells is a key step in the pathogenesis of type 2 diabetes. The amyloidogenic peptide Islet Amyloid Polypeptide (IAPP, also known as amylin) has been shown to disrupt β-cell membranes leading to β-cell death. Despite the strong evidence linking IAPP to the destruction of β-cell membrane integrity and cell death, the mechanism of IAPP toxicity is poorly understood. In particular, the effect of IAPP on the bilayer structure has largely been uncharacterized. In this study, we have determined the effect of the amyloidogenic and toxic hIAPP 1-37 peptide and the non-toxic and non-amyloidogenic rIAPP 1-37 peptide on membranes by a combination of DSC and solid-state NMR spectroscopy. We also characterized the toxic but largely non-amyloidogenic rIAPP 1-19 and hIAPP 1-19 fragments. DSC shows that both amyloidogenic (hIAPP 1-37 ) and largely non-amyloidogenic (hIAPP 1-19 and rIAPP [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] ) toxic versions of the peptide strongly favor the formation of negative curvature in lipid bilayers, while the non-toxic full-length rat IAPP 1-37 peptide does not. This result was confirmed by solid-state NMR spectroscopy which shows that in bicelles composed of regions of high curvature and low curvature, non-toxic rIAPP 1-37 binds to the regions of low curvature while toxic rIAPP [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] binds to regions of high curvature. Similarly, solid-state NMR spectroscopy shows that the toxic rIAPP 1-19 peptide significantly disrupts the lipid bilayer structure, whereas the non-toxic rIAPP1-37 does not have a significant effect. These results indicate IAPP may induce the formation of pores by the induction of excess membrane curvature and can be used to guide the design of compounds that can prevent the cell-toxicity of IAPP. This mechanism may be important to understand the toxicity of other amyloidogenic proteins. Our solid-state NMR results also demonstrate the possibility of using bicelles to measure the affinity of biomolecules for negatively or positively curved regions of the membrane, which we believe will be useful in a variety of biochemical and biophysical investigations related to the cell membrane.

Clustering and Internalization of Toxic Amylin Oligomers in Pancreatic Cells Require Plasma Membrane Cholesterol

“…Other amyloidogenic proteins such as ␤-amyloid also display higher capacity for binding to GM1 clusters formed both on synthetic and native membranes (66,68). It is possible that cholesterol, by modulating membrane fluidity and/or membrane curvature (69,70), stimulates amylin oligomer clustering on the PM and subsequent internalization, as observed in this study. In addition to lipids, protein-protein interactions may also play a role in the binding of amylin to lipid rafts, as direct interactions between lipid raft proteins such as flotillin and ␤-amyloid in synaptic membranes was demonstrated (71).…”

Ganglioside‐induced amyloid formation by human islet amyloid polypeptide in lipid rafts

“…We previously reported that gangliosidebound form of amyloid b-protein generates negative curvature strain on lipid bilayers [37]. hIAPP also provokes negative mem- brane curvature [38], suggesting that the membrane distortion might contribute to the hIAPP-induced cytotoxic effect.…”

Common mechanism unites membrane poration by amyloid and antimicrobial peptides

“…This penalty could be attenuated by peptide binding. IAPP and magainin 2 have each been reported to induce membrane curvature (34)(35)(36). It is therefore reasonable to hypothesize that these peptides can stabilize a stochastically formed rift by binding to the pore.…”