Activity and Architecture of Pyroglutamate-Modified Amyloid-β (Aβ_pE3-42) Pores

Abstract

Among the family of Aβ peptides, pyroglutamate-modified Aβ (AβpE) peptides are particularly associated with cytotoxicity in Alzheimer’s disease (AD). They represent the dominant fraction of Aβ oligomers in the brains of AD patients, but their accumulation in the brains of elderly individuals with normal cognition is significantly lower. Accumulation of AβpE plaques precedes the formation of plaques of full-length Aβ (Aβ1-40/42). Most of these properties appear to be associated with the higher hydrophobicity of AβpE as well as an increased resistance to enzymatic degradation. However, the important question of whether AβpE peptides induce pore activity in lipid membranes and their potential toxicity compared with other Aβ pores is still open. Here we examine the activity of AβpE pores in anionic membranes using planar bilayer electrical recording and provide their structures using molecular dynamics simulations. We find that AβpE pores spontaneously induce ionic current across the membrane and have some similar properties to the other previously studied pores of the Aβ family. However, there are also some significant differences. The onset of AβpE3-42 pore activity is generally delayed compared with Aβ1-42 pores. However, once formed, AβpE3-42 pores produce increased ion permeability of the membrane, as indicated by a greater occurrence of higher conductance electrical events. Structurally, the lactam ring of AβpE peptides induces a change in the conformation of the N-terminal strands of the AβpE3-42 pores. While the N-termini of wild-type Aβ1–42 peptides normally reside in the bulk water region, the N-termini of AβpE3-42 peptides tend to reside in the hydrophobic lipid core. These studies provide a first step to an understanding of the enhanced toxicity attributed to AβpE peptides.

Amyloid-β Peptide Aβ3pE-42 Induces Lipid Peroxidation, Membrane Permeabilization, and Calcium Influx in Neurons

“…Additionally, we found that that the neuronal membrane damage caused by A␤3pE-42 results in a functional loss of plasma membrane integrity. These findings are consistent with recent publications demonstrating the capacity for A␤3pE-42 to form membrane-disrupting pores in synthetic lipid bilayers (22,23). Similarly, previous studies have shown that pE-A␤ oligomers disrupt lysosome membrane integrity in cultured neurons (50) and cause lactate dehydrogenase leakage from cultured astrocytes (49).…”

“…Neurons-Recent reports of pE-A␤ interactions with synthetic lipid membranes have suggested that pE-A␤ neurotoxicity is exerted via formation of ion-permeable membrane pores (22,23). We compared the capacity of A␤(1-42) and A␤3pE-42 to alter cellular ion homeostasis by measuring Ca 2ϩ flux in cortical neurons immediately following application of freshly prepared A␤.…”

“…pE-A␤ peptides also demonstrate increased ␤-sheet (aggregate structure) stability (16,17), differences in fibril ultrastructure (18,19), and altered interactions with copper ions (20,21) and synthetic lipid membranes (22,23). Notably, trace quantities of A␤3pE-42 have been observed to dramatically enhance the aggregation and neurotoxicity of A␤ (24), prompting descriptions of pE-A␤ as "prionlike."…”

Mechanisms of Membrane Binding of Small GTPase K-Ras4B Farnesylated Hypervariable Region

“…Two types of zwitterionic lipid bilayers, containing DPPC and DOPC, and an anionic lipid bilayer containing DOPC/DOPS (mole ratio 4:1) were used in the simulations. Similar anionic lipid bilayers have been extensively simulated (33)(34)(35)(36)(37)(38)(39)(40)(41)(42). For each combination of two HVR peptides with three types of lipid bilayers, six independent simulations labeled HP1 to HP6 were performed.…”

Computational Methods for Structural and Functional Studies of Alzheimer’s Amyloid Ion Channels

“…The AFM images revealed that the amyloid channels exhibited various shapes from rectangular with four subunits to octahedral with eight. The heterogeneity in the Aβ channel conformations was further confirmed by recent extensive molecular dynamics (MD) simulations [30][31][32][33][34][35][36][37][38][39][40][41][42]. These showed that Aβ channels consisted of β-sheet-rich subunits with morphologies and dimensions in good agreement with the imaged AFM channels [12,29].…”