Neuroprotective amyloid-beta N-terminal peptides differentially alter
human α7- and α7β2-nicotinic acetylcholine receptor single-channel
properties
Abstract
Background and Purpose: Oligomeric Aβ1-42 (oAβ42) exhibits agonist-like
action at human α7- and α7β2-nicotinic receptors (collectively,
α7*-nAChR). Aβ1-42 and an N-terminal Aβ peptide fragment (N-Aβ fragment:
Aβ1-15/16) have been shown to modulate presynaptic Ca2+ and enhance
hippocampus-based synaptic plasticity via α7* nAChR. Both the N-Aβ
fragment and its essential core sequence, the N-Aβcore hexapeptide
(Aβ10-15), protect against Aβ-associated synapto- and neurotoxicity,
also involving nAChR. Here, we investigated how oAβ42, the N-Aβ fragment
and N-Aβcore regulate the functional activity of α7*-nAChRs.
Experimental approach: Single-channel patch clamp recordings measured
the impact of ACh, oAβ42, the N-Aβ fragment, and the N-Aβcore on the
function of concatenated, human α7- and α7β2-containing nAChR expressed
in nAChR-null SH-EP1 cells. Molecular dynamics simulations identified
potential sites of interaction between the N-Aβ fragment and the
orthosteric α7*-nAChR binding interfaces. Key Results: Relative to the
effects of ACh alone, oAβ42 preferentially enhanced α7β2-nAChR open
probability and open-dwell times. Co-application with the N-Aβcore
neutralized these effects. Further, we demonstrate that the N-Aβ
fragment alone, or in combination with ACh or oAβ42, resulted in
selective enhancement of α7-nAChR single-channel open probability and
open-dwell times (compared to ACh or oAβ42). Conclusions and
Implications: Our findings show the functional diversity of Aβ peptides
in regulating α7*-nAChR function, with implications for a wide range of
nAChR-mediated functions in AD. Single-channel recordings of the
differential effects of oAβ42, N-Aβ fragment and/or N-Aβcore on
α7*-nAChR isoform function revealed the complexities of their
interactions with α7*-nAChR, with new insights into the neuroprotective
actions of these N-Aβ-derived peptides.