Single-channel Ca imaging implicates Aβ1–42 amyloid pores in Alzheimer’s disease pathology

Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697, USA.
The Journal of Cell Biology (Impact Factor: 9.83). 10/2011; 195(3):515-24. DOI: 10.1083/jcb.201104133
Source: PubMed


Oligomeric forms of Aβ peptides are implicated in Alzheimer's disease (AD) and disrupt membrane integrity, leading to cytosolic calcium (Ca(2+)) elevation. Proposed mechanisms by which Aβ mediates its effects include lipid destabilization, activation of native membrane channels, and aggregation of Aβ into Ca(2+)-permeable pores. We distinguished between these using total internal reflection fluorescence (TIRF) microscopy to image Ca(2+) influx in Xenopus laevis oocytes. Aβ1-42 oligomers evoked single-channel Ca(2+) fluorescence transients (SCCaFTs), which resembled those from classical ion channels but which were not attributable to endogenous oocyte channels. SCCaFTs displayed widely variable open probabilities (P(o)) and stepwise transitions among multiple amplitude levels reminiscent of subconductance levels of ion channels. The proportion of high P(o), large amplitude SCCaFTs grew with time, suggesting that continued oligomer aggregation results in the formation of highly toxic pores. We conclude that formation of intrinsic Ca(2+)-permeable membrane pores is a major pathological mechanism in AD and introduce TIRF imaging for massively parallel single-channel studies of the incorporation, assembly, and properties of amyloidogenic oligomers.

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Available from: Angelo Demuro
    • "The high levels of toxicity observed when the cells are coincidentally exposed to HypF-N oligomers and high concentrations of αBc, Clu or M-TTR likely results from a small fraction of chaperone in an aggregated state, formed after the non-physiological procedure of lyophilisation/reconstitution. An early event arising from the cytotoxicity of protein oligomers is a rapid influx of Ca 2+ ions from the cell culture medium into the cytosol, attributable to the interaction of the oligomers with the cell membrane (Bucciantini et al., 2004;Demuro et al., 2005Demuro et al., , 2011Zampagni et al., 2011). We tested the effects on N2a cell Ca 2+ dyshomeostasis of HypF-N oligomers alone, αBc, Clu or M-TTR alone, and HypF-N oligomers incubated with each of these three proteins (Figure 8). "
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    • "This finding led us to propose that the increase in Ca 2+ permeability observed in cells exposed to Aβ results from the activity of calcium ion channels formed by Aβ in the cell surface membrane (Arispe et al. 1994a, b) (Arispe et al. 2010). While there is a growing consensus that Aβ peptides increase membrane conductance by forming conductive pores (Aguayo et al. 2009; Parodi et al. 2010; Sepulveda et al. 2010; Schauerte et al. 2010; Johnson et al. 2011; Tofoleanu and Buchete 2012; DeMuro et al. 2011; Sciacca et al. 2012; Prangkio et al. 2012; Schauerte et al. 2010; DeMuro et al. 2011), there has not been a systematic study on how a "
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