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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    • "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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    ABSTRACT: Interaction of the Alzheimer's Aβ peptides with the plasma membrane of cells in culture results in chronic increases in cytosolic [Ca(2+)]. Such increases can cause a variety of secondary effects leading to impaired cell growth or cell degeneration. In this investigation, we made a comprehensive study of the changes in cytosolic [Ca(2+)] in single PC12 cells and human neurons stressed by continuous exposure to a medium containing Aβ42 for several days. The differential timing and magnitude of the Aβ42-induced increase in [Ca(2+)] reveal subpopulations of cells with differential sensitivity to Aβ42. These results suggest that the effect produced by Aβ on the level of cytosolic [Ca(2+)] depends on the type of cell being monitored. Moreover, the results obtained of using potent inhibitors of Aβ cation channels such as Zn(2+) and the small peptide NA7 add further proof to the suggestion that the long-term increases in cytosolic [Ca(2+)] in cells stressed by continuous exposure to Aβ is the result of Aβ ion channel activity.
    Cell Stress and Chaperones 11/2014; 20(2). DOI:10.1007/s12192-014-0551-2 · 3.16 Impact Factor
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    • "Although the initial cause of sporadic AD is still debated, the “amyloid cascade hypothesis” states that the aberrant production, aggregation, and deposition of Aβ is a causative process in the pathogenesis of AD [5]. Some researchers have found evidence that Aβ fibrils form pores in neurons, leading to calcium influx and the neuronal death associated with AD [6]. Apart from the direct role in cell death, Aβ-mediated glutamate receptor modifications can lead to synaptic dysfunction, resulting in excitotoxic neurodegeneration during the progression of AD [7]. "
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    ABSTRACT: Chronic neuroinflammation is now considered one of the major factors in the pathogenesis of Alzheimer’s disease (AD). However, the most widely used transgenic AD models (overexpressing mutated forms of amyloid precursor protein, presenilin, and/or tau) do not demonstrate the degree of inflammation, neurodegeneration (particularly of the cholinergic system), and cognitive decline that is comparable with the human disease. Hence a more suitable animal model is needed to more closely mimic the resulting cognitive decline and memory loss in humans in order to investigate the effects of neuroinflammation on neurodegeneration. One of these models is the glial fibrillary acidic protein-interleukin 6 (GFAP-IL6) mouse, in which chronic neuroinflammation triggered constitutive expression of the cytokine interleukin-6 (IL-6) in astrocytes. These transgenic mice show substantial and progressive neurodegeneration as well as a decline in motor skills and cognitive function, starting from 6 months of age. This animal model could serve as an excellent tool for drug discovery and validation in vivo. In this review, we have also selected three potential anti-inflammatory drugs, curcumin, apigenin, and tenilsetam, as candidate drugs, which could be tested in this model.
    BioMed Research International 06/2014; 2014(3):10. DOI:10.1155/2014/309129 · 2.71 Impact Factor
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    • "A number of mechanisms by which Aβ elicits its effects on intracellular Ca 2+ homeostasis have been put forward. These include direct effects on the plasma membrane, where it has been proposed to destabilize its structure (Mueller et al., 1995; Mason et al., 1996), to induce a generalized increase in membrane permeability (Bucciantini et al., 2002; Kayed et al., 2003) or to insert into the membrane forming cation-conducting pores (Arispe et al., 1993; Mueller et al., 1995; Mason et al., 1996; Bucciantini et al., 2002; Kayed et al., 2003; Kawahara, 2004; Simakova and Arispe, 2006; Arispe et al., 2007; Demuro et al., 2011). Aβ has also been reported to activate plasma membrane receptors, including N-methyl-d-aspartate (NMDA) receptors coupled to Ca 2+ influx (Guo et al., 1996; Dobson, "
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    ABSTRACT: Dysregulation of Ca(2+) homeostasis is considered to contribute to the toxic action of the Alzheimer's disease (AD)-associated amyloid-β-peptide (Aβ). Ca(2+) fluxes across the plasma membrane and release from intracellular stores have both been reported to underlie the Ca(2+) fluxes induced by Aβ42. Here, we investigated the contribution of Ca(2+) release from the endoplasmic reticulum (ER) to the effects of Aβ42 upon Ca(2+) homeostasis and the mechanism by which Aβ42 elicited these effects. Consistent with previous reports, application of soluble oligomeric forms of Aβ42 induced an elevation in intracellular Ca(2+). The Aβ42-stimulated Ca(2+) signals persisted in the absence of extracellular Ca(2+) indicating a significant contribution of Ca(2+) release from the ER Ca(2+) store to the generation of these signals. Moreover, inositol 1,4,5-trisphosphate (InsP3) signaling contributed to Aβ42-stimulated Ca(2+) release. The Ca(2+) mobilizing effect of Aβ42 was also observed when applied to permeabilized cells deficient in InsP3 receptors, revealing an additional direct effect of Aβ42 upon the ER, and a mechanism for induction of toxicity by intracellular Aβ42.
    Frontiers in Molecular Neuroscience 11/2013; 6:36. DOI:10.3389/fnmol.2013.00036 · 4.08 Impact Factor
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