Amyloid β Protein (1−40) Forms Calcium-Permeable, Zn<sup>2+</sup>-Sensitive Channel in Reconstituted Lipid Vesicles<sup>,</sup>

Lin, Hai; Zhu, Yinwen Judy; Lal, R.

doi:10.1021/bi982997c

Cited by 166 publications

(174 citation statements)

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“…However, with the exception of the other blocking compounds modeled after the amino acid sequences forming the mouth of the Abeta pore (34,(45)(46)(47)(48), the other inhibitors, such as Tris and Zn 2ϩ could be considered somewhat on the less potent side of the concentration/efficacy scale. For example, relatively high concentrations of Tris (1-10 mM) are needed both to block Abeta channels (32) and to protect against neurotoxicity (42). Also, Zn 2ϩ is only active in the 250 M range (38,46).…”

Section: Discussionmentioning

confidence: 99%

“…The target of the A␤ peptide in biological and model membranes is phosphatidylserine (PS), the proapoptic signaling phospholipid (37). Subsequently the calcium channel properties of A␤ have been verified in many other laboratories (38)(39)(40)(41)(42). We and others have therefore hypothesized that calcium conducted into the target neurons by the A␤ channel might be responsible for A␤ neurotoxicity.…”

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confidence: 81%

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Small molecule blockers of the Alzheimer Aβ calcium channel potently protect neurons from Aβ cytotoxicity

Díaz

Šimáková

Jacobson

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

107

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Alzheimer's disease (AD) is a common, chronic neurodegenerative disease that is thought to be caused by the neurotoxic effect of the Amyloid beta peptides (A␤). We have hypothesized that the intrinsic A␤ calcium channel activity of the oligomeric A␤ polymer may be responsible for the neurotoxic properties of A␤, and that A␤ channel blockers may be candidate AD therapeutics. As a consequence of a rational search paradigm based on the model structure of the A␤ channel, we have identified two compounds of interest: MRS2481 and an enatiomeric species, MRS2485. These are amphiphilic pyridinium salts that both potently block the A␤ channel and protect neurons from A␤ toxicity. Both block the A␤ channel with similar potency (Ϸ500 nM) and efficacy (100%). However, we find that inhibition by MRS2481 is easily reversible, whereas inhibition by MRS2485 is virtually irreversible. We suggest that both species deserve consideration as candidates for Alzheimer's disease drug discovery.brain ͉ neurodegeneration ͉ rational drug design ͉ drug ͉ toxicity A lzheimer's disease (AD) is a chronic neurodegenerative disease characterized behaviorally by progressive memory loss, and neuronal degeneration in the cerebral cortex, hippocampus, and elsewhere (1, 2). The neuropathology of AD is characterized by amyloid plaques and neuro-fibrillary tangles. The amyloid plaque material has been found to be composed principally of a 40Ϫ42-residue peptide, called amyloid ␤-peptide, or ''A␤'' (3). Both forms of A␤40/42 have been found to be kill neurons and certain other cells in culture. Altogether, these findings have provided strong support for the hypothesis that AD is due to neurotoxic effects of A␤ on susceptible neurons (4-10).The mechanism of A␤ neurotoxicity has been pursued for decades in hopes of translating such knowledge into a pharmaceutical therapy for AD. Cholinesterase inhibitors were the first generation of such candidate therapeutics (11-15). A second generation of candidate therapeutics has included a series of attempts to inhibit the formation of amyloid plaques. Active (16-23) and passive (24) immunization approaches are presently being tested. However, some patients in the active human immunization trials have developed meningoencephalitis (25,26). Yet another alternative has been to reduce the levels of A␤ in the brain by inhibiting the proteolytic enzymes associated with trimming APP into A␤ 40 or 42 (27-31).An entirely different approach to the mechanism of A␤ neurotoxicity has been developed following the observation that oligomers of A␤ peptides themselves formed calcium conducting channels in bilayer membranes in vitro (32)(33)(34)(35), and in intact neurons (36). The target of the A␤ peptide in biological and model membranes is phosphatidylserine (PS), the proapoptic signaling phospholipid (37). Subsequently the calcium channel properties of A␤ have been verified in many other laboratories (38-42). We and others have therefore hypothesized that calcium conducted into the target neurons by the A␤ channel might be respo...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 81%

Small molecule blockers of the Alzheimer Aβ calcium channel potently protect neurons from Aβ cytotoxicity

Díaz

Šimáková

Jacobson

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

107

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“…Samples were rinsed with PBS for at least five times. They were then incubated with fluorescein isothiocyanate-conjugated goat anti-mouse IgG (1 g/ml, ZyMax TM , Invitrogen) for 2 h at room temperature (33). Samples were then washed again with PBS.…”

Section: Methodsmentioning

confidence: 99%

Nanomechanics of Hemichannel Conformations

Liu¹,

Arce²,

Ramachandran³

et al. 2006

Journal of Biological Chemistry

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Gap junctional hemichannels mediate cell-extracellular communication. A hemichannel is made of six connexin (Cx) subunits; each connexin has four transmembrane domains, two extracellular loops, and cytoplasmic amino-and carboxyl-terminals (CTs). The extracellular domains are arranged differently at non-junctional and junctional (gap junction) regions, although very little is known about their flexibility and conformational energetics. The cytoplasmic tail differs considerably in the size and amino acid sequence for different connexins and is predicted to be involved in the channel open and closed conformations. For large connexins, such as Cx43, the CT makes large cytoplasmic fuzz visible under electron microscopy. If this CT domain controls channel permeability by physical occlusion of the pore mouth, movement of this portion could open or close the channel. We used atomic force microscopy-based single molecule spectroscopy with antibody-modified atomic force microscopy tips and connexin mimetic peptide modified tips to examine the flexibility of extracellular loop and CT domains and to estimate the energetics of their movements. Antibody to the CT portion closer to the membrane stretches the tail to a shorter length, and the antibody to CT tail stretches the tail to a longer length. The stretch length and the energy required for stretching the various portions of the carboxyl tail support the ball and chain model for hemichannel conformational changes.

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“…Atomic force microscopic (AFM) images of Aβ peptides reconstituted in lipid bilayers show heteromeric (rectangular to hexagonal) ion channel-like structures with a ∼2.0-nm central pore and 8-to 12-nm outer diameters (7,8). Electrophysiological studies show heterodisperse cationselective single-channel conductances (7)(8)(9)(10)(11)(12)(13)(14) that are consistent with features of other amyloid ion channels (6-8).On the other hand, when APP is cleaved by γ-and α-secretases, it forms the nonamyloidogenic pathway generating ∼2.6-kDa fragments (Aβ 17-40/42 ) known as the p3 peptides (15). Cleavage by γ and BACE between Tyr10 and Glu11 generates another nonamyloidogenic Aβ peptide (Aβ 11-40/42 ) (16).…”

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confidence: 99%

Truncated β-amyloid peptide channels provide an alternative mechanism for Alzheimer’s Disease and Down syndrome

Jang

Arce

Ramachandran

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

216

344

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Full-length amyloid beta peptides (Aβ 1-40/42 ) form neuritic amyloid plaques in Alzheimer's disease (AD) patients and are implicated in AD pathology. However, recent transgenic animal models cast doubt on their direct role in AD pathology. Nonamyloidogenic truncated amyloid-beta fragments and Aβ ) are also found in amyloid plaques of AD and in the preamyloid lesions of Down syndrome, a model system for early-onset AD study. Very little is known about the structure and activity of these smaller peptides, although they could be the primary AD and Down syndrome pathological agents. Using complementary techniques of molecular dynamics simulations, atomic force microscopy, channel conductance measurements, calcium imaging, neuritic degeneration, and cell death assays, we show that nonamyloidogenic Aβ 9-42 and Aβ 17-42 peptides form ion channels with loosely attached subunits and elicit single-channel conductances. The subunits appear mobile, suggesting insertion of small oligomers, followed by dynamic channel assembly and dissociation. These channels allow calcium uptake in amyloid precursor protein-deficient cells. The channel mediated calcium uptake induces neurite degeneration in human cortical neurons. Channel conductance, calcium uptake, and neurite degeneration are selectively inhibited by zinc, a blocker of amyloid ion channel activity. Thus, truncated Aβ fragments could account for undefined roles played by full length Aβs and provide a unique mechanism of AD and Down syndrome pathologies. The toxicity of nonamyloidogenic peptides via an ion channel mechanism necessitates a reevaluation of the current therapeutic approaches targeting the nonamyloidogenic pathway as avenue for AD treatment.atomic force microscopy | molecular dynamics | cell calcium imaging | neurite degeneration and cell death assays | single-channel conductance A myloid-beta peptides (Aβ 1-40/42 ) produced by β-and γ-secretase processing of amyloid precursor protein (APP) in the amyloidogenic pathway are involved in Alzheimer's disease (AD) pathology. Aβ 1-40/42 peptides form β-sheet-rich ordered aggregates and soluble oligomers. Small oligomers are emerging as the predominant toxic species (1-3); the toxicity is believed to be a result of the loss of ionic homeostasis, presumably via ion channels formed in cellular membranes (4, 5). EM images of Aβ oligomers show doughnut-like morphologies (6). Atomic force microscopic (AFM) images of Aβ peptides reconstituted in lipid bilayers show heteromeric (rectangular to hexagonal) ion channel-like structures with a ∼2.0-nm central pore and 8-to 12-nm outer diameters (7,8). Electrophysiological studies show heterodisperse cationselective single-channel conductances (7)(8)(9)(10)(11)(12)(13)(14) that are consistent with features of other amyloid ion channels (6-8).On the other hand, when APP is cleaved by γ-and α-secretases, it forms the nonamyloidogenic pathway generating ∼2.6-kDa fragments (Aβ 17-40/42 ) known as the p3 peptides (15). Cleavage by γ and BACE between Tyr10 and Glu11 generates another...

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Amyloid β Protein (1−40) Forms Calcium-Permeable, Zn²⁺-Sensitive Channel in Reconstituted Lipid Vesicles^,

Cited by 166 publications

References 50 publications

Small molecule blockers of the Alzheimer Aβ calcium channel potently protect neurons from Aβ cytotoxicity

Small molecule blockers of the Alzheimer Aβ calcium channel potently protect neurons from Aβ cytotoxicity

Nanomechanics of Hemichannel Conformations

Truncated β-amyloid peptide channels provide an alternative mechanism for Alzheimer’s Disease and Down syndrome

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Amyloid β Protein (1−40) Forms Calcium-Permeable, Zn2+-Sensitive Channel in Reconstituted Lipid Vesicles,

Cited by 166 publications

References 50 publications

Small molecule blockers of the Alzheimer Aβ calcium channel potently protect neurons from Aβ cytotoxicity

Small molecule blockers of the Alzheimer Aβ calcium channel potently protect neurons from Aβ cytotoxicity

Nanomechanics of Hemichannel Conformations

Truncated β-amyloid peptide channels provide an alternative mechanism for Alzheimer’s Disease and Down syndrome

Contact Info

Product

Resources

About

Amyloid β Protein (1−40) Forms Calcium-Permeable, Zn²⁺-Sensitive Channel in Reconstituted Lipid Vesicles^,