Histidines 13 and 14 in the Aβ sequence are targets for inhibition of Alzheimer's disease Aβ ion channel and cytotoxicity

Abstract

The fact that Alzheimer's beta amyloid (Aβ) peptides forms cation channels in lipid bilayers was discovered during the course of our experiments in the laboratory of "Guayo" Rojas at NIH in Bethesda, Maryland (USA). Recently, we found that the Aβ ion channel could be blocked selectively with small peptides that copy the amino acid sequence of the predicted mouth region of the Aβ channel pore. We now have searched for the essential amino acid residues required for this blocking effect by mutations. We found that the ability of peptides to block Aβ channel activity could be lost by replacement of histidines 13 and 14 by alanine or lysine. The amino acid substitution also resulted in the loss of the capacity of the peptides to protect cells from Aβ cytotoxicity. These data thus contribute to the definition of the region of the Aβ sequence that participates in the formation of the channel pore. Additionally, these data support the hypothesis that the ion channel activity of Aβ contributes significantly to the cytotoxic properties of Aβ. These data also emphasize the potential value in using inhibition of Aβ ion channel activity as an end point for Alzheimer's disease drug discovery.

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

“…Thus the results lend further support to the hypothesis that the neurotoxic mechanism for A␤ is a direct consequence of the ability of A␤ to form calcium channels in the target neurons (33,45). These two compounds, however, do differ with respect to the reversibility of their interaction with A␤.…”

“…This is not the first instance in which compounds have been found that both block the Abeta channel and protect cells against Abeta neurotoxicity. In fact, previous data of this sort have contributed to the compelling support for the A␤ calcium channel hypothesis for the pathogenesis of Alzheimer's disease (45). 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.…”

“…In fact, previous data of this sort have contributed to the compelling support for the A␤ calcium channel hypothesis for the pathogenesis of Alzheimer's disease (45). 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).…”

“…More recently, basing our work on an earlier least-energy molecular model of the oligomeric Abeta channel (44 and [supporting information (SI) Fig. S1]), we found that highly selective A␤ channel blockers could be created from polypeptide segments predicted by the model to line the mouth of the A␤ pore (34,(45)(46)(47)(48). Furthermore, these polypeptide inhibitors also proved to be potent inhibitors of A␤ neurotoxicity.…”

Development of photocrosslinked sialic acid containing polymers for use in Aβ toxicity attenuation

“…Most believe that Aβ toxicity is linked to the formation of aggregated species, with the most toxic species being an intermediate between monomer and fibrils [11][12][13][14]. Some believe that Aβ acts via association with the cell membrane [15], to cause membrane depolarization, changes in membrane capacitance [16], membrane destabilization [17], pore formation [18,19] or free radical generation [20,21]. Consistent with these observations is that the first step in Aβ toxicity is Aβ binding to a membrane component.…”