Abstract
The opening of the Alzheimer's Abeta channel permits the flux of calcium into the cell, thus critically disturbing intracellular ion homeostasis. Peptide segments that include the characteristic histidine (His) diad, His(13) and His(14), efficiently block the Abeta channel activity, blocking Abeta cytotoxicity. We hypothesize that the vicinal His-His peptides coordinate with the rings of His in the mouth of the pore, thus blocking the flow of calcium ions through the channel, with consequent blocking of Abeta cytotoxicity. To test this hypothesis, we studied Abeta ion channel activity and cytotoxicity after the addition of compounds that are known to have His association capacity, such as Ni(2+), imidazole, His, and a series of His-related compounds. All compounds were effective at blocking both Abeta channel and preventing Abeta cytotoxicity. The efficiency of protection of His-related compounds was correlated with the number of imidazole side chains in the blocker compounds. These data reinforce the premise that His residues within the Abeta channel sequence are in the pathway of ion flow. Additionally, the data confirm the contribution of the Abeta channel to the cytotoxicity of exogenous Abeta.