Alzheimer's disease amyloid beta-protein forms Zn(2+)-sensitive, cation-selective channels across excised membrane patches from hypothalamic neurons.
We have previously shown that the 40-residue peptide termed amyloid beta-protein (A beta P[1-40]) in solution forms cation-selective channels across artificial phospholipid bilayer membranes. To determine whether A beta P[1-40] also forms channels across natural membranes, we used electrically silent excised membrane patches from a cell line derived from hypothalamic gonadotrophin-releasing hormone GnRH neurons. We found that exposing either the internal or the external side of excised membrane patches to A beta P[1-40] leads to the spontaneous formation of cation-selective channels. With Cs+ as the main cation in both the external as well as the internal saline, the amplitude of the A beta P[1-40] channel currents was found to follow the Cs+ gradient and to exhibit spontaneous conductance changes over a wide range (50-500 pS). We also found that free zinc (Zn2+), reported to bind to amyloid beta-protein in solution, can block the flow of Cs+ through the A beta P[1-40] channel. Because the Zn2+ chelator o-phenanthroline can reverse this blockade, we conclude that the underlying mechanism involves a direct interaction between the transition element Zn2+ and sites in the A beta P[1-40] channel pore. These properties of the A beta P[1-40] channel are rather similar to those observed in the artificial bilayer system. We also show here, by immunocytochemical confocal microscopy, that amyloid beta-protein molecules form deposits closely associated with the plasma membrane of a substantial fraction of the GnRH neurons. Taken together, these results suggest that the interactions between amyloid beta-protein and neuronal membranes also occur in vivo, lending further support to the idea that A beta P[1-40] channel formation might be a mechanism of amyloid beta-protein neurotoxicity.
Kawahara
M
M
Department of Molecular and Cellular Neurobiology, Tokyo Metropolitan Institute for Neuroscience, Japan.
Arispe
N
N
Kuroda
Y
Y
Rojas
E
E
D016229:Amyloid beta-Peptides / Q000494:pharmacology* / Q000502:physiology*; D000818:Animals; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology* / Q000502:physiology*; D010618:Phenanthrolines / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology*
D016229:Amyloid beta-Peptides; D007473:Ion Channels; D010446:Peptide Fragments; D010618:Phenanthrolines; C078592:amyloid beta-protein (1-40); D015032:Zinc; C025205:1,10-phenanthroline