期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 107, 期 14, 页码 6538-6543出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0914251107
关键词
atomic force microscopy; molecular dynamics; cell calcium imaging; neurite degeneration and cell death assays; single-channel conductance
资金
- National Institutes of Health [IIRG-05-14089]
- National Cancer Institute, National Institutes of Health [HHSN261200800001E]
- National Institutes of Health, National Cancer Institute, Center for Cancer Research
Full-length amyloid beta peptides (A beta(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 (A beta(11-42) and A beta(17-42)) 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 A beta(9-42) and A beta(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 A beta fragments could account for undefined roles played by full length A beta s 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.
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