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Amyloid-β induces caspase-dependent loss of PSD-95 and synaptophysin through NMDA receptors

Jinping Liu1, Lirong Chang, Francesco Roselli

  • 1Department of Anatomy, Capital Medical University, Beijing, China.

Journal of Alzheimer'S Disease : JAD
|September 18, 2010
PubMed

Insights

Soluble amyloid-β (Aβ) in Alzheimer's disease (AD) reduces synaptic proteins via NMDA receptor imbalance. Targeting NR2A and NR2B receptors may prevent early synaptic dysfunction in AD.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Pathology

Background:

  • Soluble oligomeric amyloid-β (Aβ) is implicated in early Alzheimer's disease (AD) pathogenesis.
  • Synaptic dysfunction, characterized by the loss of key synaptic proteins like PSD-95 and synaptophysin, is a hallmark of early AD.

Purpose of the Study:

  • To elucidate the mechanism by which soluble Aβ induces synaptic protein loss.
  • To investigate the role of NMDA receptors (NMDARs) and downstream caspases in Aβ-mediated synaptotoxicity.
  • To identify potential therapeutic targets for preventing early AD-related synaptic dysfunction.

Main Methods:

  • Treatment of neuronal cultures with soluble Aβ oligomers.
  • Assessment of synaptic protein levels (PSD-95, synaptophysin).
  • Pharmacological manipulation using NMDAR antagonists (MK-801, ifenprodil) and varying NMDA concentrations.
  • Analysis of caspase-8 and caspase-3 activation.

Main Results:

  • Soluble Aβ significantly downregulated PSD-95 and synaptophysin levels.
  • This downregulation was blocked by NMDAR antagonists MK-801 and ifenprodil.
  • Low NMDA concentrations (1 μM) showed a protective effect, while high concentrations (10 μM) potentiated Aβ actions.
  • Ifenprodil-reversible caspase-8 activation mediated Aβ synaptotoxicity, upstream of caspase-3.
  • Aβ-induced synaptic loss resulted from NR2A suppression and NR2B activation.

Conclusions:

  • Aβ initiates synaptic dysfunction by disrupting the balance of NR2A and NR2B NMDAR function.
  • This imbalance leads to caspase-8 activation and subsequent synaptic protein loss.
  • Selective enhancement of NR2A activity or reduction of NR2B activity may offer a therapeutic strategy against early AD synaptic deficits.

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