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A new paradigm for neurotoxicity by FAD mutants of betaAPP: a signaling abnormality
1Department of Pharmacology and Neurosciences, KEIO University School of Medicine, Tokyo, Japan.
Abstract:
We have demonstrated that normal betaAPP695 behave as a signaling receptor and indicated that point mutations at V642 create autoactive betaAPP in signal transduction. Cellular expression of those familial Alzheimer's disease-associated mutants causes neuronal cells to undergo apoptotic death; and procedures inhibiting the signal of normal betaAPP block the mutant-induced apoptosis. We have also shown that the mutant-induced death is mediated by intracellular G protein activity but not by secretion of Abeta peptides. Accordingly, the mutant-induced death requires a cytoplasmic domain but not the 41st and 42nd residues of the Abeta region. These studies provide a novel insight that betaAPP may play a normal role as a death receptor and that Alzheimer's disease-relevant abnormality occurred in this function may lead neurons to suicidal degeneration.
Insights
Normal betaAPP695 functions as a signaling receptor. Familial Alzheimer's disease mutations cause autoactive betaAPP, leading to neuronal death mediated by G protein activity, not Abeta secretion.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Beta-amyloid precursor protein (betaAPP) is implicated in Alzheimer's disease (AD).
- The precise role of normal betaAPP in cellular signaling and its dysregulation in AD pathogenesis remain under investigation.
Purpose of the Study:
- To investigate the signaling function of normal betaAPP695.
- To determine the impact of familial Alzheimer's disease-associated mutations on betaAPP signaling and neuronal viability.
- To elucidate the molecular mechanisms underlying mutant betaAPP-induced neuronal death.
Main Methods:
- Cellular expression of wild-type and mutant betaAPP695 constructs.
- Assessment of neuronal apoptosis using cell viability assays.
- Investigation of intracellular signaling pathways, including G protein activity.
- Analysis of the requirement for specific betaAPP domains in mediating cellular effects.
Main Results:
- Normal betaAPP695 acts as a signaling receptor.
- Point mutations at V642 render betaAPP autoactive in signal transduction.
- Expression of AD-associated mutants induces apoptotic death in neuronal cells.
- Inhibition of normal betaAPP signaling blocks mutant-induced apoptosis.
- Mutant-induced neuronal death is mediated by intracellular G protein activity, independent of Abeta peptide secretion.
- The cytoplasmic domain of betaAPP is essential for mutant-induced death, while residues 41 and 42 of the Abeta region are not required.
Conclusions:
- BetaAPP may function as a death receptor in normal physiology.
- Abnormalities in betaAPP's death receptor function contribute to neurodegeneration in Alzheimer's disease.
- Targeting betaAPP signaling pathways offers a potential therapeutic strategy for AD.
