Axon-Autonomous Effects of the Amyloid Precursor Protein Intracellular Domain (AICD) on Kinase Signaling and Fast...

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Alzheimer's disease (AD) is linked to amyloid precursor protein (APP) processing, generating amyloid beta (Aβ) and the APP intracellular domain (AICD).
• While AICD's role in signaling is known for full-length APP, its intracellular effects, especially in neuronal compartments like axons, are poorly understood.
• Alzheimer's disease pathology includes deficits in fast axonal transport (FAT) and axonopathy.

Purpose of the Study:

• To investigate the potential axon-autonomous effects of the AICD fragment on neuronal transport.
• To elucidate the molecular mechanisms by which AICD might impact axonal function.

Main Methods:

• Utilized vesicle motility assays in isolated squid axoplasm to assess FAT.
• Performed biochemical experiments to identify affected signaling pathways and protein modifications.
• Employed pharmacological inhibitors and deletion mutants to probe the AICD-mediated effects.

Main Results:

• AICD was found to inhibit FAT in the squid axoplasm model.
• This inhibition correlated with aberrant activation of axonal kinases and increased phosphorylation of conventional kinesin.
• Kinase inhibitors partially reversed the AICD-induced FAT inhibition, and a specific AICD motif (NPTY) was required.

Conclusions:

• AICD exhibits axon-autonomous effects, directly impairing FAT.
• Aberrant kinase activation and kinesin hyperphosphorylation are key mechanisms linking AICD to FAT deficits.
• These findings suggest a novel pathway connecting APP processing alterations to axonal pathology in Alzheimer's disease.