Quantitative interaction proteomics reveals differences in the interactomes of amyloid precursor protein isoforms

Area of Science:

• Neuroscience
• Molecular Biology
• Proteomics

Background:

• Alzheimer's disease pathogenesis involves amyloid-beta (Aβ) peptides generated from amyloid precursor protein (APP).
• APP exists in different isoforms (e.g., APP695, APP751) with differential processing impacting disease initiation.
• Understanding isoform-specific interactions is crucial for elucidating differential APP processing.

Purpose of the Study:

• To compare the interactomes of APP695 and APP751 isoforms.
• To identify proteins mediating differential processing of APP isoforms.
• To discover novel therapeutic targets for Alzheimer's disease by understanding APP isoform-specific functions.

Main Methods:

• Proteomics-based approach using stable isotope labeling of amino acids in cell culture (SILAC).
• Quantitative proteomics to compare interactomes of APP695 and APP751 expressed in human SH-SY5Y cells.
• Experimental validation including co-immunoprecipitation and siRNA knockdown.

Main Results:

• Identified enrichment of proteins involved in mitochondrial function, nuclear pore, and nuclear transport in the APP695 interactome.
• Discovered GAP43 as a specific modulator of APP751 proteolysis, affecting Aβ generation.
• Demonstrated that APP interactome interrogation can identify proteins influencing APP proteolysis and Aβ production in an isoform-dependent manner.

Conclusions:

• APP695 and APP751 isoforms possess distinct interactomes that mediate their differential processing.
• GAP43 plays a specific role in regulating APP751 processing and subsequent Aβ generation.
• Targeting isoform-specific APP interactions presents a promising strategy for Alzheimer's disease therapeutics.