Detection of amyloid-β protein precursor homo-interactions using beta-galactosidase enzyme fragment complementation.

Amyloidogenic processing of the amyloid-β protein precursor (AβPP) produces amyloid-β peptides (Aβ), the major constituent of amyloid plaques in the brains of Alzheimer's disease (AD) patients. Experimental evidence suggests that increased dimerization of AβPP increases Aβ while decreased dimerization of AβPP decreases Aβ production. If true, developing tools for detecting AβPP-AβPP interactions to understand AβPP processing leading to Aβ production would be important. Here, we developed the method of β-galactosidase (β-gal) enzyme fragment complementation as a means to detect AβPP-AβPP interactions. Inactive β-gal fragments are independently tagged to the C-terminal ends of monomeric AβPPs, and will come together to form a functional enzyme upon AβPP-AβPP interactions. Successful detection of β-gal activity has been used to qualitatively visualize and quantify the amount of AβPP dimers or higher oligomers. This method can be used to enhance our understanding of the biological processes dependent upon AβPP-AβPP interactions.