Visualization of Alzheimer's Disease Related alpha-/beta-/gamma-Secretase Ternary Complex by Bimolecular Fluorescence Complementation Based Fluorescence Resonance Energy Transfer

The competitive ectodomain shedding of amyloid-beta) precursor protein (APP) by alpha-secretase and beta-secretase, and the subsequent regulated intramembrane proteolysis by gamma-secretase are the key processes in amyloid-beta peptides (A beta) generation. Previous studies indicate that secretases form binary complex and the interactions between secretases take part in substrates processing. However, whether alpha-, beta- and gamma-secretase could form ternary complex remains to be explored. Here, we adopted bimolecular fluorescence complementation in combination with fluorescence resonance energy transfer (BiFC-FRET) to visualize the formation of triple secretase complex. We show that the interaction between alpha-secretase ADAM10 and beta-secretase BACE1 could be monitored by BiFC assay and the binding of APP to alpha-/beta-secretase binary complex was revealed by BiFC-FRET. Further, we observed that gamma-secretase interacts with alpha-/beta-secretase binary complex, providing evidence that alpha-, beta- and gamma-secretase might form a ternary complex. Thus our study extends the interplay among Alzheimer's disease (AD) related alpha-/beta-/gamma-secretase.