Transition-state analogue gamma-secretase inhibitors stabilize a 900 kDa presenilin/nicastrin complex.

Gamma-secretase mediates the final step, which generates Alzheimer's disease Abeta amyloid protein, by cleaving the transmembrane domain of the amyloid-beta protein precursor. Four gene products, presenilin, nicastrin, APH-1, and PEN-2, are required for gamma-secretase activity that is contained within a high molecular mass complex. To further characterize gamma-secretase, we probed membranes from human neuroblastoma SH-SY5Y cells with gamma-secretase inhibitor biotin derivatives of L-685,458, pepstatin A, and the difluoro alcohol 1-Bt.