The invention provides a previously uncharacterized protein (gamma secretase activating protein or gSAP) that activates γ-secretase to produce β-amyloid protein (Aβ). Deposition of Aβ has been associated with Alzheimer's disease and other pathologies. The invention thus additionally provides, e.g., screening methods and novel research tools, inhibitors of this novel protein, and methods of diagnosis, treatment and control of Alzheimer's disease and other neurodegenerative conditions associated with deposition of Aβ.