Background：Alzheimer's disease （AD） patients with an inherited form of the disease carry mutations in the presenilin proteins （PSEN1 or PSEN2） or the amyloid precursor protein （APP）. These disease-linked mutations result in increased production of the longer form of amyloid-beta （main component of amyloid deposits found in AD brains）. Presenilins are postulated to regulate APP processing through their effects on gamma-secretase, an enzyme that cleaves APP. Also, it is thought that the presenilins are involved in the cleavage of the Notch receptor such that, they either directly regulate gamma-secretase activity, or themselves act are protease enzymes. Two alternatively spliced transcript variants encoding different isoforms of PSEN2 have been identified.
