pfam14959: GSAP-16 (This model is not part of the current CDD release)
gamma-Secretase-activating protein C-term
GSAP, or gamma-secretase-activating protein, also known as PION, regulates gamma-secretase activity. The holo-protein is a large, approx 850 residue protein that is rapidly cleaved to an active 16 kDa C-terminal fragment that is the stable, predominant form. GSAP is expressed in inclusion bodies and is important in brain function. It dramatically and selectively increases neurotoxic beta-Amyloid production in the brain through a mechanism involving its interactions with both gamma-secretase and its substrate, the amyloid precursor protein C-terminal fragment (APP-CTF). Accumulation of neurotoxic beta-Amyloid is a major hallmark of Alzheimer's disease. Formation of beta-Amyloid is catalyzed by gamma-secretase, a protease with numerous substrates that catalyzes the intra-membrane cleavage of integral membrane proteins such as Notch receptors and APP (beta-amyloid precursor protein). The secondary structure of GSAP is largely alpha-helical, lacking well-defined tertiary structure. GSAP represents a type of gamma-secretase regulator that directs enzyme specificity by interacting with a specific substrate.
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