Gamma-secretase composed of PS1/Pen2/Aph1a can cleave notch and amyloid precursor protein in the absence of nicastrin.
Gamma-secretase composed of PS1/Pen2/Aph1a can cleave notch and amyloid precursor protein in the absence of nicastrin.
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DOI：
10.1523/jneurosci.3826-09.2010
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发表时间：
2010-02-03
期刊：
影响因子：
--
通讯作者：
Kopan R
中科院分区：
文献类型：
--
作者：
Zhao G;Liu Z;Ilagan MX;Kopan R
γ-secretase is a multiprotein intramembrane-cleaving protease with a growing list of protein substrates including the Notch receptors and the amyloid precursor protein. The four components of γ-secretase complex - presenilin (PS), nicastrin (NCT), Pen2, and Aph1 - are all thought to be essential for activity. The catalytic domain resides within PS proteins; NCT has been suggested to be critical for substrate recognition; the contributions of Pen2 and Aph1 remain unclear. The role of NCT has been challenged recently by the observation that a critical residue (E332) in NCT, thought to be essential for γ-secretase activity, is instead involved in complex maturation. Here we report that NCT is dispensable for γ-secretase activity. NCT-independent γ-secretase activity can be detected in two independent NCT-deficient MEF lines, and blocked by the γ-secretase inhibitors DAPT and L-685,458. This catalytic activity requires prior ectodomain shedding of the substrate, and can cleave ligand-activated endogenous Notch receptors, indicating presence at the plasma membrane. siRNA knockdown experiments demonstrated that NCT-independent γ-secretase activity requires the presence of PS1, Pen2 and Aph1a but can tolerate knockdown of PS2 or Aph1b. We conclude that a PS1/Pen2/Aph1a trimeric complex is an active enzyme, displaying similar biochemical properties to those of γ-secretase and roughly 50% of its activity when normalized to PS1 NTF levels. This PS1/Pen2/Aph1a complex, however, is highly unstable. Thus, NCT acts to stabilize γ-secretase, but is not required for substrate recognition.
