The transmembrane aspartates in presenilin 1 and 2 are obligatory for γ-secretase activity and amyloid β-protein generation
The transmembrane aspartates in presenilin 1 and 2 are obligatory for γ-secretase activity and amyloid β-protein generation
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DOI：
10.1074/jbc.275.5.3173
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发表时间：
2000-02-04
影响因子：
4.8
通讯作者：
Selkoe, DJ
中科院分区：
文献类型：
--
作者：
Kimberly, WT;Xia, WM;Selkoe, DJ
早老素1(PS1)的缺乏会减少淀粉样β蛋白(Aβ)的产生，这一发现证实了早老素是β-淀粉样前体蛋白(APP)伽马分泌酶裂解的重要介质。最近，我们发现PS1中的两个保守的跨膜(TM)天冬氨酸对AP的产生至关重要，这为PS1要么作为伽马分泌酶所必需的双天冬氨酸辅因子发挥功能，要么本身就是伽玛分泌酶提供了证据。早老素2(PS2)与PS1有很大的序列相似性和可能的功能同源性。在这里，我们证明了PS2中的两个TM天冬氨酸对伽马分泌酶活性也是至关重要的，这进一步证明了PS2在功能上与PS1同源。在PS1和PS2中稳定共表达TM Asp-&Gt；Ala突变的细胞表明，APP衍生的伽马分泌酶底物C83和C99进一步积累。在这些细胞的条件培养液中，Aβ的产生减少到无法检测到的水平。此外，外源Asp突变体PS2没有内蛋白降解，内源PS1 C末端片段减少到检测不到的水平。因此，PS1和PS2 TM Asp->；Ala突变体的共表达抑制了任何可检测到的PS1或PS2异二聚体片段的形成，并基本上取消了Aβ的产生。这些结果解释了PS1缺陷细胞中残留的Aβ产生，并证明了功能性早老素对Aβ产生的绝对需求。我们的结论是，早老素，特别是他们的TM天冬氨酸，是通过降低Aβ来预防阿尔茨海默病的有吸引力的靶点。
The discovery that a deficiency of presenilin 1 (PS1) decreases the production of amyloid beta-protein (A beta) identified the presenilins as important mediators of the gamma-secretase cleavage of beta-amyloid precursor protein (APP). Recently, we found that two conserved transmembrane (TM) aspartates in PS1 are critical for AP production, providing evidence that PS1 either functions as a required diaspartyl cofactor for gamma-secretase or is itself gamma-secretase. Presenilin 2 (PS2) shares substantial sequence and possibly functional homology with PS1. Here, we show that the two TM aspartates in PS2 are also critical for gamma-secretase activity, providing further evidence that PS2 is functionally homologous to PS1. Cells stably co-expressing TM Asp -> Ala mutations in both PS1 and PS2 show further accumulation of the APP-derived gamma-secretase substrates, C83 and C99. The production of A beta is reduced to undetectable levels in the conditioned media of these cells. Furthermore, endoproteolysis of the exogenous Asp mutant PS2 is absent, and endogenous PS1 C-terminal fragments are diminished to undetectable levels. Therefore, the co-expression of PS1 and PS2 TM Asp -> Ala mutants suppresses the formation of any detectable PS1 or PS2 heterodimeric fragments and essentially abolishes the production of A beta. These results explain the residual A beta production seen in PS1-deficient cells and demonstrate the absolute requirement of functional presenilins for A beta generation. We conclude that presenilins, and their TM aspartates in particular, are attractive targets for lowering A beta therapeutically to prevent Alzheimer's disease.