The Apaf-1•Kprocaspase-9 apoptosome complex functions as a proteolytic-based molecular timer
The Apaf-1•Kprocaspase-9 apoptosome complex functions as a proteolytic-based molecular timer
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DOI：
10.1038/emboj.2009.152
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发表时间：
2009-07-08
期刊：
影响因子：
11.4
通讯作者：
Bratton, Shawn B.
中科院分区：
文献类型：
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作者：
Malladi, Srinivas;Challa-Malladi, Madhavi;Bratton, Shawn B.
在应激诱导的细胞凋亡过程中，启动物caspase-9被Apaf-1凋亡体激活，必须保持结合才能保持显著的催化活性。然而，在凋亡细胞中，绝大多数加工过的caspase-9在复合物外被矛盾地观察到。我们在此表明，凋亡细胞介导的procaspase-9的切割仅通过card -位移机制发生，因此与效应物procaspase-3不同，procaspase-9不能作为典型的底物被凋亡细胞加工。事实上，procaspase-9对凋亡细胞具有更高的亲和力，可以将加工过的caspase-9从复合物中置换出来，从而促进procaspase-9从复合物中招募/激活、加工和释放的连续循环。然而，由于其快速的自催化裂解，procaspase-9本身对procaspase-3的激活贡献很小。因此，Apaf-1凋亡细胞的功能是作为一个基于蛋白水解的“分子计时器”，其中细胞内procaspase-9的浓度设定了计时器的总持续时间，procaspase-9的自动加工激活了计时器，加工的caspase-9从复合物中解离的速度（从而失去了激活procaspase-3的能力）决定了计时器“滴答”的速度。EMBO杂志（2009）28,1916-1925。doi: 10.1038 / emboj.2009.152;2009年6月4日在线发布
During stress-induced apoptosis, the initiator caspase-9 is activated by the Apaf-1 apoptosome and must remain bound to retain significant catalytic activity. Nevertheless, in apoptotic cells the vast majority of processed caspase-9 is paradoxically observed outside the complex. We show herein that apoptosome-mediated cleavage of procaspase-9 occurs exclusively through a CARD-displacement mechanism, so that unlike the effector procaspase-3, procaspase-9 cannot be processed by the apoptosome as a typical substrate. Indeed, procaspase-9 possessed higher affinity for the apoptosome and could displace the processed caspase-9 from the complex, thereby facilitating a continuous cycle of procaspase-9 recruitment/activation, processing, and release from the complex. Owing to its rapid autocatalytic cleavage, however, procaspase-9 per se contributed little to the activation of procaspase-3. Thus, the Apaf-1 apoptosome functions as a proteolytic-based 'molecular timer', wherein the intracellular concentration of procaspase-9 sets the overall duration of the timer, procaspase-9 auto-processing activates the timer, and the rate at which the processed caspase-9 dissociates from the complex (and thus loses its capacity to activate procaspase-3) dictates how fast the timer 'ticks' over. The EMBO Journal (2009) 28, 1916-1925. doi:10.1038/emboj.2009.152; Published online 4 June 2009