Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Structure. 2013 Feb 5;21(2):277-89. doi: 10.1016/j.str.2012.12.011. Epub 2013 Jan 17.
Dysregulation of apoptosis is associated with several human diseases. The main apoptotic mediators are caspases, which propagate death signals to downstream targets. Executioner caspase-3 is responsible for the majority of cleavage events and its therapeutic potential is of high interest with to date several available active site peptide inhibitors. These molecules inhibit caspase-3, but also homologous caspases. Here, we describe caspase-3 specific inhibitors D3.4 and D3.8, which have been selected from a library of designed ankyrin repeat proteins (DARPins). The crystal structures of D3.4 and mutants thereof show how high specificity and inhibition is achieved. They also show similarities in the binding mode with that of the natural caspase inhibitor XIAP (X-linked inhibitor of apoptosis). The kinetic data reveal a competitive inhibition mechanism. D3.4 is specific for caspase-3 and does not bind the highly homologous caspase-7. D3.4 therefore is an excellent tool to define the precise role of caspase-3 in the various apoptotic pathways.
细胞凋亡的失调与多种人类疾病有关。主要的凋亡介质是半胱天冬酶，它将死亡信号传递给下游靶标。执行者 caspase-3 负责大多数切割事件，其治疗潜力很高，目前已有几种可用的活性位点肽抑制剂。这些分子抑制 caspase-3，但也抑制同源的半胱天冬酶。在这里，我们描述了 caspase-3 特异性抑制剂 D3.4 和 D3.8，它们是从设计的锚蛋白重复蛋白（DARPins）文库中筛选出来的。D3.4 及其突变体的晶体结构显示了如何实现高特异性和抑制性。它们与天然 caspase 抑制剂 XIAP（凋亡抑制蛋白 X 连锁抑制剂）的结合模式也有相似之处。动力学数据揭示了竞争性抑制机制。D3.4 特异性结合 caspase-3，不结合高度同源的 caspase-7。因此，D3.4 是定义 caspase-3 在各种凋亡途径中精确作用的极好工具。
