Stennicke H R, Jürgensmeier J M, Shin H, Deveraux Q, Wolf B B, Yang X, Zhou Q, Ellerby H M, Ellerby L M, Bredesen D, Green D R, Reed J C, Froelich C J, Salvesen G S
The Program for Apoptosis & Cell Death Research, The Burnham Institute, La Jolla, California 92037, USA.
J Biol Chem. 1998 Oct 16;273(42):27084-90. doi: 10.1074/jbc.273.42.27084.
The apoptotic signal triggered by ligation of members of the death receptor family is promoted by sequential activation of caspase zymogens. We show here that in a purified system, the initiator caspases-8 and -10 directly process the executioner pro-caspase-3 with activation rates (kcat/Km) of 8.7 x 10(5) and 2.8 x 10(5) M-1 s-1, respectively. These rates are of sufficient magnitude to indicate direct processing in vivo. Differentially processed forms of caspase-3 that accumulate during its activation have similar rates of activation, activities, and specificities. The pattern and rate of caspase-8 induced activation of pro-caspase-3 in cytosolic extracts was the same as in a purified system. Moreover, immunodepletion of a putative intermediary in the pathway to activation, pro-caspase-9, was without consequence. Taken together these data demonstrate that the initiator caspase-8 can directly activate pro-caspase-3 without the requirement for an accelerator. The in vitro data thus help to deconvolute previous in vivo transfection studies which have debated the role of a direct versus indirect transmission of the apoptotic signal generated by ligation of death receptors.
死亡受体家族成员的连接所触发的凋亡信号是由半胱天冬酶原的顺序激活所促进的。我们在此表明，在一个纯化系统中，起始半胱天冬酶-8和-10直接加工执行性半胱天冬酶原-3，其激活速率（kcat/Km）分别为8.7×10⁵和2.8×10⁵ M⁻¹ s⁻¹。这些速率足以表明在体内的直接加工。在半胱天冬酶-3激活过程中积累的不同加工形式具有相似的激活速率、活性和特异性。半胱天冬酶-8在胞质提取物中诱导半胱天冬酶原-3激活的模式和速率与在纯化系统中相同。此外，对激活途径中假定的中间体半胱天冬酶原-9进行免疫去除没有影响。综合这些数据表明，起始半胱天冬酶-8可以直接激活半胱天冬酶原-3，而无需加速器。因此，体外数据有助于对先前的体内转染研究进行解卷积，这些研究曾对死亡受体连接产生的凋亡信号的直接与间接传递作用进行过争论。
