Pro-caspase-3 is a major physiologic target of caspase-8.
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.
The Program for Apoptosis & Cell Death Research, The Burnham Institute, La Jolla, California 92037, USA.
H R
HR
Stennicke
J M
JM
Jürgensmeier
H
H
Shin
Q
Q
Deveraux
B B
BB
Wolf
X
X
Yang
Q
Q
Zhou
H M
HM
Ellerby
L M
LM
Ellerby
D
D
Bredesen
D R
DR
Green
J C
JC
Reed
C J
CJ
Froelich
G S
GS
Salvesen
D017209:Apoptosis; D053455:Caspase 10; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D053804:Granzymes; D007700:Kinetics; D008954:Models, Biological; D011499:Protein Processing, Post-Translational; D012697:Serine Endopeptidases / Q000378:metabolism; D015398:Signal Transduction
D004792:Enzyme Precursors; D053804:Granzymes; D012697:Serine Endopeptidases; D053455:Caspase 10; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases