Journal
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH
Volume 1823, Issue 10, Pages 1825-1840Publisher
ELSEVIER
DOI: 10.1016/j.bbamcr.2012.07.003
Keywords
Apoptosis; Caspase cascade; FRET; Mathematical model; Positive-feedback loop
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Funding
- Japan Society for the Promotion of Science [13GS0008]
- Grants-in-Aid for Scientific Research [22310127, 20113007] Funding Source: KAKEN
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Caspase-8 (CASP8) is a cysteine protease that plays a pivotal role in the extrinsic apoptotic signaling pathway via death receptors. The kinetics, dynamics, and selectivity with which the pathway transmits apoptotic signals to downstream molecules upon CASP8 activation are not fully understood. We have developed a system for using high-sensitivity FRET-based biosensors to monitor the protease activity of CASP8 and its downstream effector, caspase-3, in living single cells. Using this system, we systematically investigated the caspase cascade by regulating the magnitude of extrinsic signals received by the cell. Furthermore, we determined the molar concentration of five caspases and Bid required for hierarchical transmission of apoptotic signals in a HeLa cell. Based on these quantitative experimental data, we validated a mathematical model suitable for estimation of the kinetics and dynamics of caspases, which predicts the minimal concentration of CASP8 required to act as an initiator. Consequently, we found that less than 1% of the total CASP8 proteins are sufficient to set the apoptotic program in motion if activated. Taken together, our findings demonstrate the precise cascade of CASP8-mediated apoptotic signals through the extrinsic pathway. (C) 2012 Elsevier BM. All rights reserved.
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