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Unformatted text preview: molecules (the extrinsic
pathway of apoptosis). Once activated,
caspase-8 can directly cleave and
activate effector caspases. In addition,
caspase-8 cleaves the BH3-only protein
Bid, which activates the intrinsic pathway of apoptosis, leading to caspase-9
activation. TNF TNF receptor Cytosol Adaptor Caspase-8
Bid activation Bid
Bak/Bax Mitochondrion Caspase-9
activation Effector caspase
activation portions of the receptors bind adaptor molecules that in turn bind caspase8. This leads to activation of caspase-8, which can then cleave and activate
downstream effector caspases. In some cells, caspase-8 activation and subsequent activation of caspases-3 and -7 is sufficient to induce apoptosis
directly. In other cells, however, amplification of the signal is needed. This
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CELL DEATH AND CELL RENEWAL results...
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