anti-apoptotic Bcl2 family proteins

Proteins (e.g., Bcl2, BclXL) on the cytosolic surface of the outer mitochondrial membrane that bind and inhibit pro-apoptotic Bcl2 family proteins and thereby help prevent inappropriate activation of the intrinsic pathway of apoptosis.

anti-IAP

Produced in response to various apoptotic stimuli and, by binding to IAPs and preventing their binding to a caspase, neutralize the inhibition of apoptosis provided by IAPs.

Apaf1

Adaptor protein of the intrinsic apoptotic pathway; on binding cytochrome c, oligomerizes to form an apoptosome.

apoptosis

Form of programmed cell death, in which a "suicide" program is activated within an animal cell, leading to rapid cell death mediated by intracellular proteolytic enzymes called caspases.

apoptosome

Heptamer of Apaf1 proteins that forms on activation of the intrinsic apoptotic pathway; it recruits and activates initiator caspases that subsequently activate downstream executioner caspases to induce apoptosis.

Bak

A main effector Bcl2 family protein of the intrinsic pathway of apoptosis in mammalian cells that is bound to the mitochondrial outer membrane even in the absence of an apoptotic signal; activation is usually by activated pro-apoptotic BH3-only proteins.

Bax

A main effector Bcl2 family protein of the intrinsic pathway of apoptosis in mammalian cells; located mainly in the cytosol and translocates to the mitochondria only after activation, usually by activated pro-apoptotic BH3-only proteins.

Bcl2

Anti-apoptotic Bcl2 family protein of the outer mitochondrial membrane that binds and inhibits pro-apoptotic Bcl2 family proteins and prevents inappropriate activation of the intrinsic pathway of apoptosis.

Bcl2 family

Family of intracellular proteins that either promote or inhibit apoptosis by regulating the release of cytochrome c and other mitochondrial proteins from the intermembrane space into the cytosol.

BclXL

Anti-apoptotic Bcl2 family protein of the outer mitochondrial membrane that binds and inhibits pro-apoptotic Bcl2 family proteins and prevents inappropriate activation of the intrinsic pathway of apoptosis.

BH3-only proteins

The largest subclass of Bcl2 family proteins. Produced or activated in response to an apoptotic stimulus and promote apoptosis mainly by inhibiting anti-apoptotic Bcl2 family proteins.

caspase

Intracellular protease that is involved in mediating the intracellular events of apoptosis.

cytochrome c

Soluble component of the mitochondrial electron-transport chain. Its release into the cytosol from the mitochondrial intermembrane space also initiates apoptosis. (Figure 14-26)

death receptor

Transmembrane receptor protein that can signal the cell to undergo apoptosis when it binds its extracellular ligand. (Figure 18-5)

death-inducing signaling complex (DISC)

Activation complex in which initiator caspases interact and are activated following binding of extracellular ligands to cell-surface death receptors in the extrinsic pathway of apoptosis.

effector Bcl2 family proteins

Pro-apoptotic proteins of the intrinsic pathway of apoptosis that in response to an apoptotic stimulus become activated and aggregate to form oligomers in the mitochondrial outer membrane, inducing the release of cytochrome c and other intermembrane prote

executioner caspases

Apoptotic caspases that catalyze the widespread cleavage events during apoptosis that kill the cell.

extrinsic pathway

Pathway of apoptosis triggered by extracellular signal proteins binding to cell-surface death receptors.

Fas (Fas protein, Fas death receptor)

Transmembrane death receptor that initiates apoptosis when it binds its extracellular ligand (Fas ligand). (Figure 18-5)

Fas ligand

Ligand that activates the cell-surface death receptor, Fas, triggering the extrinsic pathway of apoptosis.

inhibitors of apoptosis (IAPs)

Intracellular protein inhibitors of apoptosis.

initiator caspases

Apoptotic caspases that begin the apoptotic process, activating the executioner caspases.

intrinsic pathway (mitochondrial pathway)

Pathway of apoptosis activated from inside the cell in response to stress or developmental signals; depends on the release into the cytosol of mitochondrial proteins normally resident in the mitochondrial intermembrane space.

programmed cell death

A form of cell death in which a cell kills itself by activating an intracellular death program.

survival factor

Extracellular signal that promotes cell survival by inhibiting apoptosis. (Figure 18-12)