Programmed Cell Death

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

Executioner caspases

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

Intrinsic apoptosis cues

Balance of signals between anti-apoptotic factors and pro-apoptotic factors

Extrinsic apoptosis cues

Fas ligands on killer lymphocyte; Fas death receptor in target cell (related to tumor necrosis factor receptor); receptor tyrosine kinase signaling

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

Fas ligand

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

Intrinsic 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

Extrinsic pathway

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

Destruction proteins

Perform functions such as digesting proteins and DNA in a dying cell

Killer proteins

Required for a cell to begin the apoptotic process

Engulfment proteins

Required for phagocytosis of the dying cell by another cell

Cytochrome c

Soluble component of the mitochondrial electron-transport chain; its release into the cytosol from the mitochondrial intermembrane space also initiates apoptosis

T/F: Apoptosis is promoted by the release of cytochrome c from the mitochondria

True

Programmed cell death occurs ______________.

by means of an intracellular suicide program.

Apoptosis differs from necrosis in that necrosis _____________.

causes cells to swell and burst, whereas apoptotic cells shrink and condense.

Apoptosis

"Clean" cell death; DNA fragments; large vacuoles form in cytoplasm; cytoplasm collapses; cells shrink

Necrosis

"Explosive" cell death; membrane becomes dilated; cell swells; cells explode

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

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

Apoptosis and necrosis are both forms of programmed cell death. Which one of these is likely to be the mechanism for cell death in a normal developing tissue? Why?

Necrosis