Apoptosis
Intrinsic pathway
Initiation- withdrawal of growth factors or IL-2, increased levels of oxidants, damage to DNA, death
activators such as TNF-α, lymphotoxin (TNF-β) and Fas ligand (FasL) (intracellular stress signals) -
Accumulation of p53 = PUMA (The p53 upregulated modulator of apoptosis)
Permeability of OMM - following pro-apoptotic treatment of accumulated stress, by promoting the
expression (or activation) of BH3 only proteins - BH3-only proteins bind to and inhibit the anti-
apoptotic BCL-2 proteins eg. bad, bim, bid, noxa, PUMA (PUMA inhibits Bcl2 repertoire) and pro-
apoptotic proteins are activated to permeabilise the OMM through the process of MOMP in which
pro-apoptotic Bcl-2 proteins are recruited to OMM – BAX/BAK (BH123 proteins) oligomerise to form
pores in the OMM facilitating the release of cytochrome C.
Apaf1/Caspase activation – cytochrome C activates Apaf-1 by hydrolyses of bound dATP to dADP.
Apaf-1 undergoes a conformational change allowing it to bind to pro-caspase 9 via CARD (caspase
recruitment domain) forms an apoptosome of Apaf-1 – pro-caspase 9 is recruited and activated –
caspase 9 cleaves and thereby activates executioner pro-caspases.
Caspases (cysteine proteases) cleave the cytoskeleton and activate DNAses and other enzymesDNA
breaks into 50- to 300-kilobase pieces; further broken into multiples of 200 base pairs by
endonucleases (Ca++ and Mg++)- demonstrated as a “ladder pattern” on agarose gel; also proteases.
Phosphatidylserine is exposed and attracts macrophages with little “collateral damage”.
Caspases cleave cytoskeletal and nuclear matrix proteins and result in DNA cleavage into fragments
giving “DNA Ladder pattern” by agarose gel electrophoresis
,
Intrinsic pathway
Initiation- withdrawal of growth factors or IL-2, increased levels of oxidants, damage to DNA, death
activators such as TNF-α, lymphotoxin (TNF-β) and Fas ligand (FasL) (intracellular stress signals) -
Accumulation of p53 = PUMA (The p53 upregulated modulator of apoptosis)
Permeability of OMM - following pro-apoptotic treatment of accumulated stress, by promoting the
expression (or activation) of BH3 only proteins - BH3-only proteins bind to and inhibit the anti-
apoptotic BCL-2 proteins eg. bad, bim, bid, noxa, PUMA (PUMA inhibits Bcl2 repertoire) and pro-
apoptotic proteins are activated to permeabilise the OMM through the process of MOMP in which
pro-apoptotic Bcl-2 proteins are recruited to OMM – BAX/BAK (BH123 proteins) oligomerise to form
pores in the OMM facilitating the release of cytochrome C.
Apaf1/Caspase activation – cytochrome C activates Apaf-1 by hydrolyses of bound dATP to dADP.
Apaf-1 undergoes a conformational change allowing it to bind to pro-caspase 9 via CARD (caspase
recruitment domain) forms an apoptosome of Apaf-1 – pro-caspase 9 is recruited and activated –
caspase 9 cleaves and thereby activates executioner pro-caspases.
Caspases (cysteine proteases) cleave the cytoskeleton and activate DNAses and other enzymesDNA
breaks into 50- to 300-kilobase pieces; further broken into multiples of 200 base pairs by
endonucleases (Ca++ and Mg++)- demonstrated as a “ladder pattern” on agarose gel; also proteases.
Phosphatidylserine is exposed and attracts macrophages with little “collateral damage”.
Caspases cleave cytoskeletal and nuclear matrix proteins and result in DNA cleavage into fragments
giving “DNA Ladder pattern” by agarose gel electrophoresis
,
