Lecture 10 - Mitochondria 4 Flashcards
What are the differences between apoptosis and necrosis?
Apoptosis: Active requires energy and RNA and protein synthesis Characteristic morphological features DNA cleaved and chromatin condenses Formation of apoptotic body. Cleared by phagocytosis No inflammation
Necrosis: Passive cell death cells swell up and burst (conents leak out.) Nucleus disintegrates Cell ghosts Inflammation
What is the effect of UV light on cyt c?
Cytochrome C shown to disperse through cell in response to UV light
What causes cyt c release? (in general terms)
Cytochrome C released in response to a range of pro-death stimuli.
What anchors cyt c in the inner membrane?
A lipid anchor known as cardiolipin is believed to promote the localisation of cyt c to the inner membrane
What are the types of Bcl-2 family proteins?
Anti-apoptotic (Bcl-2, Bcl-w, Bcl-xL)
Pro-apoptotic (Bax, Bak, Bok)
BH3-only (Bid, Bim, Bad)
What kind of proteins are the pro and anti apoptotic Bcl-2 proteins?
C-tail anchored proteins in outer membrane of mitochondria.
What domains do anti apoptotic Bcl-2 proteins have?
Anti-apoptotic Bcl-2 proteins have 4 BH domains and a transmembrane domain. They are C-tail anchored proteins.
What domains do pro apoptotic Bcl-2 proteins have?
Pro-apoptotic Bcl-2 proteins have 3 BH domains and a transmembrane domain. These are C-tail anchored proteins
What are the domains found in BH3 proteins?
BH3 proteins have 1 BH3 domain. These proteins regulate function of anti and pro apoptotic pathway.
What are the pathways for apoptosis?
Intrinsic: from within the cell apoptosis is induced
Extrinsic: From outside of the cell apoptosis is induced
What happens when BH3 is activated?
activation of BH3 results in either inhibition of anti-apoptotic proteins or inhibition of pro-apoptotic proteins
What is the point of no return of apoptosis?
Mitochondrial Outer Membrane Permeabilization
What happens during MOMP?
Cytochrome C is released from the mitochondria, apoptosome is formed and caspase 3 is released resulting in cell death
Where do the Bcl-2 proteins perform their function?
Efforts of the Bcl-2 family converge at the level of the mitochondrial outer membrane. where they protect against or initiate MOMP
What is the function of Bax? Where is it localized when inactive?
During apoptosis Bax changes conformation and enters the mirochondrial outer membrane by exposing a mitochondrial targetting signal. This induces cyt c release. This signal is at the C-terminus and is an alpha helix.
What is Bak and where is it located?
Bak is located at the mitochondrial outer membrane. In non-apoptotic cells it is inactive but becomes active in response to separation from VDAC2.
What is the function of VDAC2 relative to Bak?
VDAC2 is a beta barrel proteins and it inhibits bak activation in healthy cells. (cross-link between VDAC2 and Bak showed a 65 kDa on an SDS gel.)
What is the function of the VDAC proteins? What types are there?
3 VDACs in human mitochondria and they all assist in diffusion of molecules across the outer membrane.
When is Bak2 formed from Bak1?
Bak2 formation occurs in mitochondria without VDAC2
How is Apaf-1 activated?
cyt c activates apaf1 exposing the CARD domain. CARD domain assembles with other CARD domains to form an oligomer (7 apaf1 molecules) apoptosome which interacts with procaspase-9 and leaves it to form caspase 9 leading to caspase cascade lading to apoptosis.
What are the domains of the Apaf1 molecule?
CARD (CAspase Recriutment Domain)
NBD ( Nucleotide Binding Domain which hydrolyses ATP)
HD (conserved Helical Domain)
WHD (Winged Helix Domain)
WD40 repeats form the beta propellar structure and also bind the cytochrome C. These repeats contain 40 amino acids composed of aspartic acid and tryptophan residues
How are caspases regulated?
Caspases are synthesized as proenzymes and then are activated soon after.
What is the difference between initiator and effector caspases?
Initiator caspases: Cleave inactive pro-forms of effector caspases.
Effector caspases cleave cellular substrates.
What is the function of SMAC/DIABLO?
SMAC/DIABLO can bind and inhibit cytosolic inhibitors of caspases. PRO APOPTOTIC
What is the function of Omi/HtrA2?
serine protease within IMS when released from mitochondria it binds to IAPs (cytosolic inhibitors of caspases)
What are the functions of Endo G and AIF?
Cleave DNA in the nucleus.
AIF is caspase independent.
