Lecture 22: Apoptosis Flashcards
What is apoptosis?
Programmed cell death
What is tissue homeostasis?
Maintaining a balance between proliferation and cell death
What are some ways apoptosis is used in the body?
Nervous system to match the number of nerve cells to target cells
Immune system in clonal selection
What are some features of normal homeostasis?
Responsible of elimination of cells in embryonic development
Cell turnover in healthy adult tissues
Physiological involution and atrophy of tissues
What are some features of pathological apoptosis?
Can be triggered by tissues
Spontaneous in untreated cancer
Contributes to chemotherapy induced tumour regression
How does the intrinsic apoptosis pathway occur?
Using internal stress
How does the extrinsic apoptosis pathway occur?
Using external signals
What is the process of cytochrome c release in the intrinsic apoptosis pathway?
- CC released from mitochondria into cytosol
- Membrane asymmetry lost so internal marker externalised
- Membrane integrity lost so DNA dye enters cell
What is the process of downstream events and caspase activation in the intrinsic apoptosis pathway?
- Cytochrome release
- Apoptosome assembly
- Caspase activation
- Proteolysis of substrates
- DNA digestion
What is the main premise of upstream events in intrinsic apoptosis?
Controlling the pore
What do pro death factors aim to do in intrinsic apoptosis?
Open the pore
What do pro survival factors aim to do in intrinsic apoptosis?
Keep pore closed
What is the Bcl-xL inhibitor?
It suppresses the pro survival function
The pore is more likely to stay open
What does the Bcl-xL inhibitor do in relation to chemotherapy?
It sensitises cancer cells to taxol-induced apoptosis
What is the process of elimination of T cells recognising self antigens? (EXTRINSIC)
- T cells recognising self antigens must be eliminated
- T cell binds to APC expressing self and FasL is expressed
- FasL binds to Fas receptor
- Apoptosis
