Module 11 Flashcards
(19 cards)
What is apoptosis
Regulated cell death / suicide
How many cells die per day due to apoptosis
50 - 70 billion cells die/ day due to apoptosis
Over a year, equivalent to the mass of a human
When does apoptosis occur
All our lives, even during early development (you would think it was only division at that point, but no)
Digit sculpting via apoptosis (what assay)
- removing finger and toe webbing
Use a TUNEL assay
- DNA in apoptotic cells has breaks (nicks)
- Enzyme terminal deoxinucleotidal transferase incorporates fluorescent dUTP into the nicks
- Allows for detection in apoptotic cells
glow bright green
Frog metamorphosis has apoptosis stimulated by ______
an increase of thyroid hormone in the blood
- Similar to human fetus during embryonic development - tail loss
Development of the nervous system and apoptosis
- Up to ½ neurons produced undergo apoptosis
- Specifically during neuronal development, those with no/faulty synaptic connections are apoptosed (synaptic pruning)
- Also ensures matched # of nerve cells to # of target cells
Nervous system and BAD apoptosis (cellular degeneration)
3 examples
+ 1 muscle example
Alzheimer’s
- Neurons in the cerebral cortex and hippocampus die
Huntington’s
- Neurons in the striatum die
Parkinson’s
- Dopamine neurons in the substantia nigra die
Duchenne muscular dystrophy
2 ways cells die
- Necrosis
- Cells swell and release contents into surrounding tissues
- Can lead to infection - Apoptosis (programmed cell death)
- Regulated suicide
- Contained and recycled debris
- Disposal of cellular debris that does not damage the surrounding cells
3 steps of the apoptotic pathway (general)
Execution, engulfment, and clearance
Nomarski visualisation of apoptosis
Cell shrinks and undergoes “blebbing” → bulges appear
Apoptosis inside the cell (general)
- Mitochondria permeability changes and so proteins released, nucleus broken down, DNA and proteins being degraded
- Cell blebs shrink
- Cell breaks into vesicles of cell debris
- Reduces all components into reusable materials
Why is c elegans a good model system (what do we already know about it)
- Has 947 somatic cells in the adult worm due to a single fertilized zygotic cell
- Undergoes rounds of mitotic divisions
- 131 cells undergo apoptosis (we know which)
What are CEDs
cell death genes (required for apoptosis)
CED-1 gene (special)
- Loss of function mutation allows apoptosis but PREVENTS phagocytosis
- So you can identify the apoptotic cells
Nematode : mammal equivalents (apoptosis)
genes that code for proteins essential for apoptosis
EGL-1 : Bh3s Bid + Bim
Ced-9 : Bcl-2 (Controls Bax and Bak)
Ced-4 : Apaf 1
Ced-3 : caspase 9
Activation of the caspase holoenzyme: nematode and mammal
Nematode - CED 9 (function loss = all cells die)
- CED 9 inhibits apoptosis by binding to CED 4 dimers and keeping them inactive
- EGL-1 binding to CED 9 releases CED 4
- Then CED 4 joins CED 3 and forms the caspase holoenzyme
- Caspase activation
= apoptosis
Mammal - BCL 2
- Apoptotic signal “bad” is inactive while phosphorylated and bound to cytosolic protein 14-3-3
- Signalling pathways = dephosphorylation of bad = release from 14-3-3
- Can bind to Bcl-2 in outer mito membrane
- Activation of Bcl-2 = activation of Bax
Bax aggregation in membrane forms pores
- Increase membrane permeability
Releases proteins such as Cyt c = essential for apoptosome formation
BCL 2 in mammals
- Impacts permeability of the outer mito membrane
- Usually low permeability
- Inactivation = pores formed = apoptosis
Caspase holoenzyme known vs apoptosome
caspase in nematode
apoptosome in mammals
Trophic factors
- Prevent apoptosis and keep the cell alive
- Initiate kinase cascade that leads to phosphorylation of bad
- Remove trophic = dephosphorylation of bad = apoptosis
