Types of apoptosis: programmed cell death Flashcards
What is apoptosis?
Regulated programmed cell death
What are the 2 types of apoptosis?
Pathological, physiological
What happens to cell size in apoptosis?
Shrinkage
What happens to the nucleus in apoptosis?
Becomes fragmented
Give 2 ways in which apoptosis is different from necrosis?
Apoptosis doesn’t trigger inflammatory response
Apoptosis keeps membrane integrity intact
Are cell membranes affected in apoptosis?
Membranes remain intact
Why does apoptosis occur during the menstrual cycle?
Endometrium breakdown in response to hormone withdrawal
Give 2 reasons why lymphocytes undergo apoptosis in germinal centres?
They fail to express useful antigen receptors, or target ‘self’
How can genotoxic stress trigger apoptosis in 2 ways?
DNA repair mechanisms fail, so apoptosis occurs to prevent malignancy development
Dysfunctional p53 tumour suppressor gene causes DNA damage that triggers apoptosis
How can ER trigger apoptosis?
Misfolded proteins accumulate in ER, causing stress
What 3 stimuli trigger the intrinsic/mitochondrial pathway?
Cell injury, DNA damage, loss of hormone stimulation
In the intrinsic/mitochondrial pathway, what anti-apoptotic molecule is inactivated?
BCL-2
In the intrinsic/mitochondrial pathway, what does the inactivation of BCL-2 stimulate?
Cytochrome C leaks from inner mitochondrial matrix into cell cytoplasm
In the intrinsic/mitochondrial pathway, what does cytochrome C activate?
Initiator then executioner Caspases (proteases that break down cell proteins)
In the extrinsic/death receptor initiated pathway, what activates caspases?
FAS ligand binds to FAS death receptor on target cell
What kind of lymphocytes activate the extrinsic/death receptor initiated pathway?
Lymphocytes that respond to ‘self’
How can Tumour Necrosis Factor activate the extrinsic/death receptor initiated pathway?
TNF binds to TNF receptor on target cell
What molecule do viruses and normal cells produce that blocks apoptosis, and what specific molecule is blocked?
FLIP blocks enzyme pro-caspase 8
In apoptotic cells, how does the plasma membrane change so that it is recognised by macrophages?
Phosphatidylserine flips to face outwards
What do apoptotic cells secrete to recruit macrophages?
Soluble factors
What 2 substances coat/bind apoptotic cells to attract macrophages?
Coated by thrombospondin, bind to C1q
How are apoptotic bodies formed, and what do they become ligands of?
Form from cytoskeleton and nucleus after they are degraded by caspases, then become ligands of macrophage receptors
What receptor and protein interact in necroptosis?
TNF receptor, Receptor-Interacting Protein (RIP) kinase
Does necroptosis have similar features to apoptosis or necrosis?
Both
What is pyroptosis?
Cell death with fever/pyrexia, as it is a highly inflammatory form of apoptosis
What condition sometimes triggers pyroptosis?
Microbial infection which is associated with fever due to release of IL-2
Which cytosolic protein is activated in pyroptosis, which further activates caspases?
Inflammasome: danger-sensing protein
What kind of infection can cause cells to be killed directly by apoptosis as well as promoting an immune response?
Viral infection
When do T cells cause apoptosis?
Tumour, transplant rejection
When duct obstruction occurs, what cells undergo apoptosis?
Atrophic cells
