Exam 4 Lecture 3: Cribbs Apoptosis Flashcards
Apoptosis is a process of ________
It’s more tidy than necrosis, where cells explode and essentially _______
During apoptosis, cell membranes are_____
Apoptosis is a process of controlled/programmed cell death
It’s more tidy than necrosis, where cells explode and spill their contents into the interstitial space, which can cause a chain reaction of cell death in neighboring cells
During apoptosis, cell membranes are kept intact
Apoptosis gets rid of unwanted cells.
Cells may be eliminated as part of the sculpting anatomy during _______.
Example: tadpole to frog and newt
Apoptosis gets rids of unwanted cells
Cells may be eliminated as part of the sculpting anatomy during animal development.
Explain how TUNEL labeling can help visualize apoptosis
During apoptosis, endonucleases get into the nucleus and will start to break up DNA. THe TUNEL label will put a fluorescent label on the DNA nick
Therefore, one can visualize cells undergoing cell death and see the nicked DNA start to fall apart from each other
Top Hat Question:
What feature of apoptosis allows for visualization of cells undergoing cell death by TUNEL labeling?
Exposed ends of DNA strand by endonuclease nicking
Explain DNA laddering
DNA laddering is also a characteristic marker of apoptosis.
It takes advantage of the same process as TUNEL labeling. DNA is cut by endonucleases between the nucelosomes, creating fragments of consistent size. The DNA can then be run on a gel.
How do macrophages recognize apoptotic cells in order to know what to attack?
Also, how does this process help apoptosis from happening rather than necrosis?
Phosphatidylserine is usually on inner leaflet of PM, but it flips to the outer PM during apoptosis.
PS is kind of like an “eat me” signal. Researches can label this PS with an annexin.
PS also blocks inflammatory pathways. If macrophages attack bacteria, they release inflammatory cytokines, but not if they are enguling apoptotic cells.
Apoptosis depends on a proteolytic cascade mediated by ______.
Cleavage of inhibitory domains activates the proteolytic activity of the ____ in a ____ feedback style called a _________.
Apoptosis depends on proteolytic cascade mediated by caspases.
Cleavage of inhibitory domains activates the proteolytic activity of the caspase in a positive feedback cycle called a caspase cascade.
Once the first caspase is activated by something cleaving its inhibitory signal, it becomes the “initator caspase” that can then activate other caspases that become “executioner caspases” that then go on to cleave other targets like cytosolic proteins or nuclear lamins.
The extrinsic pathway of apoptosis is mediated by ______.
Explain the extrinisic pathway in detail
The extrinsic pathway of apoptosis is mediated by Fas death receptors.
Killer lymphocytes bind to cells and activate the Death Receptor. Occupied death receptors recruit the death-inducing signaling complex (DISC)
How do the endonucleases get activated that start cleaving the DNA during apoptosis?
An executioner caspase cleaves iCAD (the inhibitor of CAD), therby activating CAD (caspase activated DNAse).
active cad then goes on to cleave DNA into fragments
The intrinsic pathway of apoptosis depends on the release of ________
Explain how that mechanism works.
The intrinsic pathway of apoptosis depends on the release of mitochondrial proteins into the cytoplasm.
Cytochrome C (member of ETC) then binds to a procaspase-activating adaptor protein called Apaf1, which organizes itself into an apotosome by ATP hydrolysis. Once the apoptosome is formd, it recruits procaspase 9 and cleaves it, activating the caspase cascade.
What the exclusive features of the extrinsic pathway vs the intrinsic pathway?
What are common elements of both
Extrinsic Pathway: FAS Death Receptor, FADD Adaptor Protein, DISC complex
Intrinsic Pathway: Cyct C release, ApaF1 activation, Apoptosome
Common Elements: Organization of Procaspases, Caspase Signaling Cascade, Executioner Caspases Attack Targets.
Apoptosis is a highly regulated process. Altered regulation of it can contribute to various diseases:
Increased Apoptosis Can lead to:
1.
2.
Decreased apoptosis can be a factor in:
1.
Increased Apoptosis Can Lead To:
- Autoimmune diseases like AIDS
- Neurodegenerative diseases like Alzhiemers and Parkinsons’s
Decreased Apoptosis can be a factor in CANCER
________ are key regulators of the intrinsic pathway for apoptosis
Antiapoptotic:
Pro-Apoptotic
BCL2 family of proteins are key regulators of apoptosis
Anti-apoptotic: Bcl-2, Bcl-X1 (prevent release of cytochrome c)
Pro-apoptotic: Bax, Bac (enhance the release of cyt c)
BH3- only proteins are also pro-apoptotic
Tophat:
What is a unique hallmark of the intrinsic pathway (that can be detected visually)?
Release of cytochrome c from mitochondria
What unique feature does the extrinsic pathway rely on to initiate apoptosis?
Activation of the death receptor by enviornmental signal
