L25 Proliferation and Apoptosis Flashcards
What are the 7 steps in the morphological progression of Apoptosis?
- cell shrink + rounding + cytoskeleton breakdown
- chromatin condensation + forms pathes against nuclear envelope = pyknosis
- nuclear envelope is now discontinuous + DNA is fragmented = karyorrhexis
- nucleus breaks into chromatin bodies or due to degradation of DNa
- cell membrane buds = blebs
- cell breaks into vesicles = apoptotic bodies
- phagocytised by neighboring cells
what is the normal role of apoptosis?
- tissue remodeling (e.g. digit formation)
- destroying transitory organs/tissues (e.g. pro + mesonephros
- nervous system formation (50% of neurons die during development)
- female shedding inner lining of uterus during period
- immune system function (cell elim by T cell)
- tissue renewal
- protection
what is apoptosis important in protection from?
infected cells
immune system cells
cells with DNA damage
cancer cells
what are the 3 components to the apoptotic pathway?
- regulators
- adapters
- effectors (caspases)
what is the role of regulators?
proteins that act to inhibit apoptosis (BCL-2 and BCL-xl) or stimulate apoptosis (Bak and Bax)
what is the role of adapters?
proteins act by binding to procaspases –(proteolytic)–> caspases either directly or by causing procaspases to aggregate which results in self activation … (ApaF-1)
what is the role of effectors (caspases)?
proteases that stimulate apoptosis by targeting cellular components and enzymes like
- nuclear lamins (nuclear envelope)
- inhibit of caspase activated Dnase (causes DNA fragmentation)
- DNA repair enzymes
- cytoskeleton components
- other procaspases etc.
the intrinsic pathway wants to eliminate cells that are damaged because of?
genotoxic damage
mitochondrial damage
absence of GF
loss of substrate adhesion etc.
the intrinsic pathways involves the release of ______ from the _____
cytochrome C
mitochondria
cytochrome C form the mitochondria drives the formation of what?
apoptosome
what does the intrinsic pathway use for initiation of apoptosis?
Apaf-1 (apoptotic protease-activating factor 1)
caspase 9
caspase 2
in the intrinsic pathway, what does cellular and DNA damage activate?
protein kinases that phosphorylate and activate the tumor suppressor gene p53 (transcription factor)
in the intrinsic pathway, when p53 binds to DNA, what 2 things does that cause?
- transription of Bax
2. transcription of cell cycle inhibitor p21
what does a mutation of p53 lead to?
cancer
in the intrinsic pathway, the bad protein inserts into _____ and causes the release of_______
mitochondrial membrane
cytochrome C from mitochrondria
in the intrinsic pathway, what does cytochrome C bind to? what does this cause?
Apaf-1
agrgregates and binds procaspase = apoptosome complex
procaspases and cleaved to form?
active caspases (caspase 9 or 2)
what is the extrinsic death pathway responsible for eliminating? - 3 roles?
unwanted cells during development
termination of immune response
immunosurveillance
how is the extrinsic death pathway initiated and what does it use?
activation of members of TNF receptor family such as the Fas receptor
uses caspase 8 and 10
in the extrinsic death pathway, what cells express Fas Lon their cell surface?
killer lymphocytes
in the extrinsic death pathway, the killer lymphocyte binds to the target cell via?
the Fas death receptor
in the extrinsic death pathway, what does the binding of Fas L to the Fas death receptor recruit? How?
adaptors molecules via binding between the receptor “death domain” and adaptor death domain
in the extrinsic death pathway, how is the death inducing signaling complex (DISC) formed?
procaspase aggregates + “death effector domain” binding
in the extrinsic death pathway, what has to be cleaved to lead to apoptosis?
procaspases
what are the 3 proapoptotic Bcl-2 family members?
BID
BAX
BAK
how come the extrinsic pathway can also act through the mitochondria?
because the action of BID protein which is activated by caspase 8 which was used to initiate the extrinsic pathway…
what is the perforin/granzyme pathway activated in response to?
viral infected cells
in the perforin/granzyme pathway, what cells secrete perforin and granzymes?
cytotoxic T cell
in the perforin/granzyme pathway, what is the function of perforin?
forms pore in target cell
in the perforin/granzyme pathway, what is the mechanism of action of granzyme B?
enters cells and …
- activates caspase 10 by cleavage = inactivation of apoptotic inhibitors (stimulates apoptosis…)
- activates caspase 3 = stimulates apoptosis
what types of target do caspases want to target?
- apoptosis regulators - Bcl-2, Bax, procapsase
- cell adhesion molecules - catenins, cadherins
- cytoskeletal proteins - actin, keratins, tubulin
- nuclear structural proteins - lamins
many others - ER and golgi proteins, cell cycle proteins, proteins in DNA synthesis and repair, transcription and translation, cell receptors, kinases, pho sphatases, signaling molecules etc.
binds to extracellular survival factors can inhibit what? How?
apoptosis
binding of an extracellular signaling molecule to a cell surface receptor can activate signaling pathways that can result int eh activation/production of Bcl-2 (apoptotic inhibitor) and inactivation of Bad (proapoptotic protein)
what activates p53?
cellular and DNA damage
p53 facilitates expression of what?
cell cycle inhibitor p21
how can p53 induce apoptosis?
increasing expression of…
- pro-apoptotic Bcl-2 family members
- fas receptor (CD 95)
- IGFBP-3 (sequesters cell survival proteins like IGF1/2 away from receptors)
what are the 3 markers for apoptosis?
- caspase activated Dnase enzyme
- annexin 5 and phosphatidylserine
- caspase assay
it is commonly observed that cancer cell express high levels of ______ and low levels of ____
anti-apoptotic proteins = Bcl-2
pro-apoptotic cells = p53
what levels are increased in AD brains?
proapoptotic Bak and Bad protein levels increased
anti-apoptotic Bcl-2 and Bcl-xl increase maybe as a compensatory response in surviving neurons
