Module 12: Apoptosis Flashcards
What is necrosis?
Necrosis is a form of uncontrolled cell death, caused by external damage (injury, oxygen starvation, energy depletion), leading to cell swelling, membrane rupture and inflammation.
What is apoptosis?
Apoptosis is programmed cell death involving a regulated process that leads to cell dismantling without causing inflammation or immune response. Controlled by gene expression
What are common reasons for apoptosis?
Development, tissue homeostasis, DNA damage, infection, immune regulation, and removal of damaged or dangerous cells.
What is the morphology of apoptotic cells?
Cell shrinkage, chromatin condensation, membrane blebbing, apoptotic body formation, and intact membranes. Engulfed by surrounding cells.
What is Caspase-activated DNase (CAD)?
An enzyme activated by caspases that cleaves DNA during apoptosis, causing characteristic DNA fragmentation of 180 bp long.
Can identify multiples of 200 bp on a gel, and confirm apoptotic events.
What is the TUNEL Assay used for?
Detecting DNA fragmentation during apoptosis by labeling broken DNA ends.
Tdt-mediated dUTP Nicked End Labeling
Tdt = terminal deoxynucleotide transferase
Used to add Br-dUTP which can be labeled with antibodies and flurophores
What is Annexin V used for?
Binding to phosphatidylserine exposed on the outer leaflet of the plasma membrane during early apoptosis.
Coupled with propidium iodide (PI).
What is an initiator caspase?
A caspase that begins the apoptotic signaling cascade (caspase-8, caspase-9). Pairs of caspases dimerization and self-activate through transproteolysis.
What is a caspase?
Cysteine-Aspartice proteases.A family of proteases that play a central role in initiating and executing apoptosis.
What is an executioner caspase?
A caspase that cleaves cellular targets, leading to apoptosis (caspase-3, caspase-7). Activated by an initiator caspase.
What is the C. elegans mitochondrial death pathway?
A conserved apoptotic pathway involving the proteins ced-9, ced-4, ced-3 and egl-1 in the nematode C. elegans. Egl-1 -> ced-9 -> ced-4 -> ced-3.
What are ced-9, ced-4, ced-3 and egl-1?
Key proteins in the C. elegans apoptotic pathway were egl-1 inhibits ced-9, allowing ced-4 to activate ced-3, initiating cell death. Ced-9 is anti-apoptotic, ced-3, ced-4 and egl-1 are pro-apoptotic.
What is the mammalian mitochondrial death pathway?
An intrinsic apoptotic pathway triggered by mitochondrial damage, leading to cytochrome c release and apoptosome formation.
What is cytochrome c’s role in apoptosis?
It is released from the mitochondrial during apoptosis and helps form the apoptosome by binding Apaf-1.
What is Apaf-1 with CARD?
Apaf-1 is a protein with a CARD domain that binds to cytochrome c, recruiting caspase-9 to form the apoptosome.
What is caspase-9?
An initiator caspase activated within the apoptosome that triggers downstream executioner caspases such as caspase-3 and caspase-7.
What is the apoptosome?
A multiprotein complex that activates caspase-9, initiating the intrinsic apoptotic pathway. It is composed of cytochrome c and Apaf-1 with CARD domain.
What is the Bcl2 protein family?
A family of proteins regulating apoptosis through pro-apoptotic and anti-apoptotic members. Work to regulate the release of cytochrome c.
3 classes: anti-apoptotic Bcl2 members, pro-apoptotic effector Bcl2 members, pro-apoptotic BH3-only members.
What are BH1-BH4 domains?
Structural domains in Bcl2 family proteins involved in protein-protein interactions that regulate apoptosis. BH4 domains are only found in anti-apoptotic members.
What are anti-apoptotic Bcl2 and BclXL proteins?
Proteins that inhibit apoptosis by blocking pro-apoptotic proteins like Bax and Bak. Active as dimers.
More dimers = anti-apoptosis by binding anti-apoptotic proteins.
What are pro-apoptotic Bak and Bax proteins?
Proteins that promote apoptosis by forming pores in the mitochondrial membrane, promoting the release of cyt c. Contain BH1-BH3 domains.
Bax is active as a dimer. Cell damage induces Bax to translocate to the mitochondrial membrane and aggregate.
Bak always bound to outer mitochondrial membrane.
What are pro-apoptotic Bad, Bim and Puma?
Proteins that promote apoptosis by inhibiting anti-apoptotic Bcl2 family members. Only contain the BH3 domain.
What are the effects of Bcl2 family dimerization?
The balance of dimerization between pro- and anti-apoptotic members determines whether a cell survives or undergoes apoptosis.
What is the death receptor pathway?
An intrinsic apoptotic pathway activated by death receptors like FasR binding to FasL. Initiated by an external signal that binds to the extracellular domain on a receptor.
