Final Exam - Programmed Cell Death and Development Flashcards
What is a caspase?
a cysteine-dependent asparate-directed proteases
What is the function of a caspase?
degrade proteins to ensure cellular components are degraded in a controlled and regulated way
What are caspases important in?
development and throughout life to maintain homeostasis
What are the 2 classes of caspases?
initiator caspases and other
What is the function of an initiator capsase?
once activated, they produce a chain reaction (cascade-style chain of events) which activates executioner caspases
What do the executioner caspases do?
degrade cellular components which allow the morphological changes to the cell that result in apoptosis
What is the function of ‘other’ caspases?
they require a cysteine to be in the active site and will cleave the protein to an aspartic acid residue
Discuss the mechanisms of caspase activation.
- Initiator caspase starts out as separate, inactive monomers
- an apoptotic signal acts on adapter proteins, which celaves and dimerizes the initiator caspase
- the activated initiator caspase cleaves executioner caspase to activate it
- downsteam cleavage of other substrates (cascades)
- result is apoptosis
What is the extrinsic apoptosis pathway known as?
the death receptor pathway
What does the extrinsic pathway use for activation?
a ligand and a receptor
What is the extrinsic pathway mediated by?
T-cells
Describe an example of the Extrinsic pathway.
- Fas ligand on T-cell binds to Fas death receptor
- Formation of DISC(death-inducing signaling complex) on cell interior
- Activation of caspase 8
- Activationof executioner caspases
- apoptosis
What is the intrinsic apoptosis pathway activated by?
-intracellular factors which cause cytochrome C leakage into the cytoplasm from the mitochondria
What are the triggering factors of the intrinsic pathway?
- oxidative stress
- hypoxia
- nutrient deprivation
What happens when cytochrome C leaks?
- activation of cascade of various factors
- activation of a variety of caspases
- apoptosis
What does too little proliferation lead to?
microphthalmia
What are the side effects of microphthalmia?
‘small eye’ phenotype; can be genetic, infectious, and environmental
What does too much proliferation lead to?
double muscle phenotype
What happens with the double muscle phenotype?
myostatin inhibits proliferation for muscle to develop normally
What is special about belgian blue cattle?
they have more myocytes than normal
What is syndactyly?
the fusion of digits caused by the incomplete apoptosis of interdigital cells between developing digits
What is the role of apoptosis in survival?
target cells will get survival signals that inhibit apoptosis
Proliferation and apoptosis is needed for survival, what keeps them in check?
factors that inhibit and factors that stimulate
