Oncogenes and apoptosis Flashcards
Apoptosis
- physiological cell death
- leads to removal of cells that are:
- redundant
- damaged
- obsolete
- harmful
redundant
ex- in developing nervous system, an excess of cells is first produced. Then those that fail to make contact with their targets are removed
“use it or lose it”
damaged
ex -cells with DNA damage beyond repair are removed to protect organism as a whole
obsolete
ex- in maintenance of liver tissue, where old cells are replaced with new cells, while keeping size of organ constant
harmful
ex- cytotoxic T-lymphocytes, which are removed to prevent excessive tissue damage in inflammation
What can alteration in apoptosis play a role in?
- development of cancer
- autoimmune diseases
- neurodegenerative disorders
Homeostatis
rates of mitosis and apoptosis are balanced in homeostasis
neoplasia
- rate of mitosis too high or apoptosis too low
- accumulation of cells
degeneration
- rate of mitosis too low or apoptosis too high
- decrease of cells
Description of Apoptosis process
- cell shrinking
- breakdown of cell into apoptotic bodeis w/ intact plasma membranes
- phagocytosis by neighboring cells
- NO inflammation
Description of Necrosis
- cell swelling
- breakdown of plasma membrane w/ outflow of cell contents
- cell lysis
- WITH inflammation
Death Triggers
- lack of survival factors, growth hormone, or hormones
- programmed cell death
- DNA damage
- death receptors
- Ca2+ overload, oxidative stress
Integration stage
- Death receptor pathway via caspase 8
- mitochondrial pathway via caspase 9
Execution
- activation of execution caspases 3,6, and 7
- leads to activation of proteases that cleave cytoskeleton and endonucleases that cleave DNA
- fragmentation into apoptotic bodies that bear “eat me” signals
Clean-up
phagocytosis of apoptotic bodies by marcophages and/ or neighboring cells
