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
Apoptosis involves both dimerization and trimerization. Why?
Ensures this is actually the pathway we want to complete
pronto-oncogene
genes that code for signaling molecules that are involved in the regulation of cell growth and prevention of apoptosis
oncogenes
- mutated and/or overexpressed proto-oncogenes
- cause cancer
- arise spontaneously or are introduced by retro-viruses
tumor suppressor genes
genes that signaling molecules involved in the suppression of growth
T/F Transformed cells will stop growing when they come in contact with neighboring cells.
False.
Normal cells will stop when in contact with neighboring cells. Transformed cells do NOT stop when contact with neighboring cells is made.
Reverse Transcriptase (RT)
- found in retroviruses
- makes DNA from an RNA template
