Week 13 Flashcards
Growth Factors
stimulate an increase in cell mass (stimulate cell growth) by promoting the synthesis of proteins and other macromolecules and by inhibiting their degradation
Explain how extracellular signals inhibit tissue growth.
Extracellular factors can act as a growth factor or mitogens which help ensure that cells maintain their appropriate size when they proliferate.
PI3K
promotes cell growth because it promotes the synthesis of proteins and inhibits their degradation
TOR
sensors that promote protein synthesis, lipids, and autophagy
Akt
stimulate cell growth and proliferation through mTORC1
Define the roles of cyclins and cyclin dependent kinases.
- Progression through checkpoints of the cell cycle are controlled by cyclin-dependent kinases (Cdks) –They allow progress through the cell cycle by phosphorylating other proteins.
They exhibit enzymatic activity
-oscillates up and down during the cell cycle.
Cell cycle control system
- Events take place in a set sequence; each process must be completed before the next one begins.
how cyclins and Cdks vary in concentration
- Cdk function can be regulated by proteolysis and phosphorylation
- Cdks function is further regulated by other stimulating or inhibiting factors.
How do cdks trigger different events
- Cyclin Cdk will turn on when dephosphorylated
- Cyclin Cdk will turn off when phosphorylated.
how Cdk inhibitors can help regulate progression through the cell cycle
- Inhibitors can block the assembly or action of some cyclin-CDK complexes
Review how mitogens stimulate cell division
- Mitogens (like cytokines and some hormones) and Growth factors stimulate cell division primarily by disrupting intracellular negative controls that otherwise block progress through the cell cycle. Thus, they stimulate cell proliferation (# of cells)
- One way in which mitogens stimulate cell proliferation is by inhibiting the function of an Rb protein (an inhibitor of entry to the cell cycle).
Hippo Pathway
The Hippo pathway consists of a large network of proteins that control the growth of different tissues during development, regeneration as well as pathological states such as cancer.
* Activation of hippo pathway help inhibit cell proliferation and promote cell death.
* Decreased activity of the hippo pathway results in abnormal organ size in mammals and flies.
promote cell growth and survival activate PI-3-kinase signaling pathways.
- By phosphorylating inositol phospholipids
– PI3K module promotes cell growth because it promotes the synthesis of proteins and inhibits their degradation.
Rb blocks cell proliferation and how mitogens reverse this inhibition
- Rb binds to transcription regulators and prevents them from turning on the genes required for proliferation.
- E.g. If smads activates, then p15 will activate. This will inhibit CDK4 which allows Rb to activate. Rb will inhibit E2Fs from doing any changes in gene expression therefore, no proliferation.
how Akt promotes cell survival via Bad
- Active Akt will phosphorylate Bad which will release active BcI2. BcI2 is an anti-apoptotic family protein.
