Enzyme-linked receptor: RTK is activated and will recruit Jak which then activates STAT.
STAT gets phosphorlated and will increase gene expression because STAT is a transcription factor - turn genes on
Cell Cycle: series of stages which ...
Cell Cycle: series of stages which lead to the cell
to divide; prepares the cell to divide
What are the checkpoints and what do they do?
Checkpoints to make sure all is well before it goes into synthesis and mitosis
G1 Checkpoint: (entering S) is the environment
G2 Checkpoint: (enter mitosis) is all the
DNA replicated or is any DNA damaged?
Checkpoint in Mitosis: checks if chromosomes
are properly aligned on the metaphase plate
What are the two pathways which come from the activation of the alpha subunit (GDP--> GTP) ?
signal molecule in receptor--> activate g protein --> alpha subunit -->
1) adenylyl cylase (ATP--> cAMP)
2) phospholipase C --> IP3 & DAG
gprotein/alpha/phospholipase C (inosital phospholipid) --> DAG --> what does it activate?
DAG plus Ca2+ activates PKC
These small hydrophobic extracellular signal molecules, can diffuse directly across the plasma membrane; activating intracellular proteins, which are usually either transcription regulators or enzymes.
steriods and Nitric Oxide
G-proteins-coupled receptors and enzyme-coupled receptors respond to extracellular signals by activating one or more intracellular singaling pathways
IP3 opens Ca2+ channels in the membrane of the ER, releasing a free flood of Ca2+ ions into the cytosol
Ca2+ itself = small intracellular messenger
What's up with DAG what does it activate
Ca2+ and DAG activate the PKC
rise in cAMP activates?
a rise in cyclic AMP activates PKA which
Enzyme-coupled receptors : RTK (receptor tyrosin kinases) which phosphorlates itself ...then this could go two ways: Name
Ras or Jak/STAT
Ras activates what
ras activates a three protein MAP-kinase signaling pathway
What controls the G1/S and G2 Checkpoint?
controlled by CDK's and cyclin
cyclin activate the CDK's
What controls the activity of CDK's?
1) presence of cyclin (high levels present to form CDK cyclin complex)
2) CDK will be phosphorlated which removes the inhibitor
M cyclin: cyclin that acts in G2 to trigger the entry of M-phase
M cyclin + CDK = M-CDK
Cyclins are activated by mitogens...what are those
Mitogens are growth factors which stimulate the pathway
(S-CDK) What does the pRb do:
S-CDK phosphorylates pRb --> releases E2F
E2F binds to specific genes which increase transcription
How does E2F get in the cell and what does it do?
S-CDK phosphoralates pRb --> release E2F -->
E2F enters nucleus and turns on genes (transcription)
S-CDK What does Cdc6 do?
Cdc6 is a part of the origin replication complex
S-CDK phosphorylates Cdc6 --> DNA replication and prevention of re-replication
S-CDK can be inhibited if DNA is damaged, what player does that involve?
S-CDK will be inhibited if DNA is damaged
DNA is damaged --> increase in p53 (transcription factor) --> binds to p21 gene
p21 will bind to S-CDK & inactivate it
What regulates the metaphase/anaphase checkpoint or transition of mitosis?
APC = Anaphase Promoting Complex
- cleavage of cohesions which will lead to ssiter chromatid seperation
- triggers destruction of M-cyclin and securin
M-CDK controls the G2 checkpoint and does what?
1) targets phosphorlation of lamins which the nuclear envelope
2) phosphoralats MAPs
If the cell recieves no mitogen (no growth factor), where does it go?
Compare and contrast necrosis and apoptosis
Both necrosis and apoptosis involve cell
Necrosis: death due to damage/external damage like a cut or wound
Apoptosis: stimulated by the cell/programmed cell death
- clean, neat, simply chewed up by immune system
What does the protein Bcl-2 family control and what does Bcl-2 (itself) do?
Bcl-2 family of proteins controls apoptosis BUT Bcl-2 (itself) inhibits apoptosis
What is the pathway for apoptosis?
(Starts with Bax/Bak)
Bax/Bak will lead to cytochromoe C release (mitochondria)
--> leads to the activation of caspases
What are caspases ? How do they stimulate apoptosis?
Caspases are protease which trigger a cascase of other caspases which will chew up the cell; an irreversible process which breaks down the nuclear lamina proteins
What factors stimulate cell divison?
The cell cycle is regulated by checkpoints, these checkpoints are composes of cyclin-CDK complexes which stimulate the passage
The phosphorylation of CDK will occur in response to ...
mitogens (growth factor)
Phosphorylation of pRb is by...
When the DNA damage occurs, P53 turns on what....
P53 turns on P21 which inhibits CDK
--> if there is no ablity to pass through the cell cycle --> G0