Cell Signaling Quiz 5 Flashcards
Small molecules used in signaling properties
Could be used to amplify signal
Small nonproteinaceous molecules mediate signal due to their rapid synthesis and breakdown or release and sequestration
Examples of small signal molecules
IP3, Ca2+, DAG, acetylcholine, neurotransmitters, cAMP, cGMP, Phosphoinositides, eicosanoids (ej. prostaglandins), ceramide, sphingosine phosphate, nitric oxide
Regulation of cAMP/cGMP pathway
Pathway activates PKA
ATP is modified by adenyl cyclase which creates cAMP
cAMP is then modified by phosphodiesterase to create 5’ AMP (hydrolysis)
This hydrolysis reaction breaks the phosphodiester bond which inhibits PKA and therefore the pathway
Adenyl cyclase has normal regulation and phosphodiesterase in downregulated to prolong the pathway by having more cAMP in order to not use up all the ATP
Slidenafil
Drug that inhibits cGMP phosphodiesterase
Increases blood flow
This drug is needed when O2 levels are low
Therefore is used for mountain hikers because of the low O2 levels at high altitudes
How does cAMP interact with PKA?
Activates PKA by binding to r-subunits which then dissociates from c-subunits
The c-subunits are then active and will cause signal for the pathway
When are Ca2+ pumps activated?
They activate upon Ca2+ release from ER
There are calcium channels in the ER and the PM
How much Ca2+ is in the cytoplasm and the ER?
ER: 10^-3 M
Cytoplasm: 10^-7 (low asf)
EF-hand motif?
Binds Ca2+ and has 29 A.A.
These A.A.’s have oxygens in them which forms a pentagonal bipyramidal structure
Oxygens also provide a partial - charge which will capture Ca2+
What does calmodulin fo regarding calcium?
Intermeddling Ca2+ binding protein that binds 4x Ca2+ to activate it and then directly interacts with target due to conformational change when Ca2+ is bound
How is the PM key to regulation?
PUMPS!
Ca2+ pumps, ATP dependent pumps, Na+/Ca2+ exchange, NCKX
3 Na+ go in (with concentration gradient), 1 Ca2+ is pumped out
NCKX
This is the Na+/Ca2+ pump that depends on concentration gradient
4 Na+ in and 1K+ out!
ROS
Reactive Oxygen Species
O2, H2O2
RNS
Reactive Nitrogen Species
NO^., NO-, NO+
Properties of reactive NS and OS?
Are small
Can move easily from site of origin
Have a unique and defined effect
NO^. + H2O2 are uncharged and can diffuse through membranes
When was nitric oxide discovered?
In 1987 it was discovered as a endothelium derived release factor
Nitroglycerin was used to treat angina because it turns into nitric oxide
What are the effects of nitric oxide inhibitors?
Inhibitors result in brain/nervous system degradation
NO^. free radical, why?
Unpaired e- in valence shell
Reacts with many things to become nitrate or nitrite
Reacts with superoxide to make per oxynitrate
Reacts with glutathione to make S-nitroso glutathione (GNSO)
What is peroxynitrate
Highly reactive
Apoptosis or signaling
What is GNSO thought to be?
NO^. carrier for transport around the body
NO^. has a half life of 5-10 seconds
Therefore GNSO is needed to get NO^. from one place to another
How broad ranged could NO^. diffuse?
Not far
It is uncharged which means it could diffuse across membrane into neighboring cells
Therefore the effects are local but could involve diffusion to neighboring cells
Could also mean signal is brief as NO^. is converted to nitrate/nitrite
How do you make NO^.?
Nitric oxide synthesis
Steps of nitric oxide synthesis?
Arginine reacts with NADPH and O2 to make Hydroxy-arginine
Hydrixy-arginine reacts with 1/2 NADPH and O2 to make Citrolline and nitric acid
NOS
Family of enzymes that are responsible for deriving NO^.
In 1990 found in brain tissue first
Found to bind to calmodulin (calcium dependent maybe?)
bNOS
Brain
nNOS
Neuronal
eNOS
endothelial
macNOS
macrophages
Which NOS are always on?
eNOS and macNOS
iNOS
Another type of NOS found in macrophages
cytochrome P450 reductase
Transfers e- from NADH to cytochrome P450
What suggests Ca2+ induces NO^. species?
Calmodulin binding domain
What does Calmodulin bind in the absence of Ca2+?
iNOS
iNOS has P sites
Consensus sequences for P by PKC, RKK1, PKA and CaM-K
Are at CM when P, move away from each other
Therefore negative control
NO- function?
Is associated with guanylyl cyclase activity
High levels of cGMP
NOS leaves cell as NO^., goes to cell 2 and activates guanylyl cyclase
cGMP activates what?
Kinase, cGMP and 5’GMP which results in cellular effects
When viagra is taken, GTP phosphodiesterase is increased which exaggerates this pathway to increase blood flow and a boner
What is a side effects of viagra and why?
Blue vision, is caused because cGMP affects rod cells in the eye
ROS
O2-, H2O2
Change in NADPH production
2O2+NADPH–> 2O2- + NADP+ + H+
2O2- is the superoxide radical
2O2- + 2H+ –> H2O2 + O2
Spontaneous rxn. at low pH
Superoxide dismutases (SOD)
O2- causes biological oxidation in hydrophobic enviroment
Can H2O2 inactivate enzymes?
Yes
What happens when you mix O2- with H2O2?
O2- + H2O2 –> OH^. (hydroxyl radical) + OH- + O2
Hydroxyl radical
Most reactive in biochemical rxns.
DNA damage, lipid peroxidases (therefore compromised membranes), and destroys proteins
Ends up making O1/2 which does this too
NO^. + O2- =
OONO- (Incredibly reactive)
Why is OONO- needed?
Apoptosis
What pathways can be activated by ROS?
JAK/STAT pathways
Can activate MAPK (Proliferation and Differentiation pathways)
H2O2 and guanylyl cyclase
H2O2 can activate it
Phospholipase D is activated
Breaks apart inositol phospholipids
How can H2O2 change the environment of the cell?
Change conditions and therefore alter potential for redox reactions
For example:
glutathione + H2O2 –> unusable glutathione
Therefore H2O2 changes redox reactions by stopping metabolic pathways
