Mechanisms of Inhibiton

Question 1

What inhibitors do endothelial cells release?

Answer 1

NO and PGI2

Question 2

What enzyme degrades ADP?

Answer 2

Ecto-ADPase (CD39)

Question 3

What enzymes synthesize cAMP & cGMP?

Answer 3

AC - cAMP
GC - cGMP

Question 4

What do AC and GC use to make cAMP & cGMP?

Answer 4

AC uses ATP
GC uses GTP

Question 5

What enzyme degrades cAMP & cGMP?

Answer 5

Phosphodiesterase

Question 6

What activities determine cyclic nucleotide levels?

Answer 6

Balance of AC/GC and PDE

Question 7

What signalling is adenylyl cyclase linked to?

Answer 7

GPCR signalling

Question 8

What does NO allow for with guanylyl cyclase?

Answer 8

Skips ligand receptor step - enters cell directly

Question 9

What is AC stimulated by?

Answer 9

Gs-G-protein after binding to PGI2

Question 10

What is GC stimulated by?

Answer 10

NO

Question 11

Which PDE is specific for cAMP?

Answer 11

PDE 2 & 3

Question 12

Which PDE is cGMP specific?

Answer 12

PDE5

Question 13

How does cGMP elevate cAMP levels?

Answer 13

Inhibits PDE3 - allows more cAMP to survive

Question 14

How does cGMP decrease cGMP levels (-ve feedback loop)?

Answer 14

Stimulates PDE5

Question 15

What do mutations in sGC lead to?

Answer 15

Reduced cGMP production -> increases risk for myocardial infarction & coronary artery disease

Question 16

What are the targets for cAMP?

Answer 16

PKA

Question 17

What are the targets for cGMP?

Answer 17

PKG

Question 18

What are AKAP and GKAP?

Answer 18

PKA/PKG anchoring proteins that direct PKA & PKG to specific subcellular compartments

Question 19

What is the role of PKA & PKG?

Answer 19

Phosphorylation of multiple substrate proteins -> regulation of signaling & actin dynamics -> platelet inhibition

Question 20

What do the inhibitory pathways not interact with?

Answer 20

Integrin or granule release

Question 21

What do PKA & PKG add to serine & threonine residues?

Answer 21

-vely charged phosphate groups to substrate proteins

Question 22

What does phosphate addition cause?

Answer 22

changes the function of substrate proteins by facilitating and/or blocking binding of regulatory proteins

Question 23

What is the inactive form of RAP?

Answer 23

RAPGDP
RAP1GAP2 turns RAP off

Question 24

What protein turns Gq signalling off?

Answer 24

RGS18

Question 25

Which protein inhibits RGS18 & RAP1GAP2 during platelet activation?

Answer 25

14-3-3

Question 26

What does phosphorylation of RGS18 & RAP1GAP2 cause?

Answer 26

14-3-3 detaches and RGS18 & RAP1GAP2 becomes active

Question 27

What does the phosphorylation of CD-GEF1 cause?

Answer 27

Blocks GEF activity -> RAP1 not turned on

Question 28

How does ADP help block inhibitory pathways during platelet activation?

Answer 28

By stopping cAMP synthesis

Question 29

What is the mechanism that ADP uses to reduce cAMP levels

Answer 29

P2Y12 receptor for ADP is coupled to Gi Gi inhibits adenylate cyclase cAMP levels are reduced

Question 30

What antibody is used as a marker for P2Y12 activity?

Answer 30

Antibody-based detection of VASP phosphorylation