Mechanisms of Inhibiton Flashcards
What inhibitors do endothelial cells release?
NO and PGI2
What enzyme degrades ADP?
Ecto-ADPase (CD39)
What enzymes synthesize cAMP & cGMP?
AC - cAMP
GC - cGMP
What do AC and GC use to make cAMP & cGMP?
AC uses ATP
GC uses GTP
What enzyme degrades cAMP & cGMP?
Phosphodiesterase
What activities determine cyclic nucleotide levels?
Balance of AC/GC and PDE
What signalling is adenylyl cyclase linked to?
GPCR signalling
What does NO allow for with guanylyl cyclase?
Skips ligand receptor step - enters cell directly
What is AC stimulated by?
Gs-G-protein after binding to PGI2
What is GC stimulated by?
NO
Which PDE is specific for cAMP?
PDE 2 & 3
Which PDE is cGMP specific?
PDE5
How does cGMP elevate cAMP levels?
Inhibits PDE3 - allows more cAMP to survive
How does cGMP decrease cGMP levels (-ve feedback loop)?
Stimulates PDE5
What do mutations in sGC lead to?
Reduced cGMP production -> increases risk for myocardial infarction & coronary artery disease
What are the targets for cAMP?
PKA
What are the targets for cGMP?
PKG
What are AKAP and GKAP?
PKA/PKG anchoring proteins that direct PKA & PKG to specific subcellular compartments
What is the role of PKA & PKG?
Phosphorylation of multiple substrate proteins -> regulation of signaling & actin dynamics -> platelet inhibition
What do the inhibitory pathways not interact with?
Integrin or granule release
What do PKA & PKG add to serine & threonine residues?
-vely charged phosphate groups to substrate proteins
What does phosphate addition cause?
changes the function of substrate proteins by facilitating and/or blocking binding of regulatory proteins
What is the inactive form of RAP?
RAPGDP
RAP1GAP2 turns RAP off
What protein turns Gq signalling off?
RGS18
Which protein inhibits RGS18 & RAP1GAP2 during platelet activation?
14-3-3
What does phosphorylation of RGS18 & RAP1GAP2 cause?
14-3-3 detaches and RGS18 & RAP1GAP2 becomes active
What does the phosphorylation of CD-GEF1 cause?
Blocks GEF activity -> RAP1 not turned on
How does ADP help block inhibitory pathways during platelet activation?
By stopping cAMP synthesis
What is the mechanism that ADP uses to reduce cAMP levels
P2Y12 receptor for ADP is coupled to Gi
Gi inhibits adenylate cyclase
cAMP levels are reduced
What antibody is used as a marker for P2Y12 activity?
Antibody-based detection of VASP phosphorylation
