05 - Lecture Flashcards
(21 cards)
Basic idea of what GPCR does?
passes on a signal from outside of the cell by producing a second messenger inside the cell
What is an example of a second messenger?
cAMP
What is the second messenger in the Adenylate cyclase system?
cAMP
What is the second messenger in the Calcium/phosphatidylinositol system?
IP3, DAG, Ca2+
What do second messengers do? and examples of second messenger?
They start a cascade of intracellular events resulting in a response
- cAMP, IP3, DAG, Ca2+, NO, cGMP
Another name for G-protein coupled receptors?
Heptahelical receptors (7)
What is the first messenger and what does it do?
Hormone, neurotransmitter, cytokine and it binds to the heptahelical receptor (G protein receptor) and interacts with a Heterotrimeric G-protein (can have GDP or GTP)
Is the GDP state active or inactive?
Inactive and the GTP form is active
Alpha one adrenergic receptor
At the end activates protein kinase C
- Gaq
Beta adrenergic receptor
Activation of protein kinase A
- Gas
Alpha two adrenergic receptor
Reduces of protein kinase A
- Gai
7 steps of the adenylate cyclase system…
1) Epinephrine binds to the receptor
2) Activates GDP by turning into GTP
3) Gs (alpha subunit) moves to adenylyl cyclase and activates it
4) Adenylyl cyclase catalyzes the formation of cAMP
5) PKA is activated by cAMP
6) Phosphorylation of cellular proteins by PKA causes the cellular response to epinephrine
7) cAMP is degraded reversing the activation of PKA
What has its on intrinsic off switch?
Ga subunit has its own off switch
Inactive vs active PKA?
Inactive: has regulatory subunits and catalytic subunits
Active: cAMP binds to regulatory subunits and free catalytic subunits
Cholera toxin?
Doesn’t allows the GTP mechanism to work. So it is just continuously active
What system is the cholera toxin working through?
Beta adrenergic receptor - Gas
More cAMP
What system is the pertussis toxin working through?
Alpha two adrenergic receptor - Gai
More cAMP
Second messengers of alpha one adrenergic receptor?
Inositol Tris-phosphate, Diacylglycerol, Ca
What cleaves the glycerol and the polar head group?
The glycerol and polar head group are cleaved by phospholipase C
What is the name of the alpha subunit is alpha one adrenergic receptor?
Gq
Steps of alpha one adrenergic receptor?
1) Ligand binds to G protein receptor
2) The Gq alpha subunit kicks off GDP and brings in GTP
3) The Gq alpha subunit binds to phospholipase c and becomes active
4) Phospholipase C finds and clips PIP2, releasing inositol tris-phosphate (water soluble)
5) The inositol Tris-phosphate goes to the endomembranes and causes the release of Ca
