ph6 - Patricia Pepa OH: 11-11:50 Caf Roma Handout 6: GPCR...

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Patricia Pepa OH: 11-11:50 Café Roma Handout 6: GPCR Paths and Endocrine System I. G-protein coupled Adenylyl Cylase-cAMP system (fig6-11)     a. Has an on/off state:  i. When  GDP  is bound, it is in the OFF (on/off) state and the protein  is INACTIVE(active/inactive).  ii. When  GTP  is bound, it is in the ON (on/off) state the protein is  ACTIVE active/inactive.  b. There are two different types of G proteins:  i. G (s): α  INCREASES (increases/decreases) the cAMP inside the  cell by ACTIVATING activating/inhibiting) adenylyl cyclase ii. G (s):  α INHIBITS (activates/inhibits) adenylyl cyclase and  DECREASES (increases/decreases) the amount of cAMP inside  the cell.  c. Mechanism of pathway:  i. Adenylyl cyclase= enzyme that converts ATP to second messenger  cAMP ii. cAMP activates  PKA  which phosphorylates other intracellular  proteins in part of a signal cascade and leads to a cellular  response.  Question: A pharmaceutical company developed several drugs that interact with the  transduction system of a hormone whose receptor is coupled to Gs. For the following,  indicate whether the drug will increase or decrease the effects of the hormone, and  which step is affected:  A. Drug binds to the hormone binding site of the receptor, but doesn’t activate it:  B. Drug inhibits GTPase activity of Gs.  C. Drug inhibits adenylyl cyclase D. Drug inhibits protein kinase A E. Drug inhibits cAMP phosphodiesterase F. Drug inhibits Protein phosphatases d. What are ways to turn off signals in G-protein pathway?  1. Original signal (hormone or NT) is removed and metabolized away and returns  receptor to synaptic site and stops activating G-proteins.  2. G-protein GTPase: GTP + H2O  GDP + Pi. GDP form is inactive and turns off G  proteins.  3. Decrease the receptors by down regulation. 
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This note was uploaded on 03/21/2009 for the course BIPN 100 taught by Professor French during the Spring '07 term at UCSD.

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ph6 - Patricia Pepa OH: 11-11:50 Caf Roma Handout 6: GPCR...

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