1A) What can you and your grad student mentor measure experimentally to examine

Question

1A) What can you and your grad student mentor measure experimentally to examine adenylyl cyclase activity upon treatment with ligand?

1B) Based on the above stated effects on adenylyl cyclase activity, what type of G-protein is activated by each receptor?

1. You're studying cellular signaling through G-Protein Coupled Receptors (GPCRs). Specifically you're working on a pair of newly identified GPCRs, GPCR-X and GPCR-Y. Each binds the same small ligand, but activates different heterotrimeric G-proteins that act on the effector protein, adenylyl cyclase. You have access to cells that express GPCR-X and NOT GPCR-Y, and other cells that express GPCR-Y and NOT GPCR-X. You and your grad student mentor find that the binding of ligand has opposite effects on adenylyl cyclase activity for each cell type. GPCR-X activation causes an increase in adenylyl cyclase activity, while GPCR-Y activation causes a decrease in adenylyl cyclase activity. A. (3pts) What can you and your grad student mentor measure experimentally to examine adenylyl cyclase activity upon treatment with ligand? B. (3ptsy) Based on the above stated effects on adenylyl oyclase activity, what type of G-protein is activated by each receptor?

Explanation / Answer

1. A) Adenylyl cyclase activity can be measured as the amount of cAMP produced, or as ATP and cAMP ratio. If the amount of cAMP is low, it means that adenylyl cyclase is not working efficiently, and vice versa. A ratio between ATP and cAMP will help in analyzing the direction of the reaction and checking the amount of ATP converted into cAMP.

1. B) GPCR-X activation causes an increase in adenylyl cyclase activity, which means the receptor is activated by G?s protein. On the other hand, GPCR-Y activation causes a decrease in adenylyl cyclase activity, which means the receptor is activated by G?i protein.

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