1. You\'re studying cellular signaling through G-Protein Coupled Receptors (GPCR
ID: 267582 • Letter: 1
Question
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. (3pts) Based on the above stated effects on adenylyl cyclase activity, what type of G-protein is activated by each receptor?Explanation / Answer
Answer1.
Regulation of cyclic AMP responses needs to be studied. Changes in adenylyl cyclase activity affects the cAMP cascade of which it is a part. In certain cases, cAMP accumulation may also take place and this can all be assayed. Protein binding assay is generally used for cAMP measurement, followed by radioimmunoassay, for which the samples are generally acetylated.
Answer2.
GPCR-X, on binding to the protein causes increase in adenylyl cyclase activity. Therefore, this protein could be Gs , one of the G protein families (s= stimulator). This brings about direct stimulation of adenylyl cyclase, thus stimulating cAMP production from ATP, for its function as secondary messenger.
GPCR-Y, on binding to the protein causes decrease in adenylyl cyclase activity. Therefore, this protein could be GI , one of the G protein families (i= inhibitor). In this cAMP production is decreased due to inhibition of adenylyl cyclase and thus the protein kinase activity is also decreased.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.