You are interested in cell size regulation and discover that signaling through a

Question

You are interested in cell size regulation and discover that signaling through an enzyme-coupled receptor is important for the growth (enlargement) of mouse liver cells. Activation of the receptor activates adenylyl cyclase, which ultimately leads to the activation of PKA. which then phosphory lates a transcription factor called TFS. This phosphorylation is necessary for TFS to activate the transcription of a gene that is important for liver cell growth. You find that liver cells lacking the receptor are 15% smaller tlian normal cells. where as cells that express a constitutively activated version of pKA aic 15% larger than normal liver cells. Given these results, predict whether you would expect the cell's size to bo bigger or smaller than normal cells if cells were treated in the following fashion. Explain your answer. You create a version of the receptor that is constitutively active You add a drug that inhibits adenylyl cyclase. You add a drug that increases the activity of cyclic AMP phosphodiester.

Explanation / Answer

If a receptor is constitutively active then the liver would be larger than normal due to continuous activation of signalling.

If a drug that inhibits adneyly cyclase is added , activation of PKA is inhibited which inturn inhibits the signalling pathway, thus leading to smaller liver size.

If a drug that increaases the activity of the phosphodiesterase is added, cAMPis not broken down, more cAMP remain in the cell , thus leading to activation of the signalling pathway and larger liver size

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