Question

You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells?

(a) addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive

(b) addition of a drug that prevents GTP hydrolysis by Gα

(c) addition of a drug that activates adenylyl cyclase

(d) addition of a drug that mimics the ligand of ERC1

Answer 1

Adding a drug that prevents GTP hydrolysis by Gα would lead to smaller cells.

Step-by-step explanation:

In this case, adding a drug that prevents GTP hydrolysis by Gα would lead to smaller cells. The G protein downstream of ERC1 activates adenylyl cyclase, which then leads to the activation of PKA. By preventing GTP hydrolysis by Gα, the G protein would remain active for a longer period of time, resulting in increased activation of adenylyl cyclase and subsequent activation of PKA. Since cells lacking ERC1 are 15% smaller than normal cells, inhibiting GTP hydrolysis by Gα would mimic the absence of ERC1 and therefore lead to smaller cells.