You infect human epithelial cells in culture with either nonpathogenic bacteria or Vibrio cholerae, each without any further treatment, in the presence of MDC (an inhibitor of clathrin-dependent endocytosis) or in the presence of filipin (an inhibitor of a clathrin-independent endocytic pathway). You then measure the intracellular concentration of cyclic AMP (in picomoles per milligram of total cell protein) and summarize the results in the following table. Which row (1 or 2) do you think corresponds to infection with V. cholerae? From these results, does cholera toxin enter the cell in clathrin-coated vesicles?

Question

Quizplus · Accepted Answer

Cholera toxin increases intracellular cAMP concentration through the ADP-ribosylation and activation of a Gs subunit that activates adenylyl cyclase, as shown in row 2 in the table. From the results obtained in the presence of the drugs, the toxin appears to show this effect in a clathrin-independent manner.

You Infect Human Epithelial Cells in Culture with Either Nonpathogenic