CELL BIOLOGY. For the article “β-Arrestin 1 down-regulation after insulin treatment is associated with supersensitization of β2 adrenergic receptor Gαs signaling in 3T3-L1 adipocytes,” by Christopher J. Hupfeld, Stephane Dalle, and Jerrold M. Olefsky, which appeared in number 1, January 7, 2003, of Proc. Natl. Acad. Sci. USA (100, 161–166; First Published December 30, 2002; 10.1073/pnas.0235674100), the vertical axis labels in Figs. 1 and 2 were not readable. The corrected figures appear below.
Figure 1.
Insulin enhances cAMP generation in response to isoproterenol. (A) 3T3-L1 adipocytes were incubated in serum-free media at 37°C with (dashed line) or without (solid line) 100 ng/ml insulin for 8 h. Isoproterenol (10 μM) was then added for the indicated time course at 37°C, and intracellular cAMP was determined by enzyme immunoassay, as described in Materials and Methods. Data are from a typical experiment done in triplicate wells ± SEM and are representative of three separate experiments. (B) 3T3-L1 adipocytes were incubated in serum-free media for 8 h. Where indicated, 100 ng/ml insulin was added for 15 min before isoproterenol treatment. Cells were then treated with 10 μM isoproterenol for 5 min at 37°C, and intracellular cAMP was determined by enzyme immunoassay, as described in Materials and Methods. Data are from a typical experiment done in triplicate wells ± SEM and are representative of three separate experiments.
Figure 2.
Insulin enhances cAMP generation in response to isoproterenol in desensitized cells. (A) 3T3-L1 adipocytes were incubated at 37°C in serum-free media with (dashed lines) or without (solid lines) 100 ng/ml insulin for 8 h. After this, cells were treated with 10 μM isoproterenol for 5 min at 37°C. Cells were then washed with PBS at 37°C and restimulated with a second 10 μM dose of isoproterenol for an additional 5 min at 37°C; intracellular cAMP was determined by enzyme immunoassay. (B) 3T3-L1 adipocytes were incubated at 37°C in serum-free media for 8 h in the presence (dashed lines) or absence (solid lines) of 100 ng/ml insulin. Forskolin was added for the final 5 min, and intracellular cAMP levels were determined by enzyme-linked immunoassay. Data are from typical experiments done in triplicate wells and are representative of three separate experiments.