1. Supplementary Figure 1 A. B.

2. Supplementary Figure 1. The immobile fraction of GFP-Gαs was also increased with (A) chronic but not (B) acute desipramine and escitalopram treatment. Chronic R-citalopram had no effect on immobile fraction. Data were analyzed by one-way ANOVA followed by Tukey test for post hoc multiple comparisons of means (control versus treatment, *p < 0.05, ** p < 0.01, *** p < 0.001, ****p < ). Error bars represent SEM.

3. Supplementary Figure 2

4. Supplementary Figure 2. Immobile fraction and half-time to recovery are independent measures of GFP-Gαs diffusion. C6 glioma cells stably expressing GFP-Gαs were cultured in phenol-red free DMEM after three days of 10 μM escitalopram treatment and membrane regions were rapidly photobleached. Half-time to recovery and immobile fraction were calculated using a one-phase association fit of the intensity as it recovered from photobleaching. While both values were significantly different from each between A) control and B) escitalopram, they were not associated with each other.

5. Supplementary Table 1

6. Supplementary Table 1. Not all antidepressants affect the extent of GFP-Gαs recovery. FRAP experiments were performed as above but with various additional antidepressants. Unlike half-time to recovery, the immobile fraction is not significantly different in all treatment conditions.

7. Supplementary Table 2

8. Supplementary Table 2. Cytosolic and isoproterenol stimulated GFP-Gαs diffuse faster than inactivated membrane GFP-Gαs. See figure 4 for experimental details.

9. Supplementary Table 3

10. Supplementary Table 3. Mutant C3S is more mobile than wild-type GFP-Gαs. See figure 4 for experimental details.

11. Supplementary Table 4

12. Supplementary Table 4. Fluorescent proteins diffuse at different speeds depending on their membrane association. See figure 4 for experimental details.

13. Supplementary Table 5

14. Supplementary Table 5. Immobile fraction varies among fluorescent fusion proteins. See figure 4 for experimental details.