Fifty cells were examined for colocalization of vimentin and SERT following 5HT stimulation. In all YFP-SERT transfected cells, a limited but consistent co-localization between vimentin and SERT on the plasma Homatropine Bromide membrane was seen. The colocalization of endogenously expressed vimentin and transiently expressed SERT was monitored in 5HT-stimulated CHO- cells using IF microscopy. The cellular distribution of vimentin was significantly different in 5HTstimulated cells than in control cells. To facilitate a comparison between the localization of SERT and vimentin, the SERT signal was pseudocolored in green in merged images. 5HT stimulation mostly located vimentin around the plasma membrane. Exposure of CHO-YFP-hSERT to 5-HT induced the spatial reorientation of vimentin filaments. In control cells, vimentin exhibited a curved filamentous appearance. Vimentin filaments became more straight and bundled 30 min after stimulation with 100 mM 5HT. To evaluate the association of vimentin and the Atropine sulfate truncated and mutant transporters on the plasma membrane, the second half of the same biotinylated samples were subjected to immunoblot analysis with vimentin-Ab. In untransfected cells our W/ B analysis recognized the endogenous vimentin as one of the proteins pulled by the biotinylated plasma membrane-bound proteins. Therefore, it is clear that vimentin had bound other plasma membrane proteins as well as SERT. In SERT transfected cells, the level of vimentin on the plasma membrane was much higher than the untransfected ones. This finding identifies SERT as one of the membrane-bound proteins that links vimentin to the plasma membrane. Similarly, the levels of vimentin on the plasma membrane of D26, D20, D14, and DDD transfected cells were the same as that on the plasma membrane of untransfected cells. This finding suggests a lack of association between vimentin and D26, D20, D14, or DDD on the plasma membrane. On the other hand, the vimentinbinding abilities of T616D and T613D on the plasma membrane were very similar to CHO-SERT and CHO-D6 cells. The levels of vimentin on the plasma membrane of S611D transfected cells was lower than that in wild-type transfected cells but higher than that in untransfected ones. These findings are in good 
agreement with the data in Figure 6. Collectively, they support our hypothesis that the density of transporter on the plasma membrane.