Which facilitates the association of SERT with an intermediate filament, vimentin. Recent investigations indicate a system of Danshensu phosphorylation for SERT that incorporates two phases of phosphorylation. The first phase of phosphorylation is said to affect the serine residues, whereas the second phase involves the threonine residues. It is suggested that the first phase of phosphorylation causes the transporters to shut down, and the second phase of phosphorylation tags the proteins for internalization via the SERT recycling mechanism. According to the biphasic model, a S611D construct should shut down the uptake ability of the transporter while the DD construct should demonstrate a reduced or Butenafine hydrochloride eliminated 5HT uptake capacity due to its intracellular localization. Indeed, our data agree with the study by Jayanthi et al., who reported that S611D reduces transport capacity by,39%, whereas DD demonstrates an uptake capacity of,16%. On the basis of our findings, we hypothesize that the blunted activity of S611D may be due to additional serine residues that play a role in reducing the uptake capacity of SERT. A finding that was not consistent with the biphasic theory was the localization of S611D, which is mainly found at intracellular locations. In summary, in an endogenous platelet system and in heterologous expression systems, our studies demonstrate that vimentin associates with SERT. The last 20 amino acids from the C-terminus of SERT are required and are at least one of the binding-domain of vimentin. SERT becomes a bridge between vimentin and the plasma membrane. At physiological plasma 5HT levels, vimentin-SERT association was found at intracellular locations and on the plasma membrane. However, when plasma 5HT level was higher than physiological level, their association was enhanced and the level of SERT on the plasma membrane was decreased. Therefore, we hypothesize that SERT utilizes the vimentin network during translocation from the plasma membrane. Furthermore, the 5HT-dependent phosphorylation of vimentin on the S56 residue accelerates the translocation of SERT on the 5HT-altered vimentin network. Future analysis of these mutants in stable transfection systems, as well as continued experiments with the phospho-mimicking mutants presented here, will further reveal the mechanism of action that governs transporter C-terminal phosphorylation.