Serotonin transporter whose primary function in the central nervous system involves the regulation of serotonergic signaling via transport of serotonin molecules from the synaptic cleft back into the pre-synaptic terminal for re-utilization. Plays a key role in mediating regulation of the availability of serotonin to other receptors of serotonergic systems. Terminates the action of serotonin and recycles it in a sodium-dependent manner (By similarity). Monomer or homooligomer (By similarity). Interacts (via C-terminus) with SCAMP2; the interaction is direct and retains transporter molecules intracellularly. Interacts with filamentous actin and STX1A (By similarity). Interacts with SEC23A, SEC24C and PATJ. Interacts with NOS1; the interaction may diminish the cell surface localization of SERT in the brain and, correspondingly, reduce serotonin reuptake. Interacts with TGFB1I1 (By similarity). Interacts with ITGAV:ITGB3 (By similarity). Could be part of recycling endosomes. Density of transporter molecules on the plasma membrane is itself regulated by STX1A. Density of transporter molecules on the plasma membrane is also regulated by serotonin (By similarity). Density of transporter molecules seems to be modulated by ITGAV:ITGB3 (By similarity). Phosphorylation at Thr-276 increases 5-HT uptake and is required for cGMP-mediated SERT regulation. This protein is the target of psychomotor stimulants such as amphetamines or cocaine. Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family. SLC6A4 subfamily.