title: The C-terminus is critical for the functional expression of the human serotonin transporter.
abstract: The plasma membrane serotonin transporter (SERT) has an important role in terminating serotonergic neurotransmission by re-uptake of 5-HT from the synaptic cleft. The expression of SERT on the cell surface is therefore a critical factor. In this study, we examined the role of the carboxyl terminus of SERT in trafficking to the plasma membrane. 5-HT uptake activity was used to measure the effects of systematic deletions or alanine substitutions in the C-terminus. We found that deletion of 16 amino acids in the distal C-terminus had no effect on uptake activity, whereas further deletion was detrimental for the function of SERT. Cell surface biotinylation was used to determine the role of the C-terminus in localization and trafficking. We showed that the C-terminus is crucial for the delivery of SERT to the plasma membrane and that the deletion of this part of the transporter results in a lack of mature glycosylation and impaired trafficking to the plasma membrane. Furthermore, the C-terminally truncated mutants were shown to have a dominant negative effect on wild-type SERT uptake activity.
authors.affiliation: Centre for Basic Psychiatric Research, Aarhus Psychiatric University Hospital, Risskov, Denmark.
authors.forename: Mads Breum
authors.initials: MB
authors.lastname: Larsen
authors.forename: Anja Winther
authors.initials: AW
authors.lastname: Fjorback
authors.forename: Ove
authors.initials: O
authors.lastname: Wiborg
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000235:genetics / Q000502:physiology; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002522:Chlorocebus aethiops / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017354:Point Mutation / Q000502:physiology; D012680:Sensitivity and Specificity; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D050486:Serotonin Plasma Membrane Transport Proteins