The C-terminal region of serotonin transporter is important for its trafficking and glycosylation.
We investigated the effects of brefeldin A and ilimaquinone, inhibitors of membrane trafficking, using serotonin transporter (SERT)-expressing COS-7 cells. Both drugs significantly inhibited the serotonin uptake activity of SERT and caused SERT to be retained in the endoplasmic reticulum (ER), indicating that membrane trafficking is an important factor for SERT functional regulation. In agreement with previous reports, a C-terminal-deletion mutant of SERT (SERTDeltaCT) mostly localized to the ER and completely lacked serotonin uptake activity. To further elucidate the role of the C-terminus of SERT, we investigated whether overexpression of FLAG-tagged SERT C-terminus (FLAG-SERT-CT) affected the serotonin uptake activity and glycosylation of SERT. Interestingly, when concomitantly expressed with full-length FLAG-SERT in COS-7 cells, FLAG-SERT-CT increased the serotonin uptake activity and mature glycosylation of FLAG-SERT. These results indicate that the C-terminal region of SERT plays a crucial role in the functional regulation of SERT via membrane trafficking and glycosylation. In addition, proteasome inhibitors induced apparent ER stress, significantly decreased the serotonin uptake activity and mature glycosylation of SERT and caused SERT to be localized to the ER, suggesting that SERT function would be attenuated via membrane trafficking in pathological states that trigger ER stress.
Nobukuni
Mariko
M
Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551, Japan.
Mochizuki
Hideki
H
Okada
Satoshi
S
Kameyama
Nobuhisa
N
Tanaka
Anna
A
Yamamoto
Hikaru
H
Amano
Taku
T
Seki
Takahiro
T
Sakai
Norio
N
D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D020126:Brefeldin A / Q000494:pharmacology; D019556:COS Cells; D002522:Chlorocebus aethiops; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D006031:Glycosylation; D007976:Leupeptins / Q000494:pharmacology; D049990:Membrane Transport Modulators / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics*; D011809:Quinones / Q000494:pharmacology; D017384:Sequence Deletion; D012701:Serotonin / Q000378:metabolism; D050486:Serotonin Plasma Membrane Transport Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D012717:Sesquiterpenes / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014162:Transfection
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D049990:Membrane Transport Modulators; D011809:Quinones; D050486:Serotonin Plasma Membrane Transport Proteins; D012717:Sesquiterpenes; C063261:acetylleucyl-leucyl-norleucinal; C067713:lactacystin; D020126:Brefeldin A; D012701:Serotonin; C467077:ilimaquinone; D000111:Acetylcysteine