Effects of the Chemical Chaperone 4-Phenylbutylate on the Function of the Serotonin Transporter (SERT) Expressed in COS-7 Cells

Abstract

Abstract. The serotonin transporter (SERT) is involved in various psychiatric disorders, including depression and autism. Recently, chemical chaperones have been focused as potential therapeutic drugs that can improve endoplasmic reticulum (ER) stress-related pathology. In this study, we used SERT-transfected COS-7 cells to investigate whether 4-phenylbutylate (4-PBA), a chemical chaperone, affects the membrane trafficking and uptake activity of SERT. Treatment with 4-PBA for 24 h dose-dependently increased the uptake activity of SERT. In accordance with increased SERT activity, the expression of maturely glycosylated SERT was increased, while the expression of immaturely glycosylated SERT was decreased. This finding suggests that 4-PBA increased the functional SERT with mature glycosylation via accelerating its folding and trafficking. 4-PBA also increased the activity of the C-terminus-deleted mutant SERT (SERTCT), which was stacked in the ER, and decreased SERTCT-induced ER stress, further supporting the idea that 4-PBA acts as a chemical chaperone for SERT. Imaging studies showed that fluorescencelabeled SERT was gradually and significantly translocated to the plasma membrane by 4-PBA. These results suggest that 4-PBA and related drugs can potentially affect serotonergic neural transmission by functioning as chaperones, thereby providing a novel therapeutic approach for SERT-related diseases.[Supplementary materials: available only at http://dx

Molecular Basis of the Dominant Negative Effect of a Glycine Transporter 2 Mutation Associated with Hyperekplexia

“…Still, our data did indicate that PBA produces significant rescue in mild conditions that produce no toxic effects, both in COS7 cells and in cultured neurons. PBA increases GlyT2 transport activity and plasma membrane expression by fulfilling chaperone-like activity, as proven for other misfolded pathogenic proteins (44,51). PBA is an interesting compound because not only is it a chemical chaperone approved by the Food and Drug Administration for use in humans, but it can also pass across the bloodbrain barrier, and it has been implicated as a protective agent in neurodegenerative diseases involving ER stress (52).…”

4-Phenylbutyrate Attenuates the ER Stress Response and Cyclic AMP Accumulation in DYT1 Dystonia Cell Models

“…Several groups revealed that 4-PBA reverses the mislocalization and/or aggregation of the protein associated with human disease, including the ΔF508 cystic fibrosis transmembrane conductance regulator [47], mutant α1-antitrypsin [70]. In addition, 4-PBA improves the trafficking of the serotonin transporter (SERT) [71], by reversing the misfolded proteins and decreasing the protein folding load in the ER, therefore providing protective effects against ER stress. A previous study has shown that 4-PBA treatment decreases ER stress with regard to the following general ER stress markers: BiP, CHOP, activating transcription factor 4 (ATF4), as well as sXBP1 [56].…”

Endosomal system genetics and autism spectrum disorders: A literature review

“…The mechanism was postulated to be decreased trafficking to a functional position (Iwata et al, 2014). 4-phenylbutylate increased the trafficking of SERT in COS-7 cells, thus modulating its function and again lending credence to the endosomal system as a source for etiological and pharmacological intervention for ASDs (Fujiwara et al, 2013). Trafficking and cell surface expression dysfunction were also associated with SERT in ASDs in another study that used HeLa cells (Prasad et al, 2009).…”