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Updated: Jan 18, 2026

Author Spotlight: Expression and Purification of Human Solute Carrier Transporters Using Codon-Optimized Genes
Published on: September 29, 2023
Transcriptional regulation of solute carrier family 6 member 9 gene
Mami Kirii1,2, Yui Yoshida1, Shigeo Takashima3,4,5,6
1Graduate School of Natural Science and Technology, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
Background:
Since the endoplasmic reticulum (ER) stress response is found in almost all tissues, its regulation and downstream factors have been vigorously explored.
Methods And Results:
In this study, we performed a comprehensive microarray analysis of genes induced by tunicamycin (Tm) stimulation in the rat cardiac fibroblast cell line H9c2. Tm treatment induced a marked increase in solute carrier family 6 member 9, Slc6a9, mRNA as well as typical ER stress-inducible factors GADD153 and GRP78 mRNA. Slc6a9 mRNA in H9c2 cells was also increased by ER stress inducers thapsigargin (Tg) and brefeldin A (BFA) other than Tm. The effects of inhibitors on the ER-localized stress sensors IRE1, ATF6, and PERK were examined, and the PERK inhibitor GSK2606414 significantly suppressed Tm-induced Slc6a9 mRNA expression. Analysis of Slc6a9 mRNA expression in PERK and ATF4-deficient HEK293 cells established by genome editing showed that Slc6a9 mRNA expression by Tm was suppressed in these cells. Furthermore, the long variant of Slc6a9 mRNA was increased in Tm-treated HEK293, while the short variant was negligible. Analysis of the nucleotide sequence of the 5'-flanking region of the Slc6a9 gene revealed an ATF4-binding sequence in exon1 is highly conserved among many species. As expected, our luciferase reporter assay containing the ATF4 binding sequence near the transcription start site showed a marked increase in promoter activity upon Tm stimulation and ATF4 co-expression.
Conclusions:
The ATF4-binding sequence found near the transcription start site of the Slc6a9 gene is highly conserved among species and the element is functional in the PERK-ATF4 system. This study will help elucidate Slc6a9-mediated regulation of intracellular and extracellular amino acid homeostasis under pathophysiological conditions.
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