Characterization of the Basal Promoter Element of Human Organic Cation Transporter 2 Gene

Asaka, Jun-ichi; Takato, Tsuyoshi; Ogasawara, Kunio; Katsura, Toshiya; Inui, Ken Ichi

doi:10.1124/jpet.106.118695

Cited by 20 publications

(20 citation statements)

References 40 publications

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“…For example, basal transcription of the OCT2 and MATE1 genes was stimulated by upstream stimulating factor (USF) 1 and Sp1, respectively (3,12). Although hepatic expression of OCT1 was shown to be mediated by hepatocyte nuclear factor-4␣ (HNF-4␣) via two direct repeat (DR)-2 sites (19), the core promoter region and basal transcriptional mechanisms of OCT1 gene remain unclear.…”

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confidence: 98%

Regulation of basal core promoter activity of human organic cation transporter 1 (OCT1/SLC22A1)

Kajiwara¹,

Takato²,

Asaka³

et al. 2008

American Journal of Physiology-Gastrointestinal and Liver Physi

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Kajiwara M, Terada T, Asaka J, Aoki M, Katsura T, Ikai I, Inui K. Regulation of basal core promoter activity of human organic cation transporter 1 (OCT1/SLC22A1). Human organic cation transporter 1 (OCT1/SLC22A1) plays important roles in the hepatic uptake of cationic drugs. The functional characteristics of this transporter have been well evaluated, but molecular information regarding transcriptional regulation is limited. In the present study, therefore, we examined the gene regulation of OCT1 gene focusing on basal core expression. An ϳ2.5-kb fragment of the OCT1 promoter region was isolated, and promoter activity was measured by luciferase assay in the human liver cell lines Huh7 and HepG2. Deletion analysis suggested that the region spanning Ϫ141/Ϫ69 was essential for the basal core transcriptional activity and that this region contained the sequence of a cognate E-box (CACGTG). The E-box is known to be bound by the basal transcription factors, upstream stimulating factors (USFs), and the functional involvements of USF1 and USF2 were confirmed by a transactivation effect, a mutational analysis of the E-box, and an electrophoretic mobility shift assay. The transactivation effect of USFs on the OCT1 promoter was further stimulated by hepatocyte nuclear factor 4␣, a liver-enriched transcription factor. There were no polymorphisms in the proximal promoter region (about 400 bp) of OCT1 gene (n ϭ 109). These findings indicated that both USF1 and USF2 bind to an E-box sequence located in the OCT1 core promoter region and are required for the basal gene expression of this transporter.liver; E-box

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confidence: 98%

Regulation of basal core promoter activity of human organic cation transporter 1 (OCT1/SLC22A1)

Kajiwara¹,

Takato²,

Asaka³

et al. 2008

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…The OCT2 (-91/+23) and OAT3 (-926/+21) constructs have been previously described (Ogasawara et al 2006;Asaka et al 2007). Based on the human genomic sequence (accession number NT_007422), the 1,000-bp flanking region upstream of the transcription start site ) of the OCT2 gene was amplified by PCR using genomic DNA from specimens corresponding to the wild type and heterozygote for -578_-576delAAG.…”

Section: Preparation Of Reporter Constructsmentioning

confidence: 99%

“…The nucleotide sequences of these reporter constructs were confirmed using a multicapillary DNA sequencer RISA384 system (Shimadzu). The primers used in PCR amplification and the site-directed mutagenesis are listed in Table 2. Cell culture, transfection, and luciferase assay The American opossum kidney (OK) epithelial cell line and the porcine kidney (LLC-PK 1 ) epithelial cell line were cultured, as described previously (Ogasawara et al 2006;Asaka et al 2007). Transfection and the luciferase assay were also carried out as described previously (Ogasawara et al 2006;Asaka et al 2007).…”

Section: Preparation Of Reporter Constructsmentioning

confidence: 99%

“…In the SLC22A family, Bhatnagar et al (2006) found one rSNP in the OAT1 gene and five rSNPs in the OAT3 gene, but it is unclear whether these rSNPs affect mRNA levels. In addition, the transcriptional regulation of SLC22A genes has been characterized, and cis-elements in the proximal promoter regions were identified (Ogasawara et al 2006Asaka et al 2007;Popowski et al 2005;Kikuchi et al 2006;Saji et al 2008). If rSNPs are located in these cis-elements, mRNA expression may be altered.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of regulatory polymorphisms in organic ion transporter genes (SLC22A) in the kidney

et al. 2008

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Organic cation transporters (OCTs) and organic anion transporters (OATs) (SLC22A family) play crucial roles in the renal secretion of various drugs. Messengar ribonucleic acid (mRNA) expression of transporters can be a key factor regulating interindividual differences in drug pharmacokinetics. However, the source of variations in mRNA levels of transporters is unclear. In this study, we focused on single nucleotide polymorphisms (SNP) in the promoter region [regulatory SNPs (rSNPs)] as candidates for the factor regulating mRNA levels of SLC22A. We sequenced the promoter regions of OCT2 and OAT1-4 in 63 patients and investigated the effects of the identified rSNPs on transcriptional activities and mRNA expression. In the OCT2 promoter region, one deletion polymorphism (-578_-576delAAG) was identified; -578_-576delA-AG significantly reduced OCT2 promoter activity (p \ 0.05), and carriers of -578_-576delAAG tend to have lower OCT2 mRNA levels, but the difference is not significant. There was no rSNP in the OAT1 and OAT2 genes. The five rSNPs of OAT3 and one rSNP of OAT4 were unlikely to influence mRNA expression and promoter activity. This is the first study to investigate the influences of rSNPs on mRNA expression of SLC22A in the kidney and to identify a regulatory polymorphism affecting OCT2 promoter activity.

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“…Recently, basal promoter element of hOCT2 gene was characterized. 47) In addition, there is evidence that testosterone can regulate rOCT2 activity via androgen response elements. 28) Although there is no evidence for a direct correspondence between the transcriptional factors of rodent and human, androgen receptors present in both rodent and human.…”

Section: Discussionmentioning

confidence: 99%

Regulatory Role of Testosterone in Organic Cation Transport: in Vivo and in Vitro Studies

Meetam

Srimaroeng

Soodvilai

et al. 2009

Biological & Pharmaceutical Bulletin

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Renal organic cation transporters (OCTs) play a significant role in the elimination of a wide variety of organic cations, including endogenous compounds (e.g., monoamine neurotransmitter 1) and creatinine 2) ), drugs (e.g., cimetidine 3) metformin, 4) pramipexol 5) and cisplatin 6) ) and xenobiotics (e.g., tetraethylammonium (TEA) and 1-methyl-4-phenylpyridinium (MPP ϩ ) 3) ). OCTs are expressed in the basolateral membrane of renal proximal tubular cells, where they mediate the initial step of renal secretion of organic cation compounds. [7][8][9] The OCTs mediate facilitated diffusion of organic cations driven by a transmembrane potential difference. Several members of the OCT family have been cloned and identified, including OCT1, OCT2 and OCT3. Expression studies have shown that OCT1 is expressed in liver, kidney and small intestine. [10][11][12][13] OCT2 is expressed mostly in the kidney and is considered to be the major transporter for organic cation transport.14-16) OCT3 is mainly expressed in placenta and ovary, but is also present at low levels in many tissues. 14,17) For net transepithelial organic cation transport, in addition to its uptake, extrusion at the apical membrane into tubular lumen is also important. Previously, several transporters including organic cation/carnitine transporter 1, 2 (OCTN1, OCTN2) and multidrug resistance protein 1 (MDR1) were thought to participate in the extrusion of organic cation at the apical side.18-20) Very recently, other luminal H ϩ /organic cation antiporters, human (h) multidrug and toxin extrusion (MATE)1, hMATE2, rat (r) MATE1 and mouse (m)MATE1 and mMATE2, have been also suggested to contribute to renal organic cation transport. [21][22][23] It appears that testosterone can affect plasma levels of organic cations by modulating the activity of renal OCT2. This notion is supported by the observation that OCT2 mRNA levels are higher in kidneys of male than that of female mice and rats.14,24,25) Furthermore, testosterone treatment increased rOCT2 mRNA expression and TEA accumulation in renal slices of both sexes.26) Additional studies indicated that testosterone enhanced expression of rOCT2, but not rOCT1 and rOCT3, via the androgen receptor-mediated transcriptional pathway. 27) Recently, Lickteig et al. 28) reported that mMATE1 mRNA is more highly expressed in the kidney of male than that of female mice. However, the regulatory role of testosterone in MATE1 has not been elucidated. Clearly, functional changes in OCT expression would affect the pharmacokinetics of endogenous OC as well as cationic drugs. However, little information is available regarding the physiological role of transporter regulation in the whole animal.To gain more insight into the role of testosterone in regulating renal OC transport, we first examined the effect of testosterone on organic cation transport mediated by OCTs in the whole animal. The mechanism of testosterone induced changes in OC secretion was then assessed in vitro using isolated mouse renal proximal tubule (mRPT). In additio...

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Characterization of the Basal Promoter Element of Human Organic Cation Transporter 2 Gene

Cited by 20 publications

References 40 publications

Regulation of basal core promoter activity of human organic cation transporter 1 (OCT1/SLC22A1)

Regulation of basal core promoter activity of human organic cation transporter 1 (OCT1/SLC22A1)

Analysis of regulatory polymorphisms in organic ion transporter genes (SLC22A) in the kidney

Regulatory Role of Testosterone in Organic Cation Transport: in Vivo and in Vitro Studies

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