Identification and functional characterization of the promoter region of the human organic anion transporting polypeptide gene

Abstract

The liver extracts a large variety of organic anions and The organic anion transporting polypeptide (OATP) of the amphipathic compounds from the sinusoidal blood by carbasolateral hepatocyte membrane mediates multispecific uprier-mediated transport across the basolateral hepatocyte take of anionic and other amphipathic substrates from sinumembrane. Expression cloning strategies in Xenopus laevis soidal blood plasma. To investigate the mechanisms controloocytes have led to the isolation of a sodium-bile acid coling OATP expression, the 5 -flanking region of the human transport system (Na / -taurocholate cotransporting polypep-OATP gene was isolated from a P1-derived artificial chromotide) as well as of a sodium-independent organic anion transsome genomic clone. Sequence analysis of the OATP promoter porting polypeptide (oatp) from rat and human liver. 1 The showed a number of consensus binding sites for both ubiquihuman OATP is a multispecific and polyvalent amphipathic tous and liver-enriched transcription factors. Transfection of substrate transporter that can mediate hepatocellular uptake HepG2 cells with a series of 5 -deleted promoter-luciferase of organic anions, such as bile acids, bromosulphophthalein, constructs identified the minimal promoter region within 91 estrone-3-sulfate, estradiol-17-glucuronide, the cardiac glybase pairs relative to the transcription initiation site. A puta-coside ouabain, and even the cationic compound N-(4,4-tive silencer element was localized in the 0662/0440 region. azo-n-pentyl)-21-deoxy-ajmalinium. 2,3 OATP consists of 670 The minimal promoter was also active in Chang liver, Madin-amino acids with 12 putative membrane-spanning domains Darby canine kidney, and Chinese hamster ovary cells, indi-and seven potential N-linked glycosylation sites. Based on cating that basal promoter function is independent of liver-Northern blot analysis, related proteins are also expressed in specific regulatory mechanisms. In transfected HepG2 cells, other tissues, including kidney and brain. 2 The OATP gene taurocholate (100 mmol/L) stimulated and triiodothyronine has been localized to chromosome 12p12. 4 (1 mmol/L) inhibited OATP promoter activity, whereas hydroThe factors that control the expression of OATP in normal cortisone, dexamethasone, b-estradiol, estrone-3-sulfate, and and diseased liver are as yet unknown. As a first step towards testosterone had no significant effect. Reverse-transcription understanding the regulation of OATP expression, our aim polymerase chain reaction analysis showed an increase in was to isolate the 5 -flanking region of the OATP gene and OATP messenger RNA in the livers of four patients with to investigate the response of the OATP promoter to various chronic cholestatic liver disease compared with three noncho-physiological and pathophysiological stimuli. The data prelestatic controls. The up-regulation of OATP expression by sented in this study indicate that the OATP-mediated uptake taurocholate could serve to enhance the sinusoidal efflux of of cholephilic...

OATPs, OATs and OCTs: the organic anion and cation transporters of the SLCO and SLC22A gene superfamilies

“…The mechanisms for regulating OATP expression are likely to vary by tissue type. For example, OATP1A2 expression is up-regulated in response to increased bile acid levels (Kullak-Ublick et al, 1997a), which would affect expression levels in the small intestine and liver. In breast carcinoma tissues and cell lines, however, OATP1A2 expression is significantly associated with the steroid and xenobiotic receptor (SXR) expression (Miki et al, 2006).…”

Trafficking and other regulatory mechanisms for organic anion transporting polypeptides and organic anion transporters that modulate cellular drug and xenobiotic influx and that are dysregulated in disease

“…Unchanged or higher levels of mRNAs encoding hepatic OATP1A2 (Kullak‐Ublick et al, ; Keitel et al, ), but lower levels of OATPs 1B1 and 1B3 (Keitel et al, ), have been reported to occur in patients with liver disease. Serum bile acids accumulate in hepatic cholestasis and activate the FXR, which promotes the transcription of FXR‐responsive genes that include the negative transcription factor small heterodimer partner 1 (SHP; Figure B).…”

Hepatobiliary membrane transporters in primary biliary cirrhosis

“…Impairment of NTCP in humans results in reduced Na + ‐dependent uptake of conjugated bile salts. However, sodium‐independent mechanisms for hepatic bile salt uptake persist due to continued expression of several other basolateral membrane organic anion transporters, possibly OATP1B3 in humans 10,11 . In the advanced stages of PBC 9 and primary sclerosing cholangitis (PSC), 12 the expression of OATP1B1 is reduced.…”