Amino Acid Residues in the Putative Transmembrane Domain 11 of Human Organic Anion Transporting Polypeptide 1B1 Dictate Transporter Substrate Binding, Stability, and Trafficking

Hong, Weifang; Wu, Zhiguang; Fang, Zihui; Huang, Jiujiu; Huang, Huiyan

doi:10.1021/acs.molpharmaceut.5b00466

Cited by 15 publications

(15 citation statements)

References 21 publications

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“…We confirmed that the characteristics of TCA transport ( K m values of 10.6 ± 0.3 μM and 9.5 ± 0.9 μM for OATP1B1 and OATP1B3, respectively) were similar to those of previous reports [21–23, 31]. The K m values for OATP1B1- and OATP1B3-mediated uptake of bile acids in present study and previous reports are summarized in S2 Table.…”

Section: Discussionsupporting

confidence: 92%

“…Our results indicated that glycine and taurine conjugated bile acids and unconjugated bile acids, except for UDCA and LCA, are substrates for both OATP1B1 and OATP1B3 (Fig 2). Previous studies reported that CA, GCA, TCA, GCDCA, TCDCA, TDCA, GUDCA, and TUDCA are substrates of OATP1B1 and OATP1B3 [22–27, 31–35]. However, earlier studies have demonstrated that CA and TCA were not substrates for OATP1B3 [21].…”

Section: Discussionmentioning

confidence: 99%

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Preference of Conjugated Bile Acids over Unconjugated Bile Acids as Substrates for OATP1B1 and OATP1B3

et al. 2017

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Bile acids, the metabolites of cholesterol, are signaling molecules that play critical role in many physiological functions. They undergo enterohepatic circulation through various transporters expressed in intestine and liver. Human organic anion-transporting polypeptides (OATP) 1B1 and OATP1B3 contribute to hepatic uptake of bile acids such as taurocholic acid. However, the transport properties of individual bile acids are not well understood. Therefore, we selected HEK293 cells overexpressing OATP1B1 and OATP1B3 to evaluate the transport of five major human bile acids (cholic acid, chenodeoxycholic acid, deoxycholic acid, ursodeoxycholic acid, lithocholic acid) together withtheir glycine and taurine conjugates via OATP1B1 and OATP1B3. The bile acids were quantified by liquid chromatography-tandem mass spectrometry. The present study revealed that cholic acid, chenodeoxyxcholic acid, and deoxycholic acid were transported by OATP1B1 and OATP1B3, while ursodeoxycholic acid and lithocholic acid were not significantly transported by OATPs. However, all the conjugated bile acids were taken up rapidly by OATP1B1 and OATP1B3. Kinetic analyses revealed the involvement of saturable OATP1B1- and OATP1B3-mediated transport of bile acids. The apparent Km values for OATP1B1 and OATP1B3 of the conjugated bile acids were similar (0.74–14.7 μM for OATP1B1 and 0.47–15.3 μM for OATP1B3). They exhibited higher affinity than cholic acid (47.1 μM for OATP1B1 and 42.2 μM for OATP1B3). Our results suggest that conjugated bile acids (glycine and taurine) are preferred to unconjugated bile acids as substrates for OATP1B1 and OATP1B3.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Preference of Conjugated Bile Acids over Unconjugated Bile Acids as Substrates for OATP1B1 and OATP1B3

et al. 2017

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“…A similar phenomenon was observed in our previous study of OATP1B1. It was found that several amino acid residues along TM11 are crucial for uptake function of the transporter, and they are located three and/or four residues apart from each other (Hong et al, 2015). Indeed, homology modeling (Biasini et al, 2014) of OATP2B1 (Supplemental Material) with Escherichia coli glycerol-3phosphate transporter (Protein Data Bank: 1pw4, Supplemental Material) as template revealed that V52, H55, L58, Q59, A61, Q62, S66, and L69 are all localized along one side the a-helix, facing the inner channel formed among different transmembrane domains (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies have identified quite a few essential amino acids located within transmembrane domains of OATP members. For example, amino acid residues within TM2 (Li et al, 2012), TM6 (Huang et al, 2013), TM10 (Gui andHagenbuch, 2009;Ohnishi et al, 2014), and TM11 (Weaver and Hagenbuch, 2010;Hong et al, 2015) were shown to be crucial for proper function of OATP1B1, and TM8 (Miyagawa et al, 2009) is believed to be important for substrate recognition of the transporter. As for OATP1B3, K41 in TM1 and R580 in TM11 are believed to be pivotal to the transporter function (Glaeser et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Transmembrane Domain 1 of Human Organic Anion Transporting Polypeptide 2B1 Is Essential for Transporter Function and Stability

Fang¹,

Huang²,

Chen³

et al. 2018

Mol Pharmacol

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Organic anion transporting polypeptides (OATPs, gene symbol ) are important membrane transporter proteins that mediate the uptake of wide ranges of endogenous and exogenous compounds. OATP2B1 has been found in multiple organs and tissues, including the liver, small intestine, kidney, brain, placenta, heart, skin, as well as skeletal muscle, and is proposed to be involved in the uptake of orally administered drugs. Quite a few reports have demonstrated that transmembrane domains (TMs) are crucial for proper functions of OATP family members. Comparative modeling proposed that TM1, along with TM2, 4, and 5 of the N-terminal half of OATP2B1, may be localized within the substrate interaction pocket and are important for uptake function of the transporter. Alanine scanning of the putative transmembrane domain 1 of OATP2B1 revealed that substitution of L58 with alanine dramatically altered the K value, and mutation of V52, H55, Q59, and L69 resulted in significantly reduced substrate turnover number, whereas A61V, Q62A, and S66A exhibited significant change in both K and V values. In addition, phenylalanine at position 51 seems to play an important role in maintaining proper folding of OATP2B1 because alanine replacement of F51 caused accelerated degradation of the transporter protein. Although proteasome and lysosome inhibitors could partially recover protein level, the mutant transporter remained nonfunctional. Taken together, the identification of nine essential amino acid residues within TM1 of OATP2B1 suggested that the transmembrane domain is important for maintaining proper function of the transporter.

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“…Naturally occurring coding region variants of OAT4, especially L29P and T392I in TMDs 1 and 8, exhibited greatly decreased plasma membrane expression (Zhou et al, ). Alanine‐scanning mutagenesis of TMD11 in OATP1B1 identified 7 critical amino acid residues for plasma membrane expression and function (Hong et al, ). It would now be of interest to evaluate the role of the analogous residues in other OATPs to elucidate the molecular mechanisms underlying the loss of membrane expression.…”

Section: Post‐translational Processing Of Slc Transportersmentioning

confidence: 99%

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

Murray

Zhou

2017

British J Pharmacology

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Organic anion transporters (OATs) and organic anion-transporting polypeptides (OATPs), encoded by a number of solute carrier (SLC)22A and SLC organic anion (SLCO) genes, mediate the absorption and distribution of drugs and other xenobiotics. The regulation of OATs and OATPs is complex, comprising both transcriptional and post-translational mechanisms. Plasma membrane expression is required for cellular substrate influx by OATs/OATPs. Thus, interest in post-translational regulatory processes, including membrane targeting, endocytosis, recycling and degradation of transporter proteins, is increasing because these are critical for plasma membrane expression. After being synthesized, transporters undergo N-glycosylation in the endoplasmic reticulum and Golgi apparatus and are delivered to the plasma membrane by vesicular transport. Their expression at the cell surface is maintained by de novo synthesis and recycling, which occurs after clathrin- and/or caveolin-dependent endocytosis of existing protein. Several studies have shown that phosphorylation by signalling kinases is important for the internalization and recycling processes, although the transporter protein does not appear to be directly phosphorylated. After internalization, transporters that are targeted for degradation undergo ubiquitination, most likely on intracellular loop residues. Epigenetic mechanisms, including methylation of gene regulatory regions and transcription from alternate promoters, are also significant in the regulation of certain SLC22A/SLCO genes. The membrane expression of OATs/OATPs is dysregulated in disease, which affects drug efficacy and detoxification. Several transporters are expressed in the cytoplasmic subcompartment in disease states, which suggests that membrane targeting/internalization/recycling may be impaired. This article focuses on recent developments in OAT and OATP regulation, their dysregulation in disease and the significance for drug therapy.

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Amino Acid Residues in the Putative Transmembrane Domain 11 of Human Organic Anion Transporting Polypeptide 1B1 Dictate Transporter Substrate Binding, Stability, and Trafficking

Cited by 15 publications

References 21 publications

Preference of Conjugated Bile Acids over Unconjugated Bile Acids as Substrates for OATP1B1 and OATP1B3

Preference of Conjugated Bile Acids over Unconjugated Bile Acids as Substrates for OATP1B1 and OATP1B3

Transmembrane Domain 1 of Human Organic Anion Transporting Polypeptide 2B1 Is Essential for Transporter Function and Stability

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

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