1
|
Li Y, Liu H, Liang T, Han W, Bo Z, Qiu T, Li J, Xu M, Wang W, Yang S, Gui C. Importance of N-Glycosylation for the Expression and Function of Human Organic Anion Transporting Polypeptide 2B1. ACS Pharmacol Transl Sci 2023; 6:1347-1356. [PMID: 37854627 PMCID: PMC10580385 DOI: 10.1021/acsptsci.3c00076] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Indexed: 10/20/2023]
Abstract
Human organic anion transporting polypeptide 2B1 (OATP2B1) is a membrane transporter widely expressed in organs crucial for drug absorption and disposition such as the intestine, liver, and kidney. Evidence indicates that OATP2B1 is a glycoprotein. However, the sites of glycosylation and their contribution to the function and expression of OATP2B1 are largely unknown. In this study, by site-directed mutagenesis, we determined that two of four potential N-glycosylation sites in OATP2B1, N176 and N538, are indeed glycosylated. Functional studies revealed that the transport activities of mutants N176Q and N538Q were greatly reduced as compared to that of wild-type OATP2B1. However, the reduced activity was not due to the impairment of transport function per se but due to the decreased surface expression as the Km and normalized Vmax values of N176Q and N538Q were comparable to those of OATP2B1. Quantitative polymerase chain reaction (PCR) revealed that N176Q and N538Q mutations did not affect the expression of OATP2B1 at a transcriptional level. Immunofluorescence analysis showed that deglycosylated OATP2B1 was largely retained in the endoplasmic reticulum, which may activate the endoplasmic reticulum-associated degradation pathway, and the ubiquitin-proteasome system played a major role in the degradation of OATP2B1. Taken together, OATP2B1 is N-glycosylated, and N-glycosylation is essential for the surface expression of OATP2B1 but not critical for the transport function of OATP2B1 per se.
Collapse
Affiliation(s)
| | | | | | - Wanjun Han
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| | - Zheyue Bo
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| | - Tian Qiu
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| | - Jiawei Li
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| | - Mingming Xu
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| | - Weipeng Wang
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| | - Shuang Yang
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| | - Chunshan Gui
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou, Jiangsu 215123, People’s
Republic of China
| |
Collapse
|
2
|
Peng T, Liu S, Li Y, Zhang H, Hagenbuch B, Gui C. Investigating the interactions of flavonoids with human OATP2B1: inhibition assay, IC 50 determination, and structure-activity relationship analysis. RSC Med Chem 2023; 14:890-898. [PMID: 37252098 PMCID: PMC10211325 DOI: 10.1039/d3md00078h] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 03/29/2023] [Indexed: 03/28/2024] Open
Abstract
Human organic anion transporting polypeptide 2B1 (OATP2B1) is a crucial transporter for the absorption and disposition of many drugs. Its inhibition by small molecules may alter the pharmacokinetic profile of its substrate drugs. In this study, the interactions of 29 common flavonoids with OATP2B1 were explored using the fluorescent substrate 4',5'-dibromofluorescein and structure-activity relationship analysis. Our results showed that flavonoid aglycones interact with OATP2B1 more strongly than their 3-O- and 7-O-glycoside counterparts, as hydrophilic and bulky groups at these two sites are detrimental to flavonoids' binding with OATP2B1. In contrast, hydrogen-bond forming groups at the C-6 position of ring A and the C-3' and C-4' positions of ring B could strengthen the interaction of flavonoids with OATP2B1. However, a hydroxyl or sugar moiety at the C-8 position of ring A is unfavorable. Our results also indicated that flavones usually interact more strongly with OATP2B1 than their 3-hydroxyflavones (flavonols). The obtained information could be useful for the prediction of additional flavonoids for their interaction with OATP2B1.
Collapse
Affiliation(s)
- Taotao Peng
- College of Pharmaceutical Sciences, Soochow University 199 Renai Road, Suzhou Industrial Park Suzhou Jiangsu 215123 China
| | - Shuai Liu
- College of Pharmaceutical Sciences, Soochow University 199 Renai Road, Suzhou Industrial Park Suzhou Jiangsu 215123 China
| | - Ying Li
- College of Pharmaceutical Sciences, Soochow University 199 Renai Road, Suzhou Industrial Park Suzhou Jiangsu 215123 China
| | - Hongjian Zhang
- College of Pharmaceutical Sciences, Soochow University 199 Renai Road, Suzhou Industrial Park Suzhou Jiangsu 215123 China
| | - Bruno Hagenbuch
- Department of Pharmacology, Toxicology and Therapeutics, the University of Kansas Medical Center 3901 Rainbow Boulevard Kansas City Kansas 66160 USA
| | - Chunshan Gui
- College of Pharmaceutical Sciences, Soochow University 199 Renai Road, Suzhou Industrial Park Suzhou Jiangsu 215123 China
| |
Collapse
|
3
|
Wang Z, Li Y, Peng T, Su Y, Luo X, Han W, Zhang H, Ruan J, Gui C. Human Organic Anion Transporting Polypeptides 1B1, 1B3, and 2B1 Are Involved in the Hepatic Uptake of Phenolsulfonphthalein. ACS OMEGA 2021; 6:35844-35851. [PMID: 34984313 PMCID: PMC8717568 DOI: 10.1021/acsomega.1c06163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 12/08/2021] [Indexed: 06/03/2023]
Abstract
Phenolsulfonphthalein (PSP or phenol red), a sulfonphthalein dye, has been used as a diagnostic agent and a pH indicator in cell culture medium. After administered into the body, PSP is excreted into urine and bile. The urinary excretion of PSP is mediated by organic anion transporter 1/3 (OAT1/3) and multidrug resistance protein 2 (MRP2). In biliary excretion, PSP is effluxed from hepatocytes into the bile via MRP2. However, so far, the molecular mechanism for PSP transport from the blood into hepatocytes is unclear. In the present study, six human major hepatic uptake transporters expressed on the basolateral membrane of hepatocytes, namely, organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, OATP2B1, Na+/taurocholate cotransporting polypeptide (NTCP), organic cation transporter 1 (OCT1), and OAT2, have been investigated to see whether they are involved in the hepatic uptake of PSP. An in vitro cell-based study demonstrated that PSP is a substrate for OATP1B1, OATP1B3, and OATP2B1, with OATP1B3 showing the highest transport efficiency. The K m values for OATP1B1-, OATP1B3-, and OATP2B1-mediated PSP uptake were 11.3 ± 1.5, 7.0 ± 1.5, and 5.1 ± 1.0 μM, respectively. PSP interacts with known OATP substrates/inhibitors. However, the presence of PSP in cell culture medium has no significant effect on OATP's function. In vivo pharmacokinetic study in wild-type and Oatp1b2-knockout mice showed that Oatp1b2-knockout led to elevated plasma concentration and decreased liver accumulation of PSP. Taken together, the present study showed that in the liver, OATP1B1, OATP1B3, and OATP2B1 are involved in the uptake of PSP from the blood into hepatocytes, which, along with MRP2-mediated efflux of PSP from hepatocytes into the bile, constitute the vectorial transport of PSP from the blood to the bile and may play a critical role in the biliary excretion of PSP.
Collapse
Affiliation(s)
- Zhongmin Wang
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Ying Li
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Taotao Peng
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Ying Su
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Xiaoting Luo
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Wanjun Han
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Hongjian Zhang
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Jianqing Ruan
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| | - Chunshan Gui
- College of Pharmaceutical
Sciences, Soochow University, 199 Renai Road, Suzhou Industrial
Park, Suzhou 215123, China
| |
Collapse
|
4
|
Yang J, Wang Z, Liu S, Wang W, Zhang H, Gui C. Functional Characterization Reveals the Significance of Rare Coding Variations in Human Organic Anion Transporting Polypeptide 2B1 (SLCO2B1). Mol Pharm 2020; 17:3966-3978. [DOI: 10.1021/acs.molpharmaceut.0c00747] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Jingjie Yang
- College of Pharmaceutical Sciences, Soochow University, 199 Renai Road, Suzhou Industrial Park, Suzhou 215123, China
| | - Zhongmin Wang
- College of Pharmaceutical Sciences, Soochow University, 199 Renai Road, Suzhou Industrial Park, Suzhou 215123, China
| | - Shuai Liu
- College of Pharmaceutical Sciences, Soochow University, 199 Renai Road, Suzhou Industrial Park, Suzhou 215123, China
| | - Weipeng Wang
- College of Pharmaceutical Sciences, Soochow University, 199 Renai Road, Suzhou Industrial Park, Suzhou 215123, China
| | - Hongjian Zhang
- College of Pharmaceutical Sciences, Soochow University, 199 Renai Road, Suzhou Industrial Park, Suzhou 215123, China
| | - Chunshan Gui
- College of Pharmaceutical Sciences, Soochow University, 199 Renai Road, Suzhou Industrial Park, Suzhou 215123, China
| |
Collapse
|
5
|
Groeneweg S, van Geest FS, Peeters RP, Heuer H, Visser WE. Thyroid Hormone Transporters. Endocr Rev 2020; 41:5637505. [PMID: 31754699 DOI: 10.1210/endrev/bnz008] [Citation(s) in RCA: 98] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/07/2019] [Indexed: 02/08/2023]
Abstract
Thyroid hormone transporters at the plasma membrane govern intracellular bioavailability of thyroid hormone. Monocarboxylate transporter (MCT) 8 and MCT10, organic anion transporting polypeptide (OATP) 1C1, and SLC17A4 are currently known as transporters displaying the highest specificity toward thyroid hormones. Structure-function studies using homology modeling and mutational screens have led to better understanding of the molecular basis of thyroid hormone transport. Mutations in MCT8 and in OATP1C1 have been associated with clinical disorders. Different animal models have provided insight into the functional role of thyroid hormone transporters, in particular MCT8. Different treatment strategies for MCT8 deficiency have been explored, of which thyroid hormone analogue therapy is currently applied in patients. Future studies may reveal the identity of as-yet-undiscovered thyroid hormone transporters. Complementary studies employing animal and human models will provide further insight into the role of transporters in health and disease. (Endocrine Reviews 41: 1 - 55, 2020).
Collapse
Affiliation(s)
- Stefan Groeneweg
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Ferdy S van Geest
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Robin P Peeters
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Heike Heuer
- Department of Endocrinology, Diabetes and Metabolism, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - W Edward Visser
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| |
Collapse
|
6
|
Jin H, Wang B, Hou J, Ma T, Qiao D, Miao Y, Ding J, Han X. The mechanism of Oatp1a5-mediated microcystin-leucine arginine entering into GnRH neurons. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 184:109614. [PMID: 31526925 DOI: 10.1016/j.ecoenv.2019.109614] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 08/22/2019] [Accepted: 08/26/2019] [Indexed: 06/10/2023]
Abstract
Microcystin-leucine arginine (MC-LR) enters into gonadotropin-releasing hormone (GnRH) neurons and induces decline of serum GnRH levels resulting in male reproductive toxicity via hypothalamic-pituitary-testis axis. The organic anion transporting polypeptide 1a5 (Oatp1a5) is a critical transporter for the uptake of MC-LR by GnRH neurons. However, the underlying molecular mechanisms of the transport process are still elusive. In this study, we found that the transmembrane domains 2, 8, and 9 played important roles in transporting function of Oatp1a5. In addition, our data demonstrated that N-linked glycosylation was involved in the transport of MC-LR by Oatp1a5. Moreover, we showed that N-linked glycosylation sites Asn483 and Asn492 were vital for the transport function of Oatp1a5. In summary, the study furthered our understanding of mechanisms that the uptake of MC-LR by GnRH neurons and laid a theoretical foundation for preventing MC-LR from injuring male reproductive health.
Collapse
Affiliation(s)
- Haibo Jin
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| | - Bo Wang
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| | - Jiwei Hou
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| | - Tan Ma
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| | - Dan Qiao
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| | - Yingwen Miao
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| | - Jie Ding
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| | - Xiaodong Han
- Immunology and Reproductive Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Hankou Road 22, Nanjing, Jiangsu, 210093, China; Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093, China.
| |
Collapse
|
7
|
Yue M, Yang J, Jin M, Steiert B, Xiang Y, Zhang H, Hagenbuch B, Gui C. Gly45 and Phe555 in Transmembrane Domains 1 and 10 Are Critical for the Activation of Organic Anion Transporting Polypeptide 1B3 by Epigallocatechin Gallate. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:9079-9087. [PMID: 31353905 PMCID: PMC6892160 DOI: 10.1021/acs.jafc.9b03812] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Organic anion transporting polypeptides (OATPs) 1B1 and 1B3 are two highly homologous transporters expressed in the human liver. However, epigallocatechin gallate (EGCG), which is the most predominant catechin in green tea, has opposite effects on the function of OATP1B1 and OATP1B3. In the present study, the critical structural domains and amino acid residues for the activation of OATP1B3 by EGCG have been determined by characterizing the function of a series of OATP1B3-derived chimeric transporters, site-directed mutagenesis, and kinetic studies. Our results showed that G45 and F555 in transmembrane domains 1 and 10 are the most important amino acid residues for OATP1B3 activation. Kinetic studies showed that the activation of OATP1B3 by EGCG at a low substrate concentration was due to its increased substrate binding affinity. However, EGCG caused increased Km and decreased Vmax for 1B3-G45A and 1B3-F555H. The flexibility at position 45 and aromaticity at position 555 might be important for OATP1B3 activation. While 1B3-G45A and 1B3-F555H could not be activated by EGCG, their transport activity for EGCG was comparable to that of wild-type OATP1B3. In conclusion, the present study elucidated the molecular mechanism for OATP1B3 activation by EGCG.
Collapse
Affiliation(s)
- Mei Yue
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China
| | - Jingjie Yang
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China
| | - Meng Jin
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China
| | - Brianna Steiert
- Department of Pharmacology, Toxicology and Therapeutics, the University of Kansas Medical Center, Kansas City, Kansas 66160, USA
| | - Yiqun Xiang
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China
| | - Hongjian Zhang
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China
| | - Bruno Hagenbuch
- Department of Pharmacology, Toxicology and Therapeutics, the University of Kansas Medical Center, Kansas City, Kansas 66160, USA
| | - Chunshan Gui
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China
- Corresponding author: Chunshan Gui, Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, 199 Renai Road, Suzhou Industrial Park, Suzhou 215123, China. Tel.: +86-512-65882089; Fax: +86-512-65882089
| |
Collapse
|
8
|
Nie Y, Yang J, Liu S, Sun R, Chen H, Long N, Jiang R, Gui C. Genetic polymorphisms of human hepatic OATPs: functional consequences and effect on drug pharmacokinetics. Xenobiotica 2019; 50:297-317. [DOI: 10.1080/00498254.2019.1629043] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Yingmin Nie
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Jingjie Yang
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Shuai Liu
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Ruiqi Sun
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Huihui Chen
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Nan Long
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Rui Jiang
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Chunshan Gui
- Department of Pharmaceutical Analysis, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| |
Collapse
|
9
|
Fang Z, Huang J, Chen J, Xu S, Xiang Z, Hong M. Transmembrane Domain 1 of Human Organic Anion Transporting Polypeptide 2B1 Is Essential for Transporter Function and Stability. Mol Pharmacol 2018; 94:842-849. [PMID: 29871943 DOI: 10.1124/mol.118.111914] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 05/24/2018] [Indexed: 01/09/2023] Open
Abstract
Organic anion transporting polypeptides (OATPs, gene symbol SLCO) 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 Km 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 Km and Vmax 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.
Collapse
Affiliation(s)
- Zihui Fang
- College of Life Sciences (Z.F., J.H., J.C., S.X., Z.X., M.H.) and Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms (J.H., M.H.), South China Agricultural University, Guangzhou, China
| | - Jiujiu Huang
- College of Life Sciences (Z.F., J.H., J.C., S.X., Z.X., M.H.) and Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms (J.H., M.H.), South China Agricultural University, Guangzhou, China
| | - Jie Chen
- College of Life Sciences (Z.F., J.H., J.C., S.X., Z.X., M.H.) and Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms (J.H., M.H.), South China Agricultural University, Guangzhou, China
| | - Shaopeng Xu
- College of Life Sciences (Z.F., J.H., J.C., S.X., Z.X., M.H.) and Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms (J.H., M.H.), South China Agricultural University, Guangzhou, China
| | - Zhaojian Xiang
- College of Life Sciences (Z.F., J.H., J.C., S.X., Z.X., M.H.) and Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms (J.H., M.H.), South China Agricultural University, Guangzhou, China
| | - Mei Hong
- College of Life Sciences (Z.F., J.H., J.C., S.X., Z.X., M.H.) and Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms (J.H., M.H.), South China Agricultural University, Guangzhou, China
| |
Collapse
|