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Akino S, Yasujima T, Yamashiro T, Yuasa H. Disrupted in renal carcinoma 2 (DIRC2/SLC49A4) is an H +-driven lysosomal pyridoxine exporter. Life Sci Alliance 2023; 6:e202201629. [PMID: 36456177 PMCID: PMC9719028 DOI: 10.26508/lsa.202201629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 11/20/2022] [Accepted: 11/21/2022] [Indexed: 12/02/2022] Open
Abstract
Disrupted in renal carcinoma 2 (DIRC2) has gained interest because of its association with the development of renal cancer and cosegregation with a chromosomal translocation. It is a member of the SLC49 family (SLC49A4) and is considered to be an electrogenic lysosomal metabolite transporter; however, its molecular function has not been fully defined. To perform a detailed functional analysis of human DIRC2, we used a recombinant DIRC2 protein (DIRC2-AA), in which the N-terminal dileucine motif involved in its lysosomal localization was removed by replacing with dialanine for redirected localization to the plasma membrane, exposing intralysosomal segments to the extracellular space. The DIRC2-AA mutant induced the cellular uptake of pyridoxine (vitamin B6) under acidic conditions when expressed transiently in COS-7 cells. In addition, uptake was markedly inhibited by protonophores, indicating its function through an H+-coupled mechanism. In separate experiments, the transient overexpression of unmodified DIRC2 (tagged with HA) in human embryonic kidney 293 cells reduced cellular pyridoxine accumulation induced by transiently introduced human thiamine transporter 2/SLC19A3 (tagged with FLAG), a plasma membrane thiamine transporter that also transports pyridoxine. The cellular accumulation of pyridoxine in Caco-2 cells as a cell model was increased by the knockdown of endogenous DIRC2. Overall, the results indicate that DIRC2 is an H+-driven lysosomal pyridoxine exporter. Its overexpression leads to a reduction in cellular pyridoxine accumulation associated with reduced lysosomal accumulation and, conversely, its suppression results in an increase in lysosomal and cellular pyridoxine accumulation.
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Affiliation(s)
- Shogo Akino
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Tomoya Yasujima
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Takahiro Yamashiro
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Hiroaki Yuasa
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
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Miyake K, Yasujima T, Takahashi S, Yamashiro T, Yuasa H. Identification of the amino acid residues involved in the species-dependent differences in the pyridoxine transport function of SLC19A3. J Biol Chem 2022; 298:102161. [PMID: 35724964 PMCID: PMC9293782 DOI: 10.1016/j.jbc.2022.102161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 06/10/2022] [Accepted: 06/16/2022] [Indexed: 01/19/2023] Open
Abstract
Recent studies have shown that human solute carrier SLC19A3 (hSLC19A3) can transport pyridoxine (vitamin B6) in addition to thiamine (vitamin B1), its originally identified substrate, whereas rat and mouse orthologs of hSLC19A3 can transport thiamine but not pyridoxine. This finding implies that some amino acid residues required for pyridoxine transport, but not for thiamine transport, are specific to hSLC19A3. Here, we sought to identify these residues to help clarify the unique operational mechanism of SLC19A3 through analyses comparing hSLC19A3 and mouse Slc19a3 (mSlc19a3). For our analyses, hSLC19A3 mutants were prepared by replacing selected amino acid residues with their counterparts in mSlc19a3, and mSlc19a3 mutants were prepared by substituting selected residues with their hSLC19A3 counterparts. We assessed pyridoxine and thiamine transport by these mutants in transiently transfected HEK293 cells. Our analyses indicated that the hSLC19A3-specific amino acid residues of Gln86, Gly87, Ile91, Thr93, Trp94, Ser168, and Asn173 are critical for pyridoxine transport. These seven amino acid residues were found to be mostly conserved in the SLC19A3 orthologs that can transport pyridoxine, but not in orthologs that are unable to transport pyridoxine. In addition, these residues were also found to be conserved in several SLC19A2 orthologs, including rat, mouse, and human orthologs, which were all found to effectively transport both pyridoxine and thiamine, exhibiting no species-dependent differences. Together, these findings provide a molecular basis for the unique functional characteristics of SLC19A3 and also of SLC19A2.
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Affiliation(s)
- Kohei Miyake
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Japan
| | - Tomoya Yasujima
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Japan.
| | - Syunsuke Takahashi
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Japan
| | - Takahiro Yamashiro
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Japan
| | - Hiroaki Yuasa
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Japan
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Li J, Zhang Y, Yu M, Wang A, Qiu Y, Fan W, Hovgaard L, Yang M, Li Y, Wang R, Li X, Gan Y. The upregulated intestinal folate transporters direct the uptake of ligand-modified nanoparticles for enhanced oral insulin delivery. Acta Pharm Sin B 2022; 12:1460-1472. [PMID: 35530154 PMCID: PMC9072239 DOI: 10.1016/j.apsb.2021.07.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 07/10/2021] [Accepted: 07/13/2021] [Indexed: 11/29/2022] Open
Abstract
Transporters are traditionally considered to transport small molecules rather than large-sized nanoparticles due to their small pores. In this study, we demonstrate that the upregulated intestinal transporter (PCFT), which reaches a maximum of 12.3-fold expression in the intestinal epithelial cells of diabetic rats, mediates the uptake of the folic acid-grafted nanoparticles (FNP). Specifically, the upregulated PCFT could exert its function to mediate the endocytosis of FNP and efficiently stimulate the traverse of FNP across enterocytes by the lysosome-evading pathway, Golgi-targeting pathway and basolateral exocytosis, featuring a high oral insulin bioavailability of 14.4% in the diabetic rats. Conversely, in cells with relatively low PCFT expression, the positive surface charge contributes to the cellular uptake of FNP, and FNP are mainly degraded in the lysosomes. Overall, we emphasize that the upregulated intestinal transporters could direct the uptake of ligand-modified nanoparticles by mediating the endocytosis and intracellular trafficking of ligand-modified nanoparticles via the transporter-mediated pathway. This study may also theoretically provide insightful guidelines for the rational design of transporter-targeted nanoparticles to achieve efficient drug delivery in diverse diseases.
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Affiliation(s)
- Jingyi Li
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Yaqi Zhang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Miaorong Yu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Aohua Wang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Qiu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Weiwei Fan
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Lars Hovgaard
- Oral Formulation Development, Novo Nordisk A/S, Maalov 2760, Denmark
| | - Mingshi Yang
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2100, Denmark
| | - Yiming Li
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
| | - Rui Wang
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
- Corresponding authors. Tel.: +86 021 51322181, fax: +86 021 51322193 (Rui Wang); Tel.: +01 972 883 4480, fax: +01 972 883 4440 (Xiuying Li); Tel.: +86 021 20231975, fax: +86 021 20231000 1425 (Yong Gan).
| | - Xiuying Li
- University of Texas at Dallas, Richardson, TX 75080, USA
- Corresponding authors. Tel.: +86 021 51322181, fax: +86 021 51322193 (Rui Wang); Tel.: +01 972 883 4480, fax: +01 972 883 4440 (Xiuying Li); Tel.: +86 021 20231975, fax: +86 021 20231000 1425 (Yong Gan).
| | - Yong Gan
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- NMPA Key Laboratory for Quality Research and Evaluation of Pharmaceutical Excipients, National Institutes for Food and Drug Control, Beijing 100050, China
- Corresponding authors. Tel.: +86 021 51322181, fax: +86 021 51322193 (Rui Wang); Tel.: +01 972 883 4480, fax: +01 972 883 4440 (Xiuying Li); Tel.: +86 021 20231975, fax: +86 021 20231000 1425 (Yong Gan).
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Hou Z, Gangjee A, Matherly LH. The evolving biology of the proton‐coupled folate transporter: New insights into regulation, structure, and mechanism. FASEB J 2022; 36:e22164. [PMID: 35061292 PMCID: PMC8978580 DOI: 10.1096/fj.202101704r] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/15/2021] [Accepted: 01/03/2022] [Indexed: 01/19/2023]
Abstract
The human proton‐coupled folate transporter (PCFT; SLC46A1) or hPCFT was identified in 2006 as the principal folate transporter involved in the intestinal absorption of dietary folates. A rare autosomal recessive hereditary folate malabsorption syndrome is attributable to human SLC46A1 variants. The recognition that hPCFT was highly expressed in many tumors stimulated substantial interest in its potential for cytotoxic drug targeting, taking advantage of its high‐level transport activity under acidic pH conditions that characterize many tumors and its modest expression in most normal tissues. To better understand the basis for variations in hPCFT levels between tissues including human tumors, studies have examined the transcriptional regulation of hPCFT including the roles of CpG hypermethylation and critical transcription factors and cis elements. Additional focus involved identifying key structural and functional determinants of hPCFT transport that, combined with homology models based on structural homologies to the bacterial transporters GlpT and LacY, have enabled new structural and mechanistic insights. Recently, cryo‐electron microscopy structures of chicken PCFT in a substrate‐free state and in complex with the antifolate pemetrexed were reported, providing further structural insights into determinants of (anti)folate recognition and the mechanism of pH‐regulated (anti)folate transport by PCFT. Like many major facilitator proteins, hPCFT exists as a homo‐oligomer, and evidence suggests that homo‐oligomerization of hPCFT monomeric proteins may be important for its intracellular trafficking and/or transport function. Better understanding of the structure, function and regulation of hPCFT should facilitate the rational development of new therapeutic strategies for conditions associated with folate deficiency, as well as cancer.
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Affiliation(s)
- Zhanjun Hou
- Molecular Therapeutics Program Barbara Ann Karmanos Cancer Institute Detroit Michigan USA
- Department of Oncology Wayne State University School of Medicine Detroit Michigan USA
| | - Aleem Gangjee
- Division of Medicinal Chemistry Graduate School of Pharmaceutical Sciences Duquesne University Pittsburgh Pennsylvania USA
| | - Larry H. Matherly
- Molecular Therapeutics Program Barbara Ann Karmanos Cancer Institute Detroit Michigan USA
- Department of Oncology Wayne State University School of Medicine Detroit Michigan USA
- Department of Pharmacology Wayne State University School of Medicine Detroit Michigan USA
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Shinoda Y, Yamashiro T, Hosooka A, Yasujima T, Yuasa H. Functional characterization of human organic anion transporter 10 (OAT10/SLC22A13) as an orotate transporter. Drug Metab Pharmacokinet 2021; 43:100443. [DOI: 10.1016/j.dmpk.2021.100443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/07/2021] [Accepted: 12/17/2021] [Indexed: 11/03/2022]
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Yamashiro T, Yasujima T, Said HM, Yuasa H. pH-dependent pyridoxine transport by SLC19A2 and SLC19A3: Implications for absorption in acidic microclimates. J Biol Chem 2020; 295:16998-17008. [PMID: 33008889 PMCID: PMC7863892 DOI: 10.1074/jbc.ra120.013610] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 10/01/2020] [Indexed: 11/06/2022] Open
Abstract
SLC19A2 and SLC19A3, also known as thiamine transporters (THTR) 1 and 2, respectively, transport the positively charged thiamine (vitamin B1) into cells to enable its efficient utilization. SLC19A2 and SLC19A3 are also known to transport structurally unrelated cationic drugs, such as metformin, but whether this charge selectivity extends to other molecules, such as pyridoxine (vitamin B6), is unknown. We tested this possibility using Madin-Darby canine kidney II (MDCKII) cells and human embryonic kidney 293 (HEK293) cells for transfection experiments, and also using Caco-2 cells as human intestinal epithelial model cells. The stable expression of SLC19A2 and SLC19A3 in MDCKII cells (as well as their transient expression in HEK293 cells) led to a significant induction in pyridoxine uptake at pH 5.5 compared with control cells. The induced uptake was pH-dependent, favoring acidic conditions over neutral to basic conditions, and protonophore-sensitive. It was saturable as a function of pyridoxine concentration, with an apparent Km of 37.8 and 18.5 μm, for SLC19A2 and SLC19A3, respectively, and inhibited by the pyridoxine analogs pyridoxal and pyridoxamine as well as thiamine. We also found that silencing the endogenous SLC19A3, but not SLC19A2, of Caco-2 cells with gene-specific siRNAs lead to a significant reduction in carrier-mediated pyridoxine uptake. These results show that SLC19A2 and SLC19A3 are capable of recognizing/transporting pyridoxine, favoring acidic conditions for operation, and suggest a possible role for these transporters in pyridoxine transport mainly in tissues with an acidic environment like the small intestine, which has an acidic surface microclimate.
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Affiliation(s)
- Takahiro Yamashiro
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Tomoya Yasujima
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Hamid M Said
- Departments of Medicine and Physiology/Biophysics, University of California, Irvine, California, USA; Department of Veterans Affairs Medical Center, Long Beach, California, USA
| | - Hiroaki Yuasa
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan.
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Functional characterization of monocarboxylate transporter 12 (SLC16A12/MCT12) as a facilitative creatine transporter. Drug Metab Pharmacokinet 2020; 35:281-287. [PMID: 32249133 DOI: 10.1016/j.dmpk.2020.01.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 01/27/2020] [Accepted: 01/27/2020] [Indexed: 12/20/2022]
Abstract
SLC16A12/MCT12 has been recently identified as a creatine transporter in a Xenopus oocyte expression system; however, the mechanism, by which MCT12 transports creatine, remains unclear. This study was performed to determine the functional and molecular characteristics of MCT12 in mammalian cells. The results showed that the uptake of [14C]creatine was not significantly increased in HEK293 cells transiently expressing MCT12 with or without CD147, a molecular chaperone, compared with mock cells. When [14C]creatine was accumulated in the cells with the aid of SLC6A8/CRT1, a concentrative creatine transporter, followed by assessing the remaining intracellular [14C]creatine after initiating efflux, coexpression of MCT12 resulted in a decrease in the intracellular [14C]creatine and remarkably enhanced the efflux of [14C]creatine from the cells in a time-dependent manner. This activity was not affected by extracellular pH. The creatine efflux activity involved dissipation by the mutations of conserved charged amino acids such as Arg37, Asp65 and Asp299 in the transmembrane domains, indicating direct involvement of MCT12 in the creatine efflux. These results suggest that MCT12 mediates facilitative diffusion of creatine, depending on the concentration gradient across the plasma membrane in mammalian cells. The finding may provide important clues to understanding the disposition kinetics of creatine and its derivatives.
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