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Ding L, Chen X, Zhang W, Dai X, Guo H, Pan X, Xu Y, Feng J, Yuan M, Gao X, Wang J, Xu X, Li S, Wu H, Cao J, He Q, Yang B. Canagliflozin primes antitumor immunity by triggering PD-L1 degradation in endocytic recycling. J Clin Invest 2023; 133:e154754. [PMID: 36594471 PMCID: PMC9797339 DOI: 10.1172/jci154754] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 10/26/2022] [Indexed: 01/04/2023] Open
Abstract
Understanding the regulatory mechanisms of PD-L1 expression in tumors provides key clues for improving immune checkpoint blockade efficacy or developing novel oncoimmunotherapy. Here, we showed that the FDA-approved sodium-glucose cotransporter-2 (SGLT2) inhibitor canagliflozin dramatically suppressed PD-L1 expression and enhanced T cell-mediated cytotoxicity. Mechanistic study revealed that SGLT2 colocalized with PD-L1 at the plasma membrane and recycling endosomes and thereby prevented PD-L1 from proteasome-mediated degradation. Canagliflozin disturbed the physical interaction between SGLT2 and PD-L1 and subsequently allowed the recognition of PD-L1 by Cullin3SPOP E3 ligase, which triggered the ubiquitination and proteasome-mediated degradation of PD-L1. In mouse models and humanized immune-transformation models, either canagliflozin treatment or SGLT2 silencing significantly reduced PD-L1 expression and limited tumor progression - to a level equal to the PD-1 mAb - which was correlated with an increase in the activity of antitumor cytotoxic T cells. Notably, prolonged progression-free survival and overall survival curves were observed in the group of PD-1 mAb-treated patients with non-small cell lung cancer with high expression of SGLT2. Therefore, our study identifies a regulator of cell surface PD-L1, provides a ready-to-use small-molecule drug for PD-L1 degradation, and highlights a potential therapeutic target to overcome immune evasion by tumor cells.
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Affiliation(s)
- Ling Ding
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Xi Chen
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Wenxin Zhang
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Xiaoyang Dai
- Center of Drug Safety Evaluation and Research, Zhejiang University, Hangzhou, China
| | - Hongjie Guo
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Xiaohui Pan
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Yanjun Xu
- Department of Medical Thoracic Oncology and
| | - Jianguo Feng
- Institute of Basic Medicine and Cancer, The Cancer Hospital of the University of Chinese Academy of Sciences, Zhejiang Cancer Hospital, Chinese Academy of Sciences, Hangzhou, China
| | - Meng Yuan
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Xiaomeng Gao
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Jian Wang
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Xiaqing Xu
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Sicheng Li
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Honghai Wu
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Ji Cao
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
| | - Qiaojun He
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
- The Innovation Institute for Artificial Intelligence in Medicine and
- Cancer Center of Zhejiang University, Hangzhou, China
| | - Bo Yang
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, and
- The Innovation Institute for Artificial Intelligence in Medicine and
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Zhao S, Che F, Yang L, Zheng Y, Wang D, Yang Y, Wang Y. First report of paternal uniparental disomy of chromosome 8 with SLC52A2 mutation in Brown-vialetto-van laere syndrome type 2 and an analysis of genotype-phenotype correlations. Front Genet 2022; 13:977914. [PMID: 36186484 PMCID: PMC9520306 DOI: 10.3389/fgene.2022.977914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Accepted: 08/23/2022] [Indexed: 11/17/2022] Open
Abstract
Purpose: This study reports the clinical and genetic features of Brown-Vialetto-Van Laere syndrome (BVVL) type 2 in a case of uniparental disomy of chromosome 8 in mainland China and analyzes the genotype-phenotype correlation through a review of the literature of BVVL type 2 cases. Methods: The clinical characteristics, treatment, and follow-up data of the patient were summarized, and the etiology was identified by whole-exome sequencing and gene chip analysis. Correlations between the genotype and phenotype were analyzed by collecting clinical and genetic data of published cases and our patient. Results: We identified a homozygous mutation in SLC52A2 (NM_001253815.2 c.1255G>A) by trio-WES. Sanger sequencing confirmed that his father was heterozygous and his mother was wild type. Subsequently, paternal uniparental disomy of chromosome 8 [UPD (8)pat] was confirmed by chromosomal microarray analysis.The patient received long-term oral riboflavin treatment (7 mg/kg.d) and was followed up for 40 months by which time the child’s bulbar palsy, ataxia, and motor function had improved. A review of the literature and statistical analysis found that the symptoms of BVVL type 2 appear at the earliest shortly after birth and at the latest at 10 years of age. The median age of onset was 2.5 years, but the overall delay in diagnosis was a median of 5.6 years. The most common symptoms were hearing loss (83.9%), followed by muscle weakness (80.6%), visual impairment (64.5%), and ataxia (61.3%). To date, a total of 32 mutations in the SLC52A2 gene have been reported, with the most common being a missense mutation. Mutations occur throughout the length of the gene apart from at the N-terminus. In patients with missense mutations, homozygous pattern was more likely to present with ataxia as the first symptom (p < 0.05), while compound heterozygous pattern was more likely to develop respiratory insufficiency during the course of disease (p < 0.001). Moreover, patients with one missense mutation located in inside the transmembrane domain were more likely to have respiratory insufficiency than those with mutations both inside and outside the domain (p < 0.05). Riboflavin supplementation was an important factor in determining prognosis (p < 0.001). Conclusion: We report the first UPD(8)pat with SLC52A2 homozygous pathogenic mutation case in BVVL type 2, which expand the mutation spectrum of gene.
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Affiliation(s)
- Siyu Zhao
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Fengyu Che
- Shaanxi Institute of Pediatric Diseases, Xi’an Children’s Hospital, Xi’an, China
| | - Le Yang
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Yanyan Zheng
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Dong Wang
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Ying Yang
- Shaanxi Institute of Pediatric Diseases, Xi’an Children’s Hospital, Xi’an, China
- *Correspondence: Ying Yang, Yan Wang,
| | - Yan Wang
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
- *Correspondence: Ying Yang, Yan Wang,
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Zhang H, Hassan YI, Liu R, Mats L, Yang C, Liu C, Tsao R. Molecular Mechanisms Underlying the Absorption of Aglycone and Glycosidic Flavonoids in a Caco-2 BBe1 Cell Model. ACS OMEGA 2020; 5:10782-10793. [PMID: 32455198 PMCID: PMC7240828 DOI: 10.1021/acsomega.0c00379] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 04/24/2020] [Indexed: 05/13/2023]
Abstract
The mechanisms of cellular absorption and transport underlying the differences between flavonoid aglycones and glycosides and the effect of the structural feature are not well established. In this study, aglycone, mono-, and diglycosides of quercetin and cyanidin were selected to examine the effects of the structural feature on the bioavailability of flavonoids using hexose transporters SGLT1 and GLUT2 in a Caco-2 BBe1 cell model. Cellular uptake and transport of all glycosides were significantly different. The glycosides also significantly inhibited cellular uptake of d-glucose, indicating the involvement of the two hexose transporters SGLT1 and GLUT2 in the absorption, and the potential of the glycosides in lowering the blood glucose level. The in silico prediction model also supported these observations. The absorption of glycosides, especially diglycosides but not the aglycones, was significantly blocked by SGLT1 and GLUT2 inhibitors (phloridzin and phloretin) and further validated in SGLT1 knockdown Caco-2 BBe1 cells.
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Affiliation(s)
- Hua Zhang
- Guelph
Research & Development Centre, Agriculture
and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario N1G 5C9, Canada
| | - Yousef I. Hassan
- Guelph
Research & Development Centre, Agriculture
and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario N1G 5C9, Canada
| | - Ronghua Liu
- Guelph
Research & Development Centre, Agriculture
and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario N1G 5C9, Canada
| | - Lili Mats
- Guelph
Research & Development Centre, Agriculture
and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario N1G 5C9, Canada
| | - Cheng Yang
- Food
Science Department, Jiangnan University, 1800 Lihu Avenue, Binhu Qu, Wuxi Shi, Jiangsu Province 214122, China
| | - Chunming Liu
- Central
Laboratory, Changchun Normal University, No. 677 North Chang-ji Road, Changchun 130032, China
| | - Rong Tsao
- Guelph
Research & Development Centre, Agriculture
and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario N1G 5C9, Canada
- . Phone: +1 226 217 8180. Fax: +1 226 217 8183
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Jensen VF, Mølck AM, Lykkesfeldt J, Bøgh IB. Effect of maternal hypoglycaemia during gestation on materno-foetal nutrient transfer and embryo-foetal development: Evidence from experimental studies focused primarily on the rat. Reprod Toxicol 2018; 77:1-24. [DOI: 10.1016/j.reprotox.2018.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 12/07/2017] [Accepted: 01/30/2018] [Indexed: 01/14/2023]
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Dobbins RL, Greenway FL, Chen L, Liu Y, Breed SL, Andrews SM, Wald JA, Walker A, Smith CD. Selective sodium-dependent glucose transporter 1 inhibitors block glucose absorption and impair glucose-dependent insulinotropic peptide release. Am J Physiol Gastrointest Liver Physiol 2015; 308:G946-54. [PMID: 25767259 DOI: 10.1152/ajpgi.00286.2014] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 03/04/2015] [Indexed: 02/07/2023]
Abstract
GSK-1614235 and KGA-2727 are potent, selective inhibitors of the SGLT1 sodium-dependent glucose transporter. Nonclinical (KGA-2727) and clinical (GSK-1614235) trials assessed translation of SGLT1 inhibitor effects from rats to normal human physiology. In rats, KGA-2727 (0.1 mg/kg) or vehicle was given before oral administration of 3-O-methyl-α-d-glucopyranose (3-O-methylglucose, 3-OMG) containing 3-[3H]OMG tracer. Tracer absorption and distribution were assessed from plasma, urine, and fecal samples. SGLT1 inhibition reduced urine 3-OMG recovery and increased fecal excretion. SGLT1 inhibitor effects on plasma glucose, insulin, gastric inhibitory peptide (GIP), and glucagon-like peptide-1 (GLP-1) concentrations were also measured during a standard meal. Incremental glucose, insulin, and GIP concentrations were decreased, indicating downregulation of β-cell and K cell secretion. Minimal effects were observed in the secretion of the L cell product, GLP-1. With the use of a three-way, crossover design, 12 healthy human subjects received placebo or 20 mg GSK-1614235 immediately before or after a meal. Five minutes into the meal, 3-OMG was ingested. Postmeal dosing had little impact, yet premeal dosing delayed and reduced 3-OMG absorption, with an AUC0-10 of 231±31 vs. 446±31 μg·h(-1)·ml(-1), for placebo. Recovery of tracer in urine was 1.2±0.7 g for premeal dosing and 2.2±0.1 g for placebo. Incremental concentrations of insulin, C-peptide, and GIP were reduced for 2 h with premeal GSK-1614235. Total GLP-1 concentrations were significantly increased, and a trend for increased peptide YY (PYY) was noted. SGLT1 inhibitors block intestinal glucose absorption and reduce GIP secretion in rats and humans, suggesting SGLT1 glucose transport is critical for GIP release. Conversely, GLP-1 and PYY secretion are enhanced by SGLT1 inhibition in humans.
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Affiliation(s)
- Robert L Dobbins
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
| | - Frank L Greenway
- Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana
| | - Lihong Chen
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
| | - Yaping Liu
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
| | - Sharon L Breed
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
| | - Susan M Andrews
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
| | - Jeffrey A Wald
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
| | - Ann Walker
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
| | - Chari D Smith
- GlaxoSmithKline, Enteroendocrine Unit, Research Triangle Park, North Carolina; and
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Subramanian VS, Kapadia R, Ghosal A, Said HM. Identification of residues/sequences in the human riboflavin transporter-2 that is important for function and cell biology. Nutr Metab (Lond) 2015; 12:13. [PMID: 25798182 PMCID: PMC4367879 DOI: 10.1186/s12986-015-0008-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 02/18/2015] [Indexed: 11/26/2022] Open
Abstract
Background Riboflavin (RF) is essential for normal cellular metabolic activities. Human cells obtain RF from their surroundings via a carrier-mediated process that involves RF transporters -1, -2 & -3 (hRFVT -1, -2 & -3; products of SLC52A1, -A2 and -A3 genes, respectively). Little is known about the structural features of these transporters that are important for their function/cell biology. Our aim in this study was to address these issues for the hRFVT-2, a transporter linked to the neurodegenerative disorder Brown-Vialetto-Van Laere Syndrome (BVVLS). Methods We used comparative protein-structure modelling to predict residues that interact with two amino acids known to be critical for hRFVT-2 function (the clinical mutants L123 and L339), site-directed mutagenesis, and truncation approach in the human-derived brain U87 cell model. Results First we showed that the defect in the function of the L123 and L339 hRFVT-2 clinical mutants is related to a reduction in protein stability/translation efficiency and to retention of the protein in the ER. Mutating V120 and L121 (residues predicted to interact with L123) and L342 (a residue predicted to interact with L339) also led to a significant inhibition in hRFVT-2 function (with no change in membrane expression); this inhibition was associated with changes in protein stability/translation efficiency (in the case of V120A and L342A) and an impairment in transport function (in the case of L121). Truncating the N- and C- terminals of hRFVT-2 led to significant inhibition in RF uptake, which was associated with changes in protein stability/translation efficiency (it was also associated with a partial impairment in membrane targeting in the case of the N-terminal truncation). Conclusion These investigations report on identification of residues/sequences in the hRFVT-2 protein that is important for its physiological function and cell biology.
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Affiliation(s)
- Veedamali S Subramanian
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, CA 92697 USA ; Department of Veterans Affairs Medical Center, Long Beach, CA 90822 USA
| | - Rubina Kapadia
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, CA 92697 USA ; Department of Veterans Affairs Medical Center, Long Beach, CA 90822 USA
| | - Abhisek Ghosal
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, CA 92697 USA ; Department of Veterans Affairs Medical Center, Long Beach, CA 90822 USA
| | - Hamid M Said
- Departments of Medicine, Physiology/Biophysics, University of California, Irvine, CA 92697 USA ; Department of Veterans Affairs Medical Center, Long Beach, CA 90822 USA
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Bibee KP, Augustin R, Gazit V, Moley KH. The apical sorting signal for human GLUT9b resides in the N-terminus. Mol Cell Biochem 2013; 376:163-73. [PMID: 23361362 DOI: 10.1007/s11010-013-1564-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Accepted: 01/18/2013] [Indexed: 12/11/2022]
Abstract
The two splice variants of human glucose transporter 9 (hGLUT9) are targeted to different polarized membranes. hGLUT9a traffics to the basolateral membrane, whereas hGLUT9b traffics to the apical region. This study examines the sorting mechanism of these variants, which differ only in their N-terminal domain. Mutating a di-leucine motif unique to GLUT9a did not affect targeting. Chimeric proteins were made using GLUT1, a basolaterally targeted transporter, and GLUT3, an apically targeted protein whose signal lies in the C-terminus. Overexpression of the chimeric proteins in polarized cells demonstrates that the N-terminus of hGLUT9b contains a signal capable of redirecting GLUT1 to the apical membrane. The N-terminus of hGLUT9a, however, does not contain a basolateral signal sufficient enough to redirect GLUT3. Portions of the GLUT9a N-terminus were substituted with corresponding portions of the GLUT9b N-terminus to determine the motif responsible for apical targeting. The first 16 amino acids were not found to be a sufficient apical signal. The last ten amino acids of the N-termini differ only in amino-acid class at one location. In the B-form, leucine, a hydrophobic residue, is substituted for lysine, a basic residue, found in the A-form. However, mutation of the leucine in hGLUT9b to a lysine resulted in retention of the apical signal. We therefore believe the apical signal exists as an interplay between the final ten amino acids of the N-terminus and another motif within the protein such as the intracellular loop or other motifs within the N-terminus.
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Affiliation(s)
- Kristin P Bibee
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Abstract
There are two classes of glucose transporters involved in glucose homeostasis in the body, the facilitated transporters or uniporters (GLUTs) and the active transporters or symporters (SGLTs). The energy for active glucose transport is provided by the sodium gradient across the cell membrane, the Na(+) glucose cotransport hypothesis first proposed in 1960 by Crane. Since the cloning of SGLT1 in 1987, there have been advances in the genetics, molecular biology, biochemistry, biophysics, and structure of SGLTs. There are 12 members of the human SGLT (SLC5) gene family, including cotransporters for sugars, anions, vitamins, and short-chain fatty acids. Here we give a personal review of these advances. The SGLTs belong to a structural class of membrane proteins from unrelated gene families of antiporters and Na(+) and H(+) symporters. This class shares a common atomic architecture and a common transport mechanism. SGLTs also function as water and urea channels, glucose sensors, and coupled-water and urea transporters. We also discuss the physiology and pathophysiology of SGLTs, e.g., glucose galactose malabsorption and familial renal glycosuria, and briefly report on targeting of SGLTs for new therapies for diabetes.
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Affiliation(s)
- Ernest M Wright
- Department of Physiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California 90095-1751, USA.
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Suzuki T, Matsuzaki T, Hagiwara H, Aoki T, Tajika-Takahashi Y, Takata K. Apical localization of sodium-dependent glucose transporter SGLT1 is maintained by cholesterol and microtubules. Acta Histochem Cytochem 2006; 39:155-61. [PMID: 17327902 PMCID: PMC1779948 DOI: 10.1267/ahc.06024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 10/23/2006] [Indexed: 01/10/2023] Open
Abstract
A GFP-labeled sodium-dependent glucose transporter SGLT1 (SGLT-GFP) was transfected into MDCK cells. SGLT-GFP was localized at the apical membrane in confluent cells. When cellular cholesterol was depleted by methyl-β-cyclodextrin (MβCD) treatment, the localization of SGLT-GFP gradually switched from apical to whole plasma membrane. Time-lapse microscopy revealed that the effect of MβCD appeared within 30 min, and that the transition of SGLT-GFP to the whole plasma membrane was completed within 2 hr after the administration. Immunofluorescence microscopy revealed that the tight junction framework remained steady during this process. The effect of MβCD on SGLT-GFP localization was counterbalanced by the addition of cholesterol into the culture medium. Disruption of microtubules by colcemid also perturbed SGLT-GFP localization. SGLT-GFP localized to the whole plasma membrane by colcemid treatment, and apical localization was restored within 1 hr after removal of colcemid. Inhibition of protein synthesis by cycloheximide had no effect on the transition of SGLT-GFP induced by the MβCD or colcemid. These results indicated that the apical localization of SGLT-GFP is maintained by cellular cholesterol and microtubules, possibly with an apical recycling machinery.
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Affiliation(s)
- Takeshi Suzuki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
- Correspondence to: Takeshi Suzuki, Ph.D., Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Showa-machi 3–39–22, Maebashi, Gunma 371–8511, Japan. E-mail:
| | - Toshiyuki Matsuzaki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Haruo Hagiwara
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Takeo Aoki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Yukiko Tajika-Takahashi
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
| | - Kuniaki Takata
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371–8511, Japan
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Subramanian VS, Marchant JS, Said HM. Targeting and trafficking of the human thiamine transporter-2 in epithelial cells. J Biol Chem 2005; 281:5233-45. [PMID: 16371350 DOI: 10.1074/jbc.m512765200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Humans lack biochemical pathways for thiamine synthesis, so cellular requirements are met via specific carrier-mediated uptake pathways. Two proteins from the solute carrier SLC19A gene family have been identified as human thiamine transporters (hTHTRs), SLC19A1 (hTHTR1) and SLC19A2 (hTHTR2). Both of these transporters are co-expressed but are differentially targeted in polarized cell types that mediate vectorial thiamine transport (e.g. renal and intestinal epithelia). It is important to understand the domain structure of these proteins, namely which regions within the polypeptide sequence are important for physiological delivery to the cell surface, in order to understand the impact of clinically relevant mutations on thiamine transport. Here we have characterized the mechanisms regulating hTHTR2 distribution by using live cell imaging methods that resolve the targeting and trafficking dynamics of full-length hTHTR2, a series of hTHTR2 truncation mutants, as well as chimeras comprising the hTHTR1 and hTHTR2 sequence. We showed the following: (i) that the cytoplasmic COOH-tail of hTHTR2 is not essential for apical targeting in polarized cells; (ii) that delivery of hTHTR2 to the cell surface is critically dependent on the integrity of the transmembrane backbone of the polypeptide so that minimal truncations abrogate cell surface expression of hTHTR2; and (iii) video rate images of hTHTR2-containing intracellular vesicles displayed rapid bi-directional trafficking events to and from the cell surface impaired by microtubule-disrupting but not microfilament-disrupting agents as well as by overexpression of the dynactin subunit dynamitin (p50). Finally, we compared the behavior of hTHTR2 with that of hTHTR1 and the human reduced folate carrier (SLC19A1) to underscore commonalities in the cell surface targeting mechanisms of the entire SLC19A gene family.
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Tajika Y, Matsuzaki T, Suzuki T, Ablimit A, Aoki T, Hagiwara H, Kuwahara M, Sasaki S, Takata K. Differential regulation of AQP2 trafficking in endosomes by microtubules and actin filaments. Histochem Cell Biol 2005; 124:1-12. [PMID: 16049696 DOI: 10.1007/s00418-005-0010-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2005] [Indexed: 01/02/2023]
Abstract
Vasopressin-induced trafficking of aquaporin-2 (AQP2) water channels in kidney collecting duct cells is critical to regulate the urine concentration. To better understand the mechanism of subcellular trafficking of AQP2, we examined MDCK cells expressing AQP2 as a model. We first performed double-immunolabeling of AQP2 with endosomal marker proteins, and showed that AQP2 is stored at a Rab11-positive subapical compartment. After the translocation to the plasma membrane, AQP2 was endocytosed to EEA1-positive early endosomes, and then transferred back to the original Rab11-positive compartment. When Rab11 was depleted by RNA interference, retention of AQP2 at the subapical storage compartment was impaired. We next examined the role of cytoskeleton in the AQP2 trafficking and localization. By the treatment with microtubule-disrupting agent such as nocodazole or colcemid, the distribution of AQP2 storage compartment was altered. The disruption of actin filaments with cytochalasin D or latrunculin B induced the accumulation of AQP2 in EEA1-positive early endosomes. Altogether, our data suggest that Rab11 and microtubules maintain the proper distribution of the subapical AQP2 storage compartment, and actin filaments regulate the trafficking of AQP2 from early endosomes to the storage compartment.
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Affiliation(s)
- Yuki Tajika
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan
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Xia X, Wang G, Peng Y, Jen J. Cys351 and Cys361 of the Na+/glucose cotransporter are important for both function and cell-surface expression. Arch Biochem Biophys 2005; 438:63-9. [PMID: 15885653 DOI: 10.1016/j.abb.2005.04.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Revised: 04/12/2005] [Accepted: 04/12/2005] [Indexed: 11/30/2022]
Abstract
Here, we identify Cys351 and Cys361 as novel residues critical for the function and plasma membrane targeting of the Na+/glucose transporter-1 (SGLT1). HEK-293 cells expressing the C351A and C361A mutants showed no detectable Na(+)-coupled uptake for alpha-methyl glucoside (AMG). Cell-surface biotinylation and Western blot revealed that the two mutants were overexpressed in 293 cells; however, none of them exhibited normal cell-surface expression. When reconstituted in proteoliposomes, mutant SGLT1s demonstrated significantly lower affinity for AMG compared with the wild-type transporter. Incubation with the reducing agent dithiothreitol did not alter the catalytic activity of wild-type protein, but surprisingly, it nearly restored the ability of SGLT1-C351A and -C361A to bind and translocate AMG. Thus, the C351A and C361A mutations might cause a global reorganization of the disulfide bonds of SGLT1. Furthermore, we showed that a double mutation (C351A/C361A) restored the cell-surface expression of the single C-to-A mutants (C351A and C361A).
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Affiliation(s)
- Xiaobing Xia
- Beijing Institute for Infectious Diseases, Beijing 100039, China.
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13
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Runembert I, Couette S, Federici P, Colucci-Guyon E, Babinet C, Briand P, Friedlander G, Terzi F. Recovery of Na-glucose cotransport activity after renal ischemia is impaired in mice lacking vimentin. Am J Physiol Renal Physiol 2004; 287:F960-8. [PMID: 15238351 DOI: 10.1152/ajprenal.00064.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vimentin, an intermediate filament protein mainly expressed in mesenchyma-derived cells, is reexpressed in renal tubular epithelial cells under many pathological conditions, characterized by intense cell proliferation. Whether vimentin reexpression is only a marker of cell dedifferentiation or is instrumental in the maintenance of cell structure and/or function is still unknown. Here, we used vimentin knockout mice ( Vim−/−) and an experimental model of acute renal injury (30-min bilateral renal ischemia) to explore the role of vimentin. Bilateral renal ischemia induced an initial phase of acute tubular necrosis that did not require vimentin and was similar, in terms of morphological and functional changes, in Vim+/+and Vim−/−mice. However, vimentin was essential to favor Na-glucose cotransporter 1 localization to brush-border membranes and to restore Na-glucose cotransport activity in regenerating tubular cells. We show that the effect of vimentin inactivation is specific and results in persistent glucosuria. We propose that vimentin is part of a structural network that favors carrier localization to plasma membranes to restore transport activity in injured kidneys.
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Affiliation(s)
- Isabelle Runembert
- INSERM U426, Faculté de Médecine Xavier Bichat, 16 Rue Henri Huchard, BP 416, 75870 Paris Cedex 18, France
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14
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Abstract
In order to carry out their physiological functions, ion transport proteins must be targeted to the appropriate domains of cell membranes. Regulation of ion transport activity frequently involves the tightly controlled delivery of intracellular populations of transport proteins to the plasma membrane or the endocytic retrieval of transport proteins from the cell surface. Transport proteins carry signals embedded within their structures that specify their subcellular distributions and endow them with the capacity to participate in regulated membrane trafficking processes. Recently, a great deal has been learned about the biochemical nature of these signals, as well as about the cellular machinery that interprets them and acts upon their messages.
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Affiliation(s)
- Theodore R Muth
- Department of Biology, CUNY Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11231, USA.
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15
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Kipp H, Khoursandi S, Scharlau D, Kinne RKH. More than apical: Distribution of SGLT1 in Caco-2 cells. Am J Physiol Cell Physiol 2003; 285:C737-49. [PMID: 12773314 DOI: 10.1152/ajpcell.00041.2003] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the distribution of the endogenous sodium-d-glucose cotransporter (SGLT1) in polarized Caco-2 cells, a model for enterocytes. A cellular organelle fraction was separated by free-flow electrophoresis and subjected to the analysis of endogenous and exogenous marker enzymes for various membrane vesicle components. Furthermore, the presence of SGLT1 was tested by an ELISA assay employing newly developed epitope specific antibodies. Thereby it was found that the major amount of SGLT1 resided in intracellular compartments and only a minor amount in apical plasma membranes. The distribution ratio between intracellular SGLT1 and apical membrane-associated SGLT1 was approximately 2:1. Further immunocytochemical investigation of SGLT1 distribution in fixed Caco-2 cells by epifluorescence and confocal microscopy revealed that the intracellular compartments containing SGLT1 were associated with microtubules. Elimination of SGLT1 synthesis by incubation of cells with cycloheximide did not significantly reduce the size of the intracellular SGLT1 pool. Furthermore, the half-life of SGLT1 in Caco-2 cells was determined to be 2.5 days by metabolic labeling followed by immunoprecipitation. Our data suggest that most of the intracellular SGLT1 are not transporters en route from biosynthesis to their cellular destination but represent an intracellular reserve pool. We therefore propose that intracellular compartments containing SGLT1 are involved in the regulation of SGLT1 abundance at the apical cell surface.
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Affiliation(s)
- Helmut Kipp
- Abteilung Epithelphysiologie, Max-Planck-Institut für molekulare Physiologie, Postfach 50 02 47, 44202 Dortmund, Germany.
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16
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Subramanian VS, Marchant JS, Parker I, Said HM. Cell biology of the human thiamine transporter-1 (hTHTR1). Intracellular trafficking and membrane targeting mechanisms. J Biol Chem 2003; 278:3976-84. [PMID: 12454006 DOI: 10.1074/jbc.m210717200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The human thiamine transporter hTHTR1 is involved in the cellular accumulation of thiamine (vitamin B1) in many tissues. Thiamine deficiency disorders, such as thiamine-responsive megaloblastic anemia (TRMA), which is associated with specific mutations within hTHTR1, likely impairs the functionality and/or intracellular targeting of hTHTR1. Unfortunately, nothing is known about the mechanisms that control the intracellular trafficking or membrane targeting of hTHTR1. To identify molecular determinants involved in hTHTR1 targeting, we generated a series of hTHTR1 truncations fused with the green fluorescent protein and imaged the targeting and trafficking dynamics of each construct in living duodenal epithelial cells. Whereas the full-length fusion protein was functionally expressed at the plasma membrane, analysis of the truncated mutants demonstrated an essential role for both NH(2)-terminal sequence and the integrity of the backbone polypeptide for cell surface expression. Most notably, truncation of hTHTR1 within a region where several TRMA truncations are clustered resulted in intracellular retention of the mutant protein. Finally, confocal imaging of the dynamics of intracellular hTHTR1 vesicles revealed a critical role for microtubules, but not microfilaments, in hTHTR1 trafficking. Taken together, these results correlate hTHTR1 structure with cellular expression profile and reveal a critical dependence on hTHTR1 backbone integrity and microtubule-based trafficking processes for functional expression of hTHTR1.
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Shinoda Y, Matsuzaki T, Yokoo-Sugawara M, Suzuki T, Aoki T, Hagiwara H, Kuwano H, Takata K. Introduction and Expression of Glucose Transporters in Pancreatic Acinar Cells by In Vivo Electroporation. Acta Histochem Cytochem 2003. [DOI: 10.1267/ahc.36.77] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Affiliation(s)
- Yasuo Shinoda
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
- First Department of Surgery, Gunma University School of Medicine
| | | | | | - Takeshi Suzuki
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
| | - Takeo Aoki
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
| | - Haruo Hagiwara
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
| | - Hiroyuki Kuwano
- First Department of Surgery, Gunma University School of Medicine
| | - Kuniaki Takata
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
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Tajika Y, Matsuzaki T, Suzuki T, Aoki T, Hagiwara H, Takata K. Cryosectioning of Cultured Cells on Permeable Support. Acta Histochem Cytochem 2003. [DOI: 10.1267/ahc.36.119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Yuki Tajika
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
| | | | - Takeshi Suzuki
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
| | - Takeo Aoki
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
| | - Haruo Hagiwara
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
| | - Kuniaki Takata
- Department of Anatomy and Cell Biology, Gunma University School of Medicine
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Marchant JS, Subramanian VS, Parker I, Said HM. Intracellular trafficking and membrane targeting mechanisms of the human reduced folate carrier in Mammalian epithelial cells. J Biol Chem 2002; 277:33325-33. [PMID: 12087110 DOI: 10.1074/jbc.m205955200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The major pathway for cellular uptake of the water-soluble vitamin folic acid in mammalian cells is via a plasma membrane protein known as the reduced folate carrier (RFC). The molecular determinants that dictate plasma membrane expression of RFC as well as the cellular mechanisms that deliver RFC to the cell surface remain poorly defined. Therefore, we designed a series of fusion proteins of the human RFC (hRFC) with green fluorescent protein to image the targeting and trafficking dynamics of hRFC in living epithelial cells. We show that, in contrast to many other nutrient transporters, the molecular determinants that dictate hRFC plasma membrane expression reside within the hydrophobic backbone of the polypeptide and not within the cytoplasmic NH(2)- or COOH-terminal domains of the protein. Further, the integrity of the hRFC backbone is critical for export of the polypeptide from the endoplasmic reticulum to the cell surface. This trafficking is critically dependent on intact microtubules because microtubule disruption inhibits motility of hRFC-containing vesicles as well as final expression of hRFC in the plasma membrane. For the first time, these data define the mechanisms that control the intracellular trafficking and cell surface localization of hRFC within mammalian epithelia.
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Affiliation(s)
- Jonathan S Marchant
- Department of Neurobiology and Behavior, University of California, Irvine, California 92697, USA
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