1
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Koe JC, Parker SJ. The posttranslational regulation of amino acid transporters is critical for their function in the tumor microenvironment. Curr Opin Biotechnol 2024; 85:103022. [PMID: 38056204 DOI: 10.1016/j.copbio.2023.103022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Revised: 10/28/2023] [Accepted: 11/06/2023] [Indexed: 12/08/2023]
Abstract
Amino acid transporters (AATs) facilitate nutrient uptake and nutrient exchange between cancer and stromal cells. The posttranslational modification (PTM) of transporters is an important mechanism that tumor-associated cells use to dynamically regulate their function and stability in response to microenvironmental cues. In this review, we summarize recent findings that demonstrate the significance of N-glycosylation, phosphorylation, and ubiquitylation for the function of AATs. We also highlight powerful approaches that hijack the PTM machinery that could be used as therapeutics or tools to modulate transporter activity.
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Affiliation(s)
- Jessica C Koe
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC, Canada; Centre for Molecular Medicine and Therapeutics, Vancouver, BC, Canada
| | - Seth J Parker
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC, Canada; Centre for Molecular Medicine and Therapeutics, Vancouver, BC, Canada; British Columbia Children's Hospital Research Institute, Vancouver, BC, Canada.
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2
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Yang T, Xiao H, Chen X, Zheng L, Guo H, Wang J, Jiang X, Zhang CY, Yang F, Ji X. Characterization of N-glycosylation and its functional role in SIDT1-Mediated RNA uptake. J Biol Chem 2024; 300:105654. [PMID: 38237680 PMCID: PMC10850970 DOI: 10.1016/j.jbc.2024.105654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/04/2024] [Accepted: 01/05/2024] [Indexed: 02/08/2024] Open
Abstract
The mammalian SID-1 transmembrane family members, SIDT1 and SIDT2, are multipass transmembrane proteins that mediate the cellular uptake and intracellular trafficking of nucleic acids, playing important roles in the immune response and tumorigenesis. Previous work has suggested that human SIDT1 and SIDT2 are N-glycosylated, but the precise site-specific N-glycosylation information and its functional contribution remain unclear. In this study, we use high-resolution liquid chromatography tandem mass spectrometry to comprehensively map the N-glycosites and quantify the N-glycosylation profiles of SIDT1 and SIDT2. Further molecular mechanistic probing elucidates the essential role of N-linked glycans in regulating cell surface expression, RNA binding, protein stability, and RNA uptake of SIDT1. Our results provide crucial information about the potential functional impact of N-glycosylation in the regulation of SIDT1-mediated RNA uptake and provide insights into the molecular mechanisms of this promising nucleic acid delivery system with potential implications for therapeutic applications.
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Affiliation(s)
- Tingting Yang
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Haonan Xiao
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Xiulan Chen
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Le Zheng
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Hangtian Guo
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Jiaqi Wang
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Xiaohong Jiang
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Chen-Yu Zhang
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China; Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, Jiangsu, China.
| | - Fuquan Yang
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
| | - Xiaoyun Ji
- The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China; Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, Jiangsu, China; Institute of Artificial Intelligence Biomedicine, Nanjing University, Nanjing, Jiangsu, China; Engineering Research Center of Protein and Peptide Medicine, Ministry of Education, Nanjing, Jiangsu, China.
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3
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Pujol‐Giménez J, Mirzaa G, Blue EE, Albano G, Miller DE, Allworth A, Bennett JT, Byers PH, Chanprasert S, Chen J, Doherty D, Folta AB, Gillentine MA, Glass I, Hing A, Horike‐Pyne M, Leppig KA, Parhin A, Ranchalis J, Raskind WH, Rosenthal EA, Schwarze U, Sheppeard S, Strohbehn S, Sybert VP, Timms A, Wener M, Bamshad MJ, Hisama FM, Jarvik GP, Dipple KM, Hediger MA, Stergachis AB. Dominant-negative variant in SLC1A4 causes an autosomal dominant epilepsy syndrome. Ann Clin Transl Neurol 2023; 10:1046-1053. [PMID: 37194416 PMCID: PMC10270265 DOI: 10.1002/acn3.51786] [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: 01/30/2023] [Revised: 03/29/2023] [Accepted: 04/15/2023] [Indexed: 05/18/2023] Open
Abstract
SLC1A4 is a trimeric neutral amino acid transporter essential for shuttling L-serine from astrocytes into neurons. Individuals with biallelic variants in SLC1A4 are known to have spastic tetraplegia, thin corpus callosum, and progressive microcephaly (SPATCCM) syndrome, but individuals with heterozygous variants are not thought to have disease. We identify an 8-year-old patient with global developmental delay, spasticity, epilepsy, and microcephaly who has a de novo heterozygous three amino acid duplication in SLC1A4 (L86_M88dup). We demonstrate that L86_M88dup causes a dominant-negative N-glycosylation defect of SLC1A4, which in turn reduces the plasma membrane localization of SLC1A4 and the transport rate of SLC1A4 for L-serine.
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Affiliation(s)
- Jonai Pujol‐Giménez
- Department of Nephrology and HypertensionUniversity Hospital Bern, InselspitalBernSwitzerland
- Department of Biomedical ResearchUniversity of BernBernSwitzerland
| | - Ghayda Mirzaa
- Center for Integrative Brain ResearchSeattle Children's Research InstituteSeattleWashingtonUSA
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Elizabeth E. Blue
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Department of Laboratory Medicine and PathologyUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Giuseppe Albano
- Department of Nephrology and HypertensionUniversity Hospital Bern, InselspitalBernSwitzerland
- Department of Biomedical ResearchUniversity of BernBernSwitzerland
| | - Danny E. Miller
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Aimee Allworth
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - James T. Bennett
- Center for Integrative Brain ResearchSeattle Children's Research InstituteSeattleWashingtonUSA
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- Center for Developmental Biology and Regenerative MedicineSeattle Children's Research InstituteSeattleWashingtonUSA
| | - Peter H. Byers
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Sirisak Chanprasert
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Jingheng Chen
- Department of Laboratory Medicine and PathologyUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Daniel Doherty
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Andrew B. Folta
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | | | - Ian Glass
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Anne Hing
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
| | - Martha Horike‐Pyne
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Kathleen A. Leppig
- Group Health CooperativeKaiser Permanente WashingtonSeattleWashingtonUSA
| | - Azma Parhin
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Jane Ranchalis
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Wendy H. Raskind
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | | | - Ulrike Schwarze
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Sam Sheppeard
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Samuel Strohbehn
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Virginia P. Sybert
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Andrew Timms
- Center for Developmental Biology and Regenerative MedicineSeattle Children's Research InstituteSeattleWashingtonUSA
| | - Mark Wener
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Michael J. Bamshad
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Fuki M. Hisama
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Gail P. Jarvik
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Genome SciencesUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Katrina M. Dipple
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Matthias A. Hediger
- Department of Nephrology and HypertensionUniversity Hospital Bern, InselspitalBernSwitzerland
- Department of Biomedical ResearchUniversity of BernBernSwitzerland
| | - Andrew B. Stergachis
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Genome SciencesUniversity of Washington School of MedicineSeattleWashingtonUSA
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4
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Wang C, Chu C, Ji X, Luo G, Xu C, He H, Yao J, Wu J, Hu J, Jin Y. Biology of Peptide Transporter 2 in Mammals: New Insights into Its Function, Structure and Regulation. Cells 2022; 11:cells11182874. [PMID: 36139448 PMCID: PMC9497230 DOI: 10.3390/cells11182874] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 09/09/2022] [Accepted: 09/12/2022] [Indexed: 11/16/2022] Open
Abstract
Peptide transporter 2 (PepT2) in mammals plays essential roles in the reabsorption and conservation of peptide-bound amino acids in the kidney and in maintaining neuropeptide homeostasis in the brain. It is also of significant medical and pharmacological significance in the absorption and disposing of peptide-like drugs, including angiotensin-converting enzyme inhibitors, β-lactam antibiotics and antiviral prodrugs. Understanding the structure, function and regulation of PepT2 is of emerging interest in nutrition, medical and pharmacological research. In this review, we provide a comprehensive overview of the structure, substrate preferences and localization of PepT2 in mammals. As PepT2 is expressed in various organs, its function in the liver, kidney, brain, heart, lung and mammary gland has also been addressed. Finally, the regulatory factors that affect the expression and function of PepT2, such as transcriptional activation and posttranslational modification, are also discussed.
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Affiliation(s)
- Caihong Wang
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310032, China
- Department of Bioinformatics, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
- Zhejiang Conba Pharmaceutical Limited Company, Hangzhou 310052, China
| | - Chu Chu
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310032, China
| | - Xiang Ji
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310032, China
| | - Guoliang Luo
- Zhejiang Conba Pharmaceutical Limited Company, Hangzhou 310052, China
- Zhejiang Institute of Modern Chinese Medicine and Natural Medicine, Hangzhou 310052, China
| | - Chunling Xu
- Zhejiang Conba Pharmaceutical Limited Company, Hangzhou 310052, China
- Zhejiang Institute of Modern Chinese Medicine and Natural Medicine, Hangzhou 310052, China
| | - Houhong He
- Zhejiang Conba Pharmaceutical Limited Company, Hangzhou 310052, China
- Zhejiang Institute of Modern Chinese Medicine and Natural Medicine, Hangzhou 310052, China
| | - Jianbiao Yao
- Zhejiang Conba Pharmaceutical Limited Company, Hangzhou 310052, China
- Zhejiang Institute of Modern Chinese Medicine and Natural Medicine, Hangzhou 310052, China
| | - Jian Wu
- Zhejiang Conba Pharmaceutical Limited Company, Hangzhou 310052, China
- Zhejiang Institute of Modern Chinese Medicine and Natural Medicine, Hangzhou 310052, China
| | - Jiangning Hu
- Zhejiang Conba Pharmaceutical Limited Company, Hangzhou 310052, China
- Zhejiang Institute of Modern Chinese Medicine and Natural Medicine, Hangzhou 310052, China
- Correspondence: (J.H.); (Y.J.)
| | - Yuanxiang Jin
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310032, China
- Correspondence: (J.H.); (Y.J.)
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5
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Guo J, Tan M, Zhu J, Tian Y, Liu H, Luo F, Wang J, Huang Y, Zhang Y, Yang Y, Wang G. Proteomic Analysis of Human Milk Reveals Nutritional and Immune Benefits in the Colostrum from Mothers with COVID-19. Nutrients 2022; 14:nu14122513. [PMID: 35745243 PMCID: PMC9227629 DOI: 10.3390/nu14122513] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/13/2022] [Accepted: 06/14/2022] [Indexed: 02/05/2023] Open
Abstract
Despite the well-known benefits of breastfeeding and the World Health Organization’s breastfeeding recommendations for COVID-19 infected mothers, whether these mothers should be encouraged to breastfeed is under debate due to concern about the risk of virus transmission and lack of evidence of breastmilk’s protective effects against the virus. Here, we provide a molecular basis for the breastfeeding recommendation through mass spectrometry (MS)-based proteomics and glycosylation analysis of immune-related proteins in both colostrum and mature breastmilk collected from COVID-19 patients and healthy donors. The total protein amounts in the COVID-19 colostrum group were significantly higher than in the control group. While casein proteins in COVID-19 colostrum exhibited significantly lower abundances, immune-related proteins, especially whey proteins with antiviral properties against SARS-CoV-2, were upregulated. These proteins were detected with unique site-specific glycan structures and improved glycosylation diversity that are beneficial for recognizing epitopes and blocking viral entry. Such adaptive differences in milk from COVID-19 mothers tended to fade in mature milk from the same mothers one month postpartum. These results suggest that feeding infants colostrum from COVID-19 mothers confers both nutritional and immune benefits, and provide molecular-level insights that aid breastmilk feeding decisions in cases of active infection.
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Affiliation(s)
- Juanjuan Guo
- Department of Gynaecology and Obstetrics, Zhongnan Hospital of Wuhan University, Hubei Clinical Research Center for Prenatal Diagnosis and Birth Health, Wuhan 430071, China; (J.G.); (H.L.); (Y.Z.)
| | - Minjie Tan
- Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China; (M.T.); (Y.T.); (Y.H.)
| | - Jing Zhu
- Institute of Biotechnology and Health, Beijing Academy of Science and Technology, Beijing 100089, China
- Correspondence: (J.Z.); (G.W.)
| | - Ye Tian
- Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China; (M.T.); (Y.T.); (Y.H.)
| | - Huanyu Liu
- Department of Gynaecology and Obstetrics, Zhongnan Hospital of Wuhan University, Hubei Clinical Research Center for Prenatal Diagnosis and Birth Health, Wuhan 430071, China; (J.G.); (H.L.); (Y.Z.)
| | - Fan Luo
- State Key Laboratory of Virology, Institute of Medical Virology, School of Basic Medical Sciences, Wuhan University, Wuhan 430071, China;
| | - Jianbin Wang
- School of Life Sciences, Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China;
| | - Yanyi Huang
- Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China; (M.T.); (Y.T.); (Y.H.)
- Biomedical Pioneering Innovation Center, Peking University, Beijing 100871, China
| | - Yuanzhen Zhang
- Department of Gynaecology and Obstetrics, Zhongnan Hospital of Wuhan University, Hubei Clinical Research Center for Prenatal Diagnosis and Birth Health, Wuhan 430071, China; (J.G.); (H.L.); (Y.Z.)
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, Wuhan 430071, China
| | - Yuexin Yang
- National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention, Beijing 100050, China;
| | - Guanbo Wang
- Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China; (M.T.); (Y.T.); (Y.H.)
- Biomedical Pioneering Innovation Center, Peking University, Beijing 100871, China
- Correspondence: (J.Z.); (G.W.)
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6
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Wu Q, Liang Y, Kong Y, Zhang F, Feng Y, Ouyang Y, Wang C, Guo Z, Xiao J, Feng N. Role of glycated proteins in vivo: Enzymatic glycated proteins and non-enzymatic glycated proteins. Food Res Int 2022; 155:111099. [DOI: 10.1016/j.foodres.2022.111099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/24/2022] [Accepted: 03/03/2022] [Indexed: 11/04/2022]
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7
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Esmail S, Manolson MF. Advances in understanding N-glycosylation structure, function, and regulation in health and disease. Eur J Cell Biol 2021; 100:151186. [PMID: 34839178 DOI: 10.1016/j.ejcb.2021.151186] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 11/14/2021] [Accepted: 11/18/2021] [Indexed: 01/17/2023] Open
Abstract
N-linked glycosylation is a post-translational modification crucial for membrane protein folding, stability and other cellular functions. Alteration of membrane protein N-glycans is implicated in wide range of pathological conditions including cancer metastasis, chronic inflammatory diseases, and viral pathogenesis. Even though the roles of N-glycans have been studied extensively, our knowledge of their mechanisms remains unclear due to the lack of detailed structural analysis of the N-glycome. Mapping the N-glycome landscape will open new avenues to explore disease mechanisms and identify novel therapeutic targets. This review discusses the diverse structure of N-linked glycans, the function and regulation of N-glycosylation in health and disease, and ends with a focus on recent approaches to target N-glycans in rheumatoid arthritis and cancer metastasis.
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Affiliation(s)
- Sally Esmail
- Faculty of Dentistry, University of Toronto, Toronto, Ontario M5G 1G6, Canada.
| | - Morris F Manolson
- Faculty of Dentistry, University of Toronto, Toronto, Ontario M5G 1G6, Canada
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Rowland R, Brandariz-Nuñez A. Analysis of the Role of N-Linked Glycosylation in Cell Surface Expression, Function, and Binding Properties of SARS-CoV-2 Receptor ACE2. Microbiol Spectr 2021; 9:e0119921. [PMID: 34494876 PMCID: PMC8557876 DOI: 10.1128/spectrum.01199-21] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 08/13/2021] [Indexed: 12/28/2022] Open
Abstract
Human angiotensin I-converting enzyme 2 (hACE2) is a type I transmembrane glycoprotein that serves as the major cell entry receptor for SARS-CoV and SARS-CoV-2. The viral spike (S) protein is required for the attachment to ACE2 and subsequent virus-host cell membrane fusion. Previous work has demonstrated the presence of N-linked glycans in ACE2. N-glycosylation is implicated in many biological activities, including protein folding, protein activity, and cell surface expression of biomolecules. However, the contribution of N-glycosylation to ACE2 function is poorly understood. Here, we examined the role of N-glycosylation in the activity and localization of two species with different susceptibility to SARS-CoV-2 infection, porcine ACE2 (pACE2) and hACE2. The elimination of N-glycosylation by tunicamycin (TM) treatment, or mutagenesis, showed that N-glycosylation is critical for the proper cell surface expression of ACE2 but not for its carboxiprotease activity. Furthermore, nonglycosylable ACE2 was localized predominantly in the endoplasmic reticulum (ER) and not at the cell surface. Our data also revealed that binding of SARS-CoV or SARS-CoV-2 S protein to porcine or human ACE2 was not affected by deglycosylation of ACE2 or S proteins, suggesting that N-glycosylation does not play a role in the interaction between SARS coronaviruses and the ACE2 receptor. Impairment of hACE2 N-glycosylation decreased cell-to-cell fusion mediated by SARS-CoV S protein but not that mediated by SARS-CoV-2 S protein. Finally, we found that hACE2 N-glycosylation is required for an efficient viral entry of SARS-CoV/SARS-CoV-2 S pseudotyped viruses, which may be the result of low cell surface expression of the deglycosylated ACE2 receptor. IMPORTANCE Understanding the role of glycosylation in the virus-receptor interaction is important for developing approaches that disrupt infection. In this study, we showed that deglycosylation of both ACE2 and S had a minimal effect on the spike-ACE2 interaction. In addition, we found that the removal of N-glycans of ACE2 impaired its ability to support an efficient transduction of SARS-CoV and SARS-CoV-2 S pseudotyped viruses. Our data suggest that the role of deglycosylation of ACE2 on reducing infection is likely due to a reduced expression of the viral receptor on the cell surface. These findings offer insight into the glycan structure and function of ACE2 and potentially suggest that future antiviral therapies against coronaviruses and other coronavirus-related illnesses involving inhibition of ACE2 recruitment to the cell membrane could be developed.
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Affiliation(s)
- Raymond Rowland
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Alberto Brandariz-Nuñez
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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9
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Scalise M, Console L, Cosco J, Pochini L, Galluccio M, Indiveri C. ASCT1 and ASCT2: Brother and Sister? SLAS DISCOVERY 2021; 26:1148-1163. [PMID: 34269129 DOI: 10.1177/24725552211030288] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The SLC1 family includes seven members divided into two groups, namely, EAATs and ASCTs, that share similar 3D architecture; the first one includes high-affinity glutamate transporters, and the second one includes SLC1A4 and SLC1A5, known as ASCT1 and ASCT2, respectively, responsible for the traffic of neutral amino acids across the cell plasma membrane. The physiological role of ASCT1 and ASCT2 has been investigated over the years, revealing different properties in terms of substrate specificities, affinities, and regulation by physiological effectors and posttranslational modifications. Furthermore, ASCT1 and ASCT2 are involved in pathological conditions, such as neurodegenerative disorders and cancer. This has driven research in the pharmaceutical field aimed to find drugs able to target the two proteins.This review focuses on structural, functional, and regulatory aspects of ASCT1 and ASCT2, highlighting similarities and differences.
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Affiliation(s)
- Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Lara Console
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Jessica Cosco
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Lorena Pochini
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia e Scienze della Terra), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy.,CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnology (IBIOM), Bari, Italy
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10
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ARL15 modulates magnesium homeostasis through N-glycosylation of CNNMs. Cell Mol Life Sci 2021; 78:5427-5445. [PMID: 34089346 PMCID: PMC8257531 DOI: 10.1007/s00018-021-03832-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 03/23/2021] [Accepted: 03/30/2021] [Indexed: 02/06/2023]
Abstract
Cyclin M (CNNM1-4) proteins maintain cellular and body magnesium (Mg2+) homeostasis. Using various biochemical approaches, we have identified members of the CNNM family as direct interacting partners of ADP-ribosylation factor-like GTPase 15 (ARL15), a small GTP-binding protein. ARL15 interacts with CNNMs at their carboxyl-terminal conserved cystathionine-β-synthase (CBS) domains. In silico modeling of the interaction between CNNM2 and ARL15 supports that the small GTPase specifically binds the CBS1 and CNBH domains. Immunocytochemical experiments demonstrate that CNNM2 and ARL15 co-localize in the kidney, with both proteins showing subcellular localization in the endoplasmic reticulum, Golgi apparatus and the plasma membrane. Most importantly, we found that ARL15 is required for forming complex N-glycosylation of CNNMs. Overexpression of ARL15 promotes complex N-glycosylation of CNNM3. Mg2+ uptake experiments with a stable isotope demonstrate that there is a significant increase of 25Mg2+ uptake upon knockdown of ARL15 in multiple kidney cancer cell lines. Altogether, our results establish ARL15 as a novel negative regulator of Mg2+ transport by promoting the complex N-glycosylation of CNNMs.
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11
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Flores J, Takvorian PM, Weiss LM, Cali A, Gao N. Human microsporidian pathogen Encephalitozoon intestinalis impinges on enterocyte membrane trafficking and signaling. J Cell Sci 2021; 134:jcs253757. [PMID: 33589497 PMCID: PMC7938802 DOI: 10.1242/jcs.253757] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 02/01/2021] [Indexed: 12/23/2022] Open
Abstract
Microsporidia are a large phylum of obligate intracellular parasites. Approximately a dozen species of microsporidia infect humans, where they are responsible for a variety of diseases and occasionally death, especially in immunocompromised individuals. To better understand the impact of microsporidia on human cells, we infected human colonic Caco2 cells with Encephalitozoon intestinalis, and showed that these enterocyte cultures can be used to recapitulate the life cycle of the parasite, including the spread of infection with infective spores. Using transmission electron microscopy, we describe this lifecycle and demonstrate nuclear, mitochondrial and microvillar alterations by this pathogen. We also analyzed the transcriptome of infected cells to reveal host cell signaling alterations upon infection. These high-resolution imaging and transcriptional profiling analysis shed light on the impact of the microsporidial infection on its primary human target cell type.This article has an associated First Person interview with the first authors of the paper.
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Affiliation(s)
- Juan Flores
- Department of Biological Sciences, Rutgers University, Newark, New Jersey 07102, USA
| | - Peter M Takvorian
- Department of Biological Sciences, Rutgers University, Newark, New Jersey 07102, USA
- Departments of Medicine and Pathology, Albert Einstein College of Medicine Bronx, New York 10461, USA
| | - Louis M Weiss
- Departments of Medicine and Pathology, Albert Einstein College of Medicine Bronx, New York 10461, USA
| | - Ann Cali
- Department of Biological Sciences, Rutgers University, Newark, New Jersey 07102, USA
| | - Nan Gao
- Department of Biological Sciences, Rutgers University, Newark, New Jersey 07102, USA
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12
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Target the human Alanine/Serine/Cysteine Transporter 2(ASCT2): Achievement and Future for Novel Cancer Therapy. Pharmacol Res 2020; 158:104844. [DOI: 10.1016/j.phrs.2020.104844] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 04/12/2020] [Accepted: 04/13/2020] [Indexed: 12/11/2022]
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13
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Zhu J, Lin YH, Dingess KA, Mank M, Stahl B, Heck AJR. Quantitative Longitudinal Inventory of the N-Glycoproteome of Human Milk from a Single Donor Reveals the Highly Variable Repertoire and Dynamic Site-Specific Changes. J Proteome Res 2020; 19:1941-1952. [PMID: 32125861 PMCID: PMC7252941 DOI: 10.1021/acs.jproteome.9b00753] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Protein N-glycosylation on human milk proteins assists in protecting an infant's health and functions among others as competitive inhibitors of pathogen binding and immunomodulators. Due to the individual uniqueness of each mother's milk and the overall complexity and temporal changes of protein N-glycosylation, analysis of the human milk N-glycoproteome requires longitudinal personalized approaches, providing protein- and N-site-specific quantitative information. Here, we describe an automated platform using hydrophilic-interaction chromatography (HILIC)-based cartridges enabling the proteome-wide monitoring of intact N-glycopeptides using just a digest of 150 μg of breast milk protein. We were able to map around 1700 glycopeptides from 110 glycoproteins covering 191 glycosites, of which 43 sites have not been previously reported with experimental evidence. We next quantified 287 of these glycopeptides originating from 50 glycoproteins using a targeted proteomics approach. Although each glycoprotein, N-glycosylation site, and attached glycan revealed distinct dynamic changes, we did observe a few general trends. For instance, fucosylation, especially terminal fucosylation, increased across the lactation period. Building on the improved glycoproteomics approach outlined above, future studies are warranted to reveal the potential impact of the observed glycosylation microheterogeneity on the healthy development of infants.
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Affiliation(s)
- Jing Zhu
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Beijing Institute of Nutritional Resources, 100069 Beijing, China
| | - Yu-Hsien Lin
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Kelly A Dingess
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Marko Mank
- Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands
| | - Bernd Stahl
- Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands.,Chemical Biology & Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, 3584 CG Utrecht, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands
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14
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Li Q, Xie Y, Wong M, Lebrilla CB. Characterization of Cell Glycocalyx with Mass Spectrometry Methods. Cells 2019; 8:E882. [PMID: 31412618 PMCID: PMC6721671 DOI: 10.3390/cells8080882] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/05/2019] [Accepted: 08/12/2019] [Indexed: 02/06/2023] Open
Abstract
The cell membrane plays an important role in protecting the cell from its extracellular environment. As such, extensive work has been devoted to studying its structure and function. Crucial intercellular processes, such as signal transduction and immune protection, are mediated by cell surface glycosylation, which is comprised of large biomolecules, including glycoproteins and glycosphingolipids. Because perturbations in glycosylation could result in dysfunction of cells and are related to diseases, the analysis of surface glycosylation is critical for understanding pathogenic mechanisms and can further lead to biomarker discovery. Different mass spectrometry-based techniques have been developed for glycan analysis, ranging from highly specific, targeted approaches to more comprehensive profiling studies. In this review, we summarized the work conducted for extensive analysis of cell membrane glycosylation, particularly those employing liquid chromatography with mass spectrometry (LC-MS) in combination with various sample preparation techniques.
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Affiliation(s)
- Qiongyu Li
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Yixuan Xie
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Maurice Wong
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Carlito B Lebrilla
- Department of Chemistry, University of California, Davis, CA 95616, USA.
- Department of Biochemistry, University of California, Davis, CA 95616, USA.
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15
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Rao MC. Physiology of Electrolyte Transport in the Gut: Implications for Disease. Compr Physiol 2019; 9:947-1023. [PMID: 31187895 DOI: 10.1002/cphy.c180011] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We now have an increased understanding of the genetics, cell biology, and physiology of electrolyte transport processes in the mammalian intestine, due to the availability of sophisticated methodologies ranging from genome wide association studies to CRISPR-CAS technology, stem cell-derived organoids, 3D microscopy, electron cryomicroscopy, single cell RNA sequencing, transgenic methodologies, and tools to manipulate cellular processes at a molecular level. This knowledge has simultaneously underscored the complexity of biological systems and the interdependence of multiple regulatory systems. In addition to the plethora of mammalian neurohumoral factors and their cross talk, advances in pyrosequencing and metagenomic analyses have highlighted the relevance of the microbiome to intestinal regulation. This article provides an overview of our current understanding of electrolyte transport processes in the small and large intestine, their regulation in health and how dysregulation at multiple levels can result in disease. Intestinal electrolyte transport is a balance of ion secretory and ion absorptive processes, all exquisitely dependent on the basolateral Na+ /K+ ATPase; when this balance goes awry, it can result in diarrhea or in constipation. The key transporters involved in secretion are the apical membrane Cl- channels and the basolateral Na+ -K+ -2Cl- cotransporter, NKCC1 and K+ channels. Absorption chiefly involves apical membrane Na+ /H+ exchangers and Cl- /HCO3 - exchangers in the small intestine and proximal colon and Na+ channels in the distal colon. Key examples of our current understanding of infectious, inflammatory, and genetic diarrheal diseases and of constipation are provided. © 2019 American Physiological Society. Compr Physiol 9:947-1023, 2019.
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Affiliation(s)
- Mrinalini C Rao
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA
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16
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Modulation of Endocannabinoid-Binding Receptors in Human Neuroblastoma Cells by Tunicamycin. Molecules 2019; 24:molecules24071432. [PMID: 30979007 PMCID: PMC6479803 DOI: 10.3390/molecules24071432] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/09/2019] [Accepted: 04/09/2019] [Indexed: 01/22/2023] Open
Abstract
Endocannabinoid (eCB)-binding receptors can be modulated by several ligands and membrane environment, yet the effect of glycosylation remains to be assessed. In this study, we used human neuroblastoma SH-SY5Y cells to interrogate whether expression, cellular localization, and activity of eCB-binding receptors may depend on N-linked glycosylation. Following treatment with tunicamycin (a specific inhibitor of N-linked glycosylation) at the non-cytotoxic dose of 1 µg/mL, mRNA, protein levels and localization of eCB-binding receptors, as well as N-acetylglucosamine (GlcNAc) residues, were evaluated in SH-SY5Y cells by means of quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR), fluorescence-activated cell sorting (FACS), and confocal microscopy, respectively. In addition, the activity of type-1 and type-2 cannabinoid receptors (CB1 and CB2) was assessed by means of rapid binding assays. Significant changes in gene and protein expression were found upon tunicamycin treatment for CB1 and CB2, as well as for GPR55 receptors, but not for transient receptor potential vanilloid 1 (TRPV1). Deglycosylation experiments with N-glycosidase-F and immunoblot of cell membranes derived from SH-SY5Y cells confirmed the presence of one glycosylated form in CB1 (70 kDa), that was reduced by tunicamycin. Morphological studies demonstrated the co-localization of CB1 with GlcNAc residues, and showed that tunicamycin reduced CB1 membrane expression with a marked nuclear localization, as confirmed by immunoblotting. Cleavage of the carbohydrate side chain did not modify CB receptor binding affinity. Overall, these results support N-linked glycosylation as an unprecedented post-translational modification that may modulate eCB-binding receptors’ expression and localization, in particular for CB1.
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17
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cAMP Stimulates SLC26A3 Activity in Human Colon by a CFTR-Dependent Mechanism That Does Not Require CFTR Activity. Cell Mol Gastroenterol Hepatol 2019; 7:641-653. [PMID: 30659943 PMCID: PMC6438990 DOI: 10.1016/j.jcmgh.2019.01.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 01/07/2019] [Accepted: 01/07/2019] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS SLC26A3 (DRA) is an electroneutral Cl-/HCO3- exchanger that is present in the apical domain of multiple intestinal segments. An area that has continued to be poorly understood is related to DRA regulation in acute adenosine 3',5'-cyclic monophosphate (cAMP)-related diarrheas, in which DRA appears to be both inhibited as part of NaCl absorption and stimulated to contribute to increased HCO3- secretion. Different cell models expressing DRA have shown that cAMP inhibits, stimulates, or does not affect its activity. METHODS This study re-evaluated cAMP regulation of DRA using new tools, including a successful knockout cell model, a specific DRA inhibitor (DRAinh-A250), specific antibodies, and a transport assay that did not rely on nonspecific inhibitors. The studies compared DRA regulation in colonoids made from normal human colon with regulation in the colon cancer cell line, Caco-2. RESULTS DRA is an apical protein in human proximal colon, differentiated colonoid monolayers, and Caco-2 cells. It is glycosylated and appears as 2 bands. cAMP (forskolin) acutely stimulated DRA activity in human colonoids and Caco-2 cells. In these cells, DRA is the predominant apical Cl-/HCO3- exchanger and is inhibited by DRAinh-A250 with a median inhibitory concentration of 0.5 and 0.2 μmol/L, respectively. However, there was no effect of cAMP in HEK293/DRA cells that lacked a cystic fibrosis transmembrane conductance regulator (CFTR). When CFTR was expressed in HEK293/DRA cells, cAMP also stimulated DRA activity. In all cases, cAMP stimulation of DRA was not inhibited by CFTRinh-172. CONCLUSIONS DRA is acutely stimulated by cAMP by a process that is CFTR-dependent, but appears to be one of multiple regulatory effects of CFTR that does not require CFTR activity.
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18
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Rapp CL, Li J, Badior KE, Williams DB, Casey JR, Reithmeier RAF. Role of N-glycosylation in the expression of human SLC26A2 and A3 anion transport membrane glycoproteins 1. Biochem Cell Biol 2018; 97:290-306. [PMID: 30462520 DOI: 10.1139/bcb-2018-0139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The human solute carrier 26 (SLC26) gene family of anion transporters consists of 10 members (SLC26A1-A11, A10 being a pseudogene) that encode membrane glycoproteins with 14 transmembrane segments and a C-terminal cytoplasmic sulfate transporter anti-sigma antagonist domain. Thus far, mutations in eight members of the SLC26 family (A1-A6, A8, and A9) have been linked to diseases in humans. Our goal is to characterize the role of N-glycosylation and the effect of mutations in SLC26A2 and A3 proteins on their functional expression in transfected HEK-293 cells. We found that certain mutants were retained in the endoplamic reticulum via an interaction with the lectin chaperone calnexin. Some could escape protein quality control and traffic to the cell surface upon removal of the N-glycosylation sites. Furthermore, we found that loss of N-glycosylation reduced expression of SLC26A2 at the cell surface. Loss of N-glycosylation had no effect on the stability of SLC26A3, yet resulted in a profound decrease in transport activity. Thus, N-glycosylation plays three roles in the functional expression of SLC26 proteins: (1) to retain misfolded proteins in the endoplamic reticulum, (2) to stabilize the protein at the cell surface, and (3) to maintain the transport protein in a functional state.
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Affiliation(s)
- Chloe L Rapp
- a Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Jing Li
- a Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Katherine E Badior
- b Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - David B Williams
- a Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Joseph R Casey
- b Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
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19
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Scalise M, Pochini L, Console L, Losso MA, Indiveri C. The Human SLC1A5 (ASCT2) Amino Acid Transporter: From Function to Structure and Role in Cell Biology. Front Cell Dev Biol 2018; 6:96. [PMID: 30234109 PMCID: PMC6131531 DOI: 10.3389/fcell.2018.00096] [Citation(s) in RCA: 150] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/08/2018] [Indexed: 12/30/2022] Open
Abstract
SLC1A5, known as ASCT2, is a neutral amino acid transporter belonging to the SLC1 family and localized in the plasma membrane of several body districts. ASCT2 is an acronym standing for Alanine, Serine, Cysteine Transporter 2 even if the preferred substrate is the conditionally essential amino acid glutamine, with cysteine being a modulator and not a substrate. The studies around amino acid transport in cells and tissues began in the '60s by using radiolabeled compounds and competition assays. After identification of murine and human genes, the function of the coded protein has been studied in cell system and in proteoliposomes revealing that this transporter is a Na+ dependent antiporter of neutral amino acids, some of which are only inwardly transported and others are bi-directionally exchanged. The functional asymmetry merged with the kinetic asymmetry in line with the physiological role of amino acid pool harmonization. An intriguing function has been described for ASCT2 that is exploited as a receptor by a group of retroviruses to infect human cells. Interactions with scaffold proteins and post-translational modifications regulate ASCT2 stability, trafficking and transport activity. Two asparagine residues, namely N163 and N212, are the sites of glycosylation that is responsible for the definitive localization into the plasma membrane. ASCT2 expression increases in highly proliferative cells such as inflammatory and stem cells to fulfill the augmented glutamine demand. Interestingly, for the same reason, the expression of ASCT2 is greatly enhanced in many human cancers. This finding has generated interest in its candidacy as a pharmacological target for new anticancer drugs. The recently solved 3D structure of ASCT2 will aid in the rational design of such therapeutic compounds.
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Affiliation(s)
- Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Maria A Losso
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy.,CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnology, Bari, Italy
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20
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Yamada M, Takahashi N, Matsuda Y, Sato K, Yokoji M, Sulijaya B, Maekawa T, Ushiki T, Mikami Y, Hayatsu M, Mizutani Y, Kishino S, Ogawa J, Arita M, Tabeta K, Maeda T, Yamazaki K. A bacterial metabolite ameliorates periodontal pathogen-induced gingival epithelial barrier disruption via GPR40 signaling. Sci Rep 2018; 8:9008. [PMID: 29899364 PMCID: PMC5998053 DOI: 10.1038/s41598-018-27408-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 06/04/2018] [Indexed: 01/15/2023] Open
Abstract
Several studies have demonstrated the remarkable properties of microbiota and their metabolites in the pathogenesis of several inflammatory diseases. 10-Hydroxy-cis-12-octadecenoic acid (HYA), a bioactive metabolite generated by probiotic microorganisms during the process of fatty acid metabolism, has been studied for its protective effects against epithelial barrier impairment in the intestines. Herein, we examined the effect of HYA on gingival epithelial barrier function and its possible application for the prevention and treatment of periodontal disease. We found that GPR40, a fatty acid receptor, was expressed on gingival epithelial cells; activation of GPR40 by HYA significantly inhibited barrier impairment induced by Porphyromonas gingivalis, a representative periodontopathic bacterium. The degradation of E-cadherin and beta-catenin, basic components of the epithelial barrier, was prevented in a GPR40-dependent manner in vitro. Oral inoculation of HYA in a mouse experimental periodontitis model suppressed the bacteria-induced degradation of E-cadherin and subsequent inflammatory cytokine production in the gingival tissue. Collectively, these results suggest that HYA exerts a protective function, through GPR40 signaling, against periodontopathic bacteria-induced gingival epithelial barrier impairment and contributes to the suppression of inflammatory responses in periodontal diseases.
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Affiliation(s)
- Miki Yamada
- Research Unit for Oral-Systemic Connection, Division of Oral Science for Health Promotion, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Naoki Takahashi
- Research Center for Advanced Oral Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
| | - Yumi Matsuda
- Research Unit for Oral-Systemic Connection, Division of Oral Science for Health Promotion, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Keisuke Sato
- Research Unit for Oral-Systemic Connection, Division of Oral Science for Health Promotion, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Mai Yokoji
- Research Unit for Oral-Systemic Connection, Division of Oral Science for Health Promotion, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Benso Sulijaya
- Research Unit for Oral-Systemic Connection, Division of Oral Science for Health Promotion, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Tomoki Maekawa
- Research Center for Advanced Oral Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Tatsuo Ushiki
- Division of Microscopic Anatomy and Bio-imaging, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Yoshikazu Mikami
- Division of Microscopic Anatomy and Bio-imaging, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Manabu Hayatsu
- Division of Microscopic Anatomy and Bio-imaging, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Yusuke Mizutani
- Division of Microscopic Anatomy and Bio-imaging, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Shigenobu Kishino
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Jun Ogawa
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Makoto Arita
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Koichi Tabeta
- Division of Periodontology, Department of Oral Biological Science, Niigata University Faculty of Dentistry, Niigata, Japan
| | - Takeyasu Maeda
- Research Center for Advanced Oral Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Kazuhisa Yamazaki
- Research Unit for Oral-Systemic Connection, Division of Oral Science for Health Promotion, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
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21
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Hu J, Shi Y, Wang C, Wan H, Wu D, Wang H, Peng X. Role of intestinal trefoil factor in protecting intestinal epithelial cells from burn-induced injury. Sci Rep 2018; 8:3201. [PMID: 29453360 PMCID: PMC5816625 DOI: 10.1038/s41598-018-21282-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 01/30/2018] [Indexed: 12/19/2022] Open
Abstract
Although intestinal trefoil factor (ITF) can alleviate the burn-induced intestinal mucosa injury, the underlying mechanisms remains elusive. In this study, we investigated if ITF alters glutamine transport on the brush border membrane vesicles (BBMVs) of the intestines in Sprague-Dawley rats inflicted with 30% TBSA and the underlying mechanisms. We found that ITF significantly stimulated intestinal glutamine transport in burned rats. Mechanistically, ITF enhanced autophagy, reduces endoplasmic reticulum stress (ERS), and alleviates the impaired PDI, ASCT2, and B0AT1 in IECs and BBMVs after burn injury likely through AMPK activation. Therefore, ITF may protect intestinal epithelial cells from burn-induced injury through improving glutamine transport by alleviating ERS.
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Affiliation(s)
- Jianhong Hu
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, 400038, China
| | - Yan Shi
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, 400038, China
| | - Chao Wang
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, 400038, China
| | - Hanxing Wan
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, 400038, China
| | - Dan Wu
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, 400038, China
| | - Hongyu Wang
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, 400038, China
| | - Xi Peng
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, 400038, China.
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22
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Dieho K, van Baal J, Kruijt L, Bannink A, Schonewille J, Carreño D, Hendriks W, Dijkstra J. Effect of supplemental concentrate during the dry period or early lactation on rumen epithelium gene and protein expression in dairy cattle during the transition period. J Dairy Sci 2017; 100:7227-7245. [DOI: 10.3168/jds.2016-12403] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 05/08/2017] [Indexed: 11/19/2022]
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23
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Wang HY, Sun J, Xia LY, Li YH, Chen Z, Wu FG. Permeabilization-Tolerant Plasma Membrane Imaging Reagent Based on Amine-Rich Glycol Chitosan Derivatives. ACS Biomater Sci Eng 2017; 3:2570-2578. [DOI: 10.1021/acsbiomaterials.7b00448] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hong-Yin Wang
- State
Key Laboratory of Bioelectronics, School of Biological Science and
Medical Engineering, Southeast University, 2 Sipailou Road, Nanjing 210096, P. R. China
| | - Jie Sun
- State
Key Laboratory of Bioelectronics, School of Biological Science and
Medical Engineering, Southeast University, 2 Sipailou Road, Nanjing 210096, P. R. China
| | - Liu-Yuan Xia
- State
Key Laboratory of Bioelectronics, School of Biological Science and
Medical Engineering, Southeast University, 2 Sipailou Road, Nanjing 210096, P. R. China
| | - Yan-Hong Li
- State
Key Laboratory of Bioelectronics, School of Biological Science and
Medical Engineering, Southeast University, 2 Sipailou Road, Nanjing 210096, P. R. China
| | - Zhan Chen
- Department
of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Fu-Gen Wu
- State
Key Laboratory of Bioelectronics, School of Biological Science and
Medical Engineering, Southeast University, 2 Sipailou Road, Nanjing 210096, P. R. China
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24
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Abstract
OBJECTIVES We aimed to improve the knowledge of pathogenic mutations in sporadic cases of congenital chloride diarrhea (CCD) and emphasize the importance of functional studies to define the effect of novel mutations. METHODS All member 3 of solute carrier family 26 (SLC26A3) coding regions were sequenced in 17 sporadic patients with CCD. Moreover, the minigene system was used to analyze the effect of 2 novel splicing mutations. RESULTS We defined the SLC26A3 genotype of all 17 patients with CCD and identified 12 novel mutations. Using the minigene system, we confirmed the in silico prediction of a complete disruption of splicing pattern caused by 2 of these novel mutations: the c.971+3_971+4delAA and c.735+4_c.735+7delAGTA. Moreover, several prediction tools and a structure-function prediction defined the pathogenic role of 6 novel missense mutations. CONCLUSIONS We confirm the molecular heterogeneity of sporadic CCD adding 12 novel mutations to the list of known pathogenic mutations. Moreover, we underline the importance, for laboratories that offer molecular diagnosis and genetic counseling, to perform fast functional analysis of novel mutations.
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Stelzl T, Geillinger-Kästle KE, Stolz J, Daniel H. Glycans in the intestinal peptide transporter PEPT1 contribute to function and protect from proteolysis. Am J Physiol Gastrointest Liver Physiol 2017; 312:G580-G591. [PMID: 28336547 DOI: 10.1152/ajpgi.00343.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 03/16/2017] [Accepted: 03/17/2017] [Indexed: 01/31/2023]
Abstract
Despite the fact that many membrane proteins carry extracellular glycans, little is known about whether the glycan chains also affect protein function. We recently demonstrated that the proton-coupled oligopeptide transporter 1 (PEPT1) in the intestine is glycosylated at six asparagine residues (N50, N406, N439, N510, N515, and N532). Mutagenesis-induced disruption of the individual N-glycosylation site N50, which is highly conserved among mammals, was detected to significantly enhance the PEPT1-mediated inward transport of peptides. Here, we show that for the murine protein the inhibition of glycosylation at sequon N50 by substituting N50 with glutamine, lysine, or cysteine or by replacing S52 with alanine equally altered PEPT1 transport kinetics in oocytes. Furthermore, we provide evidence that the uptake of [14C]glycyl-sarcosine in immortalized murine small intestinal (MODE-K) or colonic epithelial (PTK-6) cells stably expressing the PEPT1 transporter N50Q is also significantly increased relative to the wild-type protein. By using electrophysiological recordings and tracer flux studies, we further demonstrate that the rise in transport velocity observed for PEPT1 N50Q is bidirectional. In line with these findings, we show that attachment of biotin derivatives, comparable in weight with two to four monosaccharides, to the PEPT1 N50C transporter slows down the transport velocity. In addition, our experiments provide strong evidence that glycosylation of PEPT1 confers resistance against proteolytic cleavage by proteinase K, whereas a remarkable intrinsic stability against trypsin, even in the absence of N-linked glycans, was detected.NEW & NOTEWORTHY This study highlights the role of N50-linked glycans in modulating the bidirectional transport activity of the murine peptide transporter PEPT1. Electrophysiological and tracer flux measurements in Xenopus oocytes have shown that removal of the N50 glycans increases the maximal peptide transport rate in the inward and outward directions. This effect could be largely reversed by replacement of N50 glycans with structurally dissimilar biotin derivatives. In addition, N-glycans were detected to stabilize PEPT1 against proteolytic cleavage.
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Affiliation(s)
- Tamara Stelzl
- Nutritional Physiology, Technische Universität München, Freising, Germany
| | | | - Jürgen Stolz
- Nutritional Physiology, Technische Universität München, Freising, Germany
| | - Hannelore Daniel
- Nutritional Physiology, Technische Universität München, Freising, Germany
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Thomson RB, Thomson CL, Aronson PS. N-glycosylation critically regulates function of oxalate transporter SLC26A6. Am J Physiol Cell Physiol 2016; 311:C866-C873. [PMID: 27681177 DOI: 10.1152/ajpcell.00171.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 09/22/2016] [Indexed: 11/22/2022]
Abstract
The brush border Cl--oxalate exchanger SLC26A6 plays an essential role in mediating intestinal secretion of oxalate and is crucial for the maintenance of oxalate homeostasis and the prevention of hyperoxaluria and calcium oxalate nephrolithiasis. Previous in vitro studies have suggested that SLC26A6 is heavily N-glycosylated. N-linked glycosylation is known to critically affect folding, trafficking, and function in a wide variety of integral membrane proteins and could therefore potentially have a critical impact on SLC26A6 function and subsequent oxalate homeostasis. Through a series of enzymatic deglycosylation studies we confirmed that endogenously expressed mouse and human SLC26A6 are indeed glycosylated, that the oligosaccharides are principally attached via N-glycosidic linkage, and that there are tissue-specific differences in glycosylation. In vitro cell culture experiments were then used to elucidate the functional significance of the addition of the carbohydrate moieties. Biotinylation studies of SLC26A6 glycosylation mutants indicated that glycosylation is not essential for cell surface delivery of SLC26A6 but suggested that it may affect the efficacy with which it is trafficked and maintained in the plasma membrane. Functional studies of transfected SLC26A6 demonstrated that glycosylation at two sites in the putative second extracellular loop of SLC26A6 is critically important for chloride-dependent oxalate transport and that enzymatic deglycosylation of SLC26A6 expressed on the plasma membrane of intact cells strongly reduced oxalate transport activity. Taken together, these studies indicated that oxalate transport function of SLC26A6 is critically dependent on glycosylation and that exoglycosidase-mediated deglycosylation of SLC26A6 has the capacity to profoundly modulate SLC26A6 function.
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Affiliation(s)
- R Brent Thomson
- Section of Nephrology, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Claire L Thomson
- Section of Nephrology, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Peter S Aronson
- Section of Nephrology, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
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27
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N-linked glycosylation of N48 is required for equilibrative nucleoside transporter 1 (ENT1) function. Biosci Rep 2016; 36:BSR20160063. [PMID: 27480168 PMCID: PMC5006311 DOI: 10.1042/bsr20160063] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 08/01/2016] [Indexed: 11/29/2022] Open
Abstract
Our study confirmed that Asn48 of hENT1 is the only N-glycosylated residue when expressed in HEK293 cells, and loss of the N-glycan resulted in less hENT1 at the plasma membrane, as well as a loss of function and protein–protein self-interaction. Human equilibrative nucleoside transporter 1 (hENT1) transports nucleosides and nucleoside analogue drugs across cellular membranes and is necessary for the uptake of many anti-cancer, anti-parasitic and anti-viral drugs. Previous work, and in silico prediction, suggest that hENT1 is glycosylated at Asn48 in the first extracellular loop of the protein and that glycosylation plays a role in correct localization and function of hENT1. Site-directed mutagenesis of wild-type (wt) hENT1 removed potential glycosylation sites. Constructs (wt 3xFLAG-hENT1, N48Q-3xFLAG-hENT1 or N288Q-3xFLAG-hENT2) were transiently transfected into HEK293 cells and cell lysates were treated with or without peptide–N-glycosidase F (PNGase-F), followed by immunoblotting analysis. Substitution of N48 prevents hENT1 glycosylation, confirming a single N-linked glycosylation site. N48Q-hENT1 protein is found at the plasma membrane in HEK293 cells but at lower levels compared with wt hENT1 based on S-(4-nitrobenzyl)-6-thioinosine (NBTI) binding analysis (wt 3xFLAG-ENT1 Bmax, 41.5±2.9 pmol/mg protein; N48Q-3xFLAG-ENT1 Bmax, 13.5±0.45 pmol/mg protein) and immunofluorescence microscopy. Although present at the membrane, chloroadenosine transport assays suggest that N48Q-hENT1 is non-functional (wt 3xFLAG-ENT1, 170.80±44.01 pmol/mg protein; N48Q-3xFLAG-ENT1, 57.91±17.06 pmol/mg protein; mock-transfected 74.31±19.65 pmol/mg protein). Co-immunoprecipitation analyses suggest that N48Q ENT1 is unable to interact with self or with wt hENT1. Based on these data we propose that glycosylation at N48 is critical for the localization, function and oligomerization of hENT1.
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28
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Di Stadio CS, Altieri F, Miselli G, Elce A, Severino V, Chambery A, Quagliariello V, Villano V, de Dominicis G, Rippa E, Arcari P. AMP18 interacts with the anion exchanger SLC26A3 and enhances its expression in gastric cancer cells. Biochimie 2015; 121:151-60. [PMID: 26700142 DOI: 10.1016/j.biochi.2015.12.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 12/01/2015] [Indexed: 01/05/2023]
Abstract
AMP18 is a stomach-specific secreted protein expressed in normal gastric mucosa but absent in gastric cancer. AMP18 plays a major role in maintaining gastric mucosa integrity and is characterized by the presence of a BRICHOS domain consisting of about 100 amino acids, present also in several unrelated proteins, and probably endowed with a chaperon-like activity. In this work, we exploited a functional proteomic strategy to identify potential AMP18 interactors with the aim to add knowledge on its functional role within gastric cell lines and tissues. To this purpose, recombinant biotinylated AMP18 was purified and incubated with protein extract from human normal gastric mucosa by applying an affinity chromatography strategy. The interacting proteins were identified by peptide mass fingerprinting using MALDI-TOF mass spectrometry. The pool of interacting proteins contained SLC26A3, a protein expressed in the apical membrane of intestinal epithelial cells, supposed to play a critical role in Cl(-) absorption and fluid homeostasis. The interaction was also confirmed by Western blot with anti-SLC26A3 on transfected AGS cell extract following AMP18 pull-down. Furthermore, the interaction between AMP18 and SLC26A3 was also validated by confocal microscopy that showed a co-localization of both proteins at plasma membrane level. More importantly, for the first time, we showed that SLC26A3 is down-regulated in gastric cancer and that the overexpression of AMP18 in AMP-transfected gastric cancer cells up-regulated the expression of SLC26A3 both at transcriptional and translational level, the latter probably through the activation of the MAP kinases pathway. These findings strongly suggest that AMP18 might play an anti-inflammatory role in maintaining mucosal integrity also by regulating SLC26A3 level.
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Affiliation(s)
- Chiara Stella Di Stadio
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Filomena Altieri
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Giuseppina Miselli
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Ausilia Elce
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Valeria Severino
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Caserta, Italy
| | - Angela Chambery
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Caserta, Italy; IRCCS Multimedica, Milan, Italy
| | - Vincenzo Quagliariello
- Laboratory of Biotechnology, Department of Anesthesia, Surgical and Emergency Sciences, Second University of Naples, Via Costantinopoli 16, I-80138, Naples, Italy
| | - Valentina Villano
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | | | - Emilia Rippa
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy.
| | - Paolo Arcari
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy; CEINGE, Advanced Biotechnology Scarl, Via Gaetano Salvatore 486, I-80145, Naples, Italy.
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29
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Glycosylation of solute carriers: mechanisms and functional consequences. Pflugers Arch 2015; 468:159-76. [PMID: 26383868 DOI: 10.1007/s00424-015-1730-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/19/2015] [Accepted: 08/21/2015] [Indexed: 12/21/2022]
Abstract
Solute carriers (SLCs) are one of the largest groups of multi-spanning membrane proteins in mammals and include ubiquitously expressed proteins as well as proteins with highly restricted tissue expression. A vast number of studies have addressed the function and organization of SLCs as well as their posttranslational regulation, but only relatively little is known about the role of SLC glycosylation. Glycosylation is one of the most abundant posttranslational modifications of animal proteins and through recent advances in our understanding of protein-glycan interactions, the functional roles of SLC glycosylation are slowly emerging. The purpose of this review is to provide a concise overview of the aspects of glycobiology most relevant to SLCs, to discuss the roles of glycosylation in the regulation and function of SLCs, and to outline the major open questions in this field, which can now be addressed given major technical advances in this and related fields of study in recent years.
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Reimold FR, Balasubramanian S, Doroquez DB, Shmukler BE, Zsengeller ZK, Saslowsky D, Thiagarajah JR, Stillman IE, Lencer WI, Wu BL, Villalpando-Carrion S, Alper SL. Congenital chloride-losing diarrhea in a Mexican child with the novel homozygous SLC26A3 mutation G393W. Front Physiol 2015; 6:179. [PMID: 26157392 PMCID: PMC4477073 DOI: 10.3389/fphys.2015.00179] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 05/27/2015] [Indexed: 12/15/2022] Open
Abstract
Congenital chloride diarrhea is an autosomal recessive disease caused by mutations in the intestinal lumenal membrane Cl−/HCO−3 exchanger, SLC26A3. We report here the novel SLC26A3 mutation G393W in a Mexican child, the first such report in a patient from Central America. SLC26A3 G393W expression in Xenopus oocytes exhibits a mild hypomorphic phenotype, with normal surface expression and moderately reduced anion transport function. However, expression of HA-SLC26A3 in HEK-293 cells reveals intracellular retention and greatly decreased steady-state levels of the mutant polypeptide, in contrast to peripheral membrane expression of the wildtype protein. Whereas wildtype HA-SLC26A3 is apically localized in polarized monolayers of filter-grown MDCK cells and Caco2 cells, mutant HA-SLC26A3 G393W exhibits decreased total polypeptide abundance, with reduced or absent surface expression and sparse punctate (or absent) intracellular distribution. The WT protein is similarly localized in LLC-PK1 cells, but the mutant fails to accumulate to detectable levels. We conclude that the chloride-losing diarrhea phenotype associated with homozygous expression of SLC26A3 G393W likely reflects lack of apical surface expression in enterocytes, secondary to combined abnormalities in polypeptide trafficking and stability. Future progress in development of general or target-specific folding chaperonins and correctors may hold promise for pharmacological rescue of this and similar genetic defects in membrane protein targeting.
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Affiliation(s)
- Fabian R Reimold
- Renal Division, Beth Israel Deaconess Medical Center Boston, MA, USA
| | | | - David B Doroquez
- Renal Division, Beth Israel Deaconess Medical Center Boston, MA, USA
| | - Boris E Shmukler
- Renal Division, Beth Israel Deaconess Medical Center Boston, MA, USA
| | - Zsuzsanna K Zsengeller
- Department of Pathology, Beth Israel Deaconess Medical Center Boston, MA, USA ; Department of Pathology, Harvard Medical School Boston, MA, USA
| | - David Saslowsky
- Division of Pediatric Gastroenterology, Boston Children's Hospital Boston, MA, USA ; Department of Pediatrics, Harvard Medical School Boston, MA, USA ; Harvard Digestive Diseases Center, Harvard Medical School Boston, MA, USA
| | - Jay R Thiagarajah
- Division of Pediatric Gastroenterology, Boston Children's Hospital Boston, MA, USA ; Department of Pediatrics, Harvard Medical School Boston, MA, USA ; Harvard Digestive Diseases Center, Harvard Medical School Boston, MA, USA
| | - Isaac E Stillman
- Renal Division, Beth Israel Deaconess Medical Center Boston, MA, USA ; Department of Pathology, Beth Israel Deaconess Medical Center Boston, MA, USA ; Department of Pathology, Harvard Medical School Boston, MA, USA
| | - Wayne I Lencer
- Division of Pediatric Gastroenterology, Boston Children's Hospital Boston, MA, USA ; Department of Pediatrics, Harvard Medical School Boston, MA, USA ; Harvard Digestive Diseases Center, Harvard Medical School Boston, MA, USA
| | - Bai-Lin Wu
- Department of Pathology, Harvard Medical School Boston, MA, USA ; Genetics Diagnostic Laboratory and Claritas Genetics, Boston Children's Hospital Boston, MA, USA ; Children's Hospital and Institute of Biomedical Sciences of Fudan University Shanghai, China
| | - Salvador Villalpando-Carrion
- Department of Pediatric Gastroenterology and Nutrition, Hospital Infantil de Mexico Federico Gomez Mexico City, Mexico
| | - Seth L Alper
- Renal Division, Beth Israel Deaconess Medical Center Boston, MA, USA ; Harvard Digestive Diseases Center, Harvard Medical School Boston, MA, USA ; Department of Medicine, Harvard Medical School Boston, MA, USA
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31
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Muthusamy S, Malhotra P, Hosameddin M, Dudeja AK, Borthakur S, Saksena S, Gill RK, Dudeja PK, Alrefai WA. N-glycosylation is essential for ileal ASBT function and protection against proteases. Am J Physiol Cell Physiol 2015; 308:C964-71. [PMID: 25855079 DOI: 10.1152/ajpcell.00023.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 04/07/2015] [Indexed: 12/22/2022]
Abstract
The bile acid transporter ASBT is a glycoprotein responsible for active absorption of bile acids. Inhibiting ASBT function and bile acid absorption is an attractive approach to lower plasma cholesterol and improve glucose imbalance in diabetic patients. Deglycosylation of ASBT was shown to decrease its function. However, the exact roles of N-glycosylation of ASBT, and how it affects its function, is not known. Current studies investigated the roles of N-glycosylation in ASBT protein stability and protection against proteases utilizing HEK-293 cells stably transfected with ASBT-V5 fusion protein. ASBT-V5 protein was detected as two bands with molecular mass of ~41 and ~35 kDa. Inhibition of glycosylation by tunicamycin significantly decreased ASBT activity and shifted ASBT bands to ~30 kDa, representing a deglycosylated protein. Treatment of total cellular lysates with PNGase F or Endo H glycosidases showed that the upper 41-kDa band represents a fully mature N-acetylglucosamine-rich glycoprotein and the lower 35-kDa band represents a mannose-rich core glycoprotein. Studies with the glycosylation deficient ASBT mutant (N10Q) showed that the N-glycosylation is not essential for ASBT targeting to plasma membrane. However, mature glycosylation significantly increased the half-life and protected ASBT protein from digestion with trypsin. Incubating the cells with high glucose (25 mM) for 48 h increased mature glycosylated ASBT along with an increase in its function. These results unravel novel roles for N-glycosylation of ASBT and suggest that high levels of glucose alter the composition of the glycan and may contribute to the increase in ASBT function in diabetes mellitus.
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Affiliation(s)
- Saminathan Muthusamy
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Pooja Malhotra
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Mobashir Hosameddin
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Amish K Dudeja
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Sujata Borthakur
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Seema Saksena
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Ravinder K Gill
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Pradeep K Dudeja
- Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Waddah A Alrefai
- Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
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32
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Console L, Scalise M, Tarmakova Z, Coe IR, Indiveri C. N-linked glycosylation of human SLC1A5 (ASCT2) transporter is critical for trafficking to membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1636-45. [PMID: 25862406 DOI: 10.1016/j.bbamcr.2015.03.017] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 03/26/2015] [Accepted: 03/31/2015] [Indexed: 12/11/2022]
Abstract
The human amino acid transporter SLC1A5 (ASCT2) contains two N-glycosylation sites (N163 and N212) located in the large extracellular loop. In the homology structural model of ASCT2 these Asn residues are extracellularly exposed. Mutants of the two Asn exhibited altered electrophoretic mobility. N163Q and N212Q displayed multiple bands with apparent molecular masses from 80kDa to 50kDa. N163/212Q displayed a single band of 50kDa corresponding to the unglycosylated protein. The presence in membrane of WT and mutants was evaluated by protein biotinylation assay followed by immunoblotting. The double mutation significantly impaired the presence of the protein in membrane, without impairment in protein synthesis. [(3)H]glutamine transport was measured in cells transiently transfected with the WT or mutants. N163/212Q exhibited a strongly reduced transport activity correlating with reduced surface expression. The same proteins extracted from cells and reconstituted in liposomes showed comparable transport activities demonstrating that the intrinsic transport function of the mutants was not affected. The rate of endocytosis of ASCT2 was assayed by a reversible biotinylation strategy. N212Q and N163/212Q showed strongly increased rates of endocytosis respect to WT. ASCT2 stability was determined using cycloheximide. N163Q or N163/212Q showed a slightly or significantly lower stability with respect to WT. To assess trafficking to the membrane, a brefeldin-based assay, which caused retention of proteins in ER, was performed. One hour after brefeldin removal WT protein was localized to the plasma membrane while the double mutant was localized in the cytosol. The results demonstrate that N-glycosylation is critical for trafficking.
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Affiliation(s)
- Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy; Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto M5B 2K3, Canada
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy
| | - Zlatina Tarmakova
- Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto M5B 2K3, Canada
| | - Imogen R Coe
- Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto M5B 2K3, Canada
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via P. Bucci 4C, 87036 Arcavacata di Rende, Italy
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Hadley B, Maggioni A, Ashikov A, Day CJ, Haselhorst T, Tiralongo J. Structure and function of nucleotide sugar transporters: Current progress. Comput Struct Biotechnol J 2014; 10:23-32. [PMID: 25210595 PMCID: PMC4151994 DOI: 10.1016/j.csbj.2014.05.003] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The proteomes of eukaryotes, bacteria and archaea are highly diverse due, in part, to the complex post-translational modification of protein glycosylation. The diversity of glycosylation in eukaryotes is reliant on nucleotide sugar transporters to translocate specific nucleotide sugars that are synthesised in the cytosol and nucleus, into the endoplasmic reticulum and Golgi apparatus where glycosylation reactions occur. Thirty years of research utilising multidisciplinary approaches has contributed to our current understanding of NST function and structure. In this review, the structure and function, with reference to various disease states, of several NSTs including the UDP-galactose, UDP-N-acetylglucosamine, UDP-N-acetylgalactosamine, GDP-fucose, UDP-N-acetylglucosamine/UDP-glucose/GDP-mannose and CMP-sialic acid transporters will be described. Little is known regarding the exact structure of NSTs due to difficulties associated with crystallising membrane proteins. To date, no three-dimensional structure of any NST has been elucidated. What is known is based on computer predictions, mutagenesis experiments, epitope-tagging studies, in-vitro assays and phylogenetic analysis. In this regard the best-characterised NST to date is the CMP-sialic acid transporter (CST). Therefore in this review we will provide the current state-of-play with respect to the structure–function relationship of the (CST). In particular we have summarised work performed by a number groups detailing the affect of various mutations on CST transport activity, efficiency, and substrate specificity.
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Affiliation(s)
- Barbara Hadley
- Institute for Glycomics, Griffith University, Gold Coast Campus, Queensland 4222, Australia
| | - Andrea Maggioni
- Institute for Glycomics, Griffith University, Gold Coast Campus, Queensland 4222, Australia
| | - Angel Ashikov
- Institut für Zelluläre Chemie, Zentrum Biochemie, Medizinische Hochschule Hannover, Carl-Neuberg Strasse 1, 30625 Hannover, Germany ; Laboratory of Genetic, Endocrine and Metabolic Diseases, Department of Neurology, Radboud University Medical Center, Geert Grooteplein Zuid 10 (route 830), Nijmegen, The Netherlands
| | - Christopher J Day
- Institute for Glycomics, Griffith University, Gold Coast Campus, Queensland 4222, Australia
| | - Thomas Haselhorst
- Institute for Glycomics, Griffith University, Gold Coast Campus, Queensland 4222, Australia
| | - Joe Tiralongo
- Institute for Glycomics, Griffith University, Gold Coast Campus, Queensland 4222, Australia
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Li J, Xia F, Reithmeier RAF. N-glycosylation and topology of the human SLC26 family of anion transport membrane proteins. Am J Physiol Cell Physiol 2014; 306:C943-60. [PMID: 24647542 DOI: 10.1152/ajpcell.00030.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human solute carrier (SLC26) family of anion transporters consists of 10 members (SLCA1-11, SLCA10 being a pseudogene) that encode membrane proteins containing ~12 transmembrane (TM) segments with putative N-glycosylation sites (-NXS/T-) in extracellular loops and a COOH-terminal cytosolic STAS domain. All 10 members of the human SLC26 family, FLAG-tagged at the NH2 terminus, were transiently expressed in HEK-293 cells. While most proteins were observed to contain both high-mannose and complex oligosaccharides, SLC26A2 was mainly in the complex form, SLC26A4 in the high-mannose form, and SLC26A8 was not N-glycosylated. Mutation of the putative N-glycosylation sites showed that most members contain multiple N-glycosylation sites in the second extracytosolic (EC) loop, except SLC26A11, which was N-glycosylated in EC loop 4. Immunofluorescence staining of permeabilized cells localized the proteins to the plasma membrane and the endoplasmic reticulum, with SLC26A2 highly localized to the plasma membrane. N-glycosylation was not a necessary requirement for cell surface expression as the localization of nonglycosylated proteins was similar to their wild-type counterparts, although a lower level of cell-surface biotinylation was observed. No immunostaining of intact cells was observed for any SLC26 members, demonstrating that the NH2-terminal FLAG tag was located in the cytosol. Topological models of the SLC26 proteins that contain an even number of transmembrane segments with both the NH2 and COOH termini located in the cytosol and utilized N-glycosylation sites defining the positions of two EC loops are presented.
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Affiliation(s)
- Jing Li
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Fan Xia
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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35
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Cai B, Xie S, Liu F, Simone LC, Caplan S, Qin X, Naslavsky N. Rapid degradation of the complement regulator, CD59, by a novel inhibitor. J Biol Chem 2014; 289:12109-12125. [PMID: 24616098 DOI: 10.1074/jbc.m113.547083] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
There is increased interest in immune-based monoclonal antibody therapies for different malignancies because of their potential specificity and limited toxicity. The activity of some therapeutic monoclonal antibodies is partially dependent on complement-dependent cytolysis (CDC), in which the immune system surveys for invading pathogens, infected cells, and malignant cells and facilitates their destruction. CD59 is a ubiquitously expressed cell-surface glycosylphosphatidylinositol-anchored protein that protects cells from CDC. However, in certain tumors, CD59 expression is enhanced, posing a significant obstacle for treatment, by hindering effective monoclonal antibody-induced CDC. In this study, we used non-small lung carcinoma cells to characterize the mechanism of a novel CD59 inhibitor: the 114-amino acid recombinant form of the 4th domain of intermedilysin (rILYd4), a pore forming toxin secreted by Streptococcus intermedius. We compared the rates of internalization of CD59 in the presence of rILYd4 or anti-CD59 antibodies and determined that rILYd4 induces more rapid CD59 uptake at early time points. Most significantly, upon binding to rILYd4, CD59 is internalized and undergoes massive degradation in lysosomes within minutes. The remaining rILYd4·CD59 complexes recycle to the PM and are shed from the cell. In comparison, upon internalization of CD59 via anti-CD59 antibody binding, the antibody·CD59 complex is recycled via early and recycling endosomes, mostly avoiding degradation. Our study supports a novel role for rILYd4 in promoting internalization and rapid degradation of the complement inhibitor CD59, and highlights the potential for improving CDC-based immunotherapy.
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Affiliation(s)
- Bishuang Cai
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Shuwei Xie
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Fengming Liu
- Department of Neuroscience and Center for Neurovirology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Laura C Simone
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Steve Caplan
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198.
| | - Xuebin Qin
- Department of Neuroscience and Center for Neurovirology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
| | - Naava Naslavsky
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198.
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Cordat E, Reithmeier RA. Structure, Function, and Trafficking of SLC4 and SLC26 Anion Transporters. CURRENT TOPICS IN MEMBRANES 2014; 73:1-67. [DOI: 10.1016/b978-0-12-800223-0.00001-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Abstract
Lectin poisoning occurred in Japan in 2006 after a TV broadcast that introduced a new diet of eating staple foods with powdered toasted white kidney beans, seeds of Phaseolus vulgaris. Although the method is based on the action of a heat-stable α-amylase inhibitor in the beans, phaseolamin, more than 1,000 viewers who tried the method suffered from acute intestinal symptoms and 100 people were hospitalized. Lectins in the white kidney beans were suspected to be the cause of the trouble. We were asked to investigate the lectin activity remaining in the beans after the heat treatment recommended on the TV program. The test suggested that the heat treatment was insufficient to inactivate the lectin activity, which, combined with our ignorance of carbohydrate signaling in the intestine, was the cause of the problem.
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Affiliation(s)
- Haruko Ogawa
- Graduate School of Humanities and Sciences and Glycoscience Institute, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo, 112-8610, Japan,
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38
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Hang Q, Zhou Y, Hou S, Zhang D, Yang X, Chen J, Ben Z, Cheng C, Shen A. Asparagine-linked glycosylation of bone morphogenetic protein-2 is required for secretion and osteoblast differentiation. Glycobiology 2013; 24:292-304. [DOI: 10.1093/glycob/cwt110] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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39
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Meighan SE, Meighan PC, Rich ED, Brown RL, Varnum MD. Cyclic nucleotide-gated channel subunit glycosylation regulates matrix metalloproteinase-dependent changes in channel gating. Biochemistry 2013; 52:8352-62. [PMID: 24164424 DOI: 10.1021/bi400824x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Cyclic-nucleotide gated (CNG) channels are essential for phototransduction within retinal photoreceptors. We have demonstrated previously that the enzymatic activity of matrix metalloproteinase-2 and -9, members of the matrix metalloproteinase (MMP) family of extracellular, Ca(2+)- and Zn(2+)-dependent proteases, enhances the ligand sensitivity of both rod (CNGA1 and CNGB1) and cone (CNGA3 and CNGB3) CNG channels. Additionally, we have observed a decrease in the maximal CNG channel current (Imax) that begins late during MMP-directed gating changes. Here we demonstrate that CNG channels become nonconductive after prolonged MMP exposure. Concurrent with the loss of conductive channels is the increased relative contribution of channels exhibiting nonmodified gating properties, suggesting the presence of a subpopulation of channels that are protected from MMP-induced gating effects. CNGA subunits are known to possess one extracellular core glycosylation site, located at one of two possible positions within the turret loop near the pore-forming region. Our results indicate that CNGA glycosylation can impede MMP-dependent modification of CNG channels. Furthermore, the relative position of the glycosylation site within the pore turret influences the extent of MMP-dependent proteolysis. Glycosylation at the site found in CNGA3 subunits was found to be protective, while glycosylation at the bovine CNGA1 site was not. Relocating the glycosylation site in CNGA1 to the position found in CNGA3 recapitulated CNGA3-like protection from MMP-dependent processing. Taken together, these data indicate that CNGA glycosylation may protect CNG channels from MMP-dependent proteolysis, consistent with MMP modification of channel function having a requirement for physical access to the extracellular face of the channel.
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Affiliation(s)
- Starla E Meighan
- Program in Neuroscience, Department of Integrative Physiology and Neuroscience, ‡WWAMI Medical Education Program, and §Center for Integrated Biotechnology, Washington State University , P.O. Box 647620, Pullman, Washington 99164, United States
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40
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Alper SL, Sharma AK. The SLC26 gene family of anion transporters and channels. Mol Aspects Med 2013; 34:494-515. [PMID: 23506885 DOI: 10.1016/j.mam.2012.07.009] [Citation(s) in RCA: 256] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/21/2012] [Indexed: 02/08/2023]
Abstract
The phylogenetically ancient SLC26 gene family encodes multifunctional anion exchangers and anion channels transporting a broad range of substrates, including Cl(-), HCO3(-), sulfate, oxalate, I(-), and formate. SLC26 polypeptides are characterized by N-terminal cytoplasmic domains, 10-14 hydrophobic transmembrane spans, and C-terminal cytoplasmic STAS domains, and appear to be homo-oligomeric. SLC26-related SulP proteins of marine bacteria likely transport HCO3(-) as part of oceanic carbon fixation. SulP genes present in antibiotic operons may provide sulfate for antibiotic biosynthetic pathways. SLC26-related Sultr proteins transport sulfate in unicellular eukaryotes and in plants. Mutations in three human SLC26 genes are associated with congenital or early onset Mendelian diseases: chondrodysplasias for SLC26A2, chloride diarrhea for SLC26A3, and deafness with enlargement of the vestibular aqueduct for SLC26A4. Additional disease phenotypes evident only in mouse knockout models include oxalate urolithiasis for Slc26a6 and Slc26a1, non-syndromic deafness for Slc26a5, gastric hypochlorhydria for Slc26a7 and Slc26a9, distal renal tubular acidosis for Slc26a7, and male infertility for Slc26a8. STAS domains are required for cell surface expression of SLC26 proteins, and contribute to regulation of the cystic fibrosis transmembrane regulator in complex, cell- and tissue-specific ways. The protein interactomes of SLC26 polypeptides are under active investigation.
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Affiliation(s)
- Seth L Alper
- Renal Division and Division of Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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Zhao N, Enns CA. N-linked glycosylation is required for transferrin-induced stabilization of transferrin receptor 2, but not for transferrin binding or trafficking to the cell surface. Biochemistry 2013; 52:3310-9. [PMID: 23556518 PMCID: PMC3656769 DOI: 10.1021/bi4000063] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Transferrin receptor 2 (TfR2) is
a member of the transferrin receptor-like
family of proteins. Mutations in TfR2 can lead to a rare form of the
iron overload disease, hereditary hemochromatosis. TfR2 is proposed
to sense body iron levels and increase the level of expression of
the iron regulatory hormone, hepcidin. Human TfR2 (hTfR2) contains
four potential Asn-linked (N-linked) glycosylation sites on its ectodomain.
The importance of glycosylation in TfR2 function has not been elucidated.
In this study, by employing site-directed mutagenesis to remove glycosylation
sites of hTfR2 individually or in combination, we found that hTfR2
was glycosylated at Asn 240, 339, and 754, while the consensus sequence
for N-linked glycosylation at Asn 540 was not utilized. Cell surface
protein biotinylation and biotin-labeled Tf indicated that in the
absence of N-linked oligosaccharides, hTfR2 still moved to the plasma
membrane and bound its ligand, holo-Tf. However, without N-linked
glycosylation, hTfR2 did not form the intersubunit disulfide bonds
as efficiently as the wild type (WT). Moreover, the unglycosylated
form of hTfR2 could not be stabilized by holo-Tf. We further provide
evidence that the unglycosylated hTfR2 behaved in manner different
from that of the WT in response to holo-Tf treatment. Thus, the putative
iron-sensing function of TfR2 could not be achieved in the absence
of N-linked oligosaccharides. On the basis of our analyses, we conclude
that unlike TfR1, N-linked glycosylation is dispensable for the cell
surface expression and holo-Tf binding, but it is required for efficient
intersubunit disulfide bond formation and holo-Tf-induced stabilization
of TfR2.
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Affiliation(s)
- Ningning Zhao
- Department of Cell and Developmental Biology, Oregon Health & Science University , Portland, Oregon 97239, United States
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