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Zhang Z, Yao J, Jiang Z, Huang X, Wang S, Xu F. Golgi-localized APYRASE 1 is critical for Arabidopsis growth by affecting cell wall integrity under boron deficiency. PHYSIOLOGIA PLANTARUM 2024; 176:e14320. [PMID: 38686642 DOI: 10.1111/ppl.14320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 04/10/2024] [Accepted: 04/11/2024] [Indexed: 05/02/2024]
Abstract
Many nucleoside triphosphate-diphosphohydrolases (NTPDases/APYRASEs, APYs) play a key role in modulating extracellular nucleotide levels. However, the Golgi-localized APYs, which help control glycosylation, have rarely been studied. Here, we identified AtAPY1, a gene encoding an NTPDase in the Golgi apparatus, which is required for cell wall integrity and plant growth under boron (B) limited availability. Loss of function in AtAPY1 hindered cell elongation and division in root tips while increasing the number of cortical cell layers, leading to swelling of the root tip and abundant root hairs under low B stress. Further, expression pattern analysis revealed that B deficiency significantly induced AtAPY1, especially in the root meristem and stele. Fluorescent-labeled AtAPY1-GFP localized to the Golgi stack. Biochemical analysis showed that AtAPY1 exhibited a preference of UDP and GDP hydrolysis activities. Consequently, the loss of function in AtAPY1 might disturb the homoeostasis of NMP-driven NDP-sugar transport, which was closely related to the synthesis of cell wall polysaccharides. Further, cell wall-composition analysis showed that pectin content increased and borate-dimerized RG-II decreased in apy1 mutants, along with a decrease in cellulose content. Eventually, altered polysaccharide characteristics presumably cause growth defects in apy1 mutants under B deficiency. Altogether, these data strongly support a novel role for AtAPY1 in mediating responses to low B availability by regulating cell wall integrity.
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Affiliation(s)
- Ziwei Zhang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China
- Microelement Research Center, College of Resources & Environment, Huazhong Agricultural University, Wuhan, China
| | - Jinliang Yao
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China
- Microelement Research Center, College of Resources & Environment, Huazhong Agricultural University, Wuhan, China
| | - Zhexuan Jiang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China
- Microelement Research Center, College of Resources & Environment, Huazhong Agricultural University, Wuhan, China
| | - XinXuan Huang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China
- Microelement Research Center, College of Resources & Environment, Huazhong Agricultural University, Wuhan, China
| | - Sheliang Wang
- Microelement Research Center, College of Resources & Environment, Huazhong Agricultural University, Wuhan, China
| | - Fangsen Xu
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China
- Microelement Research Center, College of Resources & Environment, Huazhong Agricultural University, Wuhan, China
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2
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Savizi ISP, Motamedian E, E Lewis N, Jimenez Del Val I, Shojaosadati SA. An integrated modular framework for modeling the effect of ammonium on the sialylation process of monoclonal antibodies produced by CHO cells. Biotechnol J 2021; 16:e2100019. [PMID: 34021707 DOI: 10.1002/biot.202100019] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 05/19/2021] [Accepted: 05/20/2021] [Indexed: 12/11/2022]
Abstract
BACKGROUND Monoclonal antibodies (mABs) have emerged as one of the most important therapeutic recombinant proteins in the pharmaceutical industry. Their immunogenicity and therapeutic efficacy are influenced by post-translational modifications, specifically the glycosylation process. Bioprocess conditions can influence the intracellular process of glycosylation. Among all the process conditions that have been recognized to affect the mAB glycoforms, the detailed mechanism underlying how ammonium could perturb glycosylation remains to be fully understood. It was shown that ammonium induces heterogeneity in protein glycosylation by altering the sialic acid content of glycoproteins. Hence, understanding this mechanism would aid pharmaceutical manufacturers to ensure consistent protein glycosylation. METHODS Three different mechanisms have been proposed to explain how ammonium influences the sialylation process. In the first, the inhibition of CMP-sialic acid transporter, which transports CMP-sialic acid (sialylation substrate) into the Golgi, by an increase in UDP-GlcNAc content that is brought about by the augmented incorporation of ammonium into glucosamine formation. In the second, ammonia diffuses into the Golgi and raises its pH, thereby decreasing the sialyltransferase enzyme activity. In the third, the reduction of sialyltransferase enzyme expression level in the presence of ammonium. We employed these mechanisms in a novel integrated modular platform to link dynamic alteration in mAB sialylation process with extracellular ammonium concentration to elucidate how ammonium alters the sialic acid content of glycoproteins. RESULTS Our results show that the sialylation reaction rate is insensitive to the first mechanism. At low ammonium concentration, the second mechanism is the controlling mechanism in mAB sialylation and by increasing the ammonium level (< 8 mM) the third mechanism becomes the controlling mechanism. At higher ammonium concentrations (> 8 mM) the second mechanism becomes predominant again. CONCLUSION The presented model in this study provides a connection between extracellular ammonium and the monoclonal antibody sialylation process. This computational tool could help scientists to develop and formulate cell culture media. The model illustrated here can assist the researchers to select culture media that ensure consistent mAB sialylation.
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Affiliation(s)
- Iman Shahidi Pour Savizi
- Faculty of Chemical Engineering, Biotechnology Department, Tarbiat Modares University, Tehran, Iran
| | - Ehsan Motamedian
- Faculty of Chemical Engineering, Biotechnology Department, Tarbiat Modares University, Tehran, Iran
| | - Nathan E Lewis
- Department of Bioengineering, University of California, La Jolla, California, USA.,School of Medicine, Novo Nordisk Foundation Center for Biosustainability at the University of California, La Jolla, California, USA.,Department of Pediatrics, School of Medicine, University of California, La Jolla, California, USA
| | | | - Seyed Abbas Shojaosadati
- Faculty of Chemical Engineering, Biotechnology Department, Tarbiat Modares University, Tehran, Iran
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3
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Inhibition of CMP-sialic acid transport by endogenous 5-methyl CMP. PLoS One 2021; 16:e0249905. [PMID: 34081697 PMCID: PMC8174729 DOI: 10.1371/journal.pone.0249905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 03/26/2021] [Indexed: 12/03/2022] Open
Abstract
Nucleotide-sugar transporters (NSTs) transport nucleotide-sugar conjugates into the Golgi lumen where they are then used in the synthesis of glycans. We previously reported crystal structures of a mammalian NST, the CMP-sialic acid transporter (CST) (Ahuja and Whorton 2019). These structures elucidated many aspects of substrate recognition, selectivity, and transport; however, one fundamental unaddressed question is how the transport activity of NSTs might be physiologically regulated as a means to produce the vast diversity of observed glycan structures. Here, we describe the discovery that an endogenous methylated form of cytidine monophosphate (m5CMP) binds and inhibits CST. The presence of m5CMP in cells results from the degradation of RNA that has had its cytosine bases post-transcriptionally methylated through epigenetic processes. Therefore, this work not only demonstrates that m5CMP represents a novel physiological regulator of CST, but it also establishes a link between epigenetic control of gene expression and regulation of glycosylation.
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4
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Drew D, North RA, Nagarathinam K, Tanabe M. Structures and General Transport Mechanisms by the Major Facilitator Superfamily (MFS). Chem Rev 2021; 121:5289-5335. [PMID: 33886296 PMCID: PMC8154325 DOI: 10.1021/acs.chemrev.0c00983] [Citation(s) in RCA: 165] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Indexed: 12/12/2022]
Abstract
The major facilitator superfamily (MFS) is the largest known superfamily of secondary active transporters. MFS transporters are responsible for transporting a broad spectrum of substrates, either down their concentration gradient or uphill using the energy stored in the electrochemical gradients. Over the last 10 years, more than a hundred different MFS transporter structures covering close to 40 members have provided an atomic framework for piecing together the molecular basis of their transport cycles. Here, we summarize the remarkable promiscuity of MFS members in terms of substrate recognition and proton coupling as well as the intricate gating mechanisms undergone in achieving substrate translocation. We outline studies that show how residues far from the substrate binding site can be just as important for fine-tuning substrate recognition and specificity as those residues directly coordinating the substrate, and how a number of MFS transporters have evolved to form unique complexes with chaperone and signaling functions. Through a deeper mechanistic description of glucose (GLUT) transporters and multidrug resistance (MDR) antiporters, we outline novel refinements to the rocker-switch alternating-access model, such as a latch mechanism for proton-coupled monosaccharide transport. We emphasize that a full understanding of transport requires an elucidation of MFS transporter dynamics, energy landscapes, and the determination of how rate transitions are modulated by lipids.
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Affiliation(s)
- David Drew
- Department
of Biochemistry and Biophysics, Stockholm
University, SE 106 91 Stockholm, Sweden
| | - Rachel A. North
- Department
of Biochemistry and Biophysics, Stockholm
University, SE 106 91 Stockholm, Sweden
| | - Kumar Nagarathinam
- Center
of Structural and Cell Biology in Medicine, Institute of Biochemistry, University of Lübeck, D-23538, Lübeck, Germany
| | - Mikio Tanabe
- Structural
Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Oho 1-1, Tsukuba, Ibaraki 305-0801, Japan
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5
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Structural basis for the delivery of activated sialic acid into Golgi for sialyation. Nat Struct Mol Biol 2019; 26:415-423. [PMID: 31133698 DOI: 10.1038/s41594-019-0225-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 04/09/2019] [Indexed: 01/08/2023]
Abstract
The decoration of secretory glycoproteins and glycolipids with sialic acid is critical to many physiological and pathological processes. Sialyation is dependent on a continuous supply of sialic acid into Golgi organelles in the form of CMP-sialic acid. Translocation of CMP-sialic acid into Golgi is carried out by the CMP-sialic acid transporter (CST). Mutations in human CST are linked to glycosylation disorders, and CST is important for glycopathway engineering, as it is critical for sialyation efficiency of therapeutic glycoproteins. The mechanism of how CMP-sialic acid is recognized and translocated across Golgi membranes in exchange for CMP is poorly understood. Here we have determined the crystal structure of a Zea mays CST in complex with CMP. We conclude that the specificity of CST for CMP-sialic acid is established by the recognition of the nucleotide CMP to such an extent that they are mechanistically capable of both passive and coupled antiporter activity.
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6
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Ahuja S, Whorton MR. Structural basis for mammalian nucleotide sugar transport. eLife 2019; 8:45221. [PMID: 30985278 PMCID: PMC6508934 DOI: 10.7554/elife.45221] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 04/13/2019] [Indexed: 12/12/2022] Open
Abstract
Nucleotide-sugar transporters (NSTs) are critical components of the cellular glycosylation machinery. They transport nucleotide-sugar conjugates into the Golgi lumen, where they are used for the glycosylation of proteins and lipids, and they then subsequently transport the nucleotide monophosphate byproduct back to the cytoplasm. Dysregulation of human NSTs causes several debilitating diseases, and NSTs are virulence factors for many pathogens. Here we present the first crystal structures of a mammalian NST, the mouse CMP-sialic acid transporter (mCST), in complex with its physiological substrates CMP and CMP-sialic acid. Detailed visualization of extensive protein-substrate interactions explains the mechanisms governing substrate selectivity. Further structural analysis of mCST’s unique lumen-facing partially-occluded conformation, coupled with the characterization of substrate-induced quenching of mCST’s intrinsic tryptophan fluorescence, reveals the concerted conformational transitions that occur during substrate transport. These results provide a framework for understanding the effects of disease-causing mutations and the mechanisms of this diverse family of transporters. The cells in our body are tiny machines which, amongst other things, produce proteins. One of the production steps involves a compartment in the cell called the Golgi, where proteins are tagged and packaged before being sent to their final destination. In particular, sugars can be added onto an immature protein to help to fold it, stabilize it, and to affect how it works. Before sugars can be attached to a protein, they need to be ‘activated’ outside of the Golgi by attaching to a small molecule known as a nucleotide. Then, these ‘nucleotide-sugars’ are ferried across the Golgi membrane and inside the compartment by nucleotide-sugar transporters, or NSTs. Humans have seven different kinds of NSTs, each responsible for helping specific types of nucleotide-sugars cross the Golgi membrane. Changes in NSTs are linked to several human diseases, including certain types of epilepsy; these proteins are also important for dangerous microbes to be able to infect cells. Yet, scientists know very little about how the transporters recognize their cargo, and how they transport it. To shed light on these questions, Ahuja and Whorton set to uncover for the first time the 3D structure of a mammalian NST using a method known as X-ray crystallography. This revealed how nearly every component of this transporter is arranged when the protein is bound to two different molecules: a specific nucleotide, or a type of nucleotide-sugar. The results help to understand how changes in certain components of the NST can lead to a problem in the way the protein works. Ultimately, this knowledge may be useful to prevent diseases linked to faulty NSTs, or to stop microbes from using the transporters to their own advantage.
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Affiliation(s)
- Shivani Ahuja
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Matthew R Whorton
- Vollum Institute, Oregon Health & Science University, Portland, United States
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7
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Büll C, Boltje TJ, Wassink M, de Graaf AMA, van Delft FL, den Brok MH, Adema GJ. Targeting aberrant sialylation in cancer cells using a fluorinated sialic acid analog impairs adhesion, migration, and in vivo tumor growth. Mol Cancer Ther 2013; 12:1935-46. [PMID: 23974695 DOI: 10.1158/1535-7163.mct-13-0279] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cancer cells decorate their surface with a dense layer of sialylated glycans by upregulating the expression of sialyltransferases and other glycogenes. Although sialic acids play a vital role in many biologic processes, hypersialylation in particular has been shown to contribute to cancer cell progression and metastasis. Accordingly, selective strategies to interfere with sialic acid synthesis might offer a powerful approach in cancer therapy. In the present study, we assessed the potential of a recently developed fluorinated sialic acid analogue (P-3F(ax)-Neu5Ac) to block the synthesis of sialoglycans in murine melanoma cells and the consequences on cell adhesion, migration, and in vivo growth. The results showed that P-3F(ax)-Neu5Ac readily caused depletion of α2,3-/α2,6-linked sialic acids in B16F10 cells for several days. Long-term inhibition of sialylation for 28 days was feasible without affecting cell viability or proliferation. Moreover, P-3F(ax)-Neu5Ac proved to be a highly potent inhibitor of sialylation even at high concentrations of competing sialyltransferase substrates. P-3F(ax)-Neu5Ac-treated cancer cells exhibited impaired binding to poly-l-lysine, type I collagen, and fibronectin and diminished migratory capacity. Finally, blocking sialylation of B16F10 tumor cells with this novel sialic acid analogue reduced their growth in vivo. These results indicate that P-3F(ax)-Neu5Ac is a powerful glycomimetic capable of inhibiting aberrant sialylation that can potentially be used for anticancer therapy.
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Affiliation(s)
- Christian Büll
- Corresponding Author: Gosse J. Adema, 278 Department of Tumor Immunology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre P.O. Box 9101, Nijmegen 6500 HB, the Netherlands.
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8
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Rillahan CD, Antonopoulos A, Lefort CT, Sonon R, Azadi P, Ley K, Dell A, Haslam SM, Paulson JC. Global metabolic inhibitors of sialyl- and fucosyltransferases remodel the glycome. Nat Chem Biol 2012; 8:661-8. [PMID: 22683610 PMCID: PMC3427410 DOI: 10.1038/nchembio.999] [Citation(s) in RCA: 325] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 05/05/2012] [Indexed: 12/23/2022]
Abstract
Despite the fundamental roles of sialyl- and fucosyltransferases in mammalian physiology, there are few pharmacological tools to manipulate their function in a cellular setting. Although fluorinated analogs of the donor substrates are well-established transition state inhibitors of these enzymes, they are not membrane permeable. By exploiting promiscuous monosaccharide salvage pathways, we show that fluorinated analogs of sialic acid and fucose can be taken up and metabolized to the desired donor substrate-based inhibitors inside the cell. Because of the existence of metabolic feedback loops, they also act to prevent the de novo synthesis of the natural substrates, resulting in a global, family-wide shutdown of sialyl- and/or fucosyltransferases and remodeling of cell-surface glycans. As an example of the functional consequences, the inhibitors substantially reduce expression of the sialylated and fucosylated ligand sialyl Lewis X on myeloid cells, resulting in loss of selectin binding and impaired leukocyte rolling.
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Affiliation(s)
- Cory D. Rillahan
- Department of Chemical Physiology The Scripps Research Institute La Jolla, CA 92037 (USA)
| | - Aristotelis Antonopoulos
- Division of Molecular Biosciences Faculty of Natural Sciences mperial College London, London SW7 2AZ (UK)
| | - Craig T. Lefort
- La Jolla Institute for Allergy and Immunology Division of Inflammation Biology La Jolla, CA 92037 (USA)
| | - Roberto Sonon
- Complex Carbohydrate Research Center The University of Georgia Athens, GA 30602 (USA)
| | - Parastoo Azadi
- Complex Carbohydrate Research Center The University of Georgia Athens, GA 30602 (USA)
| | - Klaus Ley
- La Jolla Institute for Allergy and Immunology Division of Inflammation Biology La Jolla, CA 92037 (USA)
| | - Anne Dell
- Division of Molecular Biosciences Faculty of Natural Sciences mperial College London, London SW7 2AZ (UK)
| | - Stuart M. Haslam
- Division of Molecular Biosciences Faculty of Natural Sciences mperial College London, London SW7 2AZ (UK)
| | - James C. Paulson
- Department of Chemical Physiology The Scripps Research Institute La Jolla, CA 92037 (USA)
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9
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Liu L, Hirschberg CB. Developmental diseases caused by impaired nucleotide sugar transporters. Glycoconj J 2012; 30:5-10. [PMID: 22527830 DOI: 10.1007/s10719-012-9375-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 03/28/2012] [Indexed: 01/24/2023]
Abstract
Nucleotide sugar transporters play critical roles in glycosylation of proteins, lipids and proteoglycans, which are essential for organogenesis, development, mammalian cellular immunity and pathogenicity of human pathogenic agents. Functional deficiencies of these transporters result in global defects of glycoconjugates, which in turn lead to a diversity of biochemical, physiological and pathological phenotypes. In this short review, we will highlight human and bovine diseases caused by mutations of these transporters.
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Affiliation(s)
- Li Liu
- Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Evans-E438, 72 East Concord Street, Boston, MA 02118, USA
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10
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Lizzi AR, D'Alessandro AM, Bozzi A, Cinque B, Oratore A, D'Andrea G. Pattern expression of glycan residues in AZT-treated K562 cells analyzed by lectin cytochemistry. Mol Cell Biochem 2007; 300:29-37. [PMID: 17440690 DOI: 10.1007/s11010-006-9343-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Accepted: 09/28/2006] [Indexed: 10/23/2022]
Abstract
The present paper shows that human chronic myeloid (K562) cells exposed 3 h to 20 microM 3'-azido-3'-deoxythymidine (AZT) exhibit marked variations of the oligosaccharide moiety of glycoconjugates. These changes were analyzed by confocal fluorescence microscopy, upon incubation of control and AZT-treated cells with biotin-lectin conjugates to visualize cell surface glycans or total glycans after cells permeabilization. In addition, cell fluorescence distribution of the biotinylated lectins, localized with streptavidin conjugates labeled with Alexa Fluor 488, was analyzed by flow cytometry. The results obtained show significant variations on the expression/distribution of membrane surface glycans as detected by both WGA and SNA, two lectins that recognize primarily cellular internal membrane glycolipids. A further interesting result was the significant increase of N-acetylglucosamine linked glycans localized either at the cell surface or intracellularly but only in K562 cells exposed to AZT. On the whole, our data demonstrate that AZT alters both lipid and N-linked glycosylations thus confirming previous observations, from our laboratory and from other Authors, that the drug impair the nucleotide-sugar import in the Golgi's lumen. AZT does also alter the O-linked glycosylations that occur in the Golgi complex since these reactions require the incorporation of sialic acid, GlcNAc and GalNAc all of which are sensitive to the drug.
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Affiliation(s)
- Anna Rita Lizzi
- Department of Biomedical Sciences and Technologies, University of L'Aquila, 67100 L'Aquila, Italy
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11
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Caffaro CE, Hirschberg CB. Nucleotide sugar transporters of the Golgi apparatus: from basic science to diseases. Acc Chem Res 2006; 39:805-12. [PMID: 17115720 DOI: 10.1021/ar0400239] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Approximately 80% of secreted and membrane proteins (40% of all proteins) of eukaryotes become covalently linked to sugars in the lumen of the Golgi apparatus, a cellular organelle that is part of the secretory system of all eukaryotes. The sugar donors are mostly nucleoside diphosphate sugars (nucleotide sugars) and must be translocated from the cytosol, their site of synthesis, across the Golgi apparatus membrane and into the lumen by specific transporters. These are hydrophobic, homodimeric proteins that span the membrane multiple times. Mutants of these proteins have developmental phenotypes including diseases in humans and cattle.
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Affiliation(s)
- Carolina E Caffaro
- Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts 02118, USA
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12
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Zhao W, Chen TLL, Vertel BM, Colley KJ. The CMP-sialic acid transporter is localized in the medial-trans Golgi and possesses two specific endoplasmic reticulum export motifs in its carboxyl-terminal cytoplasmic tail. J Biol Chem 2006; 281:31106-18. [PMID: 16923816 DOI: 10.1074/jbc.m605564200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The addition of sialic acid to glycoproteins and glycolipids requires Golgi sialyltransferases to have access to their glycoconjugate substrates and nucleotide sugar donor, CMP-sialic acid. CMP-sialic acid is transported into the lumen of the Golgi complex through the CMP-sialic acid transporter, an antiporter that also functions to transport CMP into the cytosol. We localized the transporter using immunofluorescence and deconvolution microscopy to test the prediction that it is broadly distributed across the Golgi stack to serve the many sialyltransferases involved in glycoconjugate sialylation. The transporter co-localized with ST6GalI in the medial and trans Golgi, showed partial overlap with a medial Golgi marker and little overlap with early Golgi or trans Golgi network markers. Endoplasmic reticulum-retained forms of sialyltransferases did not redistribute the transporter from the Golgi to the endoplasmic reticulum, suggesting that transporter-sialyltransferase complexes are not involved in transporter localization. Next we evaluated the role of the transporter's N- and C-terminal cytoplasmic tails in its trafficking and localization. The N-tail was not required for either endoplasmic reticulum export or Golgi localization. The C-tail was required for endoplasmic reticulum export and contained di-Ile and terminal Val motifs at its very C terminus that function as independent endoplasmic reticulum export signals. Deletion of the last four amino acids of the C-tail (IIGV) eliminated these export signals and prevented endoplasmic reticulum export of the transporter. This form of the transporter supplied limited amounts of CMP-sialic acid to Golgi sialyltransferases but was unable to completely rescue the transporter defect of Lec2 Chinese hamster ovary cells.
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Affiliation(s)
- Weihan Zhao
- Department of Biochemistry and Molecular Genetics, University of Illinois, College of Medicine, Chicago, Illinois 60607, USA
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13
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D'Alessio C, Caramelo JJ, Parodi AJ. Absence of nucleoside diphosphatase activities in the yeast secretory pathway does not abolish nucleotide sugar-dependent protein glycosylation. J Biol Chem 2005; 280:40417-27. [PMID: 16172132 DOI: 10.1074/jbc.m503149200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It is accepted that glycosyltransferase-generated nucleoside diphosphates are converted to monophosphates in the secretory pathway by nucleoside diphosphatases (NDPases) to provide substrates for antiport transport systems by which entrance of nucleotide sugars from the cytosol into the lumen is coupled to exit of nucleoside monophosphates. Working with Saccharomyces cerevisiae mutants affected in anterograde and/or retrograde endoplasmic reticulum (ER)-Golgi vesicular traffic and/or defective in one or both secretory pathway (Golgi) NDPases, we show that UDP-Glc: glycoprotein glucosyltransferase-mediated glucosylation is not dependent on the presence of NDPases or on ER-Golgi vesicular traffic and that GDP-Man-dependent N- and O-mannosylations are reduced but not abolished in the absence of NDPases in the secretory pathway. Further, the absence of the main Man-1-P transferase (a Golgi GMP-generating enzyme) does not modify the limited mannosylation observed in the absence of NDPases. Based on these results and on available additional information, we suggest that in the absence of NDPases, the already characterized nucleotide sugar transporters allow entrance of nucleotide sugars into the luminal compartments and that resulting nucleoside diphosphates exit to the cytosol by a still unknown mechanism. Further, an unexpected side result suggests that formation of Ser/Thr-Man(2) may occur in the ER and not exclusively in the Golgi.
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Affiliation(s)
- Cecilia D'Alessio
- Laboratory of Glycobiology, Fundación Instituto Leloir, Avda. Patricias Argentinas 435, Buenos Aires C1405BWE, Argentina
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Segawa H, Soares RP, Kawakita M, Beverley SM, Turco SJ. Reconstitution of GDP-mannose transport activity with purified Leishmania LPG2 protein in liposomes. J Biol Chem 2004; 280:2028-35. [PMID: 15542612 DOI: 10.1074/jbc.m404915200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activated nucleotide sugars required for the synthesis of glycoconjugates within the secretory pathway of eukaryotes are provided by the action of nucleotide sugar transporters (NSTs). Typically, NSTs are studied in microsomal preparations from wild-type or mutant lines; however, in this setting it can be difficult to assess NST properties because of the presence of glycosyltransferases and other interfering activities. Here we have engineered Leishmania donovani to express high levels of an active LPG2 Golgi GDP-Man transporter bearing a C-terminal polyhistidine tag. The functional LPG2-HIS was solubilized, purified by metal affinity chromatography, and reconstituted into phosphatidylcholine-containing liposomes using polystyrene SM-2 beads. The proteoliposomes exhibited robust GDP-Man transport activity with an apparent K(m) of 6.6 mum. Transport activity was enhanced by preloading of GMP and showed specificity for multiple substrates (GDP-Ara and GDP-Fuc). In contrast to the activity in crude microsomes, transport was not dependent on the presence of divalent cations. Thus, reconstitution of transport activity using purified LPG2 protein in liposomes provides firm experimental evidence that a single polypeptide is solely required for NST activity and is able to mediate the uptake of multiple substrates. These studies are relevant to the study of NST structure and function in both protozoan parasites as well as their higher eukaryotic hosts.
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Affiliation(s)
- Hiroaki Segawa
- Department of Molecular and Cellular Biochemistry, University of Kentucky Medical Center, College of Medicine, Lexington, Kentucky 40536, USA
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15
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Aoki K, Ishida N, Kawakita M. Substrate recognition by nucleotide sugar transporters: further characterization of substrate recognition regions by analyses of UDP-galactose/CMP-sialic acid transporter chimeras and biochemical analysis of the substrate specificity of parental and chimeric transporters. J Biol Chem 2003; 278:22887-93. [PMID: 12682060 DOI: 10.1074/jbc.m302620200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human UDP-Gal transporter 1 (hUGT1) and the human CMP-Sia transporter (hCST) are similar in structure, with amino acid sequences that are 43% identical, but they have quite distinct transport substrates. To define their substrate recognition regions, we constructed various chimeras between the two transporters and demonstrated that distinct submolecular regions of the transporter molecules are involved in the specific recognition of UDP-Gal and CMP-Sia (Aoki, K., Ishida, N., and Kawakita, M. (2001) J. Biol. Chem. 276, 21555-21561). In a further attempt to define the minimum submolecular regions required for the recognition of specific substrates, we found that substitution of helix 7 of hCST into the corresponding part of hUGT1 was necessary and sufficient for a chimera to show CST activity. Additional replacement of helix 2 or 3 of hUGT1 with the corresponding hCST sequence markedly increased the efficiency of CMP-Sia transport. For UGT activity, helices 1 and 8 of hUGT1 were necessary (but not sufficient), and helices 9 and 10 or helices 2, 3, and 7 derived from hUGT1 were also required to render the chimera competent for UDP-Gal transport. The in vitro analyses of a chimera with dual specificity indicated that it transported both UMP and CMP and mediated exchange reactions between these nucleotides and nucleotide sugars that are recognized specifically by either of the parental transporters.
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Affiliation(s)
- Kazuhisa Aoki
- Department of Immunology, Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan
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Martinez-Duncker I, Mollicone R, Codogno P, Oriol R. The nucleotide-sugar transporter family: a phylogenetic approach. Biochimie 2003; 85:245-60. [PMID: 12770764 DOI: 10.1016/s0300-9084(03)00046-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Nucleotide sugar transporters (NST) establish the functional link of membrane transport between the nucleotide sugars synthesized in the cytoplasm and nucleus, and the glycosylation processes that take place in the endoplasmic reticulum (ER) and Golgi apparatus. The aim of the present work was to perform a phylogenetic analysis of 87 bank annotated protein sequences comprising all the NST so far characterized and their homologues retrieved by BLAST searches, as well as the closely related triose-phosphate translocator (TPT) plant family. NST were classified in three comprehensive families by linking them to the available experimental data. This enabled us to point out both the possible ER subcellular targeting of these transporters mediated by the dy-lysine motif and the substrate recognition mechanisms specific to each family as well as an important acceptor site motif, establishing the role of evolution in the functional properties of each NST family.
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Affiliation(s)
- Ivan Martinez-Duncker
- Inserm U504 Glycobiologie et signalisation cellulaire, Université de Paris Sud XI, 16, avenue Paul-Vaillant-Couturier, 94807 Villejuif, France.
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