1
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Gao YG, McDonald J, Malinina L, Patel DJ, Brown RE. Ceramide-1-phosphate transfer protein promotes sphingolipid reorientation needed for binding during membrane interaction. J Lipid Res 2022; 63:100151. [PMID: 34808193 PMCID: PMC8953657 DOI: 10.1016/j.jlr.2021.100151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 12/16/2022] Open
Abstract
Lipid transfer proteins acquire and release their lipid cargoes by interacting transiently with source and destination biomembranes. In the GlycoLipid Transfer Protein (GLTP) superfamily, the two-layer all-α-helical GLTP-fold defines proteins that specifically target sphingolipids (SLs) containing either sugar or phosphate headgroups via their conserved but evolutionarily-modified SL recognitions centers. Despite comprehensive structural insights provided by X-ray crystallography, the conformational dynamics associated with membrane interaction and SL uptake/release by GLTP superfamily members have remained unknown. Herein, we report insights gained from molecular dynamics (MD) simulations into the conformational dynamics that enable ceramide-1-phosphate transfer proteins (CPTPs) to acquire and deliver ceramide-1-phosphate (C1P) during interaction with 1-palmitoyl-2-oleoyl phosphatidylcholine bilayers. The focus on CPTP reflects this protein's involvement in regulating pro-inflammatory eicosanoid production and autophagy-dependent inflammasome assembly that drives interleukin (IL-1β and IL-18) production and release by surveillance cells. We found that membrane penetration by CPTP involved α-6 helix and the α-2 helix N-terminal region, was confined to one bilayer leaflet, and was relatively shallow. Large-scale dynamic conformational changes were minimal for CPTP during membrane interaction or C1P uptake except for the α-3/α-4 helices connecting loop, which is located near the membrane interface and interacts with certain phosphoinositide headgroups. Apart from functioning as a shallow membrane-docking element, α-6 helix was found to adeptly reorient membrane lipids to help guide C1P hydrocarbon chain insertion into the interior hydrophobic pocket of the SL binding site.These findings support a proposed 'hydrocarbon chain-first' mechanism for C1P uptake, in contrast to the 'lipid polar headgroup-first' uptake used by most lipid-transfer proteins.
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Affiliation(s)
- Yong-Guang Gao
- Hormel Institute, University of Minnesota, Austin, MN, USA.
| | | | - Lucy Malinina
- Hormel Institute, University of Minnesota, Austin, MN, USA
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
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2
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Budani M, Auray-Blais C, Lingwood C. ATP-binding cassette transporters mediate differential biosynthesis of glycosphingolipid species. J Lipid Res 2021; 62:100128. [PMID: 34597626 PMCID: PMC8569594 DOI: 10.1016/j.jlr.2021.100128] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 08/18/2021] [Accepted: 09/03/2021] [Indexed: 01/13/2023] Open
Abstract
The cytosolic-oriented glucosylceramide (GlcCer) synthase is enigmatic, requiring nascent GlcCer translocation to the luminal Golgi membrane to access glycosphingolipid (GSL) anabolic glycosyltransferases. The mechanism by which GlcCer is flipped remains unclear. To investigate the role of GlcCer-binding partners in this process, we previously made cleavable, biotinylated, photoreactive GlcCer analogs in which the reactive nitrene was closely apposed to the GlcCer head group, while maintaining a C16-acyl chain. GlcCer-binding protein specificity was validated for both photoprobes. Using one probe, XLB, here we identified ATP-binding cassette (ABC) transporters ABCA3, ABCB4, and ABCB10 as unfractionated microsomal GlcCer-binding proteins in DU-145 prostate tumor cells. siRNA knockdown (KD) of these transporters differentially blocked GSL synthesis assessed in toto and via metabolic labeling. KD of ABCA3 reduced acid/neutral GSL levels, but increased those of LacCer, while KD of ABCB4 preferentially reduced neutral GSL levels, and KD of ABCB10 reduced levels of both neutral and acidic GSLs. Depletion of ABCA12, implicated in GlcCer transport, preferentially decreased neutral GSL levels, while ABCB1 KD preferentially reduced gangliosides, but increased neutral GSL Gb3. These results imply that multiple ABC transporters may provide distinct but overlapping GlcCer and LacCer pools within the Golgi lumen for anabolism of different GSL series by metabolic channeling. Differential ABC family member usage may fine-tune GSL biosynthesis depending on cell/tissue type. We conclude that ABC transporters provide a new tool for the regulation of GSL biosynthesis and serve as potential targets to reduce selected GSL species/subsets in diseases in which GSLs are dysregulated.
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Affiliation(s)
- Monique Budani
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada; Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Christiane Auray-Blais
- Division of Medical Genetics, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Québec, Canada
| | - Clifford Lingwood
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada; Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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3
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Gao YG, Zhai X, Boldyrev IA, Molotkovsky JG, Patel DJ, Malinina L, Brown RE. Ceramide-1-phosphate transfer protein (CPTP) regulation by phosphoinositides. J Biol Chem 2021; 296:100600. [PMID: 33781749 PMCID: PMC8091061 DOI: 10.1016/j.jbc.2021.100600] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 03/19/2021] [Accepted: 03/25/2021] [Indexed: 12/25/2022] Open
Abstract
Ceramide-1-phosphate transfer proteins (CPTPs) are members of the glycolipid transfer protein (GLTP) superfamily that shuttle ceramide-1-phosphate (C1P) between membranes. CPTPs regulate cellular sphingolipid homeostasis in ways that impact programmed cell death and inflammation. CPTP downregulation specifically alters C1P levels in the plasma and trans-Golgi membranes, stimulating proinflammatory eicosanoid production and autophagy-dependent inflammasome-mediated cytokine release. However, the mechanisms used by CPTP to target the trans-Golgi and plasma membrane are not well understood. Here, we monitored C1P intervesicular transfer using fluorescence energy transfer (FRET) and showed that certain phosphoinositides (phosphatidylinositol 4,5 bisphosphate (PI-(4,5)P2) and phosphatidylinositol 4-phosphate (PI-4P)) increased CPTP transfer activity, whereas others (phosphatidylinositol 3-phosphate (PI-3P) and PI) did not. PIPs that stimulated CPTP did not stimulate GLTP, another superfamily member. Short-chain PI-(4,5)P2, which is soluble and does not remain membrane-embedded, failed to activate CPTP. CPTP stimulation by physiologically relevant PI-(4,5)P2 levels surpassed that of phosphatidylserine (PS), the only known non-PIP stimulator of CPTP, despite PI-(4,5)P2 increasing membrane equilibrium binding affinity less effectively than PS. Functional mapping of mutations that led to altered FRET lipid transfer and assessment of CPTP membrane interaction by surface plasmon resonance indicated that di-arginine motifs located in the α-6 helix and the α3-α4 helix regulatory loop of the membrane-interaction region serve as PI-(4,5)P2 headgroup-specific interaction sites. Haddock modeling revealed specific interactions involving the PI-(4,5)P2 headgroup that left the acyl chains oriented favorably for membrane embedding. We propose that PI-(4,5)P2 interaction sites enhance CPTP activity by serving as preferred membrane targeting/docking sites that favorably orient the protein for function.
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Affiliation(s)
- Yong-Guang Gao
- Hormel Institute, University of Minnesota, Austin, Minnesota, USA
| | - Xiuhong Zhai
- Hormel Institute, University of Minnesota, Austin, Minnesota, USA
| | - Ivan A Boldyrev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation
| | - Julian G Molotkovsky
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - Lucy Malinina
- Hormel Institute, University of Minnesota, Austin, Minnesota, USA
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4
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Mishra SK, Gao YG, Zou X, Stephenson DJ, Malinina L, Hinchcliffe EH, Chalfant CE, Brown RE. Emerging roles for human glycolipid transfer protein superfamily members in the regulation of autophagy, inflammation, and cell death. Prog Lipid Res 2020; 78:101031. [PMID: 32339554 DOI: 10.1016/j.plipres.2020.101031] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 02/27/2020] [Accepted: 02/27/2020] [Indexed: 12/14/2022]
Abstract
Glycolipid transfer proteins (GLTPs) were first identified over three decades ago as ~24kDa, soluble, amphitropic proteins that specifically accelerate the intermembrane transfer of glycolipids. Upon discovery that GLTPs use a unique, all-α-helical, two-layer 'sandwich' architecture (GLTP-fold) to bind glycosphingolipids (GSLs), a new protein superfamily was born. Structure/function studies have provided exquisite insights defining features responsible for lipid headgroup selectivity and hydrophobic 'pocket' adaptability for accommodating hydrocarbon chains of differing length and unsaturation. In humans, evolutionarily-modified GLTP-folds have been identified with altered sphingolipid specificity, e. g. ceramide-1-phosphate transfer protein (CPTP), phosphatidylinositol 4-phosphate adaptor protein-2 (FAPP2) which harbors a GLTP-domain and GLTPD2. Despite the wealth of structural data (>40 Protein Data Bank deposits), insights into the in vivo functional roles of GLTP superfamily members have emerged slowly. In this review, recent advances are presented and discussed implicating human GLTP superfamily members as important regulators of: i) pro-inflammatory eicosanoid production associated with Group-IV cytoplasmic phospholipase A2; ii) autophagy and inflammasome assembly that drive surveillance cell release of interleukin-1β and interleukin-18 inflammatory cytokines; iii) cell cycle arrest and necroptosis induction in certain colon cancer cell lines. The effects exerted by GLTP superfamily members appear linked to their ability to regulate sphingolipid homeostasis by acting in either transporter and/or sensor capacities. These timely findings are opening new avenues for future cross-disciplinary, translational medical research involving GLTP-fold proteins in human health and disease. Such avenues include targeted regulation of specific GLTP superfamily members to alter sphingolipid levels as a therapeutic means for combating viral infection, neurodegenerative conditions and circumventing chemo-resistance during cancer treatment.
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Affiliation(s)
- Shrawan K Mishra
- Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Yong-Guang Gao
- Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Xianqiong Zou
- Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Daniel J Stephenson
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0614, USA; Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Lucy Malinina
- Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | | | - Charles E Chalfant
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA; Research Service, James A. Haley Veterans Hospital, Tampa, FL 33612, USA; The Moffitt Cancer Center, Tampa, FL 33620, USA
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5
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Samaha D, Hamdo HH, Wilde M, Prause K, Arenz C. Sphingolipid-Transporting Proteins as Cancer Therapeutic Targets. Int J Mol Sci 2019; 20:ijms20143554. [PMID: 31330821 PMCID: PMC6678544 DOI: 10.3390/ijms20143554] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 07/16/2019] [Accepted: 07/18/2019] [Indexed: 01/11/2023] Open
Abstract
The understanding of the role of sphingolipid metabolism in cancer has tremendously increased in the past ten years. Many tumors are characterized by imbalances in sphingolipid metabolism. In many cases, disorders of sphingolipid metabolism are also likely to cause or at least promote cancer. In this review, sphingolipid transport proteins and the processes catalyzed by them are regarded as essential components of sphingolipid metabolism. There is much to suggest that these processes are often rate-limiting steps for metabolism of individual sphingolipid species and thus represent potential target structures for pharmaceutical anticancer research. Here, we summarize empirical and biochemical data on different proteins with key roles in sphingolipid transport and their potential role in cancer.
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Affiliation(s)
- Doaa Samaha
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
- Depatment of Pharmaceutical Chemistry, College of Pharmacy, Helwan University, Cairo 11795, Egypt
| | - Housam H Hamdo
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
| | - Max Wilde
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
| | - Kevin Prause
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
| | - Christoph Arenz
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
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6
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Liu X, Zhu Y, Liu T, Xue Q, Tian F, Yuan Y, Zhao C. Exploring toxicity of perfluorinated compounds through complex network and pathway modeling. J Biomol Struct Dyn 2019; 38:2604-2612. [PMID: 31244379 DOI: 10.1080/07391102.2019.1637281] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Perfluorinated compounds (PFCs) have serious impacts on human health, which could interfere with the body's signal pathways and affect the normal hormone balance of humans. PFCs were reported to bind to many proteins causing a series of biological effects. It was quite possible that the in vivo action of PFCs was not a single target or a single pathway, suggesting the toxic effect was due to the disturbance of protein or gene network, not limited to the modification of a single target protein or gene. Thus, a PFCs-targets interaction network was constructed and the significant differences in the characteristics of complex networks between the branched PFCs and linear PFCs were observed. A molecular dynamics simulation proved that binding ability of the branched PFCs to the target protein was much weaker than that of the linear PFCs, explaining why the branched PFCs presented significantly difference from the linear PFCs in terms of complex network characteristics. In addition, four target genes were identified as the central node genes of the network. The four target genes were proved to present certain influences on some diseases, which suggested a high correlation between PFCs to these diseases, including obesity, hepatocellular carcinoma and diabetes. The present work was helpful to develop new approaches to identify the key toxic targets of compounds and to explore the toxicity effects on pathways. AbbreviationsARandrogen receptorBPAbisphenol AESR1estrogen receptor 1ESR2estrogen receptor 2GLTPglycolipid transfer proteinHbFthe fetal hemoglobinHBG1hemoglobin subunit γ-1hERαhuman ERαHSD17B1hydroxysteroid 17-β dehydrogenase 1KEGGKenya encyclopedia of genes and genomesMDmolecular dynamics simulationPFCsperfluorinated compoundsPFOAperfluorooctanoic acidPFOSperfluorooctane sulfonatePOPspersistent organic pollutantsRMSDroot-mean-square deviationSHBGsex hormone binding globulinSPC/Eextended simple point charge modelTRthyroid hormone receptorCommunicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Xinhe Liu
- School of Pharmacy, Lanzhou University, Lanzhou, China
| | - Yu Zhu
- Department of Ecology and Environment of Gansu Province, Lanzhou, China
| | - Tingting Liu
- Gansu Provincial Maternity and Child-care Hospital, Lanzhou, China
| | - Qiao Xue
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
| | - Fang Tian
- School of Pharmacy, Lanzhou University, Lanzhou, China
| | - Yongna Yuan
- School of Information Science & Engineering, Lanzhou University, Lanzhou, China
| | - Chunyan Zhao
- School of Pharmacy, Lanzhou University, Lanzhou, China
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7
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Hirano Y, Gao YG, Stephenson DJ, Vu NT, Malinina L, Simanshu DK, Chalfant CE, Patel DJ, Brown RE. Structural basis of phosphatidylcholine recognition by the C2-domain of cytosolic phospholipase A 2α. eLife 2019; 8:e44760. [PMID: 31050338 PMCID: PMC6550875 DOI: 10.7554/elife.44760] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 05/03/2019] [Indexed: 01/19/2023] Open
Abstract
Ca2+-stimulated translocation of cytosolic phospholipase A2α (cPLA2α) to the Golgi induces arachidonic acid production, the rate-limiting step in pro-inflammatory eicosanoid synthesis. Structural insights into the cPLA2α preference for phosphatidylcholine (PC)-enriched membranes have remained elusive. Here, we report the structure of the cPLA2α C2-domain (at 2.2 Å resolution), which contains bound 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) and Ca2+ ions. Two Ca2+ are complexed at previously reported locations in the lipid-free C2-domain. One of these Ca2+ions, along with a third Ca2+, bridges the C2-domain to the DHPC phosphate group, which also interacts with Asn65. Tyr96 plays a key role in lipid headgroup recognition via cation-π interaction with the PC trimethylammonium group. Mutagenesis analyses confirm that Tyr96 and Asn65 function in PC binding selectivity by the C2-domain and in the regulation of cPLA2α activity. The DHPC-binding mode of the cPLA2α C2-domain, which differs from phosphatidylserine or phosphatidylinositol 4,5-bisphosphate binding by other C2-domains, expands and deepens knowledge of the lipid-binding mechanisms mediated by C2-domains.
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Affiliation(s)
- Yoshinori Hirano
- Structural Biology ProgramMemorial Sloan-Kettering Cancer CenterNew YorkUnited States
- Graduate School of Biological SciencesNara Institute of Science and Technology (NAIST)TakayamaJapan
| | - Yong-Guang Gao
- Hormel InstituteUniversity of MinnesotaAustinUnited States
| | - Daniel J Stephenson
- Department of Biochemistry and Molecular BiologyVirginia Commonwealth University Medical CenterRichmondUnited States
- Department of Cell Biology, Microbiology and Molecular BiologyUniversity of South FloridaTampaUnited States
| | - Ngoc T Vu
- Department of Biochemistry and Molecular BiologyVirginia Commonwealth University Medical CenterRichmondUnited States
| | - Lucy Malinina
- Hormel InstituteUniversity of MinnesotaAustinUnited States
| | - Dhirendra K Simanshu
- Structural Biology ProgramMemorial Sloan-Kettering Cancer CenterNew YorkUnited States
| | - Charles E Chalfant
- Department of Cell Biology, Microbiology and Molecular BiologyUniversity of South FloridaTampaUnited States
- Research ServiceJames A. Haley Veterans HospitalTampaUnited States
- The Moffitt Cancer CenterTampaUnited States
| | - Dinshaw J Patel
- Structural Biology ProgramMemorial Sloan-Kettering Cancer CenterNew YorkUnited States
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8
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Glucosylceramide acyl chain length is sensed by the glycolipid transfer protein. PLoS One 2018; 13:e0209230. [PMID: 30550553 PMCID: PMC6294359 DOI: 10.1371/journal.pone.0209230] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 11/30/2018] [Indexed: 12/02/2022] Open
Abstract
The glycolipid transfer protein, GLTP, can be found in the cytoplasm, and it has a FFAT-like motif (two phenylalanines in an acidic tract) that targets it to the endoplasmic reticulum (ER). We have previously shown that GLTP can bind to a transmembrane ER protein, vesicle-associated membrane protein-associated protein A (VAP-A), which is involved in a wide range of ER functions. We have addressed the mechanisms that might regulate the association between GLTP and the VAP proteins by studying the capacity of GLTP to recognize different N-linked acyl chain species of glucosylceramide. We used surface plasmon resonance and a lipid transfer competition assay to show that GLTP prefers shorter N-linked fully saturated acyl chain glucosylceramides, such as C8, C12, and C16, whereas long C18, C20, and C24-glucosylceramides are all bound more weakly and transported more slowly than their shorter counterparts. Changes in the intrinsic GLTP tryptophan fluorescence blueshifts, also indicate a break-point between C16- and C18-glucosylceramide in the GLTP sensing ability. It has long been postulated that GLTP would be a sensor in the sphingolipid synthesis machinery, but how this mechanistically occurs has not been addressed before. It is unclear what proteins the GLTP VAP association would influence. Here we found that if GLTP has a bound GlcCer the association with VAP-A is weaker. We have also used a formula for identifying putative FFAT-domains, and we identified several potential VAP-interactors within the ceramide and sphingolipid synthesis pathways that could be candidates for regulation by GLTP.
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9
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Hunter CD, Guo T, Daskhan G, Richards MR, Cairo CW. Synthetic Strategies for Modified Glycosphingolipids and Their Design as Probes. Chem Rev 2018; 118:8188-8241. [DOI: 10.1021/acs.chemrev.8b00070] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Carmanah D. Hunter
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Tianlin Guo
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Gour Daskhan
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Michele R. Richards
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Christopher W. Cairo
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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10
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Functional evaluation of tryptophans in glycolipid binding and membrane interaction by HET-C2, a fungal glycolipid transfer protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1069-1076. [PMID: 29305831 DOI: 10.1016/j.bbamem.2018.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Revised: 12/16/2017] [Accepted: 01/01/2018] [Indexed: 02/07/2023]
Abstract
HET-C2 is a fungal glycolipid transfer protein (GLTP) that uses an evolutionarily-modified GLTP-fold to achieve more focused transfer specificity for simple neutral glycosphingolipids than mammalian GLTPs. Only one of HET-C2's two Trp residues is topologically identical to the three Trp residues of mammalian GLTP. Here, we provide the first assessment of the functional roles of HET-C2 Trp residues in glycolipid binding and membrane interaction. Point mutants HET-C2W208F, HET-C2W208A and HET-C2F149Y all retained >90% activity and 80-90% intrinsic Trp fluorescence intensity; whereas HET-C2F149A transfer activity decreased to ~55% but displayed ~120% intrinsic Trp emission intensity. Thus, neither W208 nor F149 is absolutely essential for activity and most Trp emission intensity (~85-90%) originates from Trp109. This conclusion was supported by HET-C2W109Y/F149Y which displayed ~8% intrinsic Trp intensity and was nearly inactive. Incubation of the HET-C2 mutants with 1-palmitoyl-2-oleoyl-phosphatidylcholine vesicles containing different monoglycosylceramides or presented by lipid ethanol-injection decreased Trp fluorescence intensity and blue-shifted the Trp λmax by differing amounts compared to wtHET-C2. With HET-C2 mutants for Trp208, the emission intensity decreases (~30-40%) and λmax blue-shifts (~12nm) were more dramatic than for wtHET-C2 or F149 mutants and closely resembled human GLTP. When Trp109 was mutated, the glycolipid induced changes in HET-C2 emission intensity and λmax blue-shift were nearly nonexistent. Our findings indicate that the HET-C2 Trp λmax blue-shift is diagnostic for glycolipid binding; whereas the emission intensity decrease reflects higher environmental polarity encountered upon nonspecific interaction with phosphocholine headgroups comprising the membrane interface and specific interaction with the hydrated glycolipid sugar.
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11
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Malinina L, Patel DJ, Brown RE. How α-Helical Motifs Form Functionally Diverse Lipid-Binding Compartments. Annu Rev Biochem 2017; 86:609-636. [PMID: 28375742 DOI: 10.1146/annurev-biochem-061516-044445] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lipids are produced site-specifically in cells and then distributed nonrandomly among membranes via vesicular and nonvesicular trafficking mechanisms. The latter involves soluble amphitropic proteins extracting specific lipids from source membranes to function as molecular solubilizers that envelope their insoluble cargo before transporting it to destination sites. Lipid-binding and lipid transfer structural motifs range from multi-β-strand barrels, to β-sheet cups and baskets covered by α-helical lids, to multi-α-helical bundles and layers. Here, we focus on how α-helical proteins use amphipathic helical layering and bundling to form modular lipid-binding compartments and discuss the functional consequences. Preformed compartments generally rely on intramolecular disulfide bridging to maintain conformation (e.g., albumins, nonspecific lipid transfer proteins, saposins, nematode polyprotein allergens/antigens). Insights into nonpreformed hydrophobic compartments that expand and adapt to accommodate a lipid occupant are few and provided mostly by the three-layer, α-helical ligand-binding domain of nuclear receptors. The simple but elegant and nearly ubiquitous two-layer, α-helical glycolipid transfer protein (GLTP)-fold now further advances understanding.
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Affiliation(s)
- Lucy Malinina
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912; ,
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065;
| | - Rhoderick E Brown
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912; ,
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12
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Zhai X, Gao YG, Mishra SK, Simanshu DK, Boldyrev IA, Benson LM, Bergen HR, Malinina L, Mundy J, Molotkovsky JG, Patel DJ, Brown RE. Phosphatidylserine Stimulates Ceramide 1-Phosphate (C1P) Intermembrane Transfer by C1P Transfer Proteins. J Biol Chem 2016; 292:2531-2541. [PMID: 28011644 DOI: 10.1074/jbc.m116.760256] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 12/21/2016] [Indexed: 11/06/2022] Open
Abstract
Genetic models for studying localized cell suicide that halt the spread of pathogen infection and immune response activation in plants include Arabidopsis accelerated-cell-death 11 mutant (acd11). In this mutant, sphingolipid homeostasis is disrupted via depletion of ACD11, a lipid transfer protein that is specific for ceramide 1-phosphate (C1P) and phyto-C1P. The C1P binding site in ACD11 and in human ceramide-1-phosphate transfer protein (CPTP) is surrounded by cationic residues. Here, we investigated the functional regulation of ACD11 and CPTP by anionic phosphoglycerides and found that 1-palmitoyl-2-oleoyl-phosphatidic acid or 1-palmitoyl-2-oleoyl-phosphatidylglycerol (≤15 mol %) in C1P source vesicles depressed C1P intermembrane transfer. By contrast, replacement with 1-palmitoyl-2-oleoyl-phosphatidylserine stimulated C1P transfer by ACD11 and CPTP. Notably, "soluble" phosphatidylserine (dihexanoyl-phosphatidylserine) failed to stimulate C1P transfer. Also, none of the anionic phosphoglycerides affected transfer action by human glycolipid lipid transfer protein (GLTP), which is glycolipid-specific and has few cationic residues near its glycolipid binding site. These findings provide the first evidence for a potential phosphoglyceride headgroup-specific regulatory interaction site(s) existing on the surface of any GLTP-fold and delineate new differences between GLTP superfamily members that are specific for C1P versus glycolipid.
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Affiliation(s)
- Xiuhong Zhai
- From the Hormel Institute, University of Minnesota, Austin, Minnesota 55912,
| | - Yong-Guang Gao
- From the Hormel Institute, University of Minnesota, Austin, Minnesota 55912
| | - Shrawan K Mishra
- From the Hormel Institute, University of Minnesota, Austin, Minnesota 55912
| | - Dhirendra K Simanshu
- the Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065
| | - Ivan A Boldyrev
- the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Linda M Benson
- the Medical Genomic Facility-Proteomics Core, Mayo Foundation, Rochester, Minnesota 55905, and
| | - H Robert Bergen
- the Medical Genomic Facility-Proteomics Core, Mayo Foundation, Rochester, Minnesota 55905, and
| | - Lucy Malinina
- From the Hormel Institute, University of Minnesota, Austin, Minnesota 55912
| | - John Mundy
- the Department of Biology, BioCenter, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Julian G Molotkovsky
- the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Dinshaw J Patel
- the Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065
| | - Rhoderick E Brown
- From the Hormel Institute, University of Minnesota, Austin, Minnesota 55912,
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13
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Budani M, Mylvaganam M, Binnington B, Lingwood C. Synthesis of a novel photoactivatable glucosylceramide cross-linker. J Lipid Res 2016; 57:1728-36. [PMID: 27412675 DOI: 10.1194/jlr.d069609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Indexed: 01/08/2023] Open
Abstract
The biosynthesis of glucosylceramide (GlcCer) is a key rate-limiting step in complex glycosphingolipid (GSL) biosynthesis. To further define interacting partners of GlcCer, we have made a cleavable, biotinylated, photoreactive GlcCer analog in which the reactive nitrene is closely apposed to the GlcCer head group, by substituting the native fatty acid with d, l-2-aminohexadecanoic acid. Two amino-GlcCer diastereomer cross-linkers (XLA and XLB) were generated. XLB proved an effective lactosylceramide (LacCer) synthase substrate while XLA was inhibitory. Both probes specifically bound and cross-linked the GlcCer binding protein, glycolipid transfer protein (GLTP), but not other GSL binding proteins (Shiga toxin and cholera toxin). GlcCer inhibited GLTP cross-linking. Both GlcCer cross-linkers competed with microsomal nitrobenzoxadiazole (NBD)-GlcCer anabolism to NBD-LacCer. GLTP showed marked, ATP-dependent enhancement of cell-free intact microsomal LacCer synthesis from endogenous or exogenous liposomal GlcCer, supporting a role in the transport/membrane translocation of cytosolic and extra-Golgi GlcCer. GLTP was specifically labeled by either XLA or XLB GlcCer cross-linker during this process, together with a (the same) small subset of microsomal proteins. These cross-linkers will serve to probe physiologically relevant GlcCer-interacting cellular proteins.
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Affiliation(s)
- Monique Budani
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Murugesapillai Mylvaganam
- Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Beth Binnington
- Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Clifford Lingwood
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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14
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Mattjus P. Specificity of the mammalian glycolipid transfer proteins. Chem Phys Lipids 2016; 194:72-8. [DOI: 10.1016/j.chemphyslip.2015.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2015] [Revised: 07/08/2015] [Accepted: 07/27/2015] [Indexed: 12/31/2022]
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15
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Malinina L, Simanshu DK, Zhai X, Samygina VR, Kamlekar R, Kenoth R, Ochoa-Lizarralde B, Malakhova ML, Molotkovsky JG, Patel DJ, Brown RE. Sphingolipid transfer proteins defined by the GLTP-fold. Q Rev Biophys 2015; 48:281-322. [PMID: 25797198 PMCID: PMC4691851 DOI: 10.1017/s003358351400016x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Glycolipid transfer proteins (GLTPs) originally were identified as small (~24 kDa), soluble, amphitropic proteins that specifically accelerate the intermembrane transfer of glycolipids. GLTPs and related homologs now are known to adopt a unique, helically dominated, two-layer 'sandwich' architecture defined as the GLTP-fold that provides the structural underpinning for the eukaryotic GLTP superfamily. Recent advances now provide exquisite insights into structural features responsible for lipid headgroup selectivity as well as the adaptability of the hydrophobic compartment for accommodating hydrocarbon chains of differing length and unsaturation. A new understanding of the structural versatility and evolutionary premium placed on the GLTP motif has emerged. Human GLTP-motifs have evolved to function not only as glucosylceramide binding/transferring domains for phosphoinositol 4-phosphate adaptor protein-2 during glycosphingolipid biosynthesis but also as selective binding/transfer proteins for ceramide-1-phosphate. The latter, known as ceramide-1-phosphate transfer protein, recently has been shown to form GLTP-fold while critically regulating Group-IV cytoplasmic phospholipase A2 activity and pro-inflammatory eicosanoid production.
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Affiliation(s)
- Lucy Malinina
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
- Structural Biology Unit, CICbioGUNE, Technology Park of Bizkaia, 48160 Derio-Bilbao, Spain
| | - Dhirendra K. Simanshu
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Xiuhong Zhai
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Valeria R. Samygina
- Structural Biology Unit, CICbioGUNE, Technology Park of Bizkaia, 48160 Derio-Bilbao, Spain
| | | | - Roopa Kenoth
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Borja Ochoa-Lizarralde
- Structural Biology Unit, CICbioGUNE, Technology Park of Bizkaia, 48160 Derio-Bilbao, Spain
| | | | - Julian G. Molotkovsky
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Dinshaw J. Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
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16
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Tuuf J, Mattjus P. Membranes and mammalian glycolipid transferring proteins. Chem Phys Lipids 2013; 178:27-37. [PMID: 24220498 DOI: 10.1016/j.chemphyslip.2013.10.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 10/29/2013] [Accepted: 10/30/2013] [Indexed: 01/04/2023]
Abstract
Glycolipids are synthesized in and on various organelles throughout the cell. Their trafficking inside the cell is complex and involves both vesicular and protein-mediated machineries. Most important for the bulk lipid transport is the vesicular system, however, lipids moved by transfer proteins are also becoming more characterized. Here we review the latest advances in the glycolipid transfer protein (GLTP) and the phosphoinositol 4-phosphate adaptor protein-2 (FAPP2) field, from a membrane point of view.
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Affiliation(s)
- Jessica Tuuf
- Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland
| | - Peter Mattjus
- Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland.
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17
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Lauria I, van Üüm J, Mjumjunov-Crncevic E, Walrafen D, Spitta L, Thiele C, Lang T. GLTP mediated non-vesicular GM1 transport between native membranes. PLoS One 2013; 8:e59871. [PMID: 23555818 PMCID: PMC3610762 DOI: 10.1371/journal.pone.0059871] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 02/19/2013] [Indexed: 11/24/2022] Open
Abstract
Lipid transfer proteins (LTPs) are emerging as key players in lipid homeostasis by mediating non-vesicular transport steps between two membrane surfaces. Little is known about the driving force that governs the direction of transport in cells. Using the soluble LTP glycolipid transfer protein (GLTP), we examined GM1 (monosialotetrahexosyl-ganglioside) transfer to native membrane surfaces. With artificial GM1 donor liposomes, GLTP can be used to increase glycolipid levels over natural levels in either side of the membrane leaflet, i.e., external or cytosolic. In a system with native donor- and acceptor-membranes, we find that GLTP balances highly variable GM1 concentrations in a population of membranes from one cell type, and in addition, transfers lipids between membranes from different cell types. Glycolipid transport is highly efficient, independent of cofactors, solely driven by the chemical potential of GM1 and not discriminating between the extra- and intracellular membrane leaflet. We conclude that GLTP mediated non-vesicular lipid trafficking between native membranes is driven by simple thermodynamic principles and that for intracellular transport less than 1 µM GLTP would be required in the cytosol. Furthermore, the data demonstrates the suitability of GLTP as a tool for artificially increasing glycolipid levels in cellular membranes.
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Affiliation(s)
- Ines Lauria
- Department of Membrane Biochemistry, LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany
| | - Jan van Üüm
- Department of Membrane Biochemistry, LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany
| | - Esmina Mjumjunov-Crncevic
- Department of Membrane Biochemistry, LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany
| | - David Walrafen
- Department of Membrane Biochemistry, LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany
| | - Luis Spitta
- Department of Membrane Biochemistry, LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany
| | - Christoph Thiele
- Department of Biochemistry and Cell Biology of Lipids, LIMES Institute, University of Bonn, Bonn, Germany
| | - Thorsten Lang
- Department of Membrane Biochemistry, LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany
- * E-mail:
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18
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Zhai X, Momsen WE, Malakhov DA, Boldyrev IA, Momsen MM, Molotkovsky JG, Brockman HL, Brown RE. GLTP-fold interaction with planar phosphatidylcholine surfaces is synergistically stimulated by phosphatidic acid and phosphatidylethanolamine. J Lipid Res 2013; 54:1103-13. [PMID: 23369752 DOI: 10.1194/jlr.m034744] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Among amphitropic proteins, human glycolipid transfer protein (GLTP) forms a structurally-unique fold that translocates on/off membranes to specifically transfer glycolipids. Phosphatidylcholine (PC) bilayers with curvature-induced packing stress stimulate much faster glycolipid intervesicular transfer than nonstressed PC bilayers raising questions about planar cytosol-facing biomembranes being viable sites for GLTP interaction. Herein, GLTP-mediated desorption kinetics of fluorescent glycolipid (tetramethyl-boron dipyrromethene (BODIPY)-label) from lipid monolayers are assessed using a novel microfluidics-based surface balance that monitors lipid lateral packing while simultaneously acquiring surface fluorescence data. At biomembrane-like packing (30-35 mN/m), GLTP uptake of BODIPY-glycolipid from POPC monolayers was nearly nonexistent but could be induced by reducing surface pressure to mirror packing in curvature-stressed bilayers. In contrast, 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE) matrices supported robust BODIPY-glycolipid uptake by GLTP at both high and low surface pressures. Unexpectedly, negatively-charged cytosol-facing lipids, i.e., phosphatidic acid and phosphatidylserine, also supported BODIPY-glycolipid uptake by GLTP at high surface pressure. Remarkably, including both 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphate (5 mol%) and POPE (15 mol%) in POPC synergistically activated GLTP at high surface pressure. Our study shows that matrix lipid headgroup composition, rather than molecular packing per se, is a key regulator of GLTP-fold function while demonstrating the novel capabilities of the microfluidics-based film balance for investigating protein-membrane interfacial interactions.
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Affiliation(s)
- Xiuhong Zhai
- The Hormel Institute, University of Minnesota, Austin, MN, USA
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19
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The glycolipid transfer protein (GLTP) domain of phosphoinositol 4-phosphate adaptor protein-2 (FAPP2): structure drives preference for simple neutral glycosphingolipids. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1831:417-27. [PMID: 23159414 DOI: 10.1016/j.bbalip.2012.10.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 10/23/2012] [Accepted: 10/29/2012] [Indexed: 11/23/2022]
Abstract
Phosphoinositol 4-phosphate adaptor protein-2 (FAPP2) plays a key role in glycosphingolipid (GSL) production using its C-terminal domain to transport newly synthesized glucosylceramide away from the cytosol-facing glucosylceramide synthase in the cis-Golgi for further anabolic processing. Structural homology modeling against human glycolipid transfer protein (GLTP) predicts a GLTP-fold for FAPP2 C-terminal domain, but no experimental support exists to warrant inclusion in the GLTP superfamily. Here, the biophysical properties and glycolipid transfer specificity of FAPP2-C-terminal domain have been characterized and compared with other established GLTP-folds. Experimental evidence for a GLTP-fold includes: i) far-UV circular dichroism (CD) showing secondary structure with high alpha-helix content and a low thermally-induced unfolding transition (~41°C); ii) near-UV-CD indicating only subtle tertiary conformational change before/after interaction with membranes containing/lacking glycolipid; iii) Red-shifted tryptophan (Trp) emission wavelength maximum (λ(max)~352nm) for apo-FAPP2-C-terminal domain consistent with surface exposed intrinsic Trp residues; iv) 'signature' GLTP-fold Trp fluorescence response, i.e., intensity decrease (~30%) accompanied by strongly blue-shifted λ(max) (~14nm) upon interaction with membranes containing glycolipid, supporting direct involvement of Trp in glycolipid binding and enabling estimation of partitioning affinities. A structurally-based preference for other simple uncharged GSLs, in addition to glucosylceramide, makes human FAPP2-GLTP more similar to fungal HET-C2 than to plant AtGLTP1 (glucosylceramide-specific) or to broadly GSL-selective human GLTP. These findings along with the distinct mRNA exon/intron organizations originating from single-copy genes on separate human chromosomes suggest adaptive evolutionary divergence by these two GLTP-folds.
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20
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Halin J, Mattjus P. Effects of bile salts on glucosylceramide containing membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2886-93. [DOI: 10.1016/j.bbamem.2011.08.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 08/15/2011] [Accepted: 08/25/2011] [Indexed: 01/17/2023]
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21
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Chiou YL, Lin SR, Chang LS. Sphingomyelin modulates interfacial binding of Taiwan cobra phospholipase A2. Chem Phys Lipids 2011; 164:378-85. [DOI: 10.1016/j.chemphyslip.2011.04.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 04/09/2011] [Accepted: 04/28/2011] [Indexed: 12/28/2022]
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22
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Gene expression profiling of oral squamous cell carcinoma by differential display rt-PCR and identification of tumor biomarkers. Indian J Surg Oncol 2011; 1:284-93. [PMID: 22693380 DOI: 10.1007/s13193-011-0054-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2010] [Accepted: 01/31/2011] [Indexed: 01/05/2023] Open
Abstract
Oral squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide. Despite progress in therapeutic and surgical treatments, its survival period at 5 years is the lowest among major cancers, and remains unchanged in the last two decades. The growing epidemiological relevance of oral cancer emphasizes the need to better understand the molecular mechanisms underlying this disease and identify predictive tumor markers and therapeutic targets. To this end, we have used the DDRT-PCR analysis to profile the oral tumor transcriptome and identify differentially regulated genes that may be used as potential biomarkers and therapeutic targets. Our DDRT-PCR analysis identified 51 differentially expressed fragments, of which 25 were revalidated by reverse Northern analysis. Northern blot analysis further corroborated these findings for a few genes. In order to ascertain the utility of some of the identified genes as molecular markers and therapeutic targets, semi-quantitative RT-PCR analysis was carried out in a panel of matched oral normal and tumor samples, that confirmed GLTP, PCNA, RBM28, C17orf75 and DIAPH1 as significantly upregulated, whereas TNKS2, PAM and TUBB2C showed significant downregulation in tumor samples. Taken together, our DDRT-PCR analysis has revealed several genes, belonging to diverse cellular pathways, that have been associated with OSCC for the first time. Thus, these genes could be investigated as biomarkers and therapeutic targets for OSCC.
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23
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Monitoring glycolipid transfer protein activity and membrane interaction with the surface plasmon resonance technique. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:47-54. [DOI: 10.1016/j.bbamem.2010.08.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 08/17/2010] [Accepted: 08/24/2010] [Indexed: 01/23/2023]
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24
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Carton I, Lucy Malinina, Richter RP. Dynamic modulation of the glycosphingolipid content in supported lipid bilayers by glycolipid transfer protein. Biophys J 2010; 99:2947-56. [PMID: 21044592 PMCID: PMC2966009 DOI: 10.1016/j.bpj.2010.09.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 09/05/2010] [Accepted: 09/08/2010] [Indexed: 11/17/2022] Open
Abstract
Supported lipid bilayers (SLBs) are popular models of cell membranes. Owing to the importance of glycosphingolipids (GSLs) in modulating structure and function of membranes and membrane proteins, methods to tune the GSL content in SLBs would be desirable. Glycolipid transfer protein (GLTP) can selectively transfer GSLs between membrane compartments. Using the ganglioside GM1 as a model GSL, and two mass-sensitive and label-free characterization techniques-quartz crystal microbalance with dissipation monitoring and ellipsometry-we demonstrate that GLTP is an efficient and robust biochemical tool to dynamically modulate the GSL content of SLBs up to 10 mol % GM1, and to quantitatively control the GSL content in the bulk-facing SLB leaflet. By exploiting what we believe to be a novel tool, we provide evidence that GM1 distributes highly asymmetrically in silica-supported lipid bilayers, with ∼85% of the ganglioside being present in the bulk-facing membrane leaflet. We report also that the pentameric B-subunit of cholera toxin binds with close-to-maximal stoichiometry to GM1 in SLBs over a large range of GM1 concentrations. Furthermore, we quantify the liganding affinity of GLTP for GM1 in an SLB context to be 1.5 μM.
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Affiliation(s)
- Ixaskun Carton
- Biosurfaces Unit, Cooperative Research Center in Biomaterials (CIC biomaGUNE), San Sebastian, Spain
| | - Lucy Malinina
- Structural Biology Unit, Cooperative Research Center in Biosciences (CIC bioGUNE), Derio, Spain
| | - Ralf P. Richter
- Biosurfaces Unit, Cooperative Research Center in Biomaterials (CIC biomaGUNE), San Sebastian, Spain
- Max-Planck-Institute for Metals Research, Stuttgart, Germany
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25
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Zou X, Gao Y, Ruvolo VR, Gardner TL, Ruvolo PP, Brown RE. Human glycolipid transfer protein gene (GLTP) expression is regulated by Sp1 and Sp3: involvement of the bioactive sphingolipid ceramide. J Biol Chem 2010; 286:1301-11. [PMID: 20974858 DOI: 10.1074/jbc.m110.127837] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycolipid transfer protein (GLTP) accelerates glycolipid intermembrane transfer via a unique lipid transfer/binding fold (GLTP fold) that defines the GLTP superfamily and is the prototype for functional GLTP-like domains in larger proteins, i.e. FAPP2. Human GLTP is encoded by the single-copy GLTP gene on chromosome 12 (12q24.11 locus), but regulation of GLTP gene expression remains completely unexplored. Herein, the ability of glycosphingolipids (and their sphingolipid metabolites) to regulate the transcriptional expression of GLTP via its promoter has been evaluated. Using luciferase and GFP reporters in concert with deletion mutants, the constitutive and basal (225 bp; ∼78% G+C) human GLTP promoters have been defined along with adjacent regulatory elements. Despite high G+C content, translational regulation was not evident by the mammalian target of rapamycin pathway. Four GC-boxes were shown to be functional Sp1/Sp3 transcription factor binding sites. Mutation of one GC-box was particularly detrimental to GLTP transcriptional activity. Sp1/Sp3 RNA silencing and mithramycin A treatment significantly inhibited GLTP promoter activity. Among tested sphingolipid analogs of glucosylceramide, sulfatide, ganglioside GM1, ceramide 1-phosphate, sphingosine 1-phosphate, dihydroceramide, sphingosine, only ceramide, a nonglycosylated precursor metabolite unable to bind to GLTP protein, induced GLTP promoter activity and raised transcript levels in vivo. Ceramide treatment partially blocked promoter activity decreases induced by Sp1/Sp3 knockdown. Ceramide treatment also altered the in vivo binding affinity of Sp1 and Sp3 for the GLTP promoter and decreased Sp3 acetylation. This study represents the first characterization of any Gltp gene promoter and links human GLTP expression to sphingolipid homeostasis through ceramide.
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Affiliation(s)
- Xianqiong Zou
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA
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26
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Kamlekar RK, Gao Y, Kenoth R, Molotkovsky JG, Prendergast FG, Malinina L, Patel DJ, Wessels WS, Venyaminov SY, Brown RE. Human GLTP: Three distinct functions for the three tryptophans in a novel peripheral amphitropic fold. Biophys J 2010; 99:2626-35. [PMID: 20959104 PMCID: PMC2955354 DOI: 10.1016/j.bpj.2010.08.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 07/27/2010] [Accepted: 08/10/2010] [Indexed: 01/17/2023] Open
Abstract
Human glycolipid transfer protein (GLTP) serves as the GLTP-fold prototype, a novel, to our knowledge, peripheral amphitropic fold and structurally unique lipid binding motif that defines the GLTP superfamily. Despite conservation of all three intrinsic Trps in vertebrate GLTPs, the Trp functional role(s) remains unclear. Herein, the issue is addressed using circular dichroism and fluorescence spectroscopy along with an atypical Trp point mutation strategy. Far-ultraviolet and near-ultraviolet circular dichroism spectroscopic analyses showed that W96F-W142Y-GLTP and W96Y-GLTP retain their native conformation and stability, whereas W85Y-W96F-GLTP is slightly altered, in agreement with relative glycolipid transfer activities of >90%, ∼85%, and ∼45%, respectively. In silico three-dimensional modeling and acrylamide quenching of Trp fluorescence supported a nativelike folding conformation. With the Trp⁹⁶-less mutants, changes in emission intensity, wavelength maximum, lifetime, and time-resolved anisotropy decay induced by phosphoglyceride membranes lacking or containing glycolipid and by excitation at different wavelengths along the absorption-spectrum red edge indicated differing functions for W142 and W85. The data suggest that W142 acts as a shallow-penetration anchor during docking with membrane interfaces, whereas the buried W85 indole helps maintain proper folding and possibly regulates membrane-induced transitioning to a glycolipid-acquiring conformation. The findings illustrate remarkable versatility for Trp, providing three distinct intramolecular functions in the novel amphitropic GLTP fold.
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Affiliation(s)
| | - Yongguang Gao
- The Hormel Institute, University of Minnesota, Austin, Minnesota
| | - Roopa Kenoth
- The Hormel Institute, University of Minnesota, Austin, Minnesota
| | - Julian G. Molotkovsky
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | | | - Lucy Malinina
- Structural Biology, Centro de Investigación Cooperativa BioGUNE, Derio, Spain
| | - Dinshaw J. Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York
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27
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Kenoth R, Simanshu DK, Kamlekar RK, Pike HM, Molotkovsky JG, Benson LM, Bergen HR, Prendergast FG, Malinina L, Venyaminov SY, Patel DJ, Brown RE. Structural determination and tryptophan fluorescence of heterokaryon incompatibility C2 protein (HET-C2), a fungal glycolipid transfer protein (GLTP), provide novel insights into glycolipid specificity and membrane interaction by the GLTP fold. J Biol Chem 2010; 285:13066-78. [PMID: 20164530 DOI: 10.1074/jbc.m109.093203] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
HET-C2 is a fungal protein that transfers glycosphingolipids between membranes and has limited sequence homology with human glycolipid transfer protein (GLTP). The human GLTP fold is unique among lipid binding/transfer proteins, defining the GLTP superfamily. Herein, GLTP fold formation by HET-C2, its glycolipid transfer specificity, and the functional role(s) of its two Trp residues have been investigated. X-ray diffraction (1.9 A) revealed a GLTP fold with all key sugar headgroup recognition residues (Asp(66), Asn(70), Lys(73), Trp(109), and His(147)) conserved and properly oriented for glycolipid binding. Far-UV CD showed secondary structure dominated by alpha-helices and a cooperative thermal unfolding transition of 49 degrees C, features consistent with a GLTP fold. Environmentally induced optical activity of Trp/Tyr/Phe (2:4:12) detected by near-UV CD was unaffected by membranes containing glycolipid but was slightly altered by membranes lacking glycolipid. Trp fluorescence was maximal at approximately 355 nm and accessible to aqueous quenchers, indicating free exposure to the aqueous milieu and consistent with surface localization of the two Trps. Interaction with membranes lacking glycolipid triggered significant decreases in Trp emission intensity but lesser than decreases induced by membranes containing glycolipid. Binding of glycolipid (confirmed by electrospray injection mass spectrometry) resulted in a blue-shifted emission wavelength maximum (approximately 6 nm) permitting determination of binding affinities. The unique positioning of Trp(208) at the HET-C2 C terminus revealed membrane-induced conformational changes that precede glycolipid uptake, whereas key differences in residues of the sugar headgroup recognition center accounted for altered glycolipid specificity and suggested evolutionary adaptation for the simpler glycosphingolipid compositions of filamentous fungi.
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Affiliation(s)
- Roopa Kenoth
- Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA
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Ligand extraction properties of the GM2 activator protein and its interactions with lipid vesicles. Biophys J 2009; 97:257-66. [PMID: 19580763 DOI: 10.1016/j.bpj.2009.03.065] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 03/25/2009] [Accepted: 03/31/2009] [Indexed: 11/23/2022] Open
Abstract
The GM2 activator protein (GM2AP) is an accessory protein required for the enzymatic conversion of GM2 to GM3 by hydrolases in the lysosomal compartments of cells. Here, GM2AP interactions with lipid vesicles are investigated by sucrose-loaded vesicle sedimentation and gel filtration assays, and the effects of pH and lipid composition on membrane binding and lipid extraction are characterized. The sedimentation experiments allow for facile quantification of the percentage of protein in solution and on the bilayer surface, with detailed analysis of the protein:lipid complex that remains in solution. Optimum binding and ligand extraction is found for pH 4.8 where <15% of the protein remains surface associated regardless of the lipid composition. In addition to extracting GM2, we find that GM2AP readily extracts dansyl-headgroup-labeled lipids as well as other phospholipids from vesicles. The ability of GM2AP to extract dansyl-DHPE from vesicles is altered by pH and the specific ligand GM2. Although the unique endosomal lipid, bis(monoacylglycero)phosphate, is not required for ligand extraction, it does enhance the extraction efficiency of GM2 when cholesterol is present in the vesicles.
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Zhai X, Malakhova ML, Pike HM, Benson LM, Bergen HR, Sugár IP, Malinina L, Patel DJ, Brown RE. Glycolipid acquisition by human glycolipid transfer protein dramatically alters intrinsic tryptophan fluorescence: insights into glycolipid binding affinity. J Biol Chem 2009; 284:13620-13628. [PMID: 19270338 PMCID: PMC2679463 DOI: 10.1074/jbc.m809089200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 02/23/2009] [Indexed: 01/28/2023] Open
Abstract
Glycolipid transfer proteins (GLTPs) are small, soluble proteins that selectively accelerate the intermembrane transfer of glycolipids. The GLTP fold is conformationally unique among lipid binding/transfer proteins and serves as the prototype and founding member of the new GLTP superfamily. In the present study, changes in human GLTP tryptophan fluorescence, induced by membrane vesicles containing glycolipid, are shown to reflect glycolipid binding when vesicle concentrations are low. Characterization of the glycolipid-induced "signature response," i.e. approximately 40% decrease in Trp intensity and approximately 12-nm blue shift in emission wavelength maximum, involved various modes of glycolipid presentation, i.e. microinjection/dilution of lipid-ethanol solutions or phosphatidylcholine vesicles, prepared by sonication or extrusion and containing embedded glycolipids. High resolution x-ray structures of apo- and holo-GLTP indicate that major conformational alterations are not responsible for the glycolipid-induced GLTP signature response. Instead, glycolipid binding alters the local environment of Trp-96, which accounts for approximately 70% of total emission intensity of three Trp residues in GLTP and provides a stacking platform that aids formation of a hydrogen bond network with the ceramide-linked sugar of the glycolipid headgroup. The changes in Trp signal were used to quantitatively assess human GLTP binding affinity for various lipids including glycolipids containing different sugar headgroups and homogenous acyl chains. The presence of the glycolipid acyl chain and at least one sugar were essential for achieving a low-to-submicromolar dissociation constant that was only slightly altered by increased sugar headgroup complexity.
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Affiliation(s)
- Xiuhong Zhai
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912
| | | | - Helen M Pike
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912
| | - Linda M Benson
- Mayo Proteomics Research Center, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - H Robert Bergen
- Mayo Proteomics Research Center, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - István P Sugár
- Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029
| | - Lucy Malinina
- Structural Biology, CIC bioGUNE, Parque Tecnológico de Vizcaya, Ed. 800, Derio 48160, Spain.
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065.
| | - Rhoderick E Brown
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912.
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Mattjus P. Glycolipid transfer proteins and membrane interaction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1788:267-72. [PMID: 19007748 DOI: 10.1016/j.bbamem.2008.10.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 10/07/2008] [Accepted: 10/07/2008] [Indexed: 12/17/2022]
Abstract
The glycolipid transfer protein is found from animals and fungi to plants and red micro-alga. Some eukaryotes that do not encode the glucosylceramide synthase like the yeast Schizosaccharomyces pombe and Saccharomyces cerevisiae do neither produce glycolipid transfer like proteins. On the other hand yeast like Eremothecium gossypii that do synthesize glucosylceramide also express glycolipid transfer protein. Based on this novel genetic relationship it is not far fetched to assume that there must be a strong correlation between the synthesis of the glycolipid precursor and the glycolipid transfer protein. Because the glycolipid transfer protein is localized in the cytosol it is unlikely that it would participate in events associated with lipid rafts or caveolar structures, since they are found on the outer leaflet of the plasma membrane. Rather, GLTP is likely to be involved in events at the cytosolic side of the plasma membrane or the endoplasmic reticulum, maybe function as a reporter or sensor of glycolipid levels. A similar function has been proposed for other proteins with affinity for lipids like the oxysterol binding proteins and phosphatidylinositol transfer proteins that are thought to be able act as lipid sensors. Recent discoveries in the glycolipid transfer protein field are discussed.
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Affiliation(s)
- Peter Mattjus
- Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
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31
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Rusyn E, Mousallem T, Persaud-Sawin DA, Miller S, Boustany RMN. CLN3p impacts galactosylceramide transport, raft morphology, and lipid content. Pediatr Res 2008; 63:625-31. [PMID: 18317235 DOI: 10.1203/pdr.0b013e31816fdc17] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Juvenile neuronal ceroid lipofuscinosis (JNCL) belongs to the neuronal ceroid lipofuscinoses characterized by blindness/seizures/motor/cognitive decline and early death. JNCL is caused by CLN3 gene mutations that negatively modulate cell growth/apoptosis. CLN3 protein (CLN3p) localizes to Golgi/Rab4-/Rab11-positive endosomes and lipid rafts, and harbors a galactosylceramide (GalCer) lipid raft-binding domain. Goals are proving CLN3p participates in GalCer transport from Golgi to rafts, and GalCer deficits negatively affect cell growth/apoptosis. GalCer/mutant CLN3p are retained in Golgi, with CLN3p rescuing GalCer deficits in rafts. Diminishing GalCer in normal cells by GalCer synthase siRNA negatively affects cell growth/apoptosis. GalCer restores JNCL cell growth. WT CLN3p binds GalCer, but not mutant CLN3p. Sphingolipid content of rafts/Golgi is perturbed with diminished GalCer in rafts and accumulation in Golgi. CLN3-deficient raft vesicular structures are small by transmission electron microscopy, reflecting altered sphingolipid composition of rafts. CLN1/CLN2/CLN6 proteins bind to lysophosphatidic acid/sulfatide, CLN6/CLN8 proteins to GalCer, and CLN8 protein to ceramide. Sphingolipid composition/morphology of CLN1-/CLN2-/CLN6-/CLN8- and CLN9-deficient rafts are altered suggesting changes in raft structure/lipid stoichiometry could be common themes underlying these diseases.
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Affiliation(s)
- Elena Rusyn
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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32
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Morley S, Cecchini M, Zhang W, Virgulti A, Noy N, Atkinson J, Manor D. Mechanisms of ligand transfer by the hepatic tocopherol transfer protein. J Biol Chem 2008; 283:17797-804. [PMID: 18458085 DOI: 10.1074/jbc.m800121200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
alpha-Tocopherol is a member of the vitamin E family that functions as the principal fat-soluble antioxidant in vertebrates. Body-wide distribution of tocopherol is regulated by the hepatic alpha-tocopherol transfer protein (alphaTTP), which stimulates secretion of the vitamin from hepatocytes to circulating lipoproteins. This biological activity of alphaTTP is thought to stem from its ability to facilitate the transfer of vitamin E between membranes, but the mechanism by which the protein exerts this activity remains poorly understood. Using a fluorescence energy transfer methodology, we found that the rate of tocopherol transfer from lipid vesicles to alphaTTP increases with increasing alphaTTP concentration. This concentration dependence indicates that ligand transfer by alphaTTP involves direct protein-membrane interaction. In support of this notion, equilibrium analyses employing filtration, dual polarization interferometry, and tryptophan fluorescence demonstrated the presence of a stable alphaTTP-bilayer complex. The physical association of alphaTTP with membranes is markedly sensitive to the presence of vitamin E in the bilayer. Some naturally occurring mutations in alphaTTP that cause the hereditary disorder ataxia with vitamin E deficiency diminish the effect of tocopherol on the protein-membrane association, suggesting a possible mechanism for the accompanying pathology.
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Zou X, Chung T, Lin X, Malakhova ML, Pike HM, Brown RE. Human glycolipid transfer protein (GLTP) genes: organization, transcriptional status and evolution. BMC Genomics 2008; 9:72. [PMID: 18261224 PMCID: PMC2262070 DOI: 10.1186/1471-2164-9-72] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Accepted: 02/08/2008] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Glycolipid transfer protein is the prototypical and founding member of the new GLTP superfamily distinguished by a novel conformational fold and glycolipid binding motif. The present investigation provides the first insights into the organization, transcriptional status, phylogenetic/evolutionary relationships of GLTP genes. RESULTS In human cells, single-copy GLTP genes were found in chromosomes 11 and 12. The gene at locus 11p15.1 exhibited several features of a potentially active retrogene, including a highly homologous (approximately 94%), full-length coding sequence containing all key amino acid residues involved in glycolipid liganding. To establish the transcriptional activity of each human GLTP gene, in silico EST evaluations, RT-PCR amplifications of GLTP transcript(s), and methylation analyses of regulator CpG islands were performed using various human cells. Active transcription was found for 12q24.11 GLTP but 11p15.1 GLTP was transcriptionally silent. Heterologous expression and purification of the GLTP paralogs showed glycolipid intermembrane transfer activity only for 12q24.11 GLTP. Phylogenetic/evolutionary analyses indicated that the 5-exon/4-intron organizational pattern and encoded sequence of 12q24.11 GLTP were highly conserved in therian mammals and other vertebrates. Orthologs of the intronless GLTP gene were observed in primates but not in rodentiates, carnivorates, cetartiodactylates, or didelphimorphiates, consistent with recent evolutionary development. CONCLUSION The results identify and characterize the gene responsible for GLTP expression in humans and provide the first evidence for the existence of a GLTP pseudogene, while demonstrating the rigorous approach needed to unequivocally distinguish transcriptionally-active retrogenes from silent pseudogenes. The results also rectify errors in the Ensembl database regarding the organizational structure of the actively transcribed GLTP gene in Pan troglodytes and establish the intronless GLTP as a primate-specific, processed pseudogene marker. A solid foundation has been established for future identification of hereditary defects in human GLTP genes.
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Affiliation(s)
- Xianqiong Zou
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA.
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Glycolipid transfer protein: Clear structure and activity, but enigmatic function. ACTA ACUST UNITED AC 2008; 48:137-51. [DOI: 10.1016/j.advenzreg.2007.11.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Brown RE, Mattjus P. Glycolipid transfer proteins. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:746-60. [PMID: 17320476 PMCID: PMC1986823 DOI: 10.1016/j.bbalip.2007.01.011] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Revised: 01/08/2007] [Accepted: 01/13/2007] [Indexed: 10/23/2022]
Abstract
Glycolipid transfer proteins (GLTPs) are small (24 kDa), soluble, ubiquitous proteins characterized by their ability to accelerate the intermembrane transfer of glycolipids in vitro. GLTP specificity encompasses both sphingoid- and glycerol-based glycolipids, but with a strict requirement that the initial sugar residue be beta-linked to the hydrophobic lipid backbone. The 3D architecture of GLTP reveals liganded structures with unique lipid-binding modes. The biochemical properties of GLTP action at the membrane surface have been studied rather comprehensively, but the biological role of GLTP remains enigmatic. What is clear is that GLTP differs distinctly from other known glycolipid-binding proteins, such as nonspecific lipid transfer proteins, lysosomal sphingolipid activator proteins, lectins, lung surfactant proteins as well as other lipid-binding/transfer proteins. Based on the unique conformational architecture that targets GLTP to membranes and enables glycolipid binding, GLTP is now considered the prototypical and founding member of a new protein superfamily in eukaryotes.
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Affiliation(s)
- Rhoderick E Brown
- The Hormel Institute, University of Minnesota-Hormel Institute, 801 16th Ave NE, Austin, MN 55912, USA.
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36
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Malinina L, Malakhova ML, Kanack AT, Lu M, Abagyan R, Brown RE, Patel DJ. The liganding of glycolipid transfer protein is controlled by glycolipid acyl structure. PLoS Biol 2006; 4:e362. [PMID: 17105344 PMCID: PMC1618416 DOI: 10.1371/journal.pbio.0040362] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Accepted: 08/29/2006] [Indexed: 11/26/2022] Open
Abstract
Glycosphingolipids (GSLs) play major roles in cellular growth and development. Mammalian glycolipid transfer proteins (GLTPs) are potential regulators of cell processes mediated by GSLs and display a unique architecture among lipid binding/transfer proteins. The GLTP fold represents a novel membrane targeting/interaction domain among peripheral proteins. Here we report crystal structures of human GLTP bound to GSLs of diverse acyl chain length, unsaturation, and sugar composition. Structural comparisons show a highly conserved anchoring of galactosyl- and lactosyl-amide headgroups by the GLTP recognition center. By contrast, acyl chain chemical structure and occupancy of the hydrophobic tunnel dictate partitioning between sphingosine-in and newly-observed sphingosine-out ligand-binding modes. The structural insights, combined with computed interaction propensity distributions, suggest a concerted sequence of events mediated by GLTP conformational changes during GSL transfer to and/or from membranes, as well as during GSL presentation and/or transfer to other proteins. Structures of glycosphingolipids bound to glycolipid transfer proteins reveal a sphingosine-in or -out binding depending on their acyl chain structure; these conformational changes suggest a mechanism for glycosphingolipid transfer.
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Affiliation(s)
- Lucy Malinina
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Margarita L Malakhova
- Hormel Institute, University of Minnesota, Austin, Minnesota, United States of America
| | - Alex T Kanack
- Hormel Institute, University of Minnesota, Austin, Minnesota, United States of America
| | - Min Lu
- Department of Biochemistry, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Ruben Abagyan
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Rhoderick E Brown
- Hormel Institute, University of Minnesota, Austin, Minnesota, United States of America
- * To whom correspondence should be addressed. E-mail: (REB); (DJP)
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail: (REB); (DJP)
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37
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West G, Nylund M, Peter Slotte J, Mattjus P. Membrane interaction and activity of the glycolipid transfer protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1732-42. [PMID: 16908009 DOI: 10.1016/j.bbamem.2006.06.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2006] [Revised: 05/29/2006] [Accepted: 06/14/2006] [Indexed: 12/17/2022]
Abstract
In this study we have addressed the ability of the glycolipid transfer protein (GLTP) to transfer anthrylvinyl-galactosylceramide at different pH and sodium chloride concentrations, and the ability of three different mutants to transfer the fluorescently labeled galactosylceramide between donor and acceptor model membranes. We constructed single tryptophan mutants with site-directed mutagenesis where two of the three tryptophan (W) of wild-type human GLTP were substituted with phenylalanine (F) and named W85 GLTP (W96F and W142F), W96 GLTP (W85F and W142F) and W142 GLTP (W85F and W96F) accordingly. Wild-type GLTP and W96 GLTP were both able to transfer anthrylvinyl-galactosylceramide, but the two variants W85 GLTP and W142 GLTP did not show any glycolipid transfer activity, indicating that the tryptophan in position 96 is crucial for transfer activity. Tryptophan fluorescence emission showed a blue shift of the maximal emission wavelength upon interaction of glycolipid containing vesicle with wild-type GLTP and W96 GLTP, while no blue shift was recorded for the protein variants W85 GLTP and W142 GLTP. The quantum yield of tryptophan emission was highest for the W96 GLTP protein whereas W85 GLTP, W142 GLTP and wild-type GLTP showed a lower and almost similar quantum yield. The lifetime and anisotropy decay of the different tryptophan mutants also changed upon binding to vesicles containing galactosylceramide. Again wild-type GLTP and W96 GLTP showed similar behavior in the presence of vesicles containing glycolipids. Taken together, our data show that the W96 is involved not only in the activity of the protein but also in the interaction between the protein and glycolipid containing membranes.
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Affiliation(s)
- Gun West
- Department of Biochemistry and Pharmacy, Abo Akademi University, Tykistökatu 6A, FI-20520, Turku, Finland
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Nylund M, Kjellberg MA, Molotkovsky JG, Byun HS, Bittman R, Mattjus P. Molecular features of phospholipids that affect glycolipid transfer protein-mediated galactosylceramide transfer between vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:807-12. [PMID: 16777057 DOI: 10.1016/j.bbamem.2006.04.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Revised: 04/25/2006] [Accepted: 04/27/2006] [Indexed: 11/16/2022]
Abstract
The glycolipid transfer protein (GLTP)-mediated movement of galactosylceramide from model membrane donor vesicles to acceptor vesicles is sensitive to the membrane environment surrounding the glycolipid. GLTP can catalyze the transfer of a fluorescently labeled GSL, anthrylvinyl-galactosylceramide (AV-GalCer), from vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and dipalmitoylphosphatidylcholine matrices, but not from vesicles prepared from N-palmitoylsphingomyelin, regardless of the cholesterol content of the vesicles. In this study, we have examined the structural features of sphingomyelin (SM) that are responsible for its inhibition of the rate of GLTP-catalyzed transfer of AV-GalCer. The rate of glycolipid transfer was enhanced when the N-palmitoyl chain of SM was replaced with an N-oleoyl chain. Analogs of N-palmitoyl-SM in which the 4,5-double bond of the long-chain base is reduced or the 3-hydroxy group is removed did not inhibit GLTP-catalyzed transfer of AV-GalCer. When the donor vesicles were prepared with phosphatidylcholines or ether-linked phosphatidylcholine analogs, the transfer rates of AV-GalCer increased with increasing degree of unsaturation. The rate of AV-GalCer transfer was strongly dependent on the unsaturation degree of the acyl and/or alkyl chains. For ester-linked PCs, the transfer rate increased in the order DPPC<POPC<DOPC, which have 0, 1, and 2 cis double bonds, respectively.
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Affiliation(s)
- Matts Nylund
- Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland
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Malakhova ML, Malinina L, Pike HM, Kanack AT, Patel DJ, Brown RE. Point mutational analysis of the liganding site in human glycolipid transfer protein. Functionality of the complex. J Biol Chem 2005; 280:26312-20. [PMID: 15901739 PMCID: PMC1393170 DOI: 10.1074/jbc.m500481200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian glycolipid transfer proteins (GLTPs) facilitate the selective transfer of glycolipids between lipid vesicles in vitro. Recent structural determinations of the apo- and glycolipid-liganded forms of human GLTP have provided the first insights into the molecular architecture of the protein and its glycolipid binding site (Malinina, L., Malakhova, M. L., Brown, R. E., and Patel, D. J. (2004) Nature 430, 1048-1053). In the present study, we have evaluated the functional consequences of point mutation of the glycolipid liganding site of human GLTP within the context of a carrier-based mechanism of glycolipid intermembrane transfer. Different approaches were developed to rapidly and efficiently assess the uptake and release of glycolipid by GLTP. They included the use of glass-immobilized, glycolipid films to load GLTP with glycolipid and separation of GLTP/glycolipid complexes from vesicles containing glycolipid (galactosylceramide or lactosylceramide) or from monosialoganglioside dispersions by employing nickel-nitrilotriacetic acid-based affinity or gel filtration strategies. Point mutants of the sugar headgroup recognition center (Trp-96, Asp-48, Asn-52) and of the ceramide-accommodating hydrophobic tunnel (Phe-148, Phe-183, Leu-136) were analyzed for their ability to acquire and release glycolipid ligand. Two manifestations of point mutation within the liganding site were apparent: (i) impaired formation of the GLTP/glycolipid complex; (ii) impaired acquisition and release of bound glycolipid by GLTP. The results are consistent with a carrier-based mode of GLTP action to accomplish the intermembrane transfer of glycolipid. Also noteworthy was the inefficient release of glycolipid by wtGLTP into phosphatidylcholine acceptor vesicles, raising the possibility of a function other than intermembrane glycolipid transfer in vivo.
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