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Schafer CM, Martin-Almedina S, Kurylowicz K, Dufton N, Osuna-Almagro L, Wu ML, Johnson CF, Shah AV, Haskard DO, Buxton A, Willis E, Wheeler K, Turner S, Chlebicz M, Scott RP, Kovats S, Cleuren A, Birdsey GM, Randi AM, Griffin CT. Cytokine-Mediated Degradation of the Transcription Factor ERG Impacts the Pulmonary Vascular Response to Systemic Inflammatory Challenge. Arterioscler Thromb Vasc Biol 2023. [PMID: 37317853 PMCID: PMC10364964 DOI: 10.1161/atvbaha.123.318926] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
BACKGROUND During infectious diseases, proinflammatory cytokines transiently destabilize interactions between adjacent vascular endothelial cells (ECs) to facilitate the passage of immune molecules and cells into tissues. However, in the lung, the resulting vascular hyperpermeability can lead to organ dysfunction. Previous work identified the transcription factor ERG (erythroblast transformation-specific-related gene) as a master regulator of endothelial homeostasis. Here we investigate whether the sensitivity of pulmonary blood vessels to cytokine-induced destabilization is due to organotypic mechanisms affecting the ability of endothelial ERG to protect lung ECs from inflammatory injury. METHODS Cytokine-dependent ubiquitination and proteasomal degradation of ERG were analyzed in cultured human umbilical vein ECs. Systemic administration of TNFα (tumor necrosis factor alpha) or the bacterial cell wall component lipopolysaccharide was used to cause a widespread inflammatory challenge in mice; ERG protein levels were assessed by immunoprecipitation, immunoblot, and immunofluorescence. Murine Erg deletion was genetically induced in ECs (Ergfl/fl;Cdh5[PAC]-CreERT2), and multiple organs were analyzed by histology, immunostaining, and electron microscopy. RESULTS In vitro, TNFα promoted the ubiquitination and degradation of ERG in human umbilical vein ECs, which was blocked by the proteasomal inhibitor MG132. In vivo, systemic administration of TNFα or lipopolysaccharide resulted in a rapid and substantial degradation of ERG within lung ECs but not ECs of the retina, heart, liver, or kidney. Pulmonary ERG was also downregulated in a murine model of influenza infection. Ergfl/fl;Cdh5(PAC)-CreERT2 mice spontaneously recapitulated aspects of inflammatory challenges, including lung-predominant vascular hyperpermeability, immune cell recruitment, and fibrosis. These phenotypes were associated with a lung-specific decrease in the expression of Tek-a gene target of ERG previously implicated in maintaining pulmonary vascular stability during inflammation. CONCLUSIONS Collectively, our data highlight a unique role for ERG in pulmonary vascular function. We propose that cytokine-induced ERG degradation and subsequent transcriptional changes in lung ECs play critical roles in the destabilization of pulmonary blood vessels during infectious diseases.
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Affiliation(s)
- Christopher M Schafer
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
| | - Silvia Martin-Almedina
- National Heart and Lung Institute, Imperial College London, United Kingdom (S.M.-A., N.D., L.O.-A., A.V.S., D.O.H., G.M.B., A.M.R.)
- Now with Molecular and Clinical Sciences Institute, St. George's University of London, United Kingdom (S.M.-A.)
| | - Katarzyna Kurylowicz
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
- Ben May Department for Cancer Research, University of Chicago, IL (K.K.)
| | - Neil Dufton
- National Heart and Lung Institute, Imperial College London, United Kingdom (S.M.-A., N.D., L.O.-A., A.V.S., D.O.H., G.M.B., A.M.R.)
- Queen Mary University, London, United Kingdom (N.D.)
| | - Lourdes Osuna-Almagro
- National Heart and Lung Institute, Imperial College London, United Kingdom (S.M.-A., N.D., L.O.-A., A.V.S., D.O.H., G.M.B., A.M.R.)
- JJC Center for Developmental Neurobiology, King's College London, United Kingdom (L.O.-A.)
| | - Meng-Ling Wu
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
| | - Charmain F Johnson
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
| | - Aarti V Shah
- National Heart and Lung Institute, Imperial College London, United Kingdom (S.M.-A., N.D., L.O.-A., A.V.S., D.O.H., G.M.B., A.M.R.)
| | - Dorian O Haskard
- National Heart and Lung Institute, Imperial College London, United Kingdom (S.M.-A., N.D., L.O.-A., A.V.S., D.O.H., G.M.B., A.M.R.)
| | - Andrianna Buxton
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
| | - Erika Willis
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
| | - Kate Wheeler
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
| | - Sean Turner
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation. (S.T., M.C., S.K.)
| | - Magdalena Chlebicz
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation. (S.T., M.C., S.K.)
| | - Rizaldy P Scott
- Division of Nephrology and Hypertension, Feinberg Cardiovascular Research Institute, Northwestern University, Chicago, IL (R.P.S.)
- Department of Pathology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL (R.P.S.)
| | - Susan Kovats
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation. (S.T., M.C., S.K.)
- Department of Cell Biology, University of Oklahoma Health Sciences Center (S.K., C.T.G.)
| | - Audrey Cleuren
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
| | - Graeme M Birdsey
- National Heart and Lung Institute, Imperial College London, United Kingdom (S.M.-A., N.D., L.O.-A., A.V.S., D.O.H., G.M.B., A.M.R.)
| | - Anna M Randi
- National Heart and Lung Institute, Imperial College London, United Kingdom (S.M.-A., N.D., L.O.-A., A.V.S., D.O.H., G.M.B., A.M.R.)
| | - Courtney T Griffin
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation. (C.M.S., K.K., M.-L.W., C.F.J., A.B., E.W., K.W., A.C., C.T.G.)
- Department of Cell Biology, University of Oklahoma Health Sciences Center (S.K., C.T.G.)
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Schafer CM, Martin-Almedina S, Kurylowicz K, Dufton N, Osuna-Almagro L, Wu ML, Johnson CF, Shah AV, Haskard DO, Buxton A, Willis E, Wheeler K, Turner S, Chlebicz M, Scott RP, Kovats S, Cleuren A, Birdsey GM, Randi AM, Griffin CT. Cytokine-Mediated Degradation of the Transcription Factor ERG Impacts the Pulmonary Vascular Response to Systemic Inflammatory Challenge. bioRxiv 2023:2023.02.08.527788. [PMID: 36798267 PMCID: PMC9934599 DOI: 10.1101/2023.02.08.527788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Background During infectious diseases, pro-inflammatory cytokines transiently destabilize interactions between adjacent vascular endothelial cells (ECs) to facilitate the passage of immune molecules and cells into tissues. However, in the lung the resulting vascular hyperpermeability can lead to organ dysfunction. Previous work identified the transcription factor ERG as a master regulator of endothelial homeostasis. Here we investigate whether the sensitivity of pulmonary blood vessels to cytokine-induced destabilization is due to organotypic mechanisms affecting the ability of endothelial ERG to protect lung ECs from inflammatory injury. Methods Cytokine-dependent ubiquitination and proteasomal degradation of ERG was analyzed in cultured Human Umbilical Vein ECs (HUVECs). Systemic administration of TNFα or the bacterial cell wall component lipopolysaccharide (LPS) was used to cause a widespread inflammatory challenge in mice; ERG protein levels were assessed by immunoprecipitation, immunoblot, and immunofluorescence. Murine Erg deletion was genetically induced in ECs ( Erg fl/fl ;Cdh5(PAC)Cre ERT2 ), and multiple organs were analyzed by histology, immunostaining, and electron microscopy. Results In vitro, TNFα promoted the ubiquitination and degradation of ERG in HUVECs, which was blocked by the proteasomal inhibitor MG132. In vivo, systemic administration of TNFα or LPS resulted in a rapid and substantial degradation of ERG within lung ECs, but not ECs of the retina, heart, liver, or kidney. Pulmonary ERG was also downregulated in a murine model of influenza infection. Erg fl/fl ;Cdh5(PAC)-Cre ERT2 mice spontaneously recapitulated aspects of inflammatory challenges, including lung-predominant vascular hyperpermeability, immune cell recruitment, and fibrosis. These phenotypes were associated with a lung-specific decrease in the expression of Tek , a gene target of ERG previously implicated in maintaining pulmonary vascular stability during inflammation. Conclusions Collectively, our data highlight a unique role for ERG in pulmonary vascular function. We propose that cytokine-induced ERG degradation and subsequent transcriptional changes in lung ECs play critical roles in the destabilization of pulmonary blood vessels during infectious diseases.
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Boland AW, Gas-Pascual E, Nottingham BL, van der Wel H, Daniel NG, Sheikh MO, Schafer CM, West CM. Oxygen-dependent regulation of E3(SCF)ubiquitin ligases and a Skp1-associated JmjD6 homolog in development of the social amoeba Dictyostelium. J Biol Chem 2022; 298:102305. [PMID: 35933019 PMCID: PMC9485057 DOI: 10.1016/j.jbc.2022.102305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/10/2022] [Accepted: 07/11/2022] [Indexed: 11/01/2022] Open
Abstract
E3-SCF (Skp1/cullin-1/F-box protein) polyubiquitin ligases activate the proteasomal degradation of over a thousand proteins, but the evolutionary diversification of the F-box protein (FBP) family of substrate receptor subunits has challenged their elucidation in protists. Here, we expand the FBP candidate list in the social amoeba Dictyostelium and show that the Skp1 interactome is highly remodeled as cells transition from growth to multicellular development. Importantly, a subset of candidate FBPs was less represented when the posttranslational hydroxylation and glycosylation of Skp1 was abrogated by deletion of the O2-sensing Skp1 prolyl hydroxylase PhyA. A role for this Skp1 modification for SCF activity was indicated by partial rescue of development, which normally depends on high O2 and PhyA, of phyA-KO cells by proteasomal inhibitors. Further examination of two FBPs, FbxwD and the Jumonji C protein JcdI, suggested that Skp1 was substituted by other factors in phyA-KO cells. Although a double-KO of jcdI and its paralog jcdH did not affect development, overexpression of JcdI increased its sensitivity to O2. JcdI, a nonheme dioxygenase shown to have physiological O2 dependence, is conserved across protists with its F-box and other domains, and is related to the human oncogene JmjD6. Sensitization of JcdI-overexpression cells to O2 depended on its dioxygenase activity and other domains, but not its F-box, which may however be the mediator of its reduced levels in WT relative to Skp1 modification mutant cells. The findings suggest that activation of JcdI by O2 is tempered by homeostatic downregulation via PhyA and association with Skp1.
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Affiliation(s)
- Andrew W Boland
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA; Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Elisabet Gas-Pascual
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA; Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA
| | - Braxton L Nottingham
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Hanke van der Wel
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA; Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Nitin G Daniel
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - M Osman Sheikh
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Christopher M Schafer
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Christopher M West
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA; Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA; Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
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Sheikh MO, Halmo SM, Patel S, Middleton D, Takeuchi H, Schafer CM, West CM, Haltiwanger RS, Avci FY, Moremen KW, Wells L. Rapid screening of sugar-nucleotide donor specificities of putative glycosyltransferases. Glycobiology 2018; 27:206-212. [PMID: 28177478 DOI: 10.1093/glycob/cww114] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 10/20/2016] [Accepted: 11/17/2016] [Indexed: 01/09/2023] Open
Abstract
Determining the correct enzymatic activity of putative glycosyltransferases (GTs) can be challenging as these enzymes can utilize multiple donor and acceptor substrates. Upon initial determination of the donor-sugar nucleotide(s), a GT utilizes various acceptor molecules that can then be tested. Here, we describe a quick method to screen sugar-nucleotide donor specificities of GTs utilizing a sensitive, nonradioactive, commercially available bioluminescent uridine diphosphate detection kit. This in vitro method allowed us to validate the sugar-nucleotide donor-substrate specificities of recombinantly expressed human, bovine, bacterial and protozoan GTs. Our approach, which is less time consuming than many traditional assays that utilize radiolabeled sugars and chromatographic separations, should facilitate discovery of novel GTs that participate in diverse biological processes.
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Affiliation(s)
- M Osman Sheikh
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Stephanie M Halmo
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Sneha Patel
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Dustin Middleton
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA.,Center for Molecular Medicine, University of Georgia, Athens, GA, USA
| | - Hideyuki Takeuchi
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | | | - Christopher M West
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Robert S Haltiwanger
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Fikri Y Avci
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA.,Center for Molecular Medicine, University of Georgia, Athens, GA, USA
| | - Kelley W Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Lance Wells
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
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Sheikh MO, Thieker D, Chalmers G, Schafer CM, Ishihara M, Azadi P, Woods RJ, Glushka JN, Bendiak B, Prestegard JH, West CM. O 2 sensing-associated glycosylation exposes the F-box-combining site of the Dictyostelium Skp1 subunit in E3 ubiquitin ligases. J Biol Chem 2017; 292:18897-18915. [PMID: 28928219 PMCID: PMC5704474 DOI: 10.1074/jbc.m117.809160] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 09/12/2017] [Indexed: 11/06/2022] Open
Abstract
Skp1 is a conserved protein linking cullin-1 to F-box proteins in SCF (Skp1/Cullin-1/F-box protein) E3 ubiquitin ligases, which modify protein substrates with polyubiquitin chains that typically target them for 26S proteasome-mediated degradation. In Dictyostelium (a social amoeba), Toxoplasma gondii (the agent for human toxoplasmosis), and other protists, Skp1 is regulated by a unique pentasaccharide attached to hydroxylated Pro-143 within its C-terminal F-box-binding domain. Prolyl hydroxylation of Skp1 contributes to O2-dependent Dictyostelium development, but full glycosylation at that position is required for optimal O2 sensing. Previous studies have shown that the glycan promotes organization of the F-box-binding region in Skp1 and aids in Skp1's association with F-box proteins. Here, NMR and MS approaches were used to determine the glycan structure, and then a combination of NMR and molecular dynamics simulations were employed to characterize the impact of the glycan on the conformation and motions of the intrinsically flexible F-box-binding domain of Skp1. Molecular dynamics trajectories of glycosylated Skp1 whose calculated monosaccharide relaxation kinetics and rotational correlation times agreed with the NMR data indicated that the glycan interacts with the loop connecting two α-helices of the F-box-combining site. In these trajectories, the helices separated from one another to create a more accessible and dynamic F-box interface. These results offer an unprecedented view of how a glycan modification influences a disordered region of a full-length protein. The increased sampling of an open Skp1 conformation can explain how glycosylation enhances interactions with F-box proteins in cells.
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Affiliation(s)
- M Osman Sheikh
- From the Department of Biochemistry and Molecular Biology
- the Complex Carbohydrate Research Center, and
- the Department of Biochemistry and Molecular Biology, Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
| | | | - Gordon Chalmers
- the Complex Carbohydrate Research Center, and
- the Department of Computer Science, University of Georgia, Athens, Georgia 30602
| | - Christopher M Schafer
- the Department of Biochemistry and Molecular Biology, Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
| | | | | | - Robert J Woods
- From the Department of Biochemistry and Molecular Biology
- the Complex Carbohydrate Research Center, and
| | | | - Brad Bendiak
- the Department of Cell and Developmental Biology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045
| | - James H Prestegard
- From the Department of Biochemistry and Molecular Biology
- the Complex Carbohydrate Research Center, and
| | - Christopher M West
- From the Department of Biochemistry and Molecular Biology,
- the Department of Biochemistry and Molecular Biology, Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
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Chinoy ZS, Schafer CM, West CM, Boons GJ. Chemical Synthesis of a Glycopeptide Derived from Skp1 for Probing Protein Specific Glycosylation. Chemistry 2015; 21:11779-87. [PMID: 26179871 DOI: 10.1002/chem.201501598] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Indexed: 01/13/2023]
Abstract
Skp1 is a cytoplasmic and nuclear protein, best known as an adaptor of the SCF family of E3-ubiquitin ligases that label proteins for their degradation. Skp1 in Dictyostelium is posttranslationally modified on a specific hydroxyproline (Hyp) residue by a pentasaccharide, which consists of a Fucα1,2-Galβ-1,3-GlcNAcα core, decorated with two α-linked Gal residues. A glycopeptide derived form Skp1 was prepared to characterize the α-galactosyltransferase (AgtA) that mediates the addition of the α-Gal moieties, and to develop antibodies suitable for tracking the trisaccharide isoform of Skp1 in cells. A strategy was developed for the synthesis of the core trisaccharide-Hyp based on the use of 2-naphthylmethyl (Nap) ethers as permanent protecting groups to allow late stage installation of the Hyp moiety. Tuning of glycosyl donor and acceptor reactivities was critical for achieving high yields and anomeric selectivities of glycosylations. The trisaccharide-Hyp moiety was employed for the preparation of the glycopeptide using microwave-assisted solid phase peptide synthesis. Enzyme kinetic studies revealed that trisaccharide-Hyp and trisaccharide-peptide are poorly recognized by AgtA, indicating the importance of context provided by the native Skp1 protein for engagement with the active site. The trisaccharide-peptide was a potent immunogen capable of generating a rabbit antiserum that was highly selective toward the trisaccharide isoform of full-length Skp1.
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Affiliation(s)
- Zoeisha S Chinoy
- Complex Carbohydrate Research Center and Department of Chemistry, University of Georgia, 315 Riverbend Road, Athens, GA 30602 (USA)
| | - Christopher M Schafer
- Department of Biochemistry and Molecular Biology and Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 (USA).,Current address: Oklahoma Medical Research Foundation, 825 N.E. 13th Street, Oklahoma City, OK 73104 (USA)
| | - Christopher M West
- Department of Biochemistry and Molecular Biology and Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 (USA).,Current address: Dept. of Biochemistry and Molecular Biology, University of Georgia, 120 Green Street, Athens, GA 30602 (USA)
| | - Geert-Jan Boons
- Complex Carbohydrate Research Center and Department of Chemistry, University of Georgia, 315 Riverbend Road, Athens, GA 30602 (USA).
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Schafer CM, Sheikh MO, Zhang D, West CM. Novel regulation of Skp1 by the Dictyostelium AgtA α-galactosyltransferase involves the Skp1-binding activity of its WD40 repeat domain. J Biol Chem 2014; 289:9076-88. [PMID: 24550398 DOI: 10.1074/jbc.m113.528679] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The role of Skp1 as an adaptor protein that links Cullin-1 to F-box proteins in E3 Skp1/Cullin-1/F-box protein (SCF) ubiquitin ligases is well characterized. In the social amoeba Dictyostelium and probably many other unicellular eukaryotes, Skp1 is modified by a pentasaccharide attached to a hydroxyproline near its C terminus. This modification is important for oxygen-sensing during Dictyostelium development and is mediated by a HIF-α type prolyl 4-hydroxylase and five sequentially acting cytoplasmic glycosyltransferase activities. Gene disruption studies show that AgtA, the enzyme responsible for addition of the final two galactose residues, in α-linkages to the Skp1 core trisaccharide, is unexpectedly critical for oxygen-dependent terminal development. AgtA possesses a WD40 repeat domain C-terminal to its single catalytic domain and, by use of domain deletions, binding studies, and enzyme assays, we find that the WD40 repeats confer a salt-sensitive second-site binding interaction with Skp1 that mediates novel catalytic activation in addition to simple substrate recognition. In addition, AgtA binds similarly well to precursor isoforms of Skp1 by a salt-sensitive mechanism that competes with binding to an F-box protein and recognition by early modification enzymes, and the effect of binding is diminished when AgtA modifies Skp1. Genetic studies show that loss of AgtA is more severe when an earlier glycosylation step is blocked, and overexpressed AgtA is deleterious if catalytically inactivated. Together, the findings suggest that AgtA mediates non-enzymatic control of unmodified and substrate precursor forms of Skp1 by a binding mechanism that is normally relieved by switch-like activation of its glycosylation function.
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Affiliation(s)
- Christopher M Schafer
- From the Department of Biochemistry and Molecular Biology, Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
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Schafer CM, Zhang D, West CM. Nonenzymatic and Enzymatic Functions of the Skp1 αGalactosyltransferase in Dictyostelium Oxygen‐Sensing. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.607.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Christopher M. Schafer
- Biochemistry & Molecular BiologyUniversity of Oklahoma Health Sciences CenterOklahoma CityOK
| | - Dongmei Zhang
- Biochemistry & Molecular BiologyUniversity of Oklahoma Health Sciences CenterOklahoma CityOK
| | - Christopher M. West
- Biochemistry & Molecular BiologyUniversity of Oklahoma Health Sciences CenterOklahoma CityOK
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