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Finch NC, Neal CR, Welsh GI, Foster RR, Satchell SC. The unique structural and functional characteristics of glomerular endothelial cell fenestrations and their potential as a therapeutic target in kidney disease. Am J Physiol Renal Physiol 2023; 325:F465-F478. [PMID: 37471420 PMCID: PMC10639027 DOI: 10.1152/ajprenal.00036.2023] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 07/17/2023] [Accepted: 07/17/2023] [Indexed: 07/22/2023] Open
Abstract
Glomerular endothelial cell (GEnC) fenestrations are a critical component of the glomerular filtration barrier. Their unique nondiaphragmed structure is key to their function in glomerular hydraulic permeability, and their aberration in disease can contribute to loss of glomerular filtration function. This review provides a comprehensive update of current understanding of the regulation and biogenesis of fenestrae. We consider diseases in which GEnC fenestration loss is recognized or may play a role and discuss methods with potential to facilitate the study of these critical structures. Literature is drawn from GEnCs as well as other fenestrated cell types such as liver sinusoidal endothelial cells that most closely parallel GEnCs.
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Affiliation(s)
- Natalie C Finch
- Bristol Renal, University of Bristol, United Kingdom
- Langford Vets, University of Bristol, United Kingdom
| | - Chris R Neal
- Bristol Renal, University of Bristol, United Kingdom
| | - Gavin I Welsh
- Bristol Renal, University of Bristol, United Kingdom
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Dai X, Ma Y, Lin Q, Tang H, Chen R, Zhu Y, Shen Y, Cui N, Hong Z, Li Y, Li X. Clinical features and management of atypical hemolytic uremic syndrome patient with DGKE gene variants: a case report. Front Pediatr 2023; 11:1162974. [PMID: 37456562 PMCID: PMC10340117 DOI: 10.3389/fped.2023.1162974] [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] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 06/19/2023] [Indexed: 07/18/2023] Open
Abstract
Background Atypical hemolytic uremic syndrome (aHUS) with diacylglycerol kinase epsilon (DGKE) gene variant is a rare variant of thrombotic microangiopathy (TMA). The information on the clinical features, management and long-term outcomes of DGKE-aHUS patients have not yet been fully elucidated. The aim of this study was to report a novel variant of the DGKE gene in a Chinese population with aHUS. Case presentation The present work reports a 7-month-old boy with aHUS, possibly triggered by gastrointestinal infection, without complement activation, with little response to plasma therapy and nephroprotective measures. The patient died during the 8th week of his hospital stay. The causes of death were intracranial hemorrhage and multiorgan dysfunction. Comprehensive WES of peripheral blood-derived DNA revealed two heterozygous variations in the DGKE exon region: NM_003647.2, c.610dup, p.Thr204Asnfs*4 and deletion of exons 4-6. Conclusions This case suggest that atypical HUS with DGKE gene variant has a poor prognosis with a high mortality rate, which typically manifests in the first year of life and presents as a systemic disease with early-onset HUS with rapidly worsening renal function and chronic proteinuria. There is no specific treatment for DGKE-aHUS. There have an uncertain benefit of plasma therapy for DGKE-aHUS patients. The literature demonstrated that anti-complement therapy showed benefits for DGKE-aHUS with complement activation and autoantibodies during the overt TMA presentation but did not prevent TMA relapses. Early diagnosis and treatment may prevent complications and improve prognosis.
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Affiliation(s)
- Xiaomei Dai
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Yu Ma
- Department of Respiratory Medicine, Children’s Hospital of Soochow University, Suzhou, China
| | - Qiang Lin
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Hanyun Tang
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Ruyue Chen
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Yun Zhu
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Yunyan Shen
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Ningxun Cui
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Zhongqin Hong
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
| | - Yanhong Li
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
- Institute of Pediatric Research, Children's Hospital of Soochow University, Suzhou, China
| | - Xiaozhong Li
- Department of Nephrology and Immunology, Children’s Hospital of Soochow University, Suzhou, China
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Hernandez-Lara MA, Yadav SK, Conaway S, Shah SD, Penn RB, Deshpande DA. Crosstalk between diacylglycerol kinase and protein kinase A in the regulation of airway smooth muscle cell proliferation. Respir Res 2023; 24:155. [PMID: 37301818 DOI: 10.1186/s12931-023-02465-8] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 05/26/2023] [Indexed: 06/12/2023] Open
Abstract
BACKGROUND Diacylglycerol kinase (DGK) regulates intracellular signaling and functions by converting diacylglycerol (DAG) into phosphatidic acid. We previously demonstrated that DGK inhibition attenuates airway smooth muscle (ASM) cell proliferation, however, the mechanisms mediating this effect are not well established. Given the capacity of protein kinase A (PKA) to effect inhibition of ASM cells growth in response to mitogens, we employed multiple molecular and pharmacological approaches to examine the putative role of PKA in the inhibition of mitogen-induced ASM cell proliferation by the small molecular DGK inhibitor I (DGK I). METHODS We assayed cell proliferation using CyQUANT™ NF assay, protein expression and phosphorylation using immunoblotting, and prostaglandin E2 (PGE2) secretion by ELISA. ASM cells stably expressing GFP or PKI-GFP (PKA inhibitory peptide-GFP chimera) were stimulated with platelet-derived growth factor (PDGF), or PDGF + DGK I, and cell proliferation was assessed. RESULTS DGK inhibition reduced ASM cell proliferation in cells expressing GFP, but not in cells expressing PKI-GFP. DGK inhibition increased cyclooxygenase II (COXII) expression and PGE2 secretion over time to promote PKA activation as demonstrated by increased phosphorylation of (PKA substrates) VASP and CREB. COXII expression and PKA activation were significantly decreased in cells pre-treated with pan-PKC (Bis I), MEK (U0126), or ERK2 (Vx11e) inhibitors suggesting a role for PKC and ERK in the COXII-PGE2-mediated activation of PKA signaling by DGK inhibition. CONCLUSIONS Our study provides insight into the molecular pathway (DAG-PKC/ERK-COXII-PGE2-PKA) regulated by DGK in ASM cells and identifies DGK as a potential therapeutic target for mitigating ASM cell proliferation that contributes to airway remodeling in asthma.
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Affiliation(s)
- Miguel A Hernandez-Lara
- Department of Medicine, Center for Translational Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Santosh Kumar Yadav
- Department of Medicine, Center for Translational Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Stanley Conaway
- Department of Medicine, Center for Translational Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Sushrut D Shah
- Department of Medicine, Center for Translational Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Raymond B Penn
- Department of Medicine, Center for Translational Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Deepak A Deshpande
- Department of Medicine, Center for Translational Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA.
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Traczyk G, Świątkowska A, Hromada-Judycka A, Janikiewicz J, Kwiatkowska K. An intact zinc finger motif of the C1B domain is critical for stability and activity of diacylglycerol kinase-ε. Int J Biochem Cell Biol 2022; 152:106295. [PMID: 36113832 DOI: 10.1016/j.biocel.2022.106295] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 08/08/2022] [Accepted: 09/08/2022] [Indexed: 10/31/2022]
Abstract
Diacylglycerol kinase-ε (DGKε) phosphorylates DAG to phosphatidic acid with unique specificity toward 18:0/20:4 DAG (SAG). SAG is a typical backbone of phosphatidylinositol and its derivatives, therefore DGKε activity is crucial for the turnover of these signaling lipids. Malfunction of DGKε contributes to several pathophysiological conditions, including atypical hemolytic uremic syndrome (aHUS) linked with DGKE mutations. In the present study we analyzed the role of a zinc finger motif of the C1B domain of DGKε, as some aHUS-linked mutations affect this ill-defined part of the kinase. For this, we introduce a novel fluorescent assay for determination of DGKε activity which relies on the use of NBD-SAG in mixed micelles as a substrate, followed by TLC separation of NBD-phosphatidic acid formed. The assay reliably determines the activity of purified human GST-DGKε, also endogenous DGKε or overexpressed mouse DGKε-Myc in cell lysates, homogenates, and kinase immunoprecipitates. Using the above assay we found that four amino acids, Cys135, Cys138, His161 and Cys164, forming the zinc finger motif in the C1B domain are required for the DGKε-Myc activity and stability. Substitution of any of these amino acids with Ala or Trp in DGKε-Myc abolished its activity and led to its proteasomal degradation, possibly assisted by Hsp70/90/40 chaperones. Inhibition of the 26S proteasome prevented the degradation but the mutated proteins were inactive. The present data on the deleterious effect of the zinc finger motif disruption contribute to the understanding of the DGKε-linked aHUS, as the Cys164Trp substitution in mouse DGKε corresponds to the Cys167Trp one in human DGKε found in some aHUS patients.
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Affiliation(s)
- Gabriela Traczyk
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology PAS, 3 Pasteur St., 02-093 Warsaw, Poland.
| | - Anna Świątkowska
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology PAS, 3 Pasteur St., 02-093 Warsaw, Poland.
| | - Aneta Hromada-Judycka
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology PAS, 3 Pasteur St., 02-093 Warsaw, Poland.
| | - Justyna Janikiewicz
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology PAS, 3 Pasteur St., 02-093 Warsaw, Poland.
| | - Katarzyna Kwiatkowska
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology PAS, 3 Pasteur St., 02-093 Warsaw, Poland.
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Nakano T, Goto K. Diacylglycerol Kinase ε in Adipose Tissues: A Crosstalk Between Signal Transduction and Energy Metabolism. Front Physiol 2022; 13:815085. [PMID: 35153836 PMCID: PMC8829450 DOI: 10.3389/fphys.2022.815085] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 01/07/2022] [Indexed: 11/13/2022] Open
Abstract
Diacylglycerol (DG) is unique in lipid metabolism because it serves not only as an intermediate product for triglyceride synthesis, but also as a signaling molecule that activates proteins containing DG-responsive elements, such as protein kinase C. Consequently, DG acts as a hub between energy metabolism and intracellular signaling. Of DG metabolizing pathways, DG kinase (DGK) phosphorylates DG to produce phosphatidic acid, which also serves as a second messenger. Several lines of evidence suggest that DGK is deeply involved in metabolic diseases such as obesity and insulin resistance. Of DGK isozymes, DGKε is simplest in terms of structure, but it is characterized by substrate specificity toward arachidonoyl-DG. Recently, we have reported that DGKε deficiency promotes adipose tissue remodeling in mice during the course of high fat diet (HFD) feeding regimen including obesity, insulin resistance, and beige adipogenesis. DGKε ablation engenders altered expression of other lipid metabolizing enzymes, including adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), and diacylglycerol acyltransferase (DGAT). Subcellular localization of DGKε in the endoplasmic reticulum suggests involvement of this isozyme in lipid energy homeostasis. This review presents current findings of DGKε in lipid-orchestrated pathophysiology, especially unique phenotypes of DGKε-knockout mice in the early and late stages of obesogenic conditions.
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Yadav SK, Sharma P, Shah SD, Panettieri RA, Kambayashi T, Penn RB, Deshpande DA. Autocrine regulation of airway smooth muscle contraction by diacylglycerol kinase. J Cell Physiol 2022; 237:603-616. [PMID: 34278583 PMCID: PMC8763953 DOI: 10.1002/jcp.30528] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 07/01/2021] [Accepted: 07/06/2021] [Indexed: 01/03/2023]
Abstract
Diacylglycerol kinase (DGK), a lipid kinase, catalyzes the conversion of diacylglycerol (DAG) to phosphatidic acid, thereby terminating DAG-mediated signaling by Gq-coupled receptors that regulate contraction of airway smooth muscle (ASM). A previous study from our laboratory demonstrated that DGK inhibition or genetic ablation leads to reduced ASM contraction and provides protection for allergen-induced airway hyperresponsiveness. However, the mechanism by which DGK regulates contractile signaling in ASM is not well established. Herein, we investigated the role of prorelaxant cAMP-protein kinase A (PKA) signaling in DGK-mediated regulation of ASM contraction. Pretreatment of human ASM cells with DGK inhibitor I activated PKA as demonstrated by the phosphorylation of PKA substrates, VASP, Hsp20, and CREB, which was abrogated when PKA was inhibited pharmacologically or molecularly using overexpression of the PKA inhibitor peptide, PKI. Furthermore, inhibition of DGK resulted in induction of cyclooxygenase (COX) and generation of prostaglandin E2 (PGE2 ) with concomitant activation of Gs-cAMP-PKA signaling in ASM cells in an autocrine/paracrine fashion. Inhibition of protein kinase C (PKC) or extracellular-signal-regulated kinase (ERK) attenuated DGK-mediated production of PGE2 and activation of cAMP-PKA signaling in human ASM cells, suggesting that inhibition of DGK activates the COX-PGE2 pathway in a PKC-ERK-dependent manner. Finally, DGK inhibition-mediated attenuation of contractile agonist-induced phosphorylation of myosin light chain 20 (MLC-20), a marker of ASM contraction, involves COX-mediated cAMP production and PKA activation in ASM cells. Collectively these findings establish a novel mechanism by which DGK regulates ASM contraction and further advances DGK as a potential therapeutic target to provide effective bronchoprotection in asthma.
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Affiliation(s)
- Santosh K. Yadav
- Center for Translational Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA 19107
| | - Pawan Sharma
- Center for Translational Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA 19107
| | - Sushrut D. Shah
- Center for Translational Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA 19107
| | - Reynold A. Panettieri
- Rutgers Institute for Translational Medicine & Science, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901
| | - Taku Kambayashi
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Raymond B. Penn
- Center for Translational Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA 19107
| | - Deepak A. Deshpande
- Center for Translational Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Jane & Leonard Korman Respiratory Institute, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA 19107.,Corresponding author Deepak Deshpande, PhD, Professor, Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA, USA 19107,
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Raina R, Vijayvargiya N, Khooblall A, Melachuri M, Deshpande S, Sharma D, Mathur K, Arora M, Sethi SK, Sandhu S. Pediatric Atypical Hemolytic Uremic Syndrome Advances. Cells 2021; 10:3580. [PMID: 34944087 PMCID: PMC8700093 DOI: 10.3390/cells10123580] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/12/2021] [Accepted: 12/15/2021] [Indexed: 12/30/2022] Open
Abstract
Atypical hemolytic uremic syndrome (aHUS) is a rare disorder characterized by dysregulation of the alternate pathway. The diagnosis of aHUS is one of exclusion, which complicates its early detection and corresponding intervention to mitigate its high rate of mortality and associated morbidity. Heterozygous mutations in complement regulatory proteins linked to aHUS are not always phenotypically active, and may require a particular trigger for the disease to manifest. This list of triggers continues to expand as more data is aggregated, particularly centered around COVID-19 and pediatric vaccinations. Novel genetic mutations continue to be identified though advancements in technology as well as greater access to cohorts of interest, as in diacylglycerol kinase epsilon (DGKE). DGKE mutations associated with aHUS are the first non-complement regulatory proteins associated with the disease, drastically changing the established framework. Additional markers that are less understood, but continue to be acknowledged, include the unique autoantibodies to complement factor H and complement factor I which are pathogenic drivers in aHUS. Interventional therapeutics have undergone the most advancements, as pharmacokinetic and pharmacodynamic properties are modified as needed in addition to their as biosimilar counterparts. As data continues to be gathered in this field, future advancements will optimally decrease the mortality and morbidity of this disease in children.
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Affiliation(s)
- Rupesh Raina
- Akron Nephrology Associates/Cleveland Clinic Akron General Medical Center, Akron, OH 44307, USA; (N.V.); (A.K.); (S.D.); (K.M.); (M.A.)
- Department of Nephrology, Akron Children’s Hospital, Akron, OH 44308, USA
| | - Nina Vijayvargiya
- Akron Nephrology Associates/Cleveland Clinic Akron General Medical Center, Akron, OH 44307, USA; (N.V.); (A.K.); (S.D.); (K.M.); (M.A.)
| | - Amrit Khooblall
- Akron Nephrology Associates/Cleveland Clinic Akron General Medical Center, Akron, OH 44307, USA; (N.V.); (A.K.); (S.D.); (K.M.); (M.A.)
| | - Manasa Melachuri
- Department of Medicine, Northeast Ohio Medical University, Rootstown, OH 44272, USA; (M.M.); (D.S.)
| | - Shweta Deshpande
- Akron Nephrology Associates/Cleveland Clinic Akron General Medical Center, Akron, OH 44307, USA; (N.V.); (A.K.); (S.D.); (K.M.); (M.A.)
| | - Divya Sharma
- Department of Medicine, Northeast Ohio Medical University, Rootstown, OH 44272, USA; (M.M.); (D.S.)
| | - Kashin Mathur
- Akron Nephrology Associates/Cleveland Clinic Akron General Medical Center, Akron, OH 44307, USA; (N.V.); (A.K.); (S.D.); (K.M.); (M.A.)
| | - Manav Arora
- Akron Nephrology Associates/Cleveland Clinic Akron General Medical Center, Akron, OH 44307, USA; (N.V.); (A.K.); (S.D.); (K.M.); (M.A.)
| | - Sidharth Kumar Sethi
- Pediatric Nephrology & Pediatric Kidney Transplantation, Kidney and Urology Institute, Medanta, The Medicity Hospital, Gurgaon 122007, India;
| | - Sonia Sandhu
- Hematology and Oncology, Cleveland Clinic Akron General Medical Center, Akron, OH 44307, USA;
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Liu D, Ding Q, Dai DF, Padhy B, Nayak MK, Li C, Purvis M, Jin H, Shu C, Chauhan AK, Huang CL, Attanasio M. Loss of diacylglycerol kinase ε causes thrombotic microangiopathy by impairing endothelial VEGFA signaling. JCI Insight 2021; 6:146959. [PMID: 33986189 PMCID: PMC8262293 DOI: 10.1172/jci.insight.146959] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 03/25/2021] [Indexed: 12/24/2022] Open
Abstract
Loss of function of the lipid kinase diacylglycerol kinase ε (DGKε), encoded by the gene DGKE, causes a form of atypical hemolytic uremic syndrome that is not related to abnormalities of the alternative pathway of the complement, by mechanisms that are not understood. By generating a potentially novel endothelial specific Dgke-knockout mouse, we demonstrate that loss of Dgke in the endothelium results in impaired signaling downstream of VEGFR2 due to cellular shortage of phosphatidylinositol 4,5-biphosphate. Mechanistically, we found that, in the absence of DGKε in the endothelium, Akt fails to be activated upon VEGFR2 stimulation, resulting in defective induction of the enzyme cyclooxygenase 2 and production of prostaglandin E2 (PGE2). Treating the endothelial specific Dgke-knockout mice with a stable PGE2 analog was sufficient to reverse the clinical manifestations of thrombotic microangiopathy and proteinuria, possibly by suppressing the expression of matrix metalloproteinase 2 through PGE2-dependent upregulation of the chemokine receptor CXCR4. Our study reveals a complex array of autocrine signaling events downstream of VEGFR2 that are mediated by PGE2, that control endothelial activation and thrombogenic state, and that result in abnormalities of the glomerular filtration barrier.
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Affiliation(s)
- Dingxiao Liu
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA.,Department of Vascular Surgery, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Qiong Ding
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Dao-Fu Dai
- Department of Pathology, University of Iowa, Iowa City, Iowa, USA
| | - Biswajit Padhy
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Manasa K Nayak
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Can Li
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Madison Purvis
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Heng Jin
- Department of Emergency Medicine, Tianjin Medical University General Hospital, Tianjin, China
| | - Chang Shu
- Department of Vascular Surgery, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Anil K Chauhan
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Chou-Long Huang
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Massimo Attanasio
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
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Fu W, Li M, Lin H, Xu Y, Han W, Chen H, Sun L. Cyclosporine A relieved proteinuria and hypoproteinemia in DGKE nephropathy. Clin Chim Acta 2021; 518:78-82. [PMID: 33741360 DOI: 10.1016/j.cca.2021.02.021] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 02/19/2021] [Indexed: 12/09/2022]
Abstract
BACKGROUND The DGKE gene encodes the diacylglycerol kinase epsilon (DGKε). Loss-of-function mutations of DGKE caused a group of rare renal diseases, which are called DGKE nephropathy. We report the clinical manifestations and therapeutic effects of a patient diagnosed with DGKE nephropathy. CASE REPORT The patient's initial symptoms were fever, diarrhea, eyelid edema, acute anemia, acute thrombocytopenia, an elevation of plasm D-dimer, proteinuria, microscopic hematuria, without oliguria or renal insufficiency at the age of 7.6 months. Hemolytic uremic syndrome was diagnosed. His proteinuria and hematuria turned out negative 2 months later. Proteinuria was noticed again at the age of 5.5-year old when he was brought to the hospital because of failure to thrive. Since then, he had been noticed with persistent proteinuria. RESULTS Genetic analysis revealed 2 novel heterozygous mutations on DGKE of the patient. Renal pathology mimicked membrane proliferative glomerulonephritis (MPGN). CONCLUSIONS After a 5-month treatment of cyclosporine A (CsA), proteinuria and hypoproteinemia have relieved apparently. We also observed an improvement of his growth.
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Affiliation(s)
- Wenjun Fu
- Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Min Li
- Department of Pediatrics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Hongrong Lin
- Department of Pediatrics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Youjing Xu
- Department of Pediatrics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Wei Han
- Department of Pediatrics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Huamu Chen
- Department of Pediatrics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Liangzhong Sun
- Department of Pediatrics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China.
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Baldanzi G, Ragnoli B, Malerba M. Potential role of diacylglycerol kinases in immune-mediated diseases. Clin Sci (Lond) 2020; 134:1637-58. [PMID: 32608491 DOI: 10.1042/CS20200389] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/08/2020] [Accepted: 06/22/2020] [Indexed: 02/07/2023]
Abstract
The mechanism promoting exacerbated immune responses in allergy and autoimmunity as well as those blunting the immune control of cancer cells are of primary interest in medicine. Diacylglycerol kinases (DGKs) are key modulators of signal transduction, which blunt diacylglycerol (DAG) signals and produce phosphatidic acid (PA). By modulating lipid second messengers, DGK modulate the activity of downstream signaling proteins, vesicle trafficking and membrane shape. The biological role of the DGK α and ζ isoforms in immune cells differentiation and effector function was subjected to in deep investigations. DGK α and ζ resulted in negatively regulating synergistic way basal and receptor induced DAG signals in T cells as well as leukocytes. In this way, they contributed to keep under control the immune response but also downmodulate immune response against tumors. Alteration in DGKα activity is also implicated in the pathogenesis of genetic perturbations of the immune function such as the X-linked lymphoproliferative disease 1 and localized juvenile periodontitis. These findings suggested a participation of DGK to the pathogenetic mechanisms underlying several immune-mediated diseases and prompted several researches aiming to target DGK with pharmacologic and molecular strategies. Those findings are discussed inhere together with experimental applications in tumors as well as in other immune-mediated diseases such as asthma.
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Sim JA, Kim J, Yang D. Beyond Lipid Signaling: Pleiotropic Effects of Diacylglycerol Kinases in Cellular Signaling. Int J Mol Sci 2020; 21:E6861. [PMID: 32962151 DOI: 10.3390/ijms21186861] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 09/11/2020] [Accepted: 09/16/2020] [Indexed: 12/13/2022] Open
Abstract
The diacylglycerol kinase family, which can attenuate diacylglycerol signaling and activate phosphatidic acid signaling, regulates various signaling transductions in the mammalian cells. Studies on the regulation of diacylglycerol and phosphatidic acid levels by various enzymes, the identification and characterization of various diacylglycerol and phosphatidic acid-regulated proteins, and the overlap of different diacylglycerol and phosphatidic acid metabolic and signaling processes have revealed the complex and non-redundant roles of diacylglycerol kinases in regulating multiple biochemical and biological networks. In this review article, we summarized recent progress in the complex and non-redundant roles of diacylglycerol kinases, which is expected to aid in restoring dysregulated biochemical and biological networks in various pathological conditions at the bed side.
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Brocklebank V, Kumar G, Howie AJ, Chandar J, Milford DV, Craze J, Evans J, Finlay E, Freundlich M, Gale DP, Inward C, Mraz M, Jones C, Wong W, Marks SD, Connolly J, Corner BM, Smith-Jackson K, Walsh PR, Marchbank KJ, Harris CL, Wilson V, Wong EKS, Malina M, Johnson S, Sheerin NS, Kavanagh D. Long-term outcomes and response to treatment in diacylglycerol kinase epsilon nephropathy. Kidney Int 2020; 97:1260-1274. [PMID: 32386968 PMCID: PMC7242908 DOI: 10.1016/j.kint.2020.01.045] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 01/15/2020] [Accepted: 01/31/2020] [Indexed: 12/19/2022]
Abstract
Recessive mutations in diacylglycerol kinase epsilon (DGKE) display genetic pleiotropy, with pathological features reported as either thrombotic microangiopathy or membranoproliferative glomerulonephritis (MPGN), and clinical features of atypical hemolytic uremic syndrome (aHUS), nephrotic syndrome or both. Pathophysiological mechanisms and optimal management strategies have not yet been defined. In prospective and retrospective studies of aHUS referred to the United Kingdom National aHUS service and prospective studies of MPGN referred to the National Registry of Rare Kidney Diseases for MPGN we defined the incidence of DGKE aHUS as 0.009/million/year and so-called DGKE MPGN as 0.006/million/year, giving a combined incidence of 0.015/million/year. Here, we describe a cohort of sixteen individuals with DGKE nephropathy. One presented with isolated nephrotic syndrome. Analysis of pathological features reveals that DGKE mutations give an MPGN-like appearance to different extents, with but more often without changes in arterioles or arteries. In 15 patients presenting with aHUS, ten had concurrent substantial proteinuria. Identified triggering events were rare but coexistent developmental disorders were seen in six. Nine with aHUS experienced at least one relapse, although in only one did a relapse of aHUS occur after age five years. Persistent proteinuria was seen in the majority of cases. Only two individuals have reached end stage renal disease, 20 years after the initial presentation, and in one, renal transplantation was successfully undertaken without relapse. Six individuals received eculizumab. Relapses on treatment occurred in one individual. In four individuals eculizumab was withdrawn, with one spontaneously resolving aHUS relapse occurring. Thus we suggest that DGKE-mediated aHUS is eculizumab non-responsive and that in individuals who currently receive eculizumab therapy it can be safely withdrawn. This has important patient safety and economic implications.
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Affiliation(s)
- Vicky Brocklebank
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Gurinder Kumar
- Division of Paediatric Nephrology, Sheikh Khalifa Medical City, Abu Dhabi, United Arab Emirates
| | - Alexander J Howie
- Birmingham Women's and Children's NHS Foundation Trust, Birmingham, UK
| | - Jayanthi Chandar
- Division of Pediatric Nephrology, University of Miami, Miami, Florida, USA
| | - David V Milford
- Birmingham Women's and Children's NHS Foundation Trust, Birmingham, UK
| | - Janet Craze
- Department of General Paediatrics, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Jonathan Evans
- Children's Renal and Urology Unit, Nottingham Children's Hospital, Nottingham University Hospitals NHS Foundation Trust, Nottingham, UK
| | - Eric Finlay
- Leeds Teaching Hospitals NHS Trust, Leeds, UK
| | - Michael Freundlich
- Division of Pediatric Nephrology, University of Miami, Miami, Florida, USA
| | - Daniel P Gale
- Department of Renal Medicine, University College London, UK
| | - Carol Inward
- Department of Paediatric Nephrology, Bristol Royal Hospital For Children, University Hospitals Bristol NHS Foundation Trust, Bristol, UK
| | - Martin Mraz
- Department of Paediatric Nephrology, Bristol Royal Hospital For Children, University Hospitals Bristol NHS Foundation Trust, Bristol, UK
| | - Caroline Jones
- Department of Paediatric Nephrology, Alder Hey Children's Hospital NHS Trust, Liverpool, UK
| | - William Wong
- Department of Paediatric Nephrology, Starship Children's Hospital, Grafton, Auckland, New Zealand
| | - Stephen D Marks
- Department of Paediatric Nephrology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - John Connolly
- Centre for Nephrology, Royal Free Hospital, University College London, London, UK
| | - Bronte M Corner
- Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Kate Smith-Jackson
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Patrick R Walsh
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Kevin J Marchbank
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Claire L Harris
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Valerie Wilson
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Edwin K S Wong
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Michal Malina
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Great North Children's Hospital, Sir James Spence Institute, Royal Victoria Infirmary, Newcastle, UK
| | - Sally Johnson
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Great North Children's Hospital, Sir James Spence Institute, Royal Victoria Infirmary, Newcastle, UK
| | - Neil S Sheerin
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - David Kavanagh
- National Renal Complement Therapeutics Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Complement Therapeutics Research Group, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK.
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Baldanzi G, Malerba M. DGKα in Neutrophil Biology and Its Implications for Respiratory Diseases. Int J Mol Sci 2019; 20:E5673. [PMID: 31766109 DOI: 10.3390/ijms20225673] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/08/2019] [Accepted: 11/11/2019] [Indexed: 12/21/2022] Open
Abstract
Diacylglycerol kinases (DGKs) play a key role in phosphoinositide signaling by removing diacylglycerol and generating phosphatidic acid. Besides the well-documented role of DGKα and DGKζ as negative regulators of lymphocyte responses, a robust body of literature points to those enzymes, and specifically DGKα, as crucial regulators of leukocyte function. Upon neutrophil stimulation, DGKα activation is necessary for migration and a productive response. The role of DGKα in neutrophils is evidenced by its aberrant behavior in juvenile periodontitis patients, which express an inactive DGKα transcript. Together with in vitro experiments, this suggests that DGKs may represent potential therapeutic targets for disorders where inflammation, and neutrophils in particular, plays a major role. In this paper we focus on obstructive respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD), but also rare genetic diseases such as alpha-1-antitrypsin deficiency. Indeed, the biological role of DGKα is understudied outside the T lymphocyte field. The recent wave of research aiming to develop novel and specific inhibitors as well as KO mice will allow a better understanding of DGK's role in neutrophilic inflammation. Better knowledge and pharmacologic tools may also allow DGK to move from the laboratory bench to clinical trials.
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Abstract
Haemolytic uraemic syndrome is a form of thrombotic microangiopathy affecting predominantly the kidney and characterised by a triad of thrombocytopenia, mechanical haemolytic anaemia, and acute kidney injury. The term encompasses several disorders: shiga toxin-induced and pneumococcus-induced haemolytic uraemic syndrome, haemolytic uraemic syndrome associated with complement dysregulation or mutation of diacylglycerol kinase ɛ, haemolytic uraemic syndrome related to cobalamin C defect, and haemolytic uraemic syndrome secondary to a heterogeneous group of causes (infections, drugs, cancer, and systemic diseases). In the past two decades, experimental, genetic, and clinical studies have helped to decipher the pathophysiology of these various forms of haemolytic uraemic syndrome and undoubtedly improved diagnostic approaches. Moreover, a specific mechanism-based treatment has been made available for patients affected by atypical haemolytic uraemic syndrome due to complement dysregulation. Such treatment is, however, still absent for several other disease types, including shiga toxin-induced haemolytic uraemic syndrome.
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Affiliation(s)
- Fadi Fakhouri
- Department of Nephrology, Centre Hospitalier Universitaire, and INSERM UMR S1064, Nantes, France
| | - Julien Zuber
- Assistance Publique-Hôpitaux de Paris, Department of Nephrology and Renal Transplantation, Hôpital Necker, Université Paris Descartes, Paris, France
| | - Véronique Frémeaux-Bacchi
- Assistance Publique-Hôpitaux de Paris, Department of Biological Immunology, Hôpital Européen Georges Pompidou, and INSERM UMR S1138, Complément et Maladies, Centre de Recherche des Cordeliers, Paris, France
| | - Chantal Loirat
- Assistance Publique-Hôpitaux de Paris, Department of Pediatric Nephrology, Hôpital Robert Debré, Université Paris Diderot, Sorbonne Paris Cité, Paris, France.
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Hayashi D, Yagi K, Song C, Ueda S, Yamanoue M, Topham M, Suzaki T, Saito N, Emoto N, Shirai Y. Diacylglycerol Kinase alpha is Involved in the Vitamin E-Induced Amelioration of Diabetic Nephropathy in Mice. Sci Rep 2017; 7:2597. [PMID: 28572624 DOI: 10.1038/s41598-017-02354-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 04/10/2017] [Indexed: 02/05/2023] Open
Abstract
Diabetic nephropathy (DN) is one of vascular complications of diabetes and is caused by abnormal protein kinase C activation as a result of increased diacylglycerol (DG) production in diabetic hyperglycaemia. Diacylglycerol kinase (DGK) converts DG into phosphatidic acid. Therefore, it is expected that the activation of DGK would ameliorate DN. Indeed, it has been reported that vitamin E (VtE) ameliorates DN in rat by activating DGK, and we recently reported that VtE specifically activates DGKα isoform in vitro. However, whether DGKα is involved in the VtE-induced amelioration of DN in vivo remains unknown. Therefore, we investigated the VtE-induced amelioration of DN in wild-type (DGKα+/+) and DGKα–deficient (DGKα−/−) mice in which diabetes was induced by streptozocin. Several symptoms of DN were ameliorated by VtE treatment in the DGKα+/+ mice but not in the DGKα−/− mice. Moreover, transmission electron microscopy of glomeruli and immunofluorescent staining of glomerular epithelial cells (podocytes) indicated that VtE ameliorates podocyte pathology and prevents podocyte loss in the DGKα+/+ mice but not in the DGKα−/− mice. We showed that VtE can ameliorate DN in mice and that DGKα is involved in the VtE-induced amelioration of DN in vivo, suggesting that DGKα is an attractive therapeutic target for DN.
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Jennings W, Doshi S, Hota PK, Prodeus A, Black S, Epand RM. Expression, Purification, and Properties of a Human Arachidonoyl-Specific Isoform of Diacylglycerol Kinase. Biochemistry 2017; 56:1337-1347. [PMID: 28199087 DOI: 10.1021/acs.biochem.6b01193] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Diacylglycerol kinase ε (DGKε) catalyzes the phosphorylation of diacylglycerol, producing phosphatidic acid. DGKε demonstrates exquisite specificity for the acyl chains of diacylglycerol. This contributes to the enrichment of particular acyl chains within the lipids of the phosphatidylinositol cycle. Phosphatidylinositol is highly enriched with 1-stearoyl-2-arachidonoyl, which is important for maintaining cellular health. Dysregulation of DGKε perturbs lipid signaling and biosynthesis, which has been linked to epilepsy, Huntington's disease, and heart disease. Recessive loss-of-function mutations in the DGKε gene cause atypical hemolytic uremic syndrome. Because DGKε has never been purified, little is known about its molecular properties. We expressed human DGKε and a truncated version lacking the first 40 residues (DGKεΔ40) and purified both proteins to near homogeneity using nickel affinity chromatography. Kinase activity measurements showed that both purified constructs retained their acyl chain specificity for diacylglycerol with an activity level comparable to that of N-terminally FLAG epitope-tagged forms of these proteins expressed in COS7 cells. Both constructs lost activity upon being stored, particularly upon freezing and thawing, which was minimized by the addition of glycerol. Circular dichroism revealed that DGKε and DGKεΔ40 both contain significant amounts of α-helical and β structure and exhibit biphasic thermal denaturations. The loss of secondary structure upon heating was irreversible for both constructs, with relatively little effect of added dioleoylphosphatidylcholine. The addition of 50% glycerol stabilized both constructs and facilitated refolding of their secondary structures after heating. This is the first successful purification and characterization of DGKε's enzymatic and conformational properties. The purification of DGKε permits detailed analyses of this unique enzyme and will improve our understanding of DGKε-related diseases.
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Affiliation(s)
- William Jennings
- Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
| | - Sejal Doshi
- Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
| | - Prasanta Kumar Hota
- Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
| | - Aaron Prodeus
- Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
| | - Stephanie Black
- Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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Epand RM, So V, Jennings W, Khadka B, Gupta RS, Lemaire M. Diacylglycerol Kinase-ε: Properties and Biological Roles. Front Cell Dev Biol 2016; 4:112. [PMID: 27803897 PMCID: PMC5067486 DOI: 10.3389/fcell.2016.00112] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/27/2016] [Indexed: 12/20/2022] Open
Abstract
In mammals there are at least 10 isoforms of diacylglycerol kinases (DGK). All catalyze the phosphorylation of diacylglycerol (DAG) to phosphatidic acid (PA). Among DGK isoforms, DGKε has several unique features. It is the only DGK isoform with specificity for a particular species of DAG, i.e., 1-stearoyl-2-arachidonoyl glycerol. The smallest of all known DGK isoforms, DGKε, is also the only DGK devoid of a regulatory domain. DGKε is the only DGK isoform that has a hydrophobic segment that is predicted to form a transmembrane helix. As the only membrane-bound, constitutively active DGK isoform with exquisite specificity for particular molecular species of DAG, the functional overlap between DGKε and other DGKs is predicted to be minimal. DGKε exhibits specificity for DAG containing the same acyl chains as those found in the lipid intermediates of the phosphatidylinositol-cycle. It has also been shown that DGKε affects the acyl chain composition of phosphatidylinositol in whole cells. It is thus likely that DGKε is responsible for catalyzing one step in the phosphatidylinositol-cycle. Steps of this cycle take place in both the plasma membrane and the endoplasmic reticulum membrane. DGKε is likely present in both of these membranes. DGKε is the only DGK isoform that is associated with a human disease. Indeed, recessive loss-of-function mutations in DGKε cause atypical hemolytic-uremic syndrome (aHUS). This condition is characterized by thrombosis in the small vessels of the kidney. It causes acute renal insufficiency in infancy and most patients develop end-stage renal failure before adulthood. Disease pathophysiology is poorly understood and there is no therapy. There are also data suggesting that DGKε may play a role in epilepsy and Huntington disease. Thus, DGKε has many unique molecular and biochemical properties when compared to all other DGK isoforms. DGKε homologs also contain a number of conserved sequence features that are distinctive characteristics of either the rodents or specific groups of primate homologs. How cells, tissues and organisms harness DGKε's catalytic prowess remains unclear. The discovery of DGKε's role in causing aHUS will hopefully boost efforts to unravel the mechanisms by which DGKε dysfunction causes disease.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Vincent So
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences CentreHamilton, ON, Canada; Nephrology Division and Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada
| | - William Jennings
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Bijendra Khadka
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Radhey S Gupta
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Mathieu Lemaire
- Nephrology Division and Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada; Department of Biochemistry, University of TorontoToronto, ON, Canada; Institute of Medicine, University of TorontoToronto, ON, Canada
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Abstract
In mammals there are at least 10 isoforms of diacylglycerol kinases (DGK). All catalyze the phosphorylation of diacylglycerol (DAG) to phosphatidic acid (PA). Among DGK isoforms, DGKε has several unique features. It is the only DGK isoform with specificity for a particular species of DAG, i.e., 1-stearoyl-2-arachidonoyl glycerol. The smallest of all known DGK isoforms, DGKε, is also the only DGK devoid of a regulatory domain. DGKε is the only DGK isoform that has a hydrophobic segment that is predicted to form a transmembrane helix. As the only membrane-bound, constitutively active DGK isoform with exquisite specificity for particular molecular species of DAG, the functional overlap between DGKε and other DGKs is predicted to be minimal. DGKε exhibits specificity for DAG containing the same acyl chains as those found in the lipid intermediates of the phosphatidylinositol-cycle. It has also been shown that DGKε affects the acyl chain composition of phosphatidylinositol in whole cells. It is thus likely that DGKε is responsible for catalyzing one step in the phosphatidylinositol-cycle. Steps of this cycle take place in both the plasma membrane and the endoplasmic reticulum membrane. DGKε is likely present in both of these membranes. DGKε is the only DGK isoform that is associated with a human disease. Indeed, recessive loss-of-function mutations in DGKε cause atypical hemolytic-uremic syndrome (aHUS). This condition is characterized by thrombosis in the small vessels of the kidney. It causes acute renal insufficiency in infancy and most patients develop end-stage renal failure before adulthood. Disease pathophysiology is poorly understood and there is no therapy. There are also data suggesting that DGKε may play a role in epilepsy and Huntington disease. Thus, DGKε has many unique molecular and biochemical properties when compared to all other DGK isoforms. DGKε homologs also contain a number of conserved sequence features that are distinctive characteristics of either the rodents or specific groups of primate homologs. How cells, tissues and organisms harness DGKε's catalytic prowess remains unclear. The discovery of DGKε's role in causing aHUS will hopefully boost efforts to unravel the mechanisms by which DGKε dysfunction causes disease.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Vincent So
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences CentreHamilton, ON, Canada; Nephrology Division and Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada
| | - William Jennings
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Bijendra Khadka
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Radhey S Gupta
- Department of Biochemistry and Biomedical Sciences, McMaster University Health Sciences Centre Hamilton, ON, Canada
| | - Mathieu Lemaire
- Nephrology Division and Cell Biology Program, Hospital for Sick ChildrenToronto, ON, Canada; Department of Biochemistry, University of TorontoToronto, ON, Canada; Institute of Medicine, University of TorontoToronto, ON, Canada
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