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Epand RM. The scientific adventures of Richard Epand. Biophys Chem 2023; 292:106931. [PMID: 36434860 DOI: 10.1016/j.bpc.2022.106931] [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: 11/01/2022] [Accepted: 11/05/2022] [Indexed: 11/13/2022]
Abstract
This essay summarizes the many areas of science that my career has contributed to. It attempts to highlight some of the innovative concepts that developed from this work. The discussion encompasses studies I undertook from graduate school to the present but it will not attempt to be comprehensive. I apologize to individuals whose work I omitted. Because of space I cannot acknowledge all the contributions from other individuals that made these achievements possible.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada.
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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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Bozelli JC, Yune J, Aulakh SS, Cao Z, Fernandes A, Seitova A, Tong Y, Schreier S, Epand RM. Human Diacylglycerol Kinase ε N-Terminal Segment Regulates the Phosphatidylinositol Cycle, Controlling the Rate but Not the Acyl Chain Composition of Its Lipid Intermediates. ACS Chem Biol 2022; 17:2495-2506. [PMID: 35767833 DOI: 10.1021/acschembio.2c00387] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Diacylglycerol kinase ε (DGKε), an enzyme of the phosphatidylinositol (PI) cycle, bears a highly conserved hydrophobic N-terminal segment, which was proposed to anchor the enzyme into the membrane. However, the importance of this segment to the DGKε function remains to be determined. To address this question, it is here reported an in silico and in vitro combined research strategy. Capitalizing on the AlphaFold 2.0 predicted structure of human DGKε, it is shown that its hydrophobic N-terminal segment anchors it into the membrane via a transmembrane α-helix. Coarse-grained based elastic network model studies showed that a conformational change in the hydrophobic N-terminal segment determines the proximity between the active site of DGKε and the membrane-water interface, likely regulating its kinase activity. In vitro studies with a purified DGKε construct lacking the hydrophobic N-terminal segment (His-SUMO*-Δ50-DGKε) corroborated the role of the N-terminus in regulating DGKε enzymatic properties. The comparison between the enzymatic properties of DGKε and His-SUMO*-Δ50-DGKε showed that the conserved N-terminal segment markedly inhibits the enzyme activity and its sensitivity to membrane intrinsic negative curvature, while also playing a role in the modulation of the enzyme by phosphatidylserine. On the other hand, this segment did not strongly affect its diacylglycerol acyl chain specificity, the modulation of the enzyme by membrane morphological changes, or the activation by phosphatidic acid-rich lipid domains. Hence, these results suggest that the conservation of the hydrophobic N-terminal segment of DGKε throughout evolution guaranteed not only membrane anchorage but also an efficient and elegant manner to regulate the rate of the PI cycle.
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Affiliation(s)
- José Carlos Bozelli
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON L8S 3L8, Canada
| | - Jenny Yune
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON L8S 3L8, Canada
| | - Sukhvershjit S Aulakh
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON L8S 3L8, Canada
| | - Zihao Cao
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON L8S 3L8, Canada
| | - Alexia Fernandes
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON L8S 3L8, Canada
| | - Alma Seitova
- Structural Genomics Consortium, University of Toronto, Toronto, ON N5G 1L7, Canada
| | - Yufeng Tong
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Shirley Schreier
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo 05508-000, Brazil
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON L8S 3L8, Canada
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Ma Q, Srinivasan L, Gabelli SB, Raben DM. Elusive structure of mammalian DGKs. Adv Biol Regul 2022; 83:100847. [PMID: 34922895 PMCID: PMC8858910 DOI: 10.1016/j.jbior.2021.100847] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 11/29/2021] [Accepted: 11/30/2021] [Indexed: 01/03/2023]
Abstract
Mammalian diacylglycerol kinases (DGKs) are a group of enzymes that catalyze the ATP-dependent phosphorylation of diacylglycerol (DAG) to produce phosphatidic acid (PtdOH). In doing so, they modulate the levels of these two important signaling lipids. Currently, ten mammalian DGKs are organized into five classes that vary with respect to domain organization, regulation, and cellular/subcellular distribution. As lipids play critical roles in cells, it is not surprising that there is increasing interest in understanding the mechanism underlying the catalysis and regulation of lipid modulating enzymes such as DGKs. However, there are no solved 3D structures for any of the eukaryotic DGKs. In this review, we summarize what is known and the current challenges in determining the structures of these important enzymes. In addition to gain critical insights into their mechanisms of catalysis and regulation, DGK structures will provide a platform for the design of isoform specific inhibitors.
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Affiliation(s)
- Qianqian Ma
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore Maryland
| | - Lakshmi Srinivasan
- Department of Biophysics and Biophysical Chemistry, The Johns Hopkins University School of Medicine, Baltimore Maryland
| | - Sandra B. Gabelli
- Department of Biophysics and Biophysical Chemistry, The Johns Hopkins University School of Medicine, Baltimore Maryland,Department of Oncology, The Johns Hopkins University School of Medicine, Baltimore Maryland,Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore Maryland,Corresponding author: Sandra B. Gabelli (), Daniel M. Raben ()
| | - Daniel M. Raben
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore Maryland,Department of Oncology, The Johns Hopkins University School of Medicine, Baltimore Maryland,Corresponding author: Sandra B. Gabelli (), Daniel M. Raben ()
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Bozelli JC, Epand RM. Determinants of lipids acyl chain specificity: A tale of two enzymes. Biophys Chem 2020; 265:106431. [DOI: 10.1016/j.bpc.2020.106431] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 07/10/2020] [Indexed: 12/12/2022]
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Bozelli JC, Epand RM. Membrane Shape and the Regulation of Biological Processes. J Mol Biol 2020; 432:5124-5136. [DOI: 10.1016/j.jmb.2020.03.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 01/06/2023]
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Bozelli JC, Yune J, Hou YH, Chatha P, Fernandes A, Cao Z, Tong Y, Epand RM. Regulation of DGKε Activity and Substrate Acyl Chain Specificity by Negatively Charged Phospholipids. Biophys J 2019; 118:957-966. [PMID: 31587830 DOI: 10.1016/j.bpj.2019.09.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 01/09/2023] Open
Abstract
Diacylglycerol kinase ε (DGKε) is a membrane-bound enzyme that catalyzes the ATP-dependent phosphorylation of diacylglycerol to form phosphatidic acid (PA) in the phosphatidylinositol cycle. DGKε lacks a putative regulatory domain and has recently been reported to be regulated by highly curved membranes. To further study the effect of other membrane properties as a regulatory mechanism of DGKε, our work reports the effect of negatively charged phospholipids on DGKε activity and substrate acyl chain specificity. These studies were conducted using purified DGKε and detergent-free phospholipid aggregates, which present a more suitable model system to access the impact of membrane physical properties on membrane-active enzymes. The structural properties of the different model membranes were studied by means of differential scanning calorimetry and 31P-NMR. It is shown that the enzyme is inhibited by a variety of negatively charged phospholipids. However, PA, which is a negatively charged phospholipid and the product of DGKε catalyzed reaction, showed a varied regulatory effect on the enzyme from being an activator to an inhibitor. The type of feedback regulation of DGKε by PA depends on the particular PA molecular species as well as the physical properties of the membrane that the enzyme binds to. In the presence of highly packed PA-rich domains, the enzyme is activated. However, its acyl chain specificity is only observed in liposomes containing 1,2-dioleoyl PA in the presence of Ca2+. It is proposed that to endow the enzyme with its substrate acyl chain specificity, a highly dehydrated (hydrophobic) membrane interface is needed. The presence of an overlap of mechanisms to regulate DGKε ensures proper phosphatidylinositol cycle function regardless of the trigged stimulus and represents a sophisticated and specialized manner of membrane-enzyme regulation.
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Affiliation(s)
- José Carlos Bozelli
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario, Canada
| | - Jenny Yune
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario, Canada
| | - You H Hou
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario, Canada
| | - Preet Chatha
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario, Canada
| | - Alexia Fernandes
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario, Canada
| | - Zihao Cao
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario, Canada
| | - Yufeng Tong
- Structural Genomics Consortium, Toronto, Ontario, Canada; Department of Chemistry and Biochemistry, University of Windsor, Ontario, Canada
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario, Canada.
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Saito T, Takahashi D, Sakane F. Expression, Purification, and Characterization of Human Diacylglycerol Kinase ζ. ACS Omega 2019; 4:5540-5546. [PMID: 31893253 PMCID: PMC6935893 DOI: 10.1021/acsomega.9b00079] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 03/08/2019] [Indexed: 05/14/2023]
Abstract
Diacylglycerol kinase ζ (DGKζ) phosphorylates diacylglycerol (DG) to generate phosphatidic acid. The dysfunction of DGKζ has been linked to several diseases, such as cardiac hypertrophy, ischemia, and seizures. Moreover, much attention has been paid to DGKζ, together with DGKα, as a potential target for cancer immunotherapy. However, DGKζ has never been purified and, thus, neither its enzymatic properties nor its structure has yet been reported, hindering our understanding of the catalytic mechanism of DGKζ and the development of a reasonable structure-based drug design. In the present study, we generated a full-length DGKζ using a baculovirus-insect cell expression system for enzymological and structural studies. Full-length DGKζ remained soluble and was purified to near homogeneity as a monomer with yields suitable for protein crystallization (0.63 mg/1 L culture). Enzymatic characterization showed that the purified DGKζ is in a fully functional state. The K m values for adenosine triphosphate (ATP) and DG were 0.05 mM and 1.5 mol %, respectively, and the EC50 for the activator phosphatidylserine was 8.6 mol %, indicating that its affinity for ATP is moderately higher than those of DGKα and DGKε, and its affinities for DG and phosphatidylserine are comparable to those of DGKα/DGKε. We further confirmed that the purified enzyme could be concentrated without any significant aggregation. Circular dichroism revealed that DGKζ is comprised of 25% α-helices and 18% β-strands. This is the first successful purification and characterization of the enzymatic and conformational properties of DGKζ. The purification of DGKζ allows detailed analyses of this important enzyme and will advance our understanding of DGKζ-related diseases and therapies.
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Affiliation(s)
- Takumi Saito
- Department
of Chemistry, Graduate School of Science, Chiba University, 1-33
Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Daisuke Takahashi
- Department
of Pharmaceutical Health Care and Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Fumio Sakane
- Department
of Chemistry, Graduate School of Science, Chiba University, 1-33
Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
- E-mail: . Tel/Fax: +81-43-290-3695
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Ma Q, Gabelli SB, Raben DM. Diacylglycerol kinases: Relationship to other lipid kinases. Adv Biol Regul 2019; 71:104-110. [PMID: 30348515 PMCID: PMC6347529 DOI: 10.1016/j.jbior.2018.09.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 09/24/2018] [Accepted: 09/25/2018] [Indexed: 04/17/2023]
Abstract
Lipid kinases regulate a wide variety of cellular functions and have emerged as one the most promising targets for drug design. Diacylglycerol kinases (DGKs) are a family of enzymes that catalyze the ATP-dependent phosphorylation of diacylglycerol (DAG) to phosphatidic acid (PtdOH). Despite the critical role in lipid biosynthesis, both DAG and PtdOH have been shown as bioactive lipids mediating a number of signaling pathways. Although there is increasing recognition of their role in signaling systems, our understanding of the key enzyme which regulate the balance of these two lipid messages remain limited. Solved structures provide a wealth of information for understanding the function and regulation of these enzymes. Solving the structures of mammalian DGKs by traditional NMR and X-ray crystallography approaches have been challenging and so far, there are still no three-dimensional structures of these DGKs. Despite this, some insights may be gained by examining the similarities and differences between prokaryotic DGKs and other mammalian lipid kinases. This review focuses on summarizing and comparing the structure of prokaryotic and mammalian DGKs as well as two other lipid kinases: sphingosine kinase and phosphatidylinositol-3-kinase. How these known lipid kinases structures relate to mammalian DGKs will also be discussed.
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Affiliation(s)
- Qianqian Ma
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Sandra B Gabelli
- The Department of Biophysics, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Daniel M Raben
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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Bozelli JC, Jennings W, Black S, Hou YH, Lameire D, Chatha P, Kimura T, Berno B, Khondker A, Rheinstädter MC, Epand RM. Membrane curvature allosterically regulates the phosphatidylinositol cycle, controlling its rate and acyl-chain composition of its lipid intermediates. J Biol Chem 2018; 293:17780-17791. [PMID: 30237168 DOI: 10.1074/jbc.ra118.005293] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 09/04/2018] [Indexed: 01/17/2023] Open
Abstract
Signaling events at membranes are often mediated by membrane lipid composition or membrane physical properties. These membrane properties could act either by favoring the membrane binding of downstream effectors or by modulating their activity. Several proteins can sense/generate membrane physical curvature (i.e. shape). However, the modulation of the activity of enzymes by a membrane's shape has not yet been reported. Here, using a cell-free assay with purified diacylglycerol kinase ϵ (DGKϵ) and liposomes, we studied the activity and acyl-chain specificity of an enzyme of the phosphatidylinositol (PI) cycle, DGKϵ. By systematically varying the model membrane lipid composition and physical properties, we found that DGKϵ has low activity and lacks acyl-chain specificity in locally flat membranes, regardless of the lipid composition. On the other hand, these enzyme properties were greatly enhanced in membrane structures with a negative Gaussian curvature. We also found that this is not a consequence of preferential binding of the enzyme to those structures, but rather is due to a curvature-mediated allosteric regulation of DGKϵ activity and acyl-chain specificity. Moreover, in a fine-tuned interplay between the enzyme and the membrane, DGKϵ favored the formation of structures with greater Gaussian curvature. DGKϵ does not bear a regulatory domain, and these findings reveal the importance of membrane curvature in regulating DGKϵ activity and acyl-chain specificity. Hence, this study highlights that a hierarchic coupling of membrane physical property and lipid composition synergistically regulates membrane signaling events. We propose that this regulatory mechanism of membrane-associated enzyme activity is likely more common than is currently appreciated.
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Affiliation(s)
- José Carlos Bozelli
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1
| | - William Jennings
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1
| | - Stephanie Black
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1
| | - Yu Heng Hou
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1
| | - Darius Lameire
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1
| | - Preet Chatha
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1
| | - Tomohiro Kimura
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1
| | | | - Adree Khondker
- Physics and Astronomy; Origins Institute, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Maikel C Rheinstädter
- Physics and Astronomy; Origins Institute, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Richard M Epand
- From the Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, Hamilton, Ontario L8S 4K1; Departments of Chemistry.
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Abstract
Tafazzin is the mitochondrial enzyme that catalyzes transacylation between a phospholipid and a lysophospholipid in remodeling. Mutations in tafazzin cause Barth syndrome, a potentially life-threatening disease with the major symptom being cardiomyopathy. In the tafazzin-deficient heart, cardiolipin (CL) acyl chains become abnormally heterogeneous unlike those in the normal heart with a single dominant linoleoyl species, tetralinoleoyl CL. In addition, the amount of CL decreases and monolysocardiolipin (MLCL) accumulates. Here we determine using high-resolution 31P nuclear magnetic resonance with cryoprobe technology the fundamental phospholipid composition, including the major but oxidation-labile plasmalogens, in the tafazzin-knockdown (TAZ-KD) mouse heart as a model of Barth syndrome. In addition to confirming a lower level of CL (6.4 ± 0.1 → 2.0 ± 0.4 mol % of the total phospholipid) and accumulation of MLCL (not detected → 3.3 ± 0.5 mol %) in the TAZ-KD, we found a substantial reduction in the level of plasmenylcholine (30.8 ± 2.8 → 18.1 ± 3.1 mol %), the most abundant phospholipid in the control wild type. A quantitative Western blot revealed that while the level of peroxisomes, where early steps of plasmalogen synthesis take place, was normal in the TAZ-KD model, expression of Far1 as a rate-determining enzyme in plasmalogen synthesis was dramatically upregulated by 8.3 (±1.6)-fold to accelerate the synthesis in response to the reduced level of plasmalogen. We confirmed lyso-plasmenylcholine or plasmenylcholine is a substrate of purified tafazzin for transacylation with CL or MLCL, respectively. Our results suggest that plasmenylcholine, abundant in linoleoyl species, is important in remodeling CL in the heart. Tafazzin deficiency thus has a major impact on the cardiac plasmenylcholine level and thereby its functions.
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Affiliation(s)
- Tomohiro Kimura
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Atsuko K. Kimura
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Mindong Ren
- Department of Cell Biology, NYU Langone Medical Center, New York, NY 10016
| | - Bob Berno
- Department of Chemistry, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Yang Xu
- Department of Anesthesiology, NYU Langone Medical Center, New York, NY 10016
| | - Michael Schlame
- Department of Cell Biology, NYU Langone Medical Center, New York, NY 10016
- Department of Anesthesiology, NYU Langone Medical Center, New York, NY 10016
| | - Richard M. Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
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