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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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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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Abstract
The effects of lithium on vascular development were examined using the chick embryo area vasculosa in shell-less culture as an experimental model. Embryos were explanted after 48 h in ovo and LiC1 (50, 100, 150 and 200 microg in 10 microl water) was applied to the centre of the blastodisc. Controls were untreated or given equimolar amounts of NaCl. At 24 h and 48 h after treatment, untreated and NaCl controls were identical, having well developed extraembryonic vessels. At doses of 100 microg and greater, LiCl significantly inhibited normal vascular development and expansion of the area vasculosa in the majority of explants. In many specimens blood islands continued to form but their assembly into primitive vessels was prevented, indicating that lithium affects the mechanism regulating the assembly of vascular endothelium. At the same time the embryos were alive but retarded in development compared with controls. When LiCl (150 microg) was applied to cultures explanted after 72 h in ovo (when the primary vascular network had already formed through vasculogenesis) no adverse effects were seen. This suggests that lithium affects vasculogenesis but not angiogenesis. Treatment with myo-inositol completely reversed the effects of lithium in a time dependent manner indicating that the phosphatidylinositol second messenger cycle may be involved in the cellular events of vasculogenesis. Finally the results of this study show that the yolk sac vasculature is particularly vulnerable to lithium and the consequent effects of this interference on embryonic development are discussed.
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Affiliation(s)
- J J Giles
- Department of Human Anatomy and Physiology, National University of Ireland, University College, Dublin
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