1
|
Chen W, Salari H, Taylor MC, Jost R, Berkowitz O, Barrow R, Qiu D, Branco R, Masle J. NMT1 and NMT3 N-Methyltransferase Activity Is Critical to Lipid Homeostasis, Morphogenesis, and Reproduction. PLANT PHYSIOLOGY 2018; 177:1605-1628. [PMID: 29777000 PMCID: PMC6084668 DOI: 10.1104/pp.18.00457] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 05/10/2018] [Indexed: 05/24/2023]
Abstract
Phosphatidylcholine (PC) is a major membrane phospholipid and a precursor for major signaling molecules. Understanding its synthesis is important for improving plant growth, nutritional value, and resistance to stress. PC synthesis is complex, involving several interconnected pathways, one of which proceeds from serine-derived phosphoethanolamine to form phosphocholine through three sequential phospho-base methylations catalyzed by phosphoethanolamine N-methyltransferases (PEAMTs). The contribution of this pathway to the production of PC and plant growth has been a matter of some debate. Although a handful of individual PEAMTs have been described, there has not been any in planta investigation of a PEAMT family. Here, we provide a comparative functional analysis of two Arabidopsis (Arabidopsis thaliana) PEAMTs, NMT1 and the little known NMT3. Analysis of loss-of-function mutants demonstrates that NMT1 and NMT3 synergistically regulate PC homeostasis, phase transition at the shoot apex, coordinated organ development, and fertility through overlapping but also specific functions. The nmt1 nmt3 double mutant shows extensive sterility, drastically reduced PC concentrations, and altered lipid profiles. These findings demonstrate that the phospho-base methylation pathway makes a major contribution to PC synthesis in Arabidopsis and that NMT1 and NMT3 play major roles in its catalysis and the regulation of PC homeostasis as well as in plant growth and reproduction.
Collapse
Affiliation(s)
- Weihua Chen
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Hooman Salari
- Agronomy and Plant Breeding Department, Razi University, Kermanshah 67155, Iran
| | - Matthew C Taylor
- Land and Water Flagship, Commonwealth Scientific and Industrial Research Organisation, Canberra, Australian Capital Territory 2601, Australia
| | - Ricarda Jost
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Oliver Berkowitz
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Russell Barrow
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Deyun Qiu
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Rémi Branco
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Josette Masle
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| |
Collapse
|
2
|
Cornell RB, Ridgway ND. CTP:phosphocholine cytidylyltransferase: Function, regulation, and structure of an amphitropic enzyme required for membrane biogenesis. Prog Lipid Res 2015; 59:147-71. [PMID: 26165797 DOI: 10.1016/j.plipres.2015.07.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 07/07/2015] [Accepted: 07/07/2015] [Indexed: 12/12/2022]
Abstract
CTP:phosphocholine cytidylyltransferase (CCT) catalyzes a rate-limiting and regulated step in the CDP-choline pathway for the synthesis of phosphatidylcholine (PC) and PC-derived lipids. Control of CCT activity is multi-layered, and includes direct regulation by reversible membrane binding involving a built-in lipid compositional sensor. Thus CCT contributes to phospholipid compositional homeostasis. CCT also modifies the curvature of its target membrane. Knowledge of CCT structure and regulation of its catalytic function are relatively advanced compared to many lipid metabolic enzymes, and are reviewed in detail. Recently the genetic origins of two human developmental and lipogenesis disorders have been traced to mutations in the gene for CCTα.
Collapse
Affiliation(s)
- Rosemary B Cornell
- Department of Molecular Biology and Biochemistry and the Department of Chemistry, Simon Fraser University, Burnaby, B.C. V5A-1S6, Canada.
| | - Neale D Ridgway
- Departments of Pediatrics, and Biochemistry and Molecular Biology, Atlantic Research Centre, Dalhousie University, Halifax, Nova Scotia B3H-4H7, Canada
| |
Collapse
|
3
|
Craddock CP, Adams N, Bryant FM, Kurup S, Eastmond PJ. PHOSPHATIDIC ACID PHOSPHOHYDROLASE Regulates Phosphatidylcholine Biosynthesis in Arabidopsis by Phosphatidic Acid-Mediated Activation of CTP:PHOSPHOCHOLINE CYTIDYLYLTRANSFERASE Activity. THE PLANT CELL 2015; 27:1251-64. [PMID: 25862304 PMCID: PMC4558698 DOI: 10.1105/tpc.15.00037] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/19/2015] [Indexed: 05/04/2023]
Abstract
Regulation of membrane lipid biosynthesis is critical for cell function. We previously reported that disruption of PHOSPHATIDIC ACID PHOSPHOHYDROLASE1 (PAH1) and PAH2 stimulates net phosphatidylcholine (PC) biosynthesis and proliferation of the endoplasmic reticulum (ER) in Arabidopsis thaliana. Here, we show that this response is caused specifically by a reduction in the catalytic activity of the protein and positively correlates with an accumulation of its substrate, phosphatidic acid (PA). The accumulation of PC in pah1 pah2 is suppressed by disruption of CTP:PHOSPHOCHOLINE CYTIDYLYLTRANSFERASE1 (CCT1), which encodes a key enzyme in the nucleotide pathway for PC biosynthesis. The activity of recombinant CCT1 is stimulated by lipid vesicles containing PA. Truncation of CCT1, to remove the predicted C-terminal amphipathic lipid binding domain, produced a constitutively active enzyme. Overexpression of native CCT1 in Arabidopsis has no significant effect on PC biosynthesis or ER morphology, but overexpression of the truncated constitutively active version largely replicates the pah1 pah2 phenotype. Our data establish that membrane homeostasis is regulated by lipid composition in Arabidopsis and reveal a mechanism through which the abundance of PA, mediated by PAH activity, modulates CCT activity to govern PC content.
Collapse
Affiliation(s)
- Christian P Craddock
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Nicolette Adams
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Fiona M Bryant
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom
| | - Smita Kurup
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom
| | - Peter J Eastmond
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom
| |
Collapse
|
4
|
Ding Z, Taneva SG, Huang HKH, Campbell SA, Semenec L, Chen N, Cornell RB. A 22-mer segment in the structurally pliable regulatory domain of metazoan CTP: phosphocholine cytidylyltransferase facilitates both silencing and activating functions. J Biol Chem 2012; 287:38980-91. [PMID: 22988242 DOI: 10.1074/jbc.m112.402081] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
CTP:phosphocholine cytidylyltransferase (CCT), an amphitropic enzyme that regulates phosphatidylcholine synthesis, is composed of a catalytic head domain and a regulatory tail. The tail region has dual functions as a regulator of membrane binding/enzyme activation and as an inhibitor of catalysis in the unbound form of the enzyme, suggesting conformational plasticity. These functions are well conserved in CCTs across diverse phyla, although the sequences of the tail regions are not. CCT regulatory tails of diverse origins are composed of a long membrane lipid-inducible amphipathic helix (m-AH) followed by a highly disordered segment, reminiscent of the Parkinson disease-linked protein, α-synuclein, which we show shares a novel sequence motif with vertebrate CCTs. To unravel features required for silencing, we created chimeric enzymes by fusing the catalytic domain of rat CCTα to the regulatory tail of CCTs from Drosophila, Caenorhabditis elegans, or Saccharomyces cerevisiae or to α-synuclein. Only the tail domains of the two invertebrate CCTs were competent for both suppression of catalytic activity and for activation by lipid vesicles. Thus, both silencing and activating functions of the m-AH can tolerate significant changes in length and sequence. We identified a highly amphipathic 22-residue segment in the m-AH with features conserved among animal CCTs but not yeast CCT or α-synuclein. Deletion of this segment from rat CCT increased the lipid-independent V(max) by 10-fold, equivalent to the effect of deleting the entire tail, and severely weakened membrane binding affinity. However, membrane binding was required for additional increases in catalytic efficiency. Thus, full activation of CCT may require not only loss of a silencing conformation in the m-AH but a gain of an activating conformation, promoted by membrane binding.
Collapse
Affiliation(s)
- Ziwei Ding
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | | | | | | | | | | | | |
Collapse
|
5
|
Keogh MR, Courtney PD, Kinney AJ, Dewey RE. Functional characterization of phospholipid N-methyltransferases from Arabidopsis and soybean. J Biol Chem 2009; 284:15439-47. [PMID: 19366698 PMCID: PMC2708841 DOI: 10.1074/jbc.m109.005991] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 04/08/2009] [Indexed: 11/06/2022] Open
Abstract
Phospholipid N-methyltransferase (PLMT) enzymes catalyze the S-adenosylmethionine-dependent methylation of ethanolamine-containing phospholipids to produce the abundant membrane lipid phosphatidylcholine (PtdCho). In mammals and yeast, PLMT activities are required for the de novo synthesis of the choline headgroup found in PtdCho. PLMT enzyme activities have also been reported in plants, yet their roles in PtdCho biosynthesis are less clear because most plants can produce the choline headgroup entirely via soluble substrates, initiated by the methylation of free ethanolamine-phosphate. To gain further insights into the function of PLMT enzymes in plants, we isolated PLMT cDNAs from Arabidopsis and soybean (Glycine max) based upon primary amino acid sequence homology to the rat PLMT, phosphatidylethanolamine N-methyltransferase. Using a heterologous yeast expression system, it was shown that plant PLMTs methylate phosphatidylmonomethylethanolamine and phosphatidyldimethylethanolamine but cannot utilize phosphatidylethanolamine as a substrate. Identification of an Arabidopsis line containing a knock-out dissociator transposon insertion within the single copy AtPLMT gene allowed us to investigate the consequences of loss of PLMT function. Although the accumulation of the PLMT substrates phosphatidylmonomethylethanolamine and phosphatidyldimethylethanolamine was considerably elevated in the atplmt knock-out line, PtdCho levels remained normal, and no obvious differences were observed in plant morphology or development under standard growth conditions. However, because the metabolic routes through which PtdCho is synthesized in plants vary greatly among differing species, it is predicted that the degree with which PtdCho synthesis is dependent upon PLMT activities will also vary widely throughout the plant kingdom.
Collapse
Affiliation(s)
- Matthew R. Keogh
- Plant Biology, North Carolina State University, Raleigh, North Carolina 27695-8009 and
| | | | - Anthony J. Kinney
- Crop Genetics Research, DuPont Experimental Station, Wilmington, Delaware 19880-0353
| | | |
Collapse
|
6
|
Tang F, Moore TS. Enzymes of the Primary Phosphatidylethanolamine Biosynthetic Pathway in Postgermination Castor Bean Endosperm (Developmental Profiles and Partial Purification of the Mitochondrial CTP:Ethanolaminephosphate Cytidylyltransferase). PLANT PHYSIOLOGY 1997; 115:1589-1597. [PMID: 12223882 PMCID: PMC158625 DOI: 10.1104/pp.115.4.1589] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Ethanolamine kinase, CTP:ethanolaminephosphate cytidylyltransferase (ECT), and ethanolaminephosphotransferase, which sequentially catalyze the primary pathway for phosphatidylethanolamine synthesis, were measured in castor bean (Ricinus communis L. var Hale) endosperm for 6 d after the onset of imbibition. Ethanolamine kinase (EC 2.7.1.82) activity was cytosolic, increasing slowly during the first 5 d and then declining. Total ECT (EC 2.7.7.14) activity increased until the 4th d, but the endoplasmic reticulum fraction of the activity peaked at d 3, and the mitochondrial activity peaked at d 4. Diacylglycerol:CDPethanolamine ethanolaminephosphotransferase (EC 2.7.8.1) increased during the first 2 d after imbibition began, after which it declined. The lowest activity of ethanolamine kinase during postgermination was more than 5-fold higher than the maximum activity of ECT, and the total activity of diacylglycerol:CDPethanolamine ethanolaminephosphotransferase at d 2 was at least triple that of ECT of the endoplasmic reticulum. We have partially purified ECT from mitochondrial fractions of postgermination castor bean endosperm starting with mitochondria purified by sucrose (Suc) density gradient centrifugation and broken by osmotic shock and homogenization. The membrane-bound ECT was solubilized with 1.5% 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate and purified approximately 118-fold by polyethylene glycol precipitation, chromatography on Sephacryl S-200, and then Suc gradient centrifugation. The continuous presence of both salt (0.5 M NaCl) and detergent (1% [w/v] 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate) was necessary to prevent aggregation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the final activity peak resulted in a prominent protein band at 35 kD, which correlated with bands from peak ECT activity fractions after both Suc gradient centrifugation and gel filtration on Sephacryl S-200. The activity of this enzyme was enhanced by the addition of several phospholipids.
Collapse
Affiliation(s)
- F Tang
- Department of Plant Biology, Louisiana State University, Baton Rouge, Louisiana 70803-1705
| | | |
Collapse
|
7
|
Nishida I, Swinhoe R, Slabas AR, Murata N. Cloning of Brassica napus CTP: phosphocholine cytidylyltransferase cDNAs by complementation in a yeast cct mutant. PLANT MOLECULAR BIOLOGY 1996; 31:205-211. [PMID: 8756587 DOI: 10.1007/bf00021784] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
CTP:phosphocholine cytidylyltransferase is a rate-limiting enzyme in biosynthesis of phosphatidylcholine in plant cells. We have isolated four cDNAs for the cytidylyltransferase from a root cDNA library of Brassica napus by complementation in a yeast cct mutant. The deduced amino-acid sequences of the B. napus enzymes resembled rat and yeast enzymes in the central domain. Although all cytidylyltransferases ever cloned from B. napus and other organisms were predicted to be structurally hydrophilic, the yeast cct mutant transformed with one of the B. napus cDNA clones restored the cytidylyltransferase activity in the microsomal fraction as well as in the soluble fraction. These results are consistent with a recent view that yeast cells contained a machinery for targeting the yeast cytidylyltransferase to membranes, and may indicate that the B. napus enzyme was compatible with the machinery.
Collapse
Affiliation(s)
- I Nishida
- National Institute for Basic Biology, Okazaki, Japan
| | | | | | | |
Collapse
|
8
|
Slabas AR, Brown A, Sinden BS, Swinhoe R, Simon JW, Ashton AR, Whitfeld PR, Elborough KM. Pivotal reactions in fatty acid synthesis. Prog Lipid Res 1994; 33:39-46. [PMID: 7910689 DOI: 10.1016/0163-7827(94)90007-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- A R Slabas
- Biological Sciences Department, University of Durham, U.K
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Prud'homme MP, Moore TS. Phosphatidylcholine Synthesis in Castor Bean Endosperm : Occurrence of an S-Adenosyl-l-Methionine:Ethanolamine N-Methyltransferase. PLANT PHYSIOLOGY 1992; 100:1536-40. [PMID: 16653154 PMCID: PMC1075816 DOI: 10.1104/pp.100.3.1536] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Methylethanolamine synthesis by S-adenosyl-l-methionine:ethanolamine N-methyltransferase from an extract of castor bean (Ricinus communis L. var Hale) endosperm was characterized. The apparent Michaelis-Menten constants of the enzyme for ethanolamine and S-adenosyl-l-methionine were estimated to be 6.7 and 1.4 mum, respectively, although the K(m) for ethanolamine is imprecise because of strong substrate inhibition. The pH optimum was 8.0, and a divalent cation was required for activity, with Mg(2+) giving the greatest stimulation at 5 mm. The enzyme was inhibited by calcium in the micromolar range and relatively high concentrations of ethanolamine (above about 7 mum). The activity was found in the 119,000g supernatant fraction and, therefore, appears to be cytoplasmic. The potential roles of S-adenosyl-l-methionine:ethanolamine N-methyltransferase in choline and phosphatidylcholine synthesis are discussed.
Collapse
Affiliation(s)
- M P Prud'homme
- Department of Botany, Louisiana State University, Baton Rouge, Louisiana 70803-1705
| | | |
Collapse
|
10
|
Wang X, Moore T. Phosphatidylethanolamine synthesis by castor bean endosperm. Intracellular distribution and characteristics of CTP:ethanolaminephosphate cytidylyltransferase. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54880-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|