Identification and characterization of a lysophosphatidylcholine acyltransferase in alveolar type II cells

Chen, Xueni; Hyatt, Brian A.; Mucenski, Michael L.; Mason, Robert J.; Shannon, John M.

doi:10.1073/pnas.0604946103

Cited by 174 publications

(203 citation statements)

References 36 publications

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“…These data agree well with the previous studies showing that the lyso-PAF acetyltransferase activity in neutrophils was competed by long chain acyl-CoAs (40,41). Recently, we and another group identified an LPC remod- eling enzyme, designated LPCAT1, which is highly expressed in lung (27,28). In contrast, LysoPAFAT/LPCAT2 is predominantly expressed in inflammatory cells with modest expression in skin, brain, and colon.…”

Section: Discussionsupporting

confidence: 81%

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A Single Enzyme Catalyzes Both Platelet-activating Factor Production and Membrane Biogenesis of Inflammatory Cells

Shindou¹,

Hishikawa²,

Nakanishi

et al. 2007

Journal of Biological Chemistry

212

239

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Platelet-activating factor (PAF) is a potent proinflammatory lipid mediator eliciting a variety of cellular functions. Lipid mediators, including PAF are produced from membrane phospholipids by enzymatic cascades. Although a G protein-coupled PAF receptor and degradation enzymes have been cloned and characterized, the PAF biosynthetic enzyme, aceyl-CoA:lyso-PAF acetyltransferase, has not been identified. Here, we cloned lyso-PAF acetyltransferase, which is critical in stimulusdependent formation of PAF. The enzyme is a 60-kDa microsomal protein with three putative membrane-spanning domains. The enzyme was induced by bacterial endotoxin (lipopolysaccharide), which was suppressed by dexamethasone treatment. Surprisingly, the enzyme catalyzed not only biosynthesis of PAF from lyso-PAF but also incorporation of arachidonoyl-CoA to produce PAF precursor membrane glycerophospholipids (lysophosphatidylcholine acyltransferase activity). Under resting conditions, the enzyme prefers arachidonoyl-CoA and contributes to membrane biogenesis. Upon acute inflammatory stimulation with lipopolysaccharide, the activated enzyme utilizes acetyl-CoA more efficiently and produces PAF. Thus, our findings provide a novel concept that a single enzyme catalyzes membrane biogenesis of inflammatory cells while producing a prophlogistic mediator in response to external stimuli.Platelet-activating factor (PAF 3 ; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a phospholipid mediator that activates a G protein-coupled receptor (1-3) and results in pleiotropic and potent biological effects, including platelet activation, airway constriction, and hypotension (1). PAF is synthesized in various cells and tissues via two distinct pathways, the de novo and remodeling pathways (2, 4, 5), and the latter is regulated by extracellular signals and plays a critical role in stimulus-coupled PAF biosynthesis (2, 4 -6). PAF synthesis induced by extracellular signals has been reported in murine peritoneal cells stimulated by calcium ionophore (7) or by PAF (8), in human eosinophils stimulated by fMet-Leu-Phe (9), in human neutrophils stimulated by acid stress (10), and in murine peritoneal macrophages stimulated by lipopolysaccharide (LPS) (11). In the remodeling pathway, the precursor of PAF, 1-Oalkyl-sn-glycero-3-phosphocholine (lyso-PAF), is synthesized from 1-O-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine (1-alkyl-phosphatidylcholine; PC) by the action of phospholipase A 2 (2, 4, 12, 13). Subsequently, lyso-PAF is converted to PAF by acetyl-CoA:lyso-PAF acetyltransferase (lyso-PAF acetyltransferase) (EC 2.3.1.67) (14). PAF is then rapidly degraded to lyso-PAF by PAF acetylhydrolases (15). Alternatively, lyso-PAF is again transformed into PC by the action of lysophosphatidylcholine (LPC) acyltransferase (2.3.1.23) (16).A G protein-coupled PAF receptor was cloned in our laboratory (17), and PAF acetylhydrolases have been cloned and characterized by others (18,19). Lyso-PAF acetyltransferase was initially demonstrated and partially characterized by ...

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Section: Discussionsupporting

confidence: 81%

“…In contrast, LysoPAFAT/LPCAT2 is predominantly expressed in inflammatory cells with modest expression in skin, brain, and colon. Because PC is biosynthesized in all cell types, a different class of LPCATs may exist in addition to LPCAT1 (27,28) and LysoPAFAT/LPCAT2 (present study).…”

Section: Discussionmentioning

confidence: 99%

A Single Enzyme Catalyzes Both Platelet-activating Factor Production and Membrane Biogenesis of Inflammatory Cells

Shindou¹,

Hishikawa²,

Nakanishi

et al. 2007

Journal of Biological Chemistry

212

239

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“…Until recently (8,9), LPCAT has been an elusive protein not identified in any organism. Previous attempts for its isolation suggested that protein(s) of an apparent molecular mass of 50-60 kDa could be labeled with a photoreactive azido-lysoPC derivative in a partially purified microsomal fraction containing a LPCAT activity (10).…”

Section: Resultsmentioning

confidence: 99%

Mammalian acyl-CoA:lysophosphatidylcholine acyltransferase enzymes

Soupène¹,

Fyrst²,

Kuypers³

2008

Proc. Natl. Acad. Sci. U.S.A.

103

107

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The mammalian RBC lacks de novo lipid synthesis but maintains its membrane composition by rapid turnover of acyl moieties at the sn-2 position of phospholipids. Plasma-derived fatty acids are esterified to acyl-CoA by acyl-CoA synthetases and transferred to lysophospholipids by acyl-CoA:lysophospholipid acyltransferases. We report the characterization of three lysophosphatidylcholine (lysoPC) acyltransferases (LPCATs), products of the AYTL1, -2, and -3 genes. These proteins are three members of a LPCAT family, of which all three genes are expressed in an erythroleukemic cell line. Aytl2 mRNA was detected in mouse reticulocytes, and the presence of the product of the human ortholog was confirmed in adult human RBCs. The three murine Aytl proteins generated phosphatidylcholine from long-chain acyl-CoA and lysoPC when expressed in Escherichia coli membranes. Spliced variants of Aytl1, affecting a conserved catalytic motif, were identified. Calcium and magnesium modulated LPCAT activity of both Aytl1 and -2 proteins that exhibit EF-hand motifs at the C terminus. Characterization of the product of the Aytl2 gene as the phosphatidylcholine reacylating enzyme in RBCs represents the identification of a plasma membrane lysophospholipid acyltransferase and establishes the function of a LPCAT protein.phosphatidylcholine ͉ RBC ͉ AYTL2

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“…The rapid turnover of the sn-2 acyl chains of glycerophospholipids was originally described by Lands (Lands, 1958;Lands, 1960;Lands and Merkl, 1963;Merkl and Lands, 1963), who proposed that acyl moieties of membrane phospholipids are rapidly metabolized by the action of phospholipase A 2 s and subsequently by lysophospholipid acyltransferases (Lands' cycle). To date, at least two lysophosphatidylcholine acyltransferases (LPCAT) were cloned from mammals: LPCAT1) catalyzes the incorporation of saturated fatty acids into lysoThis article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E07-09 -0893) on December 19, 2007. phosphatidylcholine (lysoPC) (Chen et al, 2006;Nakanishi et al, 2006), and LPCAT2 catalyzes the incorporation of acetic acid and AA into lysoPC (Shindou et al, 2007). These enzymes have conserved motifs in common with the enzymes involved in the de novo phospholipid synthesis pathway (Kennedy pathway) such as acylglycerolphosphate acyltransferase and lysophosphatidic acid acyltransferase (LPAAT).…”

Section: Introductionmentioning

confidence: 99%

“…© 2008 by The American Society for Cell Biology phosphatidylcholine (lysoPC) (Chen et al, 2006;Nakanishi et al, 2006), and LPCAT2 catalyzes the incorporation of acetic acid and AA into lysoPC (Shindou et al, 2007). These enzymes have conserved motifs in common with the enzymes involved in the de novo phospholipid synthesis pathway (Kennedy pathway) such as acylglycerolphosphate acyltransferase and lysophosphatidic acid acyltransferase (LPAAT).…”

mentioning

confidence: 99%

Caenorhabditis elegans mboa-7, a Member of the MBOAT Family, Is Required for Selective Incorporation of Polyunsaturated Fatty Acids into Phosphatidylinositol

Lee

Inoué

Imae

et al. 2008

MBoC

122

117

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Phosphatidylinositol (PI) is a component of membrane phospholipids, and it functions both as a signaling molecule and as a compartment-specific localization signal in the form of polyphosphoinositides. Arachidonic acid (AA) is the predominant fatty acid in the sn-2 position of PI in mammals. LysoPI acyltransferase (LPIAT) is thought to catalyze formation of AA-containing PI; however, the gene that encodes this enzyme has not yet been identified. In this study, we established a screening system to identify genes required for use of exogenous polyunsaturated fatty acids (PUFAs) in Caenorhabditis elegans. In C. elegans, eicosapentaenoic acid (EPA) instead of AA is the predominant fatty acid in PI. We showed that an uncharacterized gene, which we named mboa-7, is required for incorporation of PUFAs into PI. Incorporation of exogenous PUFA into PI of the living worms and LPIAT activity in the microsomes were greatly reduced in mboa-7 mutants. Furthermore, the membrane fractions of transgenic worms expressing recombinant MBOA-7 and its human homologue exhibited remarkably increased LPIAT activity. mboa-7 encodes a member of the membrane-bound O-acyltransferase family, suggesting that mboa-7 is LPIAT. Finally, mboa-7 mutants had significantly lower EPA levels in PI, and they exhibited larval arrest and egg-laying defects. INTRODUCTIONVarious kinds of fatty acids are distributed in membrane phospholipids in mammalian cells and tissues (Lands and Crawford, 1976;Holub and Kuksis, 1978;MacDonald and Sprecher, 1991). The fatty acyl residues of individual phospholipids seem to be under strict metabolic regulation. In general, saturated fatty acids are esterified at the sn-1 position, whereas polyunsaturated fatty acids (PUFAs), such as arachidonic acid (AA), are commonly found at the sn-2 position. Three-fourths or more of the phosphatidylinositol (PI) fraction in rat liver and brain constitutes the 1-stearoyl-2-arachidonoyl species (Holub and Kuksis, 1971;Baker and Thompson, 1972). In contrast, the total pool of precursor phosphatidic acid (PA) in rat liver and brain has a fatty acid composition that does not resemble that of PI, showing a low AA content (Possmayer et al., 1969;Akesson et al., 1970;Baker and Thompson, 1972). Selectivity could be expressed during de novo synthesis at the level of formation of cytidine 5Ј-diphosphate (CDP)-diacylglycerol from PA and cytidine 5Ј-triphosphate or in the use of CDP-diacylglycerol in the final reaction. In fact, CDP-diacylglycerol synthase, which prefers 1-stearoyl-2-arachidonoyl PA as a substrate in vitro, has been cloned, although expression is restricted to testis, retina, and brain (Saito et al., 1997).An alternative mechanism for species selection has been proposed on the basis of turnover studies in rat brain in vivo (Baker and Thompson, 1972). [ 3 H]AA and [ 14 C]glycerol injected intracerebrally were incorporated almost exclusively into brain phospholipids. Comparison of PI and PA radioactivity suggest that the initial flux of AA into PI was independent of de novo synthesi...

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Identification and characterization of a lysophosphatidylcholine acyltransferase in alveolar type II cells

Cited by 174 publications

References 36 publications

A Single Enzyme Catalyzes Both Platelet-activating Factor Production and Membrane Biogenesis of Inflammatory Cells

A Single Enzyme Catalyzes Both Platelet-activating Factor Production and Membrane Biogenesis of Inflammatory Cells

Mammalian acyl-CoA:lysophosphatidylcholine acyltransferase enzymes

Caenorhabditis elegans mboa-7, a Member of the MBOAT Family, Is Required for Selective Incorporation of Polyunsaturated Fatty Acids into Phosphatidylinositol

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