Publications

• Enzymatic activities of the human AGPAT isoform 3 and isoform 5: localization of AGPAT5 to mitochondria.

  Prasad S.S., Garg A., Agarwal A.K.

  The enzyme 1-acylglycerol-3-phosphate-O-acyltransferase (AGPAT) converts lysophosphatidic acid (LPA) to phosphatidic acid (PA). In this study, we show enzymatic properties, tissue distribution, and subcellular localization of human AGPAT3 and AGPAT5. In cells overexpressing these isoforms, the pro ... >> More

  The enzyme 1-acylglycerol-3-phosphate-O-acyltransferase (AGPAT) converts lysophosphatidic acid (LPA) to phosphatidic acid (PA). In this study, we show enzymatic properties, tissue distribution, and subcellular localization of human AGPAT3 and AGPAT5. In cells overexpressing these isoforms, the proteins were detected in the nuclear envelope and the endoplasmic reticulum. AGPAT5-GFP fusion protein was localized in the mitochondria of both Chinese hamster ovary and human epithelial cervical cancer cells. Using lysates of AD293 cells infected with AGPAT3 and AGPAT5 recombinant adenovirus, we show that AGPAT3 and AGPAT5 proteins have AGPAT activity. Both the isoforms have similar apparent V(max) of 6.35 and 2.42 nmol/min/mg protein, respectively, for similar LPA. The difference between the two isoforms is in their use of additional lysophospholipids. AGPAT3 shows significant esterification of lysophosphatidylinositol (LPI) in the presence of C20:4 fatty acid, whereas AGPAT5 demonstrates significant acyltransferase activity toward lysophosphatidylethanolamine (LPE) in the presence of C18:1 fatty acid. The AGPAT3 mRNA is ubiquitously expressed in human tissues with several-fold differences in the expression pattern compared with the closely related AGPAT4. In summary, we show that in the presence of different fatty acids, AGPAT3 and AGPAT5 prefer different lysophospholipids as acyl acceptors. More importantly, localization of overexpressed AGPAT5 (this study) as well as GPAT1 and 2 (previous studies) in mitochondria supports the idea that the mitochondria might be capable of synthesizing some of their own glycerophospholipids. << Less

  J. Lipid Res. 52:451-462(2011) [PubMed] [EuropePMC]

  This publication is cited by 21 other entries.

• Lysophospholipid acyltransferases and arachidonate recycling in human neutrophils.

  Gijon M.A., Riekhof W.R., Zarini S., Murphy R.C., Voelker D.R.

  The cycle of deacylation and reacylation of phospholipids plays a critical role in regulating availability of arachidonic acid for eicosanoid production. The major yeast lysophospholipid acyltransferase, Ale1p, is related to mammalian membrane-bound O-acyltransferase (MBOAT) proteins. We expressed ... >> More

  The cycle of deacylation and reacylation of phospholipids plays a critical role in regulating availability of arachidonic acid for eicosanoid production. The major yeast lysophospholipid acyltransferase, Ale1p, is related to mammalian membrane-bound O-acyltransferase (MBOAT) proteins. We expressed four human MBOATs in yeast strains lacking Ale1p and studied their acyl-CoA and lysophospholipid specificities using novel mass spectrometry-based enzyme assays. MBOAT1 is a lysophosphatidylserine (lyso-PS) acyltransferase with preference for oleoyl-CoA. MBOAT2 also prefers oleoyl-CoA, using lysophosphatidic acid and lysophosphatidylethanolamine as acyl acceptors. MBOAT5 prefers lysophosphatidylcholine and lyso-PS to incorporate linoleoyl and arachidonoyl chains. MBOAT7 is a lysophosphatidylinositol acyltransferase with remarkable specificity for arachidonoyl-CoA. MBOAT5 and MBOAT7 are particularly susceptible to inhibition by thimerosal. Human neutrophils express mRNA for these four enzymes, and neutrophil microsomes incorporate arachidonoyl chains into phosphatidylinositol, phosphatidylcholine, PS, and phosphatidylethanolamine in a thimerosal-sensitive manner. These results strongly implicate MBOAT5 and MBOAT7 in arachidonate recycling, thus regulating free arachidonic acid levels and leukotriene synthesis in neutrophils. << Less

  J. Biol. Chem. 283:30235-30245(2008) [PubMed] [EuropePMC]

  This publication is cited by 26 other entries.

• Discovery of a lysophospholipid acyltransferase family essential for membrane asymmetry and diversity.

  Hishikawa D., Shindou H., Kobayashi S., Nakanishi H., Taguchi R., Shimizu T.

  All organisms consist of cells that are enclosed by a cell membrane containing bipolar lipids and proteins. Glycerophospholipids are important not only as structural and functional components of cellular membrane but also as precursors of various lipid mediators. Polyunsaturated fatty acids compri ... >> More

  All organisms consist of cells that are enclosed by a cell membrane containing bipolar lipids and proteins. Glycerophospholipids are important not only as structural and functional components of cellular membrane but also as precursors of various lipid mediators. Polyunsaturated fatty acids comprising arachidonic acid or eicosapentaenoic acid are located at sn-2 position, but not at sn-1 position of glycerophospholipids in an asymmetrical manner. In addition to the asymmetry, the membrane diversity is important for membrane fluidity and curvature. To explain the asymmetrical distribution of fatty acids, the rapid turnover of sn-2 position was proposed in 1958 by Lands [Lands WE (1958) Metabolism of glycerolipides: A comparison of lecithin and triglyceride synthesis. J Biol Chem 231:883-888]. However, the molecular mechanisms and biological significance of the asymmetry remained unknown. Here, we describe a putative enzyme superfamily consisting mainly of three gene families, which catalyzes the transfer of acyl-CoAs to lysophospholipids to produce different classes of phospholipids. Among them, we characterized three important enzymes with different substrate specificities and tissue distributions; one, termed lysophosphatidylcholine acyltransferase-3 (a mammalian homologue of Drosophila nessy critical for embryogenesis), prefers arachidonoyl-CoA, and the other two enzymes incorporate oleoyl-CoAs to lysophosphatidylethanolamine and lysophosphatidylserine. Thus, we propose that the membrane diversity is produced by the concerted and overlapped reactions with multiple enzymes that recognize both the polar head group of glycerophospholipids and various acyl-CoAs. Our findings constitute a critical milestone for our understanding about how membrane diversity and asymmetry are established and their biological significance. << Less

  Proc. Natl. Acad. Sci. U.S.A. 105:2830-2835(2008) [PubMed] [EuropePMC]

  This publication is cited by 23 other entries.