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.

• A novel lysophosphatidic acid acyltransferase enzyme (LPAAT4) with a possible role for incorporating docosahexaenoic acid into brain glycerophospholipids.

  Eto M., Shindou H., Shimizu T.

  Glycerophospholipids are important components of cellular membranes, required for constructing structural barriers, and for providing precursors of bioactive lipid mediators. Lysophosphatidic acid acyltransferases (LPAATs) are enzymes known to function in the de novo glycerophospholipid biosynthet ... >> More

  Glycerophospholipids are important components of cellular membranes, required for constructing structural barriers, and for providing precursors of bioactive lipid mediators. Lysophosphatidic acid acyltransferases (LPAATs) are enzymes known to function in the de novo glycerophospholipid biosynthetic pathway (Kennedy pathway), using lysophosphatidic acid (LPA) and acyl-CoA to form phosphatidic acid (PA). Until now, three LPAATs (LPAAT1, 2, and 3) have been reported from the 1-acyl-glycerol-3-phosphate O-acyltransferase (AGPAT) family. In this study, we identified a fourth LPAAT enzyme, LPAAT4, previously known as an uncharacterized enzyme AGPAT4 (LPAATδ), from the AGPAT family. Although LPAAT4 was known to contain AGPAT motifs essential for acyltransferase activities, detailed biochemical properties were unknown. Here, we found that mouse LPAAT4 (mLPAAT4) possesses LPAAT activity with high acyl-CoA specificity for polyunsaturated fatty acyl-CoA, especially docosahexaenoyl-CoA (22:6-CoA, DHA-CoA). mLPAAT4 was distributed in many tissues, with relatively high expression in the brain, rich in docosahexaenoic acid (DHA, 22:6). mLPAAT4 siRNA in a neuronal cell line, Neuro 2A, caused a decrease in LPAAT activity with 22:6-CoA, suggesting that mLPAAT4 functions endogenously. siRNA in Neuro 2A cells caused a decrease in 18:0-22:6 PC, whereas mLPAAT4 overexpression in Chinese hamster ovary (CHO)-K1 cells caused an increase in this species. Although DHA is considered to have many important functions for the brain, the mechanism of its incorporation into glycerophospholipids is unknown. LPAAT4 might have a significant role for maintaining DHA in neural membranes. Identification of LPAAT4 will possibly contribute to understanding the regulation and the biological roles of DHA-containing glycerophospholipids in the brain. << Less

  Biochem. Biophys. Res. Commun. 443:718-724(2014) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Characterization of mouse lysophosphatidic acid acyltransferase 3: an enzyme with dual functions in the testis.

  Yuki K., Shindou H., Hishikawa D., Shimizu T.

  Glycerophospholipids are structural and functional components of cellular membranes as well as precursors of various lipid mediators. Using acyl-CoAs as donors, glycerophospholipids are formed by the de novo pathway (Kennedy pathway) and modified in the remodeling pathway (Lands' cycle). Various a ... >> More

  Glycerophospholipids are structural and functional components of cellular membranes as well as precursors of various lipid mediators. Using acyl-CoAs as donors, glycerophospholipids are formed by the de novo pathway (Kennedy pathway) and modified in the remodeling pathway (Lands' cycle). Various acyltransferases, including two lysophosphatidic acid acyltransferases (LPAATs), have been discovered from a 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) family. Proteins of this family contain putative acyltransferase motifs, but their biochemical properties and physiological roles are not completely understood. Here, we demonstrated that mouse LPAAT3, previously known as mouse AGPAT3, possesses strong LPAAT activity and modest lysophosphatidylinositol acyltransferase activity with a clear preference for arachidonoyl-CoA as a donor. This enzyme is highly expressed in the testis, where CDP-diacylglycerol synthase 1 preferring 1-stearoyl-2-arachidonoyl-phosphatidic acid as a substrate is also highly expressed. Since 1-stearoyl-2-arachidonoyl species are the main components of phosphatidylinositol, mouse LPAAT3 may function in both the de novo and remodeling pathways and contribute to effective biogenesis of 1-stearoyl-2-arachidonoyl-phosphatidylinositol in the testis. Additionally, the expression of this enzyme in the testis increases significantly in an age-dependent manner, and beta-estradiol may be an important regulator of this enzyme's induction. Our findings identify this acyltransferase as an alternative important enzyme to produce phosphatidylinositol in the testis. << Less

  J. Lipid Res. 50:860-869(2009) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.