Publications

• Adiponutrin functions as a nutritionally regulated lysophosphatidic acid acyltransferase.

  Kumari M., Schoiswohl G., Chitraju C., Paar M., Cornaciu I., Rangrez A.Y., Wongsiriroj N., Nagy H.M., Ivanova P.T., Scott S.A., Knittelfelder O., Rechberger G.N., Birner-Gruenberger R., Eder S., Brown H.A., Haemmerle G., Oberer M., Lass A., Kershaw E.E., Zimmermann R., Zechner R.

  Numerous studies in humans link a nonsynonymous genetic polymorphism (I148M) in adiponutrin (ADPN) to various forms of fatty liver disease and liver cirrhosis. Despite its high clinical relevance, the molecular function of ADPN and the mechanism by which I148M variant affects hepatic metabolism ar ... >> More

  Numerous studies in humans link a nonsynonymous genetic polymorphism (I148M) in adiponutrin (ADPN) to various forms of fatty liver disease and liver cirrhosis. Despite its high clinical relevance, the molecular function of ADPN and the mechanism by which I148M variant affects hepatic metabolism are unclear. Here we show that ADPN promotes cellular lipid synthesis by converting lysophosphatidic acid (LPA) into phosphatidic acid. The ADPN-catalyzed LPA acyltransferase (LPAAT) reaction is specific for LPA and long-chain acyl-CoAs. Wild-type mice receiving a high-sucrose diet exhibit substantial upregulation of Adpn in the liver and a concomitant increase in LPAAT activity. In Adpn-deficient mice, this diet-induced increase in hepatic LPAAT activity is reduced. Notably, the I148M variant of human ADPN exhibits increased LPAAT activity leading to increased cellular lipid accumulation. This gain of function provides a plausible biochemical mechanism for the development of liver steatosis in subjects carrying the I148M variant. << Less

  Cell Metab. 15:691-702(2012) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Human 1-acylglycerol-3-phosphate O-acyltransferase isoforms 1 and 2: biochemical characterization and inability to rescue hepatic steatosis in Agpat2(-/-) gene lipodystrophic mice.

  Agarwal A.K., Sukumaran S., Cortes V.A., Tunison K., Mizrachi D., Sankella S., Gerard R.D., Horton J.D., Garg A.

  Loss-of-function mutations in 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) 2 in humans and mice result in loss of both the white and brown adipose tissues from birth. AGPAT2 generates precursors for the synthesis of glycerophospholipids and triacylglycerols. Loss of adipose tissue, or lipo ... >> More

  Loss-of-function mutations in 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) 2 in humans and mice result in loss of both the white and brown adipose tissues from birth. AGPAT2 generates precursors for the synthesis of glycerophospholipids and triacylglycerols. Loss of adipose tissue, or lipodystrophy, results in hyperinsulinemia, diabetes mellitus, and severe hepatic steatosis. Here, we analyzed biochemical properties of human AGPAT2 and its close homolog, AGPAT1, and we studied their role in liver by transducing their expression via recombinant adenoviruses in Agpat2(-/-) mice. The in vitro substrate specificities of AGPAT1 and AGPAT2 are quite similar for lysophosphatidic acid and acyl-CoA. Protein homology modeling of both the AGPATs with glycerol-3-phosphate acyltransferase 1 (GPAT1) revealed that they have similar tertiary protein structure, which is consistent with their similar substrate specificities. When co-expressed, both isoforms co-localize to the endoplasmic reticulum. Despite such similarities, restoring AGPAT activity in liver by overexpression of either AGPAT1 or AGPAT2 in Agpat2(-/-) mice failed to ameliorate the hepatic steatosis. From these studies, we suggest that the role of AGPAT1 or AGPAT2 in liver lipogenesis is minimal and that accumulation of liver fat is primarily a consequence of insulin resistance and loss of adipose tissue in Agpat2(-/-) mice. << Less

  J. Biol. Chem. 286:37676-37691(2011) [PubMed] [EuropePMC]

  This publication is cited by 12 other entries.

• Functional characterization of human 1-acylglycerol-3-phosphate acyltransferase isoform 8: cloning, tissue distribution, gene structure, and enzymatic activity.

  Agarwal A.K., Barnes R.I., Garg A.

  Glycerophospholipids and triglycerides are synthesized de novo by cells through an evolutionary conserved process involving serial acylations of phosphorylated glycerol. Various isoforms of the enzyme, 1-acylglycerol-3-phosphate acyltransferase (AGPAT), acylate lysophosphatidic acid at the sn-2 po ... >> More

  Glycerophospholipids and triglycerides are synthesized de novo by cells through an evolutionary conserved process involving serial acylations of phosphorylated glycerol. Various isoforms of the enzyme, 1-acylglycerol-3-phosphate acyltransferase (AGPAT), acylate lysophosphatidic acid at the sn-2 position to produce phosphatidic acid. We cloned a cDNA predicted to be AGPAT isoform and designated it AGPAT8. Human and mouse AGPAT8 proteins are 89% homologous, and their gene structure is also highly conserved. AGPAT8 is most closely related to AGPAT5, and its cDNA is expressed most in the heart, while AGPAT5 is expressed more in the prostate and testis. In cell lysates, AGPAT8 shows moderate acyltransferase activity with [(3)H]oleoyl-CoA but lacks acyl-CoA:lysocardiolipin acyltransferase activity. In whole cells upon incubation with [(14)C]linoleic acid, most of the radioactivity was recovered in phosphatidyl ethanolamine, phosphatidyl choline and phosphatidic acid fraction. Of the two well conserved acyltransferase motifs, NHX(4)D is present in AGPAT8, whereas arginine in the EGTR motif is substituted by aspartate. However, mutation of EGTD to EGTR did not increase enzymatic activity significantly. Based on the X-ray crystallographic structure of a related acyltransferase, squash gpat, a model is proposed in which a hydrophobic pocket in AGPAT8 accommodates fatty acyl chains of both substrates in an orientation where the NHX(4)D motif participates in catalysis. << Less

  Arch. Biochem. Biophys. 449:64-76(2006) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.

• Functional characterization of the human 1-acylglycerol-3-phosphate-O-acyltransferase isoform 10/glycerol-3-phosphate acyltransferase isoform 3.

  Sukumaran S., Barnes R.I., Garg A., Agarwal A.K.

  Synthesis of phospholipids can occur de novo or via remodeling of the existing phospholipids. Synthesis of triglycerides, a form of energy storage in cells, is an end product of these pathways. Several 1-acylglycerol-3-phosphate-O-acyltransferases (AGPATs) acylate lysophosphatidic acid (LPA) at th ... >> More

  Synthesis of phospholipids can occur de novo or via remodeling of the existing phospholipids. Synthesis of triglycerides, a form of energy storage in cells, is an end product of these pathways. Several 1-acylglycerol-3-phosphate-O-acyltransferases (AGPATs) acylate lysophosphatidic acid (LPA) at the sn-2 (carbon 2) position to produce phosphatidic acid (PA). These enzymes are involved in phospholipids and triglyceride synthesis through an evolutionary conserved process involving serial acylations of glycerol-3-phosphate. We cloned a cDNA predicted to be an AGPAT isoform (AGPAT10). This cDNA has been recently identified as glycerol-3-phosphate-O-acyltransferase isoform 3 (GPAT3). When this AGPAT10/GPAT3 cDNA was expressed in Chinese Hamster ovary cells, the protein product localizes to the endoplasmic reticulum. In vitro enzymatic activity using lysates of human embryonic kidney-293 cells infected with recombinant AGPAT10/GPAT3 adenovirus show that the protein has a robust AGPAT activity with an apparent V(max) of 2 nmol/min per mg protein, but lacks GPAT enzymatic activity. This AGPAT has similar substrate specificities for LPA and acyl-CoA as shown for another known isoform, AGPAT2. We further show that when overexpressed in human Huh-7 cells depleted of endogenous AGPAT activity by sh-RNA-AGPAT2-lentivirus, the protein again demonstrates AGPAT activity. These observations strongly suggest that the cDNA previously identified as GPAT3 has AGPAT activity and thus we prefer to identify this clone as AGPAT10 as well. << Less

  J. Mol. Endocrinol. 42:469-478(2009) [PubMed] [EuropePMC]

  This publication is cited by 11 other entries.

• Enzymatic activity of the human 1-acylglycerol-3-phosphate-O-acyltransferase isoform 11: upregulated in breast and cervical cancers.

  Agarwal A.K., Garg A.

  The conversion of lysophosphatidic acid (LPA) to phosphatidic acid is carried out by the microsomal enzymes 1-acylglycerol-3-phosphate-O-acyltransferases (AGPATs). These enzymes are specific for acylating LPA at the sn-2 (carbon 2) position on the glycerol backbone and are important, because they ... >> More

  The conversion of lysophosphatidic acid (LPA) to phosphatidic acid is carried out by the microsomal enzymes 1-acylglycerol-3-phosphate-O-acyltransferases (AGPATs). These enzymes are specific for acylating LPA at the sn-2 (carbon 2) position on the glycerol backbone and are important, because they provide substrates for the synthesis of phospholipids and triglycerides. At least, mutations in one isoform, AGPAT2, cause near complete loss of adipose tissue in humans. We cloned a cDNA predicted to be an AGPAT isoform, AGPAT11. This cDNA has been recently identified also as lysophosphatidylcholine acyltransferase 2 (LPCAT2) and lyso platelet-activating factor acetyltransferase. When AGPAT11/LPCAT2/lyso platelet-activating factor acetyltransferase cDNA was expressed in CHO and HeLa cells, the protein product localized to the endoplasmic reticulum. In vitro enzymatic activity using lysates of Human Embryonic Kidney-293 cells infected with recombinant AGPAT11/LPCAT2/lyso platelet-activating factor-acetyltransferase cDNA adenovirus show that the protein has an AGPAT activity but lacks glycerol-3-phosphate acyltransferase enzymatic activity. The AGPAT11 efficiently uses C18:1 LPA as acyl acceptor and C18:1 fatty acid as an acyl donor. Thus, it has similar substrate specificities for LPA and acyl-CoA as shown for AGPAT9 and 10. Expression of AGPAT11 mRNA was significantly upregulated in human breast, cervical, and colorectal cancer tissues, indicating its adjuvant role in the progression of these cancers. Our enzymatic assays strongly suggest that the cDNA previously identified as LPCAT2/lyso platelet-activating factor-acetyltransferase cDNA has AGPAT activity and thus we prefer to identify this clone as AGPAT11 as well. << Less

  J. Lipid Res. 51:2143-2152(2010) [PubMed] [EuropePMC]

  This publication is cited by 10 other entries.

• CGI-58/ABHD5 is a coenzyme A-dependent lysophosphatidic acid acyltransferase.

  Montero-Moran G., Caviglia J.M., McMahon D., Rothenberg A., Subramanian V., Xu Z., Lara-Gonzalez S., Storch J., Carman G.M., Brasaemle D.L.

  Mutations in human CGI-58/ABHD5 cause Chanarin-Dorfman syndrome (CDS), characterized by excessive storage of triacylglycerol in tissues. CGI-58 is an alpha/beta-hydrolase fold enzyme expressed in all vertebrates. The carboxyl terminus includes a highly conserved consensus sequence (HXXXXD) for acy ... >> More

  Mutations in human CGI-58/ABHD5 cause Chanarin-Dorfman syndrome (CDS), characterized by excessive storage of triacylglycerol in tissues. CGI-58 is an alpha/beta-hydrolase fold enzyme expressed in all vertebrates. The carboxyl terminus includes a highly conserved consensus sequence (HXXXXD) for acyltransferase activity. Mouse CGI-58 was expressed in Escherichia coli as a fusion protein with two amino terminal 6-histidine tags. Recombinant CGI-58 displayed acyl-CoA-dependent acyltransferase activity to lysophosphatidic acid, but not to other lysophospholipid or neutral glycerolipid acceptors. Production of phosphatidic acid increased with time and increasing concentrations of recombinant CGI-58 and was optimal between pH 7.0 and 8.5. The enzyme showed saturation kinetics with respect to 1-oleoyl-lysophosphatidic acid and oleoyl-CoA and preference for arachidonoyl-CoA and oleoyl-CoA. The enzyme showed slight preference for 1-oleoyl lysophosphatidic acid over 1-palmitoyl, 1-stearoyl, or 1-arachidonoyl lysophosphatidic acid. Recombinant CGI-58 showed intrinsic fluorescence for tryptophan that was quenched by the addition of 1-oleoyl-lysophosphatidic acid, oleoyl-CoA, arachidonoyl-CoA, and palmitoyl-CoA, but not by lysophosphatidyl choline. Expression of CGI-58 in fibroblasts from humans with CDS increased the incorporation of radiolabeled fatty acids released from the lipolysis of stored triacylglycerols into phospholipids. CGI-58 is a CoA-dependent lysophosphatidic acid acyltransferase that channels fatty acids released from the hydrolysis of stored triacylglycerols into phospholipids. << Less

  J. Lipid Res. 51:709-719(2010) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.

• Characterization of a human lysophosphatidic acid acyltransferase that is encoded by a gene located in the class III region of the human major histocompatibility complex.

  Aguado B., Campbell R.D.

  Sequence analysis of cDNA clones corresponding to a number of genes located in the class III region of the human major histocompatibility complex (MHC), in the chromosome band 6p21.3, has shown that the G15 gene encodes a 283-amino acid polypeptide with significant homology over the entire polypep ... >> More

  Sequence analysis of cDNA clones corresponding to a number of genes located in the class III region of the human major histocompatibility complex (MHC), in the chromosome band 6p21.3, has shown that the G15 gene encodes a 283-amino acid polypeptide with significant homology over the entire polypeptide with the enzyme lysophosphatidic acid acyltransferase (LPAAT) from different yeast, plant, and bacterial species. The amino acid sequence of the MHC-encoded human LPAAT (hLPAATalpha) is 48% identical to the recently described hLPAAT (Eberhardt, C., Gray, P. W., and Tjoelker, L. W. (1997) J. Biol. Chem. 272, 20299-20305), which is encoded by a gene located on chromosome 9p34.3. LPAAT is the enzyme that in lipid metabolism converts lysophosphatidic acid (LPA) into phosphatidic acid (PA). The expression of the hLPAATalpha polypeptide in the baculovirus system and in mammalian cells has shown that it is an intracellular protein that contains LPAAT activity. Cell extracts from insect cells overexpressing hLPAATalpha were analyzed in different LPAAT enzymatic assays using, as substrates, different acyl acceptors and acyl donors. These cell extracts were found to contain up to 5-fold more LPAAT activity compared with control cell extracts, indicating that the hLPAATalpha specifically converts LPA into PA, incorporating different acyl-CoAs with different affinities. The hLPAATalpha polypeptide expressed in the mammalian Chinese hamster ovary cell line was found, by confocal immunofluorescence, to be localized in the endoplasmic reticulum. Due to the known role of LPA and PA in intracellular signaling and inflammation, the hLPAATalpha gene represents a candidate gene for some MHC-associated diseases. << Less

  J. Biol. Chem. 273:4096-4105(1998) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.