ABSTRACT: 1. The presence of palmitoyl-CoA-l-glycerol 1-phosphate palmitoyltransferase (EC2.3.1.15) has been demonstrated in a particulate fraction of baker's yeast. 2. The enzyme has been characterized, and its activity studied as a function of pH and concentration of substrates. 3. Inhibition by thiol poisons and protection by acyl-CoA have been used to obtain information on the active site. 4. By various methods of supplying acyl radicals, the species ;palmitoyl-CoA' has been shown to be the true acyl donor to the transferase.
Project description:au10-12_pa - phosphatidic acid in gene expression - Role of DGK in gene expression - Compounds were added 4h before cell harvesting. 6 dye-swap - treated vs untreated comparison
Project description:au10-12_pa - phosphatidic acid in gene expression - Role of DGK in gene expression - Compounds were added 4h before cell harvesting.
Project description:Phosphatidic acid (PA) is a potent lipid secondary messenger, the synthesis of which is tightly regulated in both space and time. Established tools for detecting PA involve ex vivo analysis and do not provide information on the subcellular locations where this lipid is synthesized. Here, a chemoenzymatic strategy for imaging sites of cellular PA synthesis by phospholipase D (PLD) enzymes is reported. PLDs were found to be able to catalyze phospholipid head-group exchange with alkynols to generate alkyne-labeled PA analogues within cells. Subsequent fluorophore tagging through Cu-catalyzed azide-alkyne cycloaddition enabled both visualization by fluorescence microscopy and quantification by HPLC. Our studies revealed several intracellular sites of PLD-mediated PA synthesis. We envision applications of this approach to dissect PA-dependent signaling pathways, image PLD activity in disease, and remodel intracellular membranes with new functionality.
Project description:Phosphatidic acid (PA) is an important signaling lipid that plays roles in a range of biological processes including both physiological and pathophysiological events. PA is one of a number of signaling lipids that can act as site-specific ligands for protein receptors in binding events that enforce membrane association and generally regulate both receptor function and subcellular localization. However, elucidation of the full scope of PA activities has proven problematic, primarily due to the lack of a consensus sequence among PA-binding receptors. Thus, experimental approaches, such as those employing lipid probes, are necessary for characterizing interactions at the molecular level. Herein, we describe an efficient modular approach to the synthesis of a range of PA probes that employs a late stage introduction of reporter groups. This strategy was exploited in the synthesis of PA probes bearing fluorescent and photoaffinity tags as well as a bifunctional probe containing both a photoaffinity moiety and an azide as a secondary handle for purification purposes. To discern the ability of these PA analogs to mimic the natural lipid in protein-binding properties, each compound was incorporated into vesicles for binding studies using a known PA receptor, the C2 domain of PKCalpha. In these studies, each compound exhibited binding properties that were comparable to those of synthetic PA, indicating their viability as probes for effectively studying the activities of PA in cellular processes.
Project description:Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to generate phosphatidic acid (PA). Mammalian DGK consists of ten isozymes (?-?) and governs a wide range of physiological and pathological events, including immune responses, neuronal networking, bipolar disorder, obsessive-compulsive disorder, fragile X syndrome, cancer, and type 2 diabetes. DG and PA comprise diverse molecular species that have different acyl chains at the sn-1 and sn-2 positions. Because the DGK activity is essential for phosphatidylinositol turnover, which exclusively produces 1-stearoyl-2-arachidonoyl-DG, it has been generally thought that all DGK isozymes utilize the DG species derived from the turnover. However, it was recently revealed that DGK isozymes, except for DGK?, phosphorylate diverse DG species, which are not derived from phosphatidylinositol turnover. In addition, various PA-binding proteins (PABPs), which have different selectivities for PA species, were recently found. These results suggest that DGK-PA-PABP axes can potentially construct a large and complex signaling network and play physiologically and pathologically important roles in addition to DGK-dependent attenuation of DG-DG-binding protein axes. For example, 1-stearoyl-2-docosahexaenoyl-PA produced by DGK? interacts with and activates Praja-1, the E3 ubiquitin ligase acting on the serotonin transporter, which is a target of drugs for obsessive-compulsive and major depressive disorders, in the brain. This article reviews recent research progress on PA species produced by DGK isozymes, the selective binding of PABPs to PA species and a phosphatidylinositol turnover-independent DG supply pathway.
Project description:The lipin phosphatidic acid phosphatase (PAP) enzymes are required for triacylglycerol (TAG) synthesis from glycerol 3-phosphate in most mammalian tissues. The 3 lipin proteins (lipin 1, lipin 2, and lipin 3) each have PAP activity, but have distinct tissue distributions, with lipin 1 being the predominant PAP enzyme in many metabolic tissues. One exception is the small intestine, which is unique in expressing exclusively lipin 2 and lipin 3. TAG synthesis in small intestinal enterocytes utilizes 2-monoacylglycerol and does not require the PAP reaction, making the role of lipin proteins in enterocytes unclear. Enterocyte TAGs are stored transiently as cytosolic lipid droplets or incorporated into lipoproteins (chylomicrons) for secretion. We determined that lipin enzymes are critical for chylomicron biogenesis, through regulation of membrane phospholipid composition and association of apolipoprotein B48 with nascent chylomicron particles. Lipin 2/3 deficiency caused phosphatidic acid accumulation and mammalian target of rapamycin complex 1 (mTORC1) activation, which were associated with enhanced protein levels of a key phospholipid biosynthetic enzyme (CTP:phosphocholine cytidylyltransferase α) and altered membrane phospholipid composition. Impaired chylomicron synthesis in lipin 2/3 deficiency could be rescued by normalizing phospholipid synthesis levels. These data implicate lipin 2/3 as a control point for enterocyte phospholipid homeostasis and chylomicron biogenesis.
Project description:mTOR, the mammalian target of rapamycin, integrates growth factor and nutrient signals to promote a transformation from catabolic to anabolic metabolism, cell growth, and cell cycle progression. Phosphatidic acid (PA) interacts with the FK506-binding protein-12-rapamycin-binding (FRB) domain of mTOR, which stabilizes both mTOR complexes: mTORC1 and mTORC2. We report here that mTORC1 and mTORC2 are activated in response to exogenously supplied fatty acids via the de novo synthesis of PA, a central metabolite for membrane phospholipid biosynthesis. We examined the impact of exogenously supplied fatty acids on mTOR in KRas-driven cancer cells, which are programmed to utilize exogenous lipids. The induction of mTOR by oleic acid was dependent upon the enzymes responsible for de novo synthesis of PA. Suppression of the de novo synthesis of PA resulted in G1 cell cycle arrest. Although it has long been appreciated that mTOR is a sensor of amino acids and glucose, this study reveals that mTOR also senses the presence of lipids via production of PA.
Project description:Squamous cell carcinomas (SCC) constitute a group of human malignancies that originate from the squamous epithelium. Most SCC patients experience treatment failure and relapse and have a poor prognosis due to de novo and acquired resistance to first-line chemotherapeutic agents. To identify chemoresistance mechanisms and explore novel targets for chemosensitization, we performed whole-transcriptome sequencing of paired resistant and parental SCC cells. We identified DLGAP1 antisense RNA 2 (D-AS2) as a crucial noncoding RNA that contributes to chemoresistance in SCC. Mechanistically, D-AS2 affected chromatin accessibility around the histone mark H3K27ac of FAM3 metabolism regulating signaling molecule D (FAM3D), reducing FAM3D mRNA transcription and extracellular protein secretion. FAM3D interacted with the Gαi-coupled G protein-coupled receptors (GPCRs) formyl peptide receptor 1 (FPR1) and FPR2 to suppress phospholipase D (PLD) activity, and reduced FAM3D increased PLD signaling. Moreover, activated PLD promoted phosphatidic acid (PA) production and subsequent nuclear translocation of yes-associated protein (YAP). Accordingly, in vivo administration of a D-AS2-targeting antisense oligonucleotide sensitized SCC to cisplatin treatment. In summary, this study shows that D-AS2/FAM3D-mediated PLD/PA lipid signaling is essential for SCC chemoresistance, suggesting D-AS2 can be targeted to sensitize SCC to cytotoxic chemotherapeutic agents.
Project description:Squamous cell carcinomas (SCC) constitute a group of human malignancies that originate from the squamous epithelium. Most SCC patients experience treatment failure and relapse and have a poor prognosis due to de novo and acquired resistance to first-line chemotherapeutic agents. To identify chemoresistance mechanisms and explore novel targets for chemosensitization, we performed whole-transcriptome sequencing of paired resistant and parental SCC cells. We identified DLGAP1 antisense RNA 2 (D-AS2) as a crucial noncoding RNA that contributes to chemoresistance in SCC. Mechanistically, D-AS2 affected chromatin accessibility around the histone mark H3K27ac of FAM3 metabolism regulating signaling molecule D (FAM3D), reducing FAM3D mRNA transcription and extracellular protein secretion. FAM3D interacted with the Gαi-coupled G protein-coupled receptors (GPCRs) formyl peptide receptor 1 (FPR1) and FPR2 to suppress phospholipase D (PLD) activity, and reduced FAM3D increased PLD signaling. Moreover, activated PLD promoted phosphatidic acid (PA) production and subsequent nuclear translocation of yes-associated protein (YAP). Accordingly, in vivo administration of a D-AS2-targeting antisense oligonucleotide sensitized SCC to cisplatin treatment. In summary, this study shows that D-AS2/FAM3D-mediated PLD/PA lipid signaling is essential for SCC chemoresistance, suggesting D-AS2 can be targeted to sensitize SCC to cytotoxic chemotherapeutic agents.