Javier Casas

The Drosophila chorion factor 1/ultraspiracle (CF1/USP) transcription factor, a homologue of the retinoid X receptor, is a developmentally important member of the family of nuclear (steroid) hormone receptors. Using newly developed monoclonal antibodies and a full-length bacterially produced protein, we have studied in detail the in vitro DNA-binding properties of this factor and aspects of its distribution in vivo. During oogenesis, CF1/USP is present both in germline cells and in the somatic follicular epithelium. We have determined the optimal binding site of partially purified bacterially produced CF1/USP by an in vitro selection procedure and also have characterized its binding to the follicular-specific chorion s15 promoter. In vitro this bacterially produced factor is unusual in binding to a single element ("half-site"); simultaneous but noncoordinate binding to a second half-site is possible if these repeated elements are organized in direct orientation and spaced adequately. However, the factor interacts synergistically with several other nuclear hormone receptors: notably, it can form in vitro heteromers with mammalian thyroid and retinoic acid receptors, binding to two half-sites that are organized in either direct or inverted orientation. In vivo the factor most probably functions as a heterodimer, but its partner(s) remains to be determined.

Lipid droplets (LD) are organelles present in all cell types, consisting of a hydrophobic core of triacylglycerols and cholesteryl esters, surrounded by a monolayer of phospholipids and cholesterol. This work shows that LD biogenesis induced by serum, by long-chain fatty acids, or the combination of both in CHO-K1 cells was prevented by phospholipase A(2) inhibitors with a pharmacological profile consistent with the implication of group IVA cytosolic phospholipase A(2) (cPLA(2)alpha). Knocking down cPLA(2)alpha expression with short interfering RNA was similar to pharmacological inhibition in terms of enzyme activity and LD biogenesis. A Chinese hamster ovary cell clone stably expressing an enhanced green fluorescent protein-cPLA(2)alpha fusion protein (EGFP-cPLA(2)) displayed higher LD occurrence under basal conditions and upon LD induction. Induction of LD took place with concurrent phosphorylation of cPLA(2)alpha at Ser(505). Transfection of a S505A mutant cPLA(2)alpha showed that phosphorylation at Ser(505) is key for enzyme activity and LD formation. cPLA(2)alpha contribution to LD biogenesis was not because of the generation of arachidonic acid, nor was it related to neutral lipid synthesis. cPLA(2)alpha inhibition in cells induced to form LD resulted in the appearance of tubulo-vesicular profiles of the smooth endoplasmic reticulum, compatible with a role of cPLA(2)alpha in the formation of nascent LD from the endoplasmic reticulum.

This work investigates the metabolic origin of triacylglycerol (TAG) formed during lipid droplet (LD) biogenesis induced by stress. Cytotoxic inhibitors of fatty acid synthase induced TAG synthesis and LD biogenesis in CHO-K1 cells, in the absence of external sources of fatty acids. TAG synthesis was required for LD biogenesis and was sensitive to inhibition and down-regulation of the expression of group VIA phospholipase A2 (iPLA2-VIA). Induction of stress with acidic pH, C2-ceramide, tunicamycin, or deprivation of glucose also stimulated TAG synthesis and LD formation in a manner dependent on iPLA2-VIA. Overexpression of the enzyme enhanced TAG synthesis from endogenous fatty acids and LD occurrence. During stress, LD biogenesis but not TAG synthesis required phosphorylation and activation of group IVA PLA2 (cPLA2α). The results demonstrate that iPLA2-VIA provides fatty acids for TAG synthesis while cPLA2α allows LD biogenesis. LD biogenesis during stress may be a survival strategy, recycling structural phospholipids into energy-generating substrates. This work investigates the metabolic origin of triacylglycerol (TAG) formed during lipid droplet (LD) biogenesis induced by stress. Cytotoxic inhibitors of fatty acid synthase induced TAG synthesis and LD biogenesis in CHO-K1 cells, in the absence of external sources of fatty acids. TAG synthesis was required for LD biogenesis and was sensitive to inhibition and down-regulation of the expression of group VIA phospholipase A2 (iPLA2-VIA). Induction of stress with acidic pH, C2-ceramide, tunicamycin, or deprivation of glucose also stimulated TAG synthesis and LD formation in a manner dependent on iPLA2-VIA. Overexpression of the enzyme enhanced TAG synthesis from endogenous fatty acids and LD occurrence. During stress, LD biogenesis but not TAG synthesis required phosphorylation and activation of group IVA PLA2 (cPLA2α). The results demonstrate that iPLA2-VIA provides fatty acids for TAG synthesis while cPLA2α allows LD biogenesis. LD biogenesis during stress may be a survival strategy, recycling structural phospholipids into energy-generating substrates. Intracellular lipid droplets (LDs) 5The abbreviations used are: LD, lipid droplets; AA, arachidonic acid; ADRP, adipophilin (adipose differentiation-related protein); BEL, bromoenol lactone; C2-ceramide, N-acetyl-d-sphingosine; CCT, CTP:phosphocholine cytidylyltransferase; DAG, diacylglycerol; EYFP, enhanced yellow fluorescent protein; FAS, fatty acid synthase; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFP, green fluorescent protein; PAP, phosphatidate phosphohydrolase; PBS, phosphate-buffered saline; PLA2, phospholipase A2; py-2, pyrrolidine-2; siRNA, short interfering RNA; TAG, triacylglycerol; CHO, Chinese hamster ovary; C1-BODIPY, 4,4-difluoro-5-methyl-4-bora-3a,4a-diaza-s-indacene-3-dodecanoic acid.5The abbreviations used are: LD, lipid droplets; AA, arachidonic acid; ADRP, adipophilin (adipose differentiation-related protein); BEL, bromoenol lactone; C2-ceramide, N-acetyl-d-sphingosine; CCT, CTP:phosphocholine cytidylyltransferase; DAG, diacylglycerol; EYFP, enhanced yellow fluorescent protein; FAS, fatty acid synthase; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFP, green fluorescent protein; PAP, phosphatidate phosphohydrolase; PBS, phosphate-buffered saline; PLA2, phospholipase A2; py-2, pyrrolidine-2; siRNA, short interfering RNA; TAG, triacylglycerol; CHO, Chinese hamster ovary; C1-BODIPY, 4,4-difluoro-5-methyl-4-bora-3a,4a-diaza-s-indacene-3-dodecanoic acid. are cytosolic inclusions present in most eukaryotic cells, containing a core of triacylglycerol (TAG) and cholesteryl esters, surrounded by a phospholipid monolayer and by specific proteins, among which the best characterized belong to the perilipin family (1Brasaemle D.L. J. Lipid Res. 2007; 48: 2547-2559Abstract Full Text Full Text PDF PubMed Scopus (758) Google Scholar, 2Martin S. Parton R.G. Nat. Rev. Mol. Cell. Biol. 2006; 7: 373-377Crossref PubMed Scopus (914) Google Scholar, 3Wolins N.E. Brasaemle D.L. Bickel P.E. FEBS Lett. 2006; 580: 5484-5491Crossref PubMed Scopus (316) Google Scholar). The biology of LD has received increasing interest, due to the link between excess lipid storage in certain tissues and pathologies such as obesity, diabetes, or atherosclerosis (3Wolins N.E. Brasaemle D.L. Bickel P.E. FEBS Lett. 2006; 580: 5484-5491Crossref PubMed Scopus (316) Google Scholar, 4Murphy D.J. Prog. Lipid Res. 2001; 40: 325-438Crossref PubMed Scopus (762) Google Scholar). LDs have been shown to interfere with membrane translocation of the insulin-sensitive glucose transporter, an observation that might account for insulin resistance in type 2 diabetes (5Boström P. Andersson L. Rutberg M. Perman J. Lidberg U. Johansson B.R. Fernandez-Rodriguez J. Ericson J. Nilsson T. Borén J. Olofsson S.O. Nat. Cell Biol. 2007; 9: 1286-1293Crossref PubMed Scopus (268) Google Scholar). The recent identification of 132 genes controlling LD number, size, and distribution in Drosophila (6Guo G. Walther T.C. Rao M. Stuurman N. Goshima G. Terayama K. Wong J.S. Vale R.D. Walter P. Farese R.V. Nature. 2008; 453: 657-661Crossref PubMed Scopus (548) Google Scholar) illustrates the complexity of this organelle, whose dynamic nature is far from being understood fully. LDs are formed in two very different environmental conditions and, presumably, the physiological significance in each case is different. First, cells accumulate LD in response to exogenous lipid availability (4Murphy D.J. Prog. Lipid Res. 2001; 40: 325-438Crossref PubMed Scopus (762) Google Scholar), present in serum lipoproteins or as free fatty acids. There is general agreement that LD content arising from the medium has a storing purpose for energy generation and membrane building. Using this experimental paradigm of exogenous lipid loading, we have shown the implication of group IVA PLA2 (cPLA2α) in LD biogenesis at a step beyond the synthesis of TAG (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). Second, many kinds of cellular stress, including inflammation, apoptosis induced by different insults or contact inhibition, also induce LD biogenesis. An account of this situation is the human T lymphoblastoid cell line (HuT 78) undergoing apoptosis triggered by Fas antibody (8Iorio E. Di Vito M. Spadaro F. Ramoni C. Lococo E. Carnevale R. Lenti L. Strom R. Podo F. Biochim. Biophys. Acta. 2003; 1634: 1-14Crossref PubMed Scopus (49) Google Scholar). In these cases, the metabolic origins of LD-associated neutral lipids and the physiological function they subserve are not known. Altering phospholipid metabolism has been shown to cause programmed cell death in some instances (9Ramos B. El-Mouedden M. Claro E. Jackowski S. Mol. Pharmacol. 2002; 62: 1068-1075Crossref PubMed Scopus (30) Google Scholar, 10Ramos B. Lahti J.M. Claro E. Jackowski S. Mol. Pharmacol. 2003; 64: 502-511Crossref PubMed Scopus (30) Google Scholar, 11Cui Z. Houweling M. Biochim. Biophys. Acta. 2002; 1585: 87-96Crossref PubMed Scopus (167) Google Scholar, 12Fuentes L. Pérez R. Nieto M.L. Balsinde J. Balboa M.A. J. Biol. Chem. 2003; 278: 44683-44690Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar), and, conversely, programmed cell death often alters phospholipid metabolism, resulting in the accumulation of lysophospholipids and fatty acids (13Balsinde J. Pérez R. Balboa M.A. Biochim. Biophys. Acta. 2006; 1761: 1344-1350Crossref PubMed Scopus (80) Google Scholar). Current evidence suggests that group VIA PLA2 (iPLA2-VIA) is involved in the generation of lysophosphatidylcholine during programmed cell death, which may mediate attraction and recognition/engulfment signals for apoptotic cell clearance by phagocytes (13Balsinde J. Pérez R. Balboa M.A. Biochim. Biophys. Acta. 2006; 1761: 1344-1350Crossref PubMed Scopus (80) Google Scholar, 14Balsinde J. Balboa M.A. Cell. Signal. 2005; 17: 1052-1062Crossref PubMed Scopus Google Scholar, D. X. N. J. 2002; PubMed Scopus Google Scholar, K. E. P. C. A. S. K. C. G. S. Cell. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, R. Balboa M.A. Balsinde J. J. 2006; PubMed Scopus Google Scholar). which a for arachidonic iPLA2-VIA has the fatty acid at the and implication in synthesis may be the enzyme has a phospholipid Balsinde J. Biochim. Biophys. Acta. PubMed Scopus Google Scholar). this in we that during cellular stress of the fatty acids by phospholipid be into TAG and in In results that TAG synthesis with the formation of LD during stress on iPLA2-VIA. we that the implication of cPLA2α in LD formation in this acid was from acid was from and was from and from and and from and cPLA2α from Cell from from from from and from tunicamycin, and from and 4,4-difluoro-5-methyl-4-bora-3a,4a-diaza-s-indacene-3-dodecanoic acid was from of human was in the the and This the expression of a fluorescent containing by enhanced yellow fluorescent cells as (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). the cells at a of in or and in medium for LD cells to medium for to conditions with of LD (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). cells with of from or the and on with phosphate-buffered with for and with with of PBS, to which of a of in was that the of and and in the in a with a the of LD by in cells was as (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). cells with during and with a with an in the cellular in the in in the different as the of each distribution of and as the of the which not LD (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). cells, in with of for with PBS, with with and with J. M.A. M. Balsinde J. Balboa M.A. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). in the was from the the of the containing and Cell with containing and also for to into the of cells, in with to or with or for with and with and as in each on and with of PBS, and lipids J. PubMed Scopus Google Scholar). the lipid the in of and which in acid and with of the was by with of TAG was by into the from to of the TAG was by of cells in with or and with lipid from by containing was into and lipid was with of 2 of and of in and the at with of of and of to and with containing and and of was by and to and in containing bovine serum and used short interfering human iPLA2-VIA and with the and for and for and and for at by to each of containing of the and of of medium containing was and the cells for to medium for to with was during these with the at in of the and cells and in a on an of a at and and was at a of cells was the cells in each for with and phospholipase was stimulated with and with or lipid by was acid acid and by with the of with phospholipase cells for with with cells with for and in a was with among different with of by the LD and TAG we that the inhibitors of fatty acid synthase and R. Nat. Rev. 2007; 7: PubMed Scopus Google Scholar) induce LD biogenesis in CHO-K1 the metabolic origin of TAG, we that stress induced by these in cells in the absence of serum a de synthesis of fatty acids is by the and is external of to sources of LD In these and cell and to fatty acids a The the of at which cell was as by a induced the biogenesis of LD and of the LD-associated adipophilin by that the of LD was that with the of LD biogenesis with FBS, which on the of serum lipoproteins (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar), LD by inhibitors in medium has to from endogenous LD by inhibitors with synthesis of TAG, we TAG content and shown in and with or induced but in TAG The in cells for with or with acid induced a in or and TAG synthesis from fatty acids. In LD with serum not synthesis of TAG from endogenous of TAG origin from fatty acids and that the was not into and of fatty acid synthesis LD biogenesis. or for with or LD was by In this in as the of the for each as the the which are in of and different from and induce TAG synthesis from fatty acids. cells for with or and lipids by and with and of DAG, of TAG of each in and cells for with or acid and with or for lipids by and in TAG was are of in and cells for with acid with or with for in TAG is shown in with that in phospholipids of TAG from the by present in and of and in as shown in which from or with that of a TAG at between and with acid different from different from Induction of LD and TAG during observation that LD biogenesis and TAG synthesis in the absence of fatty acid synthesis this in of cellular stress that not the inhibition of we the cells to kinds of which has been shown to induce LD C. Res. Google Scholar, P. C. C. 2001; PubMed Scopus Google Scholar), C2-ceramide, which cell death the inhibition of synthesis (9Ramos B. El-Mouedden M. Claro E. Jackowski S. Mol. Pharmacol. 2002; 62: 1068-1075Crossref PubMed Scopus (30) Google Scholar, 10Ramos B. Lahti J.M. Claro E. Jackowski S. Mol. Pharmacol. 2003; 64: 502-511Crossref PubMed Scopus (30) Google Scholar), tunicamycin, which and response A. M. M. Res. Google Scholar, D. Rev. 2006; PubMed Scopus Google Scholar) and M. M. Cell 2007; PubMed Scopus Google Scholar), and deprivation of a that apoptosis and T. K. T. 2003; PubMed Scopus Google Scholar, Z. S. U. S. A. 2005; PubMed Scopus Google Scholar, R. T. K. N. S. T. T. A. J. Biol. Chem. 2008; 283: Full Text Full Text PDF PubMed Scopus Google Scholar). shown in the induced LD and stimulated the synthesis of TAG, and was a between TAG synthesis and LD by the stress with stress in the of inhibitors not LD formation or TAG synthesis but results that LD biogenesis and TAG synthesis during cellular stress not fatty acid and in TAG and LD during the origin of TAG we the of and which acid and of these account for the of fatty acids into TAG, or the of phosphatidate we cells with or and in the of the phospholipase S. J. Pharmacol. Google Scholar) or J.M. Masgrau R. E. Picatoste F. J. 2001; Scopus Google Scholar), which with in a phospholipase of acid. not LD biogenesis or TAG synthesis and phospholipase acid while increasing and and VIA and IVA A2 and in TAG and LD of fatty acids by a might also account for TAG synthesis from fatty acids. that with or stimulated the of AA, in a manner that was sensitive to the at and to the at at the activation of cPLA2α and AA, was not into TAG In acid was not to the medium but was used for TAG synthesis in a manner that was by but not by This evidence suggests the of but not cPLA2α in fatty acids for TAG the LD biogenesis induced by or This with that LD biogenesis from exogenous lipid cPLA2α (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar) and LDs are induced by cellular stress. also LD formation induced by or by or by the expression of of also TAG synthesis and LD biogenesis induced by acidic pH, C2-ceramide, tunicamycin, or deprivation of glucose The family of two in VIA PLA2 (iPLA2-VIA) and PLA2 J. Balboa M.A. Cell. Signal. 2005; 17: 1052-1062Crossref PubMed Scopus Google Scholar). The of has been shown to be on iPLA2-VIA on the was on X. D.J. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). In of into TAG, and the generation of LD as stimulated by or but the of was and these the implication of iPLA2-VIA in the of fatty acids required for TAG synthesis in and the phosphorylation of cPLA2α at which is for enzyme activation during LD biogenesis (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar), and was to some by that iPLA2-VIA of this in and into account that cPLA2α is specific for for the fatty acid at the J. Balboa M.A. Cell. Signal. 2005; 17: 1052-1062Crossref PubMed Scopus Google Scholar), the inhibition of by with iPLA2-VIA a of the of iPLA2-VIA TAG and LD of for TAG synthesis is which is by is very specific for the of the PLA2 the also Balsinde J. Biochim. Biophys. Acta. PubMed Scopus Google Scholar, J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M.A. Balsinde J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). specific to iPLA2-VIA from the of the human iPLA2-VIA in human tissues in at different but two have and J. Balboa M.A. Cell. Signal. 2005; 17: 1052-1062Crossref PubMed Scopus Google Scholar). to be the in cells J. N. M. J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), the the to down-regulation of shown in iPLA2-VIA cells with siRNA, which with or expression of synthesis of TAG and LD of iPLA2-VIA the cells to or in of expression TAG synthesis and LD biogenesis but not LD biogenesis induced by or expression of the results the paradigm of LD formation from exogenous iPLA2-VIA is required for TAG synthesis during LD biogenesis stress. Overexpression of iPLA2-VIA TAG and LD of a a of by free fatty acid as in the of the In to cells, which LD content and of induced LD in conditions and to in cells stress with this LD content was by and LD conditions in cells also the expression of and TAG synthesis TAG synthesis was by but not by LD was by and of iPLA2-VIA the phosphorylation of cPLA2α at and the of in a the being also sensitive to of cells with LD and TAG synthesis and these results the implication of iPLA2-VIA in TAG synthesis and LD and a for the enzyme in the to phosphorylation and activation of in LD from results demonstrate that LD biogenesis during stress with TAG synthesis fatty acids by iPLA2-VIA and that the formed are present in we cells for with the fluorescent fatty acid and with shown in induced the formation of fluorescent LD, iPLA2-VIA inhibition the fluorescent in LD biogenesis was induced by FBS, which is an to evidence was from a in a LD induced with and cells and to and membrane was induced by and was in the the of this in have that inhibition of cPLA2α during exogenous lipid results in the of TAG in membrane (7Gubern A. Casas J. Barceló-Torns M. Barneda D. de la Rosa X. Masgrau R. Picatoste F. Balsinde J. Balboa M.A. Claro E. J. Biol. Chem. 2008; 283: 27369-27382Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). In agreement with the in in the induced by was by py-2, the was the membrane the results that TAG in LD formed during cellular stress at in from phospholipid by iPLA2-VIA. LD during a a physiological significance of LD biogenesis during stress, we cell deprivation of glucose conditions that LD shown in the this be by which TAG synthesis and cPLA2α or by which not TAG synthesis but LD biogenesis. also PAP, which that account for the of this L. Pérez R. Nieto M.L. Balsinde J. Balboa M.A. J. Biol. Chem. 2003; 278: 44683-44690Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar, J. Pérez R. Balboa M.A. Biochim. Biophys. Acta. 2006; 1761: 1344-1350Crossref PubMed Scopus (80) Google Scholar). In in CHO-K1 cells in cell some in cPLA2α inhibition with py-2, which is not a cells to at and the of deprivation during not of cells with but was glucose deprivation induced cellular in cells which and in the of the cPLA2α During glucose also induced cellular in cells which in the absence of the results that LD biogenesis during glucose deprivation has a survival results that in the absence of de synthesis and with external of fatty of cellular stress to the synthesis of TAG from fatty acids in a and to LD which In of LD by is of iPLA2-VIA. phosphorylation and of cPLA2α iPLA2-VIA inhibition and iPLA2-VIA that enzyme for TAG synthesis and LD generation in a LD biogenesis and synthesis of TAG is a of cellular stress, and was that in metabolism be the of TAG (8Iorio E. Di Vito M. Spadaro F. Ramoni C. Lococo E. Carnevale R. Lenti L. Strom R. Podo F. Biochim. Biophys. Acta. 2003; 1634: 1-14Crossref PubMed Scopus (49) Google Scholar, D. J. 2002; PubMed Scopus Google Scholar). TAG synthesis from and a fatty by the of Prog. Lipid Res. PubMed Scopus Google Scholar). In cells, and fatty acid synthase the of de DAG, which be to TAG or In TAG S. J. Biochim. Biophys. Acta. PubMed Scopus Google Scholar). and (8Iorio E. Di Vito M. Spadaro F. Ramoni C. Lococo E. Carnevale R. Lenti L. Strom R. Podo F. Biochim. Biophys. Acta. 2003; 1634: 1-14Crossref PubMed Scopus (49) Google Scholar) that the for TAG synthesis during programmed cell death a in phospholipid the activation of specific that account for LD biogenesis at the of phospholipid for the we that and are not the a very inhibition of the for synthesis has been shown to in some of with the Jackowski S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), Jackowski S. Biochim. Biophys. Acta. PubMed Scopus Google Scholar), or (9Ramos B. El-Mouedden M. Claro E. Jackowski S. Mol. Pharmacol. 2002; 62: 1068-1075Crossref PubMed Scopus (30) Google Scholar, 10Ramos B. Lahti J.M. Claro E. Jackowski S. Mol. 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This the of of exogenous fatty acids and not to experimental by and is by the and is the of for in most tissues 2006; PubMed Scopus Google Scholar). on the in which are the of free fatty acids. This has received most the (1Brasaemle D.L. J. Lipid Res. 2007; 48: 2547-2559Abstract Full Text Full Text PDF PubMed Scopus (758) Google Scholar), but tissues and cells be to fatty acids from TAG in LD Bickel P.E. 2007; Scopus Google Scholar), to In this a recent L. F. J. G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) that from LD and deprivation from which results with this that LD biogenesis in cells stress may a lipid of fatty acids used for structural be for TAG synthesis in a by iPLA2-VIA and in LD for in a