Showing papers on "Diacylglycerol kinase published in 2021"
TL;DR: In this article, two differently lipidated peptide sequences, L10 and S15, were used as Forster resonance energy transfer (FRET) pairs in intact cells to mark liquid-ordered, cholesterol-rich (Lo) and liquid-disordered and cholesterol-poor (Ld) domains of the PM.
Abstract: Possible segregation of plasma membrane (PM) phosphoinositide metabolism in membrane lipid domains is not fully understood. We exploited two differently lipidated peptide sequences, L10 and S15, to mark liquid-ordered, cholesterol-rich (Lo) and liquid-disordered, cholesterol-poor (Ld) domains of the PM, often called raft and nonraft domains, respectively. Imaging of the fluorescent labels verified that L10 segregated into cholesterol-rich Lo phases of cooled giant plasma-membrane vesicles (GPMVs), whereas S15 and the dye FAST DiI cosegregated into cholesterol-poor Ld phases. The fluorescent protein markers were used as Forster resonance energy transfer (FRET) pairs in intact cells. An increase of homologous FRET between L10 probes showed that depleting membrane cholesterol shrank Lo domains and enlarged Ld domains, whereas a decrease of L10 FRET showed that adding more cholesterol enlarged Lo and shrank Ld. Heterologous FRET signals between the lipid domain probes and phosphoinositide marker proteins suggested that phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] and phosphatidylinositol 4-phosphate (PtdIns4P) are present in both Lo and Ld domains. In kinetic analysis, muscarinic-receptor-activated phospholipase C (PLC) depleted PtdIns(4,5)P2 and PtdIns4P more rapidly and produced diacylglycerol (DAG) more rapidly in Lo than in Ld. Further, PtdIns(4,5)P2 was restored more rapidly in Lo than in Ld. Thus destruction and restoration of PtdIns(4,5)P2 are faster in Lo than in Ld. This suggests that Lo is enriched with both the receptor G protein/PLC pathway and the PtdIns/PI4-kinase/PtdIns4P pathway. The significant kinetic differences of lipid depletion and restoration also mean that exchange of lipids between these domains is much slower than free diffusion predicts.
28 citations
TL;DR: In this paper, the authors showed that the SYT-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity under multiple abiotic stresses, such as freezing, high salt, osmotic stress, and mechanical damage.
Abstract: Endoplasmic reticulum-plasma membrane contact sites (ER-PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis thaliana mutants lacking the ER-PM protein tether synaptotagmin1 (SYT1) exhibit decreased PM integrity under multiple abiotic stresses, such as freezing, high salt, osmotic stress, and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity. The ER-PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to wild-type while the levels of most glycerolipid species remain unchanged. In addition, the SYT1-green fluorescent protein fusion preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.
28 citations
TL;DR: In this article, the authors showed that constitutive acute regulatory protein (STAR) in Leydig cells is involved in DAG accumulation in lipid droplets, in addition to cholesterol transport.
Abstract: Leydig cells contain significant amounts of constitutively produced steroidogenic acute regulatory protein (STAR; STARD1). Hormone-induced STAR plays an essential role in inducing the transfer of cholesterol into the mitochondria for hormone-dependent steroidogenesis. STAR acts at the outer mitochondrial membrane, where it interacts with a protein complex, which includes the translocator protein (TSPO). Mutations in STAR cause lipoid congenital adrenal hyperplasia (lipoid CAH), a disorder characterized by severe defects in adrenal and gonadal steroid production; in Leydig cells, the defects are seen mainly after the onset of hormone-dependent androgen formation. The function of constitutive STAR in Leydig cells is unknown. We generated STAR knockout (KO) MA-10 mouse tumor Leydig cells and showed that STAR KO cells failed to form progesterone in response to dibutyryl-cAMP and to TSPO drug ligands, but not to 22(R)-hydroxycholesterol, which is a membrane-permeable intermediate of the CYP11A1 reaction. Electron microscopy of STAR KO cells revealed that the number and size of lipid droplets were similar to those in wild-type (WT) MA-10 cells. However, the density of lipid droplets in STAR KO cells was drastically different than that seen in WT cells. We isolated the lipid droplets and analyzed their content by liquid chromatography–mass spectrometry. There was a significant increase in cholesteryl ester and phosphatidylcholine content in STAR KO cell lipid droplets, but the most abundant increase was in the amount of diacylglycerol (DAG); DAG 38:1 was the predominantly affected species. Lastly, we identified genes involved in DAG signaling and lipid metabolism which were differentially expressed between WT MA-10 and STAR KO cells. These results suggest that constitutive STAR in Leydig cells is involved in DAG accumulation in lipid droplets, in addition to cholesterol transport. The former event may affect cell functions mediated by DAG signaling.
26 citations
TL;DR: In this article, the role of PIP2 in activation and maintenance of TRPC5 channel activity via its hydrolysis product diacyl glycerol (DAG), as well as the mechanism of desensitization by DAG-stimulated PKC activity, remain unclear.
22 citations
TL;DR: Histological and biochemical analyses revealed higher lipid accumulation and increased malondialdehyde and reactive oxygen species, signatures of lipid peroxidation and oxidative stress, and down-regulation of expression of mitochondriogenesis gene mRNAs indicated mitochondrial dysfunction induced by lipotoxicity, which could further result in cellular senescence.
19 citations
TL;DR: In this article, the role and mechanism of action of hypoxia-inducible lipid droplet-associated (HILPDA) in hepatocytes were investigated using a variety of biochemical and microscopic techniques, including real-time fluorescence live-cell imaging and Forster resonance energy transfer-fluorescence lifetime imaging microscopy.
Abstract: Objective Storage of triglycerides in lipid droplets is governed by a set of lipid droplet-associated proteins. One of these lipid droplet-associated proteins, hypoxia-inducible lipid droplet-associated (HILPDA), was found to impair lipid droplet breakdown in macrophages and cancer cells by inhibiting adipose triglyceride lipase. Here, we aimed to better characterize the role and mechanism of action of HILPDA in hepatocytes. Methods We performed studies in HILPDA-deficient and HILPDA-overexpressing liver cells, liver slices, and mice. The functional role and physical interactions of HILPDA were investigated using a variety of biochemical and microscopic techniques, including real-time fluorescence live-cell imaging and Forster resonance energy transfer-fluorescence lifetime imaging microscopy (FRET-FLIM). Results Levels of HILPDA were markedly induced by fatty acids in several hepatoma cell lines. Hepatocyte-specific deficiency of HILPDA in mice modestly but significantly reduced hepatic triglycerides in mice with non-alcoholic steatohepatitis. Similarly, deficiency of HILPDA in mouse liver slices and primary hepatocytes reduced lipid storage and accumulation of fluorescently-labeled fatty acids in lipid droplets, respectively, which was independent of adipose triglyceride lipase. Fluorescence microscopy showed that HILPDA partly colocalizes with lipid droplets and with the endoplasmic reticulum, is especially abundant in perinuclear areas, and mainly associates with newly added fatty acids. Real-time fluorescence live-cell imaging further revealed that HILPDA preferentially localizes to lipid droplets that are being remodeled. Overexpression of HILPDA in liver cells increased the activity of diacylglycerol acyltransferases (DGAT) and DGAT1 protein levels, concurrent with increased lipid storage. Confocal microscopy coupled to FRET-FLIM analysis demonstrated that HILPDA physically interacts with DGAT1 in living liver cells. The stimulatory effect of HILPDA on lipid storage via DGAT1 was corroborated in adipocytes. Conclusions Our data indicate that HILPDA physically interacts with DGAT1 and increases DGAT activity. Our findings suggest a novel regulatory mechanism by which fatty acids promote triglyceride synthesis and storage.
18 citations
TL;DR: HF diet caused DAG and ceramides accumulation, PKC activation, and the induction of inflammatory pathways in a fiber type-specific manner, which helps explain why oxidative and glycolytic muscles similarly develop insulin resistance, despite major differences in their metabolic characteristics and responsiveness to dietary lipid abundance.
Abstract: This study investigated whether oxidative and glycolytic rat skeletal muscles respond differently to a high-fat (HF) sucrose-enriched diet with respect to diacylglycerol (DAG) and ceramides accumulation, protein kinase C (PKC) activation, glucose metabolism, and the expression of inflammatory genes. HF diet (8 weeks) suppressed insulin-stimulated glycogen synthesis and glucose oxidation in soleus (Sol), extensor digitorum longus (EDL) and epitrochlearis (Epit) muscles. However, DAG and ceramides levels increased in Sol and EDL, but not in Epit muscles of HF-fed rats. Additionally, membrane-bound PKC-delta and PKC-theta increased in Sol and EDL, whereas in Epit muscles both PKC isoforms were reduced by HF diet. In Epit muscles, HF diet also increased the expression of tumor necrosis factor-α (TNF-α) receptors (CD40 and FAS), toll-like receptor 4 (TLR4), and nuclear factor kappa light polypeptide gene enhancer in B cells (NF-kB), whereas in Sol and EDL muscles the expression of these inflammatory genes remained unchanged upon HF feeding. In conclusion, HF diet caused DAG and ceramides accumulation, PKC activation, and the induction of inflammatory pathways in a fiber type-specific manner. These findings help explain why oxidative and glycolytic muscles similarly develop insulin resistance, despite major differences in their metabolic characteristics and responsiveness to dietary lipid abundance.
17 citations
TL;DR: In this paper, the structure and regulation of plant PLCs are described, and cellular and physiological roles of PLC in abiotic stresses, phosphorus deficiency, aluminium toxicity, pollen tube growth, and root development are discussed.
Abstract: Environmental stimuli are primarily perceived at the plasma membrane. Stimuli perception leads to membrane disintegration and generation of molecules which trigger lipid signaling. In plants, lipid signaling regulates important biological functions however, the molecular mechanism involved is unclear. Phospholipases C (PLCs) are important lipid-modifying enzymes in eukaryotes. In animals, PLCs by hydrolyzing phospholipids, such as phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] generate diacylglycerol (DAG) and inositol- 1,4,5-trisphosphate (IP3). However, in plants their phosphorylated variants i.e., phosphatidic acid (PA) and inositol hexakisphosphate (IP6) are proposed to mediate lipid signaling. Specific substrate preferences divide PLCs into phosphatidylinositol-PLC (PI-PLC) and non-specific PLCs (NPC). PLC activity is regulated by various cellular factors including, calcium (Ca2+) concentration, phospholipid substrate, and post-translational modifications. Both PI-PLCs and NPCs are implicated in plants' response to stresses and development. Emerging evidences show that PLCs regulate structural and developmental features, like stomata movement, microtubule organization, membrane remodelling and root development under abiotic stresses. Thus, crucial insights are provided into PLC mediated regulatory mechanism of abiotic stress responses in plants. In this review, we describe the structure and regulation of plant PLCs. In addition, cellular and physiological roles of PLCs in abiotic stresses, phosphorus deficiency, aluminium toxicity, pollen tube growth, and root development are discussed.
17 citations
TL;DR: In this paper, photoswitchable lipids with an azobenzene group within their acyl chains such as AzoPC are used for manipulating lipid order and dynamics through a light-induced trans-to-cis isomerization.
Abstract: Altering the properties of phospholipid membranes by light is an attractive option for the noninvasive manipulation of membrane proteins and cellular functions. Lipids with an azobenzene group within their acyl chains such as AzoPC are suitable tools for manipulating lipid order and dynamics through a light-induced trans-to-cis isomerization. However, the action of these photoswitchable lipids at the atomic level is still poorly understood. Here, liposomes containing AzoPC, POPE, and POPG have been characterized by solid-state NMR through chemical shift and dipolar CH order parameter measurements. Upon UV-light illumination, an efficient trans-to-cis conversion can be achieved resulting in a localized reduction of the CH order parameter within the bulk lipid acyl chains. This effect is even more pronounced in liposomes containing the integral membrane protein E. coli diacylglycerol kinase. The protein responds to the light-induced trans-to-cis isomerization by a site-specific increase in the molecular dynamics as observed by altered cross peak intensities in NCA spectra. This study represents a proof-of-concept demonstration for the use of photoswitchable lipids to modulate membrane properties by light for inducing dynamic changes within an embedded membrane protein.
16 citations
TL;DR: In this article, the influence of signaling crosstalk between Gq and Gi/o pathways on PIP2 metabolism in living cells using single-cell and optogenetic approaches to spatially and temporally constrain signaling.
14 citations
TL;DR: In this paper, the authors used biochemical, cellular, and genome editing approaches to investigate the function of fusions that retain the portion of the gene encoding either the catalytic domain or regulatory domain of protein kinase C (PKC).
TL;DR: In this article, a plastid-localized glycerol-3-phosphate dehydrogenase (GPDH), encoded by Gm GPDHp1 gene, catalyzes the formation of G3P, an obligate substrate required for TAG biosynthesis.
Abstract: There is growing interest in expanding the production of soybean oils (mainly triacylglycerol, or TAG) to meet rising feed demand and address global energy concerns. We report that a plastid-localized glycerol-3-phosphate dehydrogenase (GPDH), encoded by GmGPDHp1 gene, catalyzes the formation of glycerol-3-phosphate (G3P), an obligate substrate required for TAG biosynthesis. Overexpression of GmGPDHp1 increases soybean seed oil content with high levels of unsaturated fatty acids (FAs), especially oleic acid (C18:1), without detectably affecting growth or seed protein content or seed weight. Based on the lipidomic analyses, we found that the increase in G3P content led to an elevated diacylglycerol (DAG) pool, in which the Kennedy pathway-derived DAG was mostly increased, followed by PC-derived DAG, thereby promoting the synthesis of TAG containing relatively high proportion of C18:1. The increased G3P levels induced several transcriptional alterations of genes involved in the glycerolipid pathways. In particular, genes encoding the enzymes responsible for de novo glycerolipid synthesis were largely upregulated in the transgenic lines, in-line with the identified biochemical phenotype. These results reveal a key role for GmGPDHp1-mediated G3P metabolism in enhancing TAG synthesis and demonstrate a strategy to modify the FA compositions of soybean oils for improved nutrition and biofuel.
TL;DR: The trypanosoma cruzi and the T. brucei group of parasites cause neglected diseases that affect millions of people around the world as mentioned in this paper, and they have an inositol 1,4,5-trisphosphate (IP3)/diacylglycerol (DAG) signaling pathway.
TL;DR: In this paper, the authors identify DGKα as a contributor to the PD-1/PD-L1 axis that strongly limits the Ras/ERK/AP-1 pathway.
Abstract: Antibody-based therapies blocking the programmed cell death-1/ligand-1 (PD-1/PD-L1) axis have provided unprecedent clinical success in cancer treatment. Acquired resistance, however, frequently occurs, commonly associated with the upregulation of additional inhibitory molecules. Diacylglycerol kinase (DGK) α limits the extent of Ras activation in response to antigen recognition, and its upregulation facilitates hypofunctional, exhausted T cell states. Pharmacological DGKα targeting restores cytotoxic function of chimeric antigen receptor and CD8+ T cells isolated from solid tumors, suggesting a mechanism to reverse T cell exhausted phenotypes. Nevertheless, the contribution of DGKα downstream of the PD-1/PD-L1 inhibitory axis in human T cells and the consequences of combining DGKα and anti-PD-1/PD-L1 inhibitors are still unresolved relevant issues. We used a human triple parameter reporter cell line to investigate DGKα contribution to the PD-1/PD-L1 inhibitory pathway. We also addressed the impact of deleting DGKα expression in the growth dynamics and systemic tumor-derived effects of a PD-1-related tumor model, the MC38 colon adenocarcinoma. We identify DGKα as a contributor to the PD-1/PD-L1 axis that strongly limits the Ras/ERK/AP-1 pathway. DGKα function reinforces exhausted T cell phenotypes ultimately promoting tumor growth and generalized immunosuppression. Pharmacological DGKα inhibition selectively enhances AP-1 transcription and, importantly, cooperates with antibodies blocking the PD-1/PD-L1 interrelation. Our results indicate that DGKα inhibition could provide an important mechanism to revert exhausted T lymphocyte phenotypes and thus favor proper anti-tumor T cell responses. The cooperative effect observed after PD-1/PD-L1 and DGKα blockade offers a promising strategy to improve the efficacy of immunotherapy in the treatment of cancer.
TL;DR: In this article, the effect of DGAT1 genes on the accumulation of oil and other seed composition traits in soybean, transgenic lines were generated via trans-acting siRNA technology, in which three DGAT 1 genes (Glyma.13G106100, Glyma.09G065300, and Glyma 17G053300) were downregulated.
Abstract: Type I Diacylglycerol acyltransferase (DGAT1) catalyzes the final step of the biosynthesis process of triacylglycerol (TAG), the major storage lipids in plant seeds, through the esterification of diacylglycerol (DAG). To characterize the function of DGAT1 genes on the accumulation of oil and other seed composition traits in soybean, transgenic lines were generated via trans-acting siRNA technology, in which three DGAT1 genes (Glyma.13G106100, Glyma.09G065300, and Glyma.17G053300) were downregulated. The simultaneous downregulation of the three isoforms in transgenic lines was found to be associated with the reduction of seed oil concentrations by up to 18 mg/g (8.3%), which was correlated with increases in seed protein concentration up to 42 mg/g (11%). Additionally, the downregulations also influenced the fatty acid compositions in the seeds of transgenic lines through increasing the level of oleic acid, up to 121 mg/g (47.3%). The results of this study illustrate the importance of DGAT1 genes in determining the seed compositions in soybean through the development of new potential technology for manipulating seed quality in soybean to meet the demands for its various food and industrial applications.
TL;DR: In this paper, specific T-cell receptor (TCR) signaling pathways were characterized that regulate the generation of transcriptionally active P-TEFb, defined as the coordinate expression of cyclin T1 and phospho-Ser175 CDK9.
Abstract: The switch between HIV latency and productive transcription is regulated by an auto-feedback mechanism initiated by the viral trans-activator Tat, which functions to recruit the host transcription elongation factor P-TEFb to proviral HIV. A heterodimeric complex of CDK9 and one of three cyclin T subunits, P-TEFb is expressed at vanishingly low levels in resting memory CD4+ T cells and cellular mechanisms controlling its availability are central to regulation of the emergence of HIV from latency. Using a well-characterized primary T-cell model of HIV latency alongside healthy donor memory CD4+ T cells, we characterized specific T-cell receptor (TCR) signaling pathways that regulate the generation of transcriptionally active P-TEFb, defined as the coordinate expression of cyclin T1 and phospho-Ser175 CDK9. Protein kinase C (PKC) agonists, such as ingenol and prostratin, stimulated active P-TEFb expression and reactivated latent HIV with minimal cytotoxicity, even in the absence of intracellular calcium mobilization with an ionophore. Unexpectedly, inhibition-based experiments demonstrated that PKC agonists and TCR-mobilized diacylglycerol signal through MAP kinases ERK1/2 rather than through PKC to effect the reactivation of both P-TEFb and latent HIV. Single-cell and bulk RNA-seq analyses revealed that of the four known isoforms of the Ras guanine nucleotide exchange factor RasGRP, RasGRP1 is by far the predominantly expressed diacylglycerol-dependent isoform in CD4+ T cells. RasGRP1 should therefore mediate the activation of ERK1/2 via Ras-Raf signaling upon TCR co-stimulation or PKC agonist challenge. Combined inhibition of the PI3K-mTORC2-AKT-mTORC1 pathway and the ERK1/2 activator MEK prior to TCR co-stimulation abrogated active P-TEFb expression and substantially suppressed latent HIV reactivation. Therefore, contrary to prevailing models, the coordinate reactivation of P-TEFb and latent HIV in primary T cells following either TCR co-stimulation or PKC agonist challenge is independent of PKC but rather involves two complementary signaling arms of the TCR cascade, namely, RasGRP1-Ras-Raf-MEK-ERK1/2 and PI3K-mTORC2-AKT-mTORC1.
TL;DR: Zhang et al. as mentioned in this paper investigated whether modification of lipid profiles, including the contents, compositions and saturation levels of leaf lipids, may contribute to acetic acid modulated salt tolerance in C. rigescens.
TL;DR: In this article, the function and roles of a Δ6 fatty acid elongase (NoΔ6-FAE) in Nannochloropsis oceanica were unraveled and shown to be involved in the ω6 pathway in N. oceanica.
Abstract: Nannochloropsis oceanica represents a promising sunlight-driven alga for producing eicosapentaenoic acid (EPA, 20:5Δ5,8,11,14,17), a value-added very long-chain polyunsaturated fatty acid (VLC-PUFA). Here, we unraveled the function and roles of a Δ6 fatty acid elongase (NoΔ6-FAE) in N. oceanica. Heterologous expression of NoΔ6-FAE in yeast confirmed its function in elongating C18 Δ6-PUFAs rather than others. Subcellular localization experiments suggested that NoΔ6-FAE resides in the chloroplast endoplasmic reticulum. NoΔ6-FAE knockdown attenuated C20:3Δ8,11,14, C20:4Δ5,8,11,14, and EPA yet enhanced C18:3Δ6,9,12, leading to overall decreases in total fatty acids, triacylglycerol, diacylglycerol, free fatty acids, and polar membrane lipids. In contrast, NoΔ6-FAE overexpression in N. oceanica caused nearly opposite phenotypes. Moreover, N. oceanica lacked detectable C18:3Δ9,12,15, C18:4Δ6,9,12,15, and C20:4Δ8,11,14,17 even under NoΔ6-FAE knockdown or overexpression. Our results reveal the involvement of NoΔ6-FAE in EPA biosynthesis via the ω6 pathway in N. oceanica and highlight the potential of manipulating NoΔ6-FAE for improved lipid production.
TL;DR: It is revealed that microalgal DGAT can function as a lysophosphatidic acyltransferase (LPAAT) both in vitro and in vivo while losing its original function as DGAT.
Abstract: Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the final committed step in triacylglycerol biosynthesis in eukaryotes. In microalgae, the copy number of DGAT genes is extraordinarily expanded, yet the functions of many DGATs remain largely unknown. This study revealed that microalgal DGAT can function as a lysophosphatidic acyltransferase (LPAAT) both in vitro and in vivo while losing its original function as DGAT. Among the five DGAT-encoding genes identified and cloned from the green microalga Haematococcus pluvialis, four encoded HpDGATs that showed triacylglycerol synthase activities in yeast functional complementation analyses; the exception was one of the type II DGAT encoding genes, HpDGTT2. The hydrophobic recombinant HpDGTT2 protein was purified in soluble form and was found to function as a LPAAT via enzymatic assay. Introducing this gene into the green microalga Chlamydomonas reinhardtii led to retarded cellular growth, enlarged cell size, and enhanced triacylglycerol accumulation, identical to the phenotypes of transgenic strains overexpressing CrLPAAT. This study provides a framework for dissecting uncharacterized DGATs, and could pave the way to decrypting the structure-function relationship of this large group of enzymes that are critical to lipid biosynthesis.
TL;DR: This article showed that loss of function of the lipid kinase diacylglycerol kinase e (DGKe), encoded by the gene DGKE, causes a form of atypical hemolytic uremic syndrome that is not related to abnormalities of the alternative pathway of the complement, by mechanisms that are not understood.
Abstract: Loss of function of the lipid kinase diacylglycerol kinase e (DGKe), encoded by the gene DGKE, causes a form of atypical hemolytic uremic syndrome that is not related to abnormalities of the alternative pathway of the complement, by mechanisms that are not understood. By generating a potentially novel endothelial specific Dgke-knockout mouse, we demonstrate that loss of Dgke in the endothelium results in impaired signaling downstream of VEGFR2 due to cellular shortage of phosphatidylinositol 4,5-biphosphate. Mechanistically, we found that, in the absence of DGKe in the endothelium, Akt fails to be activated upon VEGFR2 stimulation, resulting in defective induction of the enzyme cyclooxygenase 2 and production of prostaglandin E2 (PGE2). Treating the endothelial specific Dgke-knockout mice with a stable PGE2 analog was sufficient to reverse the clinical manifestations of thrombotic microangiopathy and proteinuria, possibly by suppressing the expression of matrix metalloproteinase 2 through PGE2-dependent upregulation of the chemokine receptor CXCR4. Our study reveals a complex array of autocrine signaling events downstream of VEGFR2 that are mediated by PGE2, that control endothelial activation and thrombogenic state, and that result in abnormalities of the glomerular filtration barrier.
TL;DR: A review comprehensively discussed the status quo of this ubiquitously expressed phospholipase as a tumor driver and highlighted its significance as a novel therapeutic target in cancer as discussed by the authors.
TL;DR: The emerging evidence suggests that PKD plays an important role in regulating the adaptive response to the obese environment and is highlighted as a novel nutrient sensor.
Abstract: Obesity is associated with ectopic accumulation of lipids, which is implicated in the development of insulin resistance, type 2 diabetes mellitus and cardiovascular disease. As the global prevalence of obesity continues to rise, it is becoming increasingly important to understand the underlying cellular mechanisms of this disease. Protein kinase D (PKD) is an intracellular signalling kinase with well characterized roles in intracellular vesicle transport and secretion, cancer cell proliferation and cardiac hypertrophy. However, emerging evidence also highlights PKD as a novel nutrient sensor. PKD activation is mediated by the accumulation of the lipid intermediate diacylglycerol, and PKD activity in the liver, heart and adipose tissue increases upon feeding. In obesity, PKD signalling is linked to reduced insulin signalling and dysfunction in adipose tissue, liver and heart, whilst in the pancreas, PKD is essential for the compensatory increase in glucose-stimulated insulin secretion from β-cells during obesity. Collectively, these studies reveal aspects of PKD signalling that are involved in the tissue-specific responses to obesity. This review summarizes the emerging evidence suggesting that PKD plays an important role in regulating the adaptive response to the obese environment.
TL;DR: In this article, the authors showed that human Sphingomyelin synthase-related protein (SMS)-related protein showed a DG-generating activity via hydrolysis of PE, phosphatidic acid (PA), and Phosphatidylinositol (PI) in the absence of ceramide, and showed substrate selectivity for saturated and/or monounsaturated fatty acid-containing PA molecular species.
TL;DR: In this article, the effect of α-synuclein (α-syn) overexpression on neutral lipid metabolism and how this impacts on neuronal fate was investigated, and it was shown that α-Syn over-expression promoted diacylglycerol acyltransferase 2 upregulation and acyl-CoA synthetase activation, triggering TAG buildup.
Abstract: α-synuclein (α-syn) accumulation and aggregation is a common pathological factor found in synucleinopathies, a group of neurodegenerative disorders that includes Parkinson´s disease (PD). It has been proposed that lipid dyshomeostasis is responsible for the occurrence of PD-related processes, however, the precise role of lipids in the onset and progression of neurodegenerative disorders remains unclear. Our aim was to investigate the effect of α-syn overexpression on neutral lipid metabolism and how this impacts on neuronal fate. We found lipid droplet (LD) accumulation in cells overexpressing α-syn to be associated with a rise in triacylglycerol (TAG) and cholesteryl ester (CE) levels. α-syn overexpression promoted diacylglycerol acyltransferase 2 upregulation and acyl-CoA synthetase activation, triggering TAG buildup, that was accompanied by an increase in diacylglycerol acylation. Moreover, the CE increment was associated with higher activity of acyl-CoA:cholesterol acyltransferase. Interestingly, α-syn overexpression increased cholesterol lysosomal accumulation. We observed that sterol regulatory element-binding protein (SREBP)-1 and SREBP-2 were differentially regulated by α-syn overexpression. The latter gave rise to a reduction in SREBP-1 nuclear translocation and consequently in fatty acid synthase expression, whereas it produced an increase in SREBP-2 nuclear localization. Surprisingly, and despite increased cholesterol levels, SREBP-2 downstream genes related to cholesterolgenesis were not upregulated as expected. Notably, phospholipid (PL) levels were diminished in cells overexpressing α-syn. This decrease was related to the activation of phospholipase A2 (PLA2) with a concomitant imbalance of the PL deacylation-acylation cycle. Fatty acids released from PLs by iPLA2 and cPLA2 action were esterified into TAGs, thus promoting a biological response to α-syn overexpression with uncompromised cell viability. When the described steady-state was disturbed under conditions favoring higher levels of α-syn, the response was an enhanced LD accumulation, this imbalance ultimately leading to neuronal death.
TL;DR: In this article, stability and in vitro digestion of sesame oil-based high purity diacylglycerol (DAG) oil-in-water emulsions were investigated.
Abstract: In this study, stability and in vitro digestion of sesame oil-based high purity diacylglycerol (DAG) oil-in-water emulsions were investigated. Firstly, the effects of DAG content and the freeze-thaw process on the physical properties of emulsions were assessed. The fresh DAG emulsions exhibited high absolute ζ-potential values (>40 mV), small d4,3 (
TL;DR: The current status of research directed at understanding the roles of these enzymes in insect development and metabolism is discussed, with special emphasis given to studies in the model organism Drosophila melanogaster.
19 Mar 2021
TL;DR: In this article, the effects of ginsenoside Rb1 on hyperlipidemic in model mice were analyzed using stool, plasma and hepatic tissue samples, and the authors observed that the genera Blautia and Allobaculum were increased and Turicibacterium was decrease in rb1-treated mice as compared to untreated model mice.
Abstract: We analyzed the effects of ginsenoside Rb1 on hyperlipidemic in model mice. Using stool, plasma and hepatic tissue samples, we observed that the genera Blautia and Allobaculum were increased and Turicibacter was decrease in Rb1-treated mice as compared to untreated model mice. Ether lipid metabolism, glycerolipid metabolism, and glyoxylate and dicarboxylate metabolism were differentially enriched between the Rb1 and model groups. Lipidomics revealed 169 metabolites differentially expressed between the model and Rb1 groups in a positive ion model and 58 in a negative ion model. These metabolites mainly participate in glycerophospholipid, linoleic acid, and alpha-linolenic acid metabolism. The main metabolites enriched in these three pathways were phosphatidylcholine, diacylglycerol and ceramide, respectively. In a transcriptome analysis, 766 transcripts were differentially expressed between the Rb1 and model groups. KEGG analysis revealed lysine degradation, inositol phosphate metabolism, and glycerophospholipid metabolism to be the main enriched pathways. Multiomics analysis revealed glycerophospholipid metabolism to be a common pathway and phosphatidylcholine the main metabolite differentially enriched between the Rb1 and model groups. Results from fecal transplanted germ-free mice suggest that to suppress hyperlipidemia, Rb1 regulates gut microbiota by regulating the synthesis and decomposition of phosphatidylcholine in glycerophospholipid metabolism, which in turn decreases serum total cholesterol.
TL;DR: In this paper, the authors identify an essential phosphatidic acid phosphatase in Toxoplasma gondii, TgLIPIN, as the central metabolic nexus responsible for controlled lipid synthesis sustaining parasite development.
Abstract: Apicomplexa are obligate intracellular parasites responsible for major human diseases. Their intracellular survival relies on intense lipid synthesis, which fuels membrane biogenesis. Parasite lipids are generated as an essential combination of fatty acids scavenged from the host and de novo synthesized within the parasite apicoplast. The molecular and metabolic mechanisms allowing regulation and channeling of these fatty acid fluxes for intracellular parasite survival are currently unknown. Here, we identify an essential phosphatidic acid phosphatase in Toxoplasma gondii, TgLIPIN, as the central metabolic nexus responsible for controlled lipid synthesis sustaining parasite development. Lipidomics reveal that TgLIPIN controls the synthesis of diacylglycerol and levels of phosphatidic acid that regulates the fine balance of lipids between storage and membrane biogenesis. Using fluxomic approaches, we uncover the first parasite host-scavenged lipidome and show that TgLIPIN prevents parasite death by 'lipotoxicity' through effective channeling of host-scavenged fatty acids to storage triacylglycerols and membrane phospholipids.
TL;DR: A new system of membrane lipid remodeling responding to CO2 in Synechocystis sp.
Abstract: Membrane lipid remodeling in plants and microalgae has a crucial role in their survival under nutrient-deficient conditions. Aquatic microalgae have low access to CO2 , an essential carbon source for photosynthetic assimilates; however, 70-90 mol% of their membrane lipids are sugar-derived lipids (glycolipids) such as monogalactosyldiacylglycerol (MGDG). In this study, we discovered a new system of membrane lipid remodeling responding to CO2 in Synechocystis sp. PCC 6803, a unicellular, freshwater cyanobacterium. As compared with higher CO2 (HC; 1% CO2 ), under ambient air (lower CO2 : LC), phosphatidylglycerol (PG) content was increased at the expense of MGDG content. To explore the biological significance of this alteration in content, we generated a transformant of Synechocystis sp. PCC 6803 overexpressing sll0545 gene encoding a putative phosphatidic acid phosphate (oxPAP), which produces diacylglycerol that is used for the synthesis of glycolipids, and examined the effect on membrane lipid remodeling and phototrophic growth responding to LC. Photosystem II (PSII) activity and growth rate were inhibited under LC in oxPAP cells. PG content was substantially reduced, and MGDG and sulfoquinovosyldiacylglycerol contents were increased in oxPAP cells as compared with control cells. These phenotypes in oxPAP cells were recovered under the HC condition or PG supplementation. Increased PG content may be required for proper functioning of PSII under LC conditions.
TL;DR: In this paper, the authors compared the phospho-signalling networks during Toxoplasma egress from its host cell by artificially raising cGMP or calcium levels to activate PKG or CDPK, respectively.
Abstract: Fundamental processes of obligate intracellular parasites, such as Toxoplasma gondii and Plasmodium falciparum are controlled by a set of plant-like calcium dependent kinases (CDPKs), the conserved cAMP- and cGMP-dependent protein kinases (PKA and PKG), secondary messengers and lipid signalling. While some major components of the signalling networks have been identified, how these are connected is largely not known. Here, we compare the phospho-signalling networks during Toxoplasma egress from its host cell by artificially raising cGMP or calcium levels to activate PKG or CDPKs, respectively. We show that both these inducers trigger near identical signalling pathways and provide evidence for a positive feedback loop involving CDPK3. We measure phospho- and lipid signalling in parasites treated with the Ca2+ ionophore A23187 in a sub-minute timecourse and show CDPK3-dependent regulation of diacylglycerol levels and increased phosphorylation of four phosphodiesterases (PDEs), suggesting their function in the feedback loop. Disruption of CDPK3 leads to elevated cAMP levels and inhibition of PKA signalling rescues the egress defect of ΔCDPK3 parasites treated with A23187. Biochemical analysis of the four PDEs identifies PDE2 as the only cAMP-specific PDE among these candidates while the other PDEs are cGMP specific; two of which are inhibited by the predicted PDE inhibitor BIPPO. Conditional deletion of the four PDEs supports an important, but non-essential role of PDE1 and PDE2 for growth, with PDE2 controlling A23187-mediated egress. In summary we uncover a positive feedback loop that potentiates signalling during egress and links several signalling pathways together.