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Scientific Reports Nov 2023Nonalcoholic fatty liver disease (NAFLD) is characterized by an increase in hepatic lipid accumulation due to impaired lipid metabolism. Although a correlation was found...
Nonalcoholic fatty liver disease (NAFLD) is characterized by an increase in hepatic lipid accumulation due to impaired lipid metabolism. Although a correlation was found between NAFLD and sphingosine-1-phosphate (S1P), the role of the sphingolipid remains controversial. The aim of this study was to investigate any involvement of S1P in steatosis using its analog FTY720P and HepG2 cells. Lipid accumulation was induced by incubating the cells in a mixture of oleic and palmitic acid, and was quantified using Oil Red O. The involvement of signaling mediators was studied using pharmacological inhibitors and western blot analysis. FTY720P increased lipid accumulation, but this increase wasn't maintained in the presence of inhibitors of S1PR3, Gq, SREBP, mTOR, PI3K, and PPARγ indicating their involvement in the process. The results revealed that FTY720P binds to S1PR3 which activates sequentially Gq, PI3K, and mTOR leading to an increase in SREBP expression and PPARγ activation. It was concluded that in presence of a high level of fatty acids, lipid accumulation is increased in hepatocytes by the exogenously added FTY720P.
Topics: Humans; Hep G2 Cells; Non-alcoholic Fatty Liver Disease; Sterol Regulatory Element Binding Protein 1; PPAR gamma; Liver; TOR Serine-Threonine Kinases; Lipid Metabolism; Lysophospholipids; Phosphatidylinositol 3-Kinases
PubMed: 37953311
DOI: 10.1038/s41598-023-46011-4 -
Proceedings of the National Academy of... Nov 2023() enzymes cleave phosphatidylinositol 4,5-bisphosphate ( producing and (diacylglycerol). modulates the function of many ion channels, while and regulate...
() enzymes cleave phosphatidylinositol 4,5-bisphosphate ( producing and (diacylglycerol). modulates the function of many ion channels, while and regulate intracellular Ca levels and protein phosphorylation by protein kinase C, respectively. enzymes are under the control of G protein coupled receptor signaling through direct interactions with G proteins and and have been shown to be coincidence detectors for dual stimulation of and -coupled receptors. are aqueous-soluble cytoplasmic enzymes but partition onto the membrane surface to access their lipid substrate, complicating their functional and structural characterization. Using newly developed methods, we recently showed that activates by recruiting it to the membrane. Using these same methods, here we show that increases the catalytic rate constant, , of . Since stimulation of by depends on an autoinhibitory element (the X-Y linker), we propose that produces partial relief of the X-Y linker autoinhibition through an allosteric mechanism. We also determined membrane-bound structures of the and complexes, which show that these G proteins can bind simultaneously and independently of each other to regulate activity. The structures rationalize a finding in the enzyme assay, that costimulation by both G proteins follows a product rule of each independent stimulus. We conclude that baseline activity of is strongly suppressed, but the effect of G proteins, especially acting together, provides a robust stimulus upon G protein stimulation.
Topics: Hydrolysis; Phospholipase C beta; GTP-Binding Proteins; Phosphatidylinositols
PubMed: 37991948
DOI: 10.1073/pnas.2315011120 -
The Journal of Cell Biology Aug 2023As eukaryotic cells progress through cell division, the nuclear envelope (NE) membrane must expand to accommodate the formation of progeny nuclei. In Saccharomyces...
As eukaryotic cells progress through cell division, the nuclear envelope (NE) membrane must expand to accommodate the formation of progeny nuclei. In Saccharomyces cerevisiae, closed mitosis allows visualization of NE biogenesis during mitosis. During this period, the SUMO E3 ligase Siz2 binds the inner nuclear membrane (INM) and initiates a wave of INM protein SUMOylation. Here, we show these events increase INM levels of phosphatidic acid (PA), an intermediate of phospholipid biogenesis, and are necessary for normal mitotic NE membrane expansion. The increase in INM PA is driven by the Siz2-mediated inhibition of the PA phosphatase Pah1. During mitosis, this results from the binding of Siz2 to the INM and dissociation of Spo7 and Nem1, a complex required for the activation of Pah1. As cells enter interphase, the process is then reversed by the deSUMOylase Ulp1. This work further establishes a central role for temporally controlled INM SUMOylation in coordinating processes, including membrane expansion, that regulate NE biogenesis during mitosis.
Topics: Cell Nucleus; Mitosis; Nuclear Envelope; Nuclear Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Sumoylation; Organelle Biogenesis
PubMed: 37398994
DOI: 10.1083/jcb.202208137 -
Biochimica Et Biophysica Acta.... Oct 2023In phagocytes, superoxide anion (O), the precursor of reactive oxygen species, is produced by the NADPH oxidase complex to kill pathogens. Phagocyte NADPH oxidase...
In phagocytes, superoxide anion (O), the precursor of reactive oxygen species, is produced by the NADPH oxidase complex to kill pathogens. Phagocyte NADPH oxidase consists of the transmembrane cytochrome b (cyt b) and four cytosolic components: p40, p47, p67, and Rac1/2. The phagocyte activation by stimuli leads to activation of signal transduction pathways. This is followed by the translocation of cytosolic components to the membrane and their association with cyt b to form the active enzyme. To investigate the roles of membrane-interacting domains of the cytosolic proteins in the NADPH oxidase complex assembly and activity, we used giant unilamellar phospholipid vesicles (GUV). We also used the neutrophil-like cell line PLB-985 to investigate these roles under physiological conditions. We confirmed that the isolated proteins must be activated to bind to the membrane. We showed that their membrane binding was strengthened by the presence of the other cytosolic partners, with a key role for p47. We also used a fused chimera consisting of p47(aa 1-286), p67(aa 1-212) and Rac1Q61L, as well as mutated versions in the p47 PX domain and the Rac polybasic region (PB). We showed that these two domains have a crucial role in the trimera membrane-binding and in the trimera assembly to cyt b. They also have an impact on O.- production in vitro and in cellulo: the PX domain strongly binding to GUV made of a mix of polar lipids; and the PB region strongly binding to the plasma membrane of neutrophils and resting PLB-985 cells.
Topics: Phospholipids; Cytochromes b; Phagocytes; NADPH Oxidases; Cell Membrane; Binding Sites
PubMed: 37245861
DOI: 10.1016/j.bbamem.2023.184180 -
Cell Discovery Nov 2023Lipid droplets (LDs) are dynamic lipid storage organelles that can sense and respond to changes in systemic energy balance. The size and number of LDs are controlled by...
Lipid droplets (LDs) are dynamic lipid storage organelles that can sense and respond to changes in systemic energy balance. The size and number of LDs are controlled by complex and delicate mechanisms, among which, whether and which SNARE proteins mediate LD fusion, and the mechanisms governing this process remain poorly understood. Here we identified a SNARE complex, syntaxin 18 (STX18)-SNAP23-SEC22B, that is recruited to LDs to mediate LD fusion. STX18 targets LDs with its transmembrane domain spanning the phospholipid monolayer twice. STX18-SNAP23-SEC22B complex drives LD fusion in adiposome lipid mixing and content mixing in vitro assays. CIDEC/FSP27 directly binds STX18, SEC22B, and SNAP23, and promotes the lipid mixing of SNAREs-reconstituted adiposomes by promoting LD clustering. Knockdown of STX18 in mouse liver via AAV resulted in smaller liver and reduced LD size under high-fat diet conditions. All these results demonstrate a critical role of the SNARE complex STX18-SNAP23-SEC22B in LD fusion.
PubMed: 37989733
DOI: 10.1038/s41421-023-00613-4 -
Frontiers in Bioscience (Landmark... Sep 2023Serine hydroxymethyltransferase () is a serine-glycine-one-carbon metabolic enzyme in which and encode the cytoplasmic and mitochondrial isoenzymes, respectively. and...
BACKGROUND
Serine hydroxymethyltransferase () is a serine-glycine-one-carbon metabolic enzyme in which and encode the cytoplasmic and mitochondrial isoenzymes, respectively. and are key players in cancer metabolic reprogramming, and thus are attractive targets for cancer therapy. However, the role of in patients with renal cell carcinoma (RCC) has not been fully elucidated. We aimed to systematically analyze the expression, gene regulatory network, prognostic value, and target prediction of and in patients with kidney chromophobe (KICH), kidney renal clear cell carcinoma (KIRC), and kidney renal papillary cell carcinoma (KIRP); elucidate the association between expression and RCC; and identify potential new targets for clinical RCC treatment.
METHODS
Several online databases were used for the analysis, including cBioPortal, TRRUST, GeneMANIA, GEPIA, Metascape, UALCAN, LinkedOmics, and TIMER.
RESULTS
and transcript levels were significantly down- and upregulated, respectively, in patients with KICH, KIRC, and KIRP, based on sample type, individual cancer stage, sex, and patient age. Compared to men, women with KIRC and KIRP showed significantly up- and downregulated transcript levels, respectively. However, transcript levels were significantly upregulated in the patients mentioned above. KIRC and KIRP patients with high expression had longer survival periods than those with low expression. In patients with KIRC, the findings were similar to those mentioned above. However, in KICH patients, the findings were the opposite regarding expression. versus were altered by 9% versus 3% (n = 66 KICH patients), 4% versus 4% (n = 446 KIRC patients), and 6% versus 7% (n = 280 KIRP patients). versus promoter methylation levels were significantly up- and downregulated in patients with KIRP versus KIRC and KIRP, respectively. , , and their neighboring genes (NG) formed a complex network of interactions. The molecular functions of and its NG in patients with KICH, KIRC, and KIRP, included clathrin adaptor, metalloendopeptidase, and GTPase regulator activities; lipid binding, active transmembrane transporter activity, and lipid transporter activity; and type I interferon receptor binding, integrin binding, and protein heterodimerization, respectively. Their respective Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were involved in lysosome activity, human immunodeficiency virus 1 infection, and endocytosis; coronavirus disease 2019 and neurodegeneration pathways (multiple diseases); and RIG-I-like receptor signaling pathway, cell cycle, and actin cytoskeleton regulation. The molecular functions of and its NG in patients with KICH, KIRC, and KIRP included cell adhesion molecule binding and phospholipid binding; protein domain-specific binding, enzyme inhibitor activity, and endopeptidase activity; and hormone activity, integrin binding, and protein kinase regulator activity, respectively. For patients with KIRC versus KIRP, the KEGG pathways were involved in cAMP and calcium signaling pathways versus microRNAs (MiRNAs) in cancer cells and neuroactive ligand-receptor interactions, respectively. We identified the key transcription factors of and its NG.
CONCLUSIONS
and expression levels were different in patients with RCC. and may be potential therapeutic and prognostic biomarkers in these patients. Transcription factor (MYC, STAT1, PPARG, AR, SREBF2, and SP3) and miRNA (miR-17-5P, miR-422, miR-492, miR-137, miR-30A-3P, and miR-493) regulations may be important strategies for RCC treatment.
Topics: Male; Humans; Female; Carcinoma, Renal Cell; Glycine Hydroxymethyltransferase; COVID-19; MicroRNAs; Kidney Neoplasms; Integrins; Lipids
PubMed: 37796681
DOI: 10.31083/j.fbl2809196 -
Frontiers in Endocrinology 2024Successful pregnancy requires the tolerance of the maternal immune system for the semi-allogeneic embryo, as well as a synchrony between the receptive endometrium and... (Review)
Review
Successful pregnancy requires the tolerance of the maternal immune system for the semi-allogeneic embryo, as well as a synchrony between the receptive endometrium and the competent embryo. The annexin family belongs to calcium-regulated phospholipid-binding protein, which functions as a membrane skeleton to stabilize the lipid bilayer and participate in various biological processes in humans. There is an abundance of the annexin family at the maternal-fetal interface, and it exerts a crucial role in embryo implantation and the subsequent development of the placenta. Altered expression of the annexin family and dysfunction of annexin proteins or polymorphisms of the gene are involved in a range of pregnancy complications. In this review, we summarize the current knowledge of the annexin A protein family at the maternal-fetal interface and its association with female reproductive disorders, suggesting the use of ANXA as the potential therapeutic target in the clinical diagnosis and treatment of pregnancy complications.
Topics: Pregnancy; Female; Humans; Embryo Implantation; Placenta; Endometrium; Pregnancy Complications; Annexins
PubMed: 38495790
DOI: 10.3389/fendo.2024.1314214 -
Annual Review of Physiology Feb 2024Transient receptor potential (TRP) ion channels have diverse activation mechanisms including physical stimuli, such as high or low temperatures, and a variety of... (Review)
Review
Transient receptor potential (TRP) ion channels have diverse activation mechanisms including physical stimuli, such as high or low temperatures, and a variety of intracellular signaling molecules. Regulation by phosphoinositides and their derivatives is their only known common regulatory feature. For most TRP channels, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P] serves as a cofactor required for activity. Such dependence on PI(4,5)P has been demonstrated for members of the TRPM subfamily and for the epithelial TRPV5 and TRPV6 channels. Intracellular TRPML channels show specific activation by PI(3,5)P. Structural studies uncovered the PI(4,5)P and PI(3,5)P binding sites for these channels and shed light on the mechanism of channel opening. PI(4,5)P regulation of TRPV1-4 as well as some TRPC channels is more complex, involving both positive and negative effects. This review discusses the functional roles of phosphoinositides in TRP channel regulation and molecular insights gained from recent cryo-electron microscopy structures.
Topics: Humans; Transient Receptor Potential Channels; Phosphatidylinositols; Cryoelectron Microscopy
PubMed: 37871124
DOI: 10.1146/annurev-physiol-042022-013956 -
Metabolism: Clinical and Experimental Aug 2023Homeostasis of autophagy under normal conditions and nutrient stress is maintained by adaptive activation of regulatory proteins. However, the protein-lipid crosstalk...
BACKGROUND
Homeostasis of autophagy under normal conditions and nutrient stress is maintained by adaptive activation of regulatory proteins. However, the protein-lipid crosstalk that modulates the switch from suppression to activation of autophagy initiation is largely unknown.
RESULTS
Here, we show that human diazepam-binding inhibitor (DBI), also known as acyl-CoA binding protein (ACBP), binds to phosphatidylethanolamine of the phagophore membrane under nutrient-rich growth conditions, leading to inhibition of LC3 lipidation and suppression of autophagy initiation. Specific residues, including the conserved tyrosine residues of DBI, interact with phosphatidylethanolamine to stabilize the later molecule in the acyl-CoA binding cavity of the protein. Under starvation, phosphorylation of serine-21 of DBI mediated by the AMP-activated protein kinase results in a drastic reduction in the affinity of the protein for phosphatidylethanolamine. The release of serine-21 phosphorylated DBI from the phagophore upon nutrient starvation restores the high LC3 lipidation flux and maturation of the phagophore to autophagosome.
CONCLUSION
DBI acts as a strategic barrier against overactivation of phagophore maturation under nutrient-rich conditions, while triggering autophagy under nutrient-deficient conditions.
Topics: Humans; Carrier Proteins; Phosphatidylethanolamines; Autophagy; Nutrients; Serine
PubMed: 36280213
DOI: 10.1016/j.metabol.2022.155338 -
Advanced Healthcare Materials Nov 2023Liposomes play an important role in the field of drug delivery by virtue of their biocompatibility and versatility as carriers. Stealth liposomes, obtained by surface...
Liposomes play an important role in the field of drug delivery by virtue of their biocompatibility and versatility as carriers. Stealth liposomes, obtained by surface decoration with hydrophilic polyethylene glycol (PEG) molecules, represent an important turning point in liposome technology, leading to significant improvements in the pharmacokinetic profile compared to naked liposomes. Nevertheless, the generation of effective targeted liposomes-a central issue for cancer therapy-has faced several difficulties and clinical phase failures. Active targeting remains a challenge for liposomes. In this direction, a new Super Stealth Immunoliposomes (SSIL2) composed of a PEG-bi-phospholipids derivative is designed that stabilizes the polymer shielding over the liposomes. Furthermore, its counterpart, conjugated to the fragment antigen-binding of trastuzumab (Fab' -PEG-bi-phospholipids), is firmly anchored on the liposomes surface and correctly orients outward the targeting moiety. Throughout this study, the performances of SSIL2 are evaluated and compared to classic stealth liposomes and stealth immunoliposomes in vitro in a panel of cell lines and in vivo studies in zebrafish larvae and rodent models. Overall, SSIL2 shows superior in vitro and in vivo outcomes, both in terms of safety and anticancer efficacy, thus representing a step forward in targeted cancer therapy, and valuable for future development.
Topics: Animals; Liposomes; Zebrafish; Drug Delivery Systems; Phospholipids; Neoplasms; Polyethylene Glycols
PubMed: 37590033
DOI: 10.1002/adhm.202301650