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Sample records for phosphoinositide 3-kinase-dependent mechanism

  1. Phosphoinositide 3-kinase-dependent inhibition of dendritic cell interleukin-12 production by Giardia lamblia.

    PubMed

    Kamda, Joel Désiré; Singer, Steven M

    2009-02-01

    Dendritic cell interactions with pathogenic microbes initiate and direct the development of subsequent adaptive responses. The protozoan pathogen Giardia lamblia infects the mammalian small intestine, leading to nutrient malabsorption and diarrhea but rarely causing inflammation. In order to begin to understand how the innate immune system responds to this parasite and shapes the eventual adaptive response, we examined the interaction between parasites and murine bone marrow-derived dendritic cells (DCs). DCs incubated with live parasites or parasite extracts displayed enhanced levels of CD40. The expression of CD80 and CD86 also increased, but less than was seen with lipopolysaccharide-activated DCs. Small amounts of interleukin-6 (IL-6) and tumor necrosis factor alpha were secreted by these DCs, whereas no IL-10 or IL-12 could be detected. Coincubation of DCs with parasite extracts along with known Toll-like receptor (TLR) ligands resulted in enhanced secretion of IL-10 and reduced secretion of IL-12. The levels of major histocompatibility complex class II, CD80, and CD86 were also reduced compared to DCs stimulated with TLR ligands alone. Finally, studies with an extracellular signal-regulated kinase 1/2 pathway inhibitor, a phosphoinositide 3-kinase (PI3K) inhibitor, and anti-IL-10 receptor antibody revealed that the PI3K pathway is the dominant mechanism of inhibition in DCs incubated with both lipopolysaccharide and Giardia. These data suggest that this parasite actively interferes with host innate immunity, resulting in an immune response able to control the infection but devoid of strong inflammatory signals. PMID:19047410

  2. Phosphoinositide 3-kinase-dependent phosphorylation of the dual adaptor for phosphotyrosine and 3-phosphoinositides by the Src family of tyrosine kinase.

    PubMed Central

    Dowler, S; Montalvo, L; Cantrell, D; Morrice, N; Alessi, D R

    2000-01-01

    We recently identified a novel adaptor protein, termed dual adaptor for phosphotyrosine and 3-phosphoinositides (DAPP1), that possesses a Src homology (SH2) domain and a pleckstrin homology (PH) domain. DAPP1 exhibits a high-affinity interaction with PtdIns(3,4,5)P(3) and PtdIns(3,4)P(2), which bind to the PH domain. In the present study we show that when DAPP1 is expressed in HEK-293 cells, the agonists insulin, insulin-like growth factor-1 and epidermal growth factor induce the phosphorylation of DAPP1 at Tyr(139). Treatment of cells with phosphoinositide 3-kinase (PI 3-kinase) inhibitors or expression of a dominant-negative PI 3-kinase prevent phosphorylation of DAPP1 at Tyr(139), and a PH-domain mutant of DAPP1, which does not interact with PtdIns(3,4,5)P(3) or PtdIns(3,4)P(2), is not phosphorylated at Tyr(139) following agonist stimulation of cells. Overexpression of a constitutively active form of PI 3-kinase induced the phosphorylation of DAPP1 in unstimulated cells. We demonstrated that Tyr(139) of DAPP1 is likely to be phosphorylated in vivo by a Src-family tyrosine kinase, since the specific Src-family inhibitor, PP2, but not an inactive variant of this drug, PP3, prevented the agonist-induced tyrosine phosphorylation of DAPP1. Src, Lyn and Lck tyrosine kinases phosphorylate DAPP1 at Tyr(139) in vitro at similar rates in the presence or absence of PtdIns(3,4,5)P(3), and overexpression of these kinases in HEK-293 cells induces the phosphorylation of Tyr(139). These findings indicate that, following activation of PI 3-kinases, PtdIns(3,4,5)P(3) or PtdIns(3,4)P(2) bind to DAPP1, recruiting it to the plasma membrane where it becomes phosphorylated at Tyr(139) by a Src-family tyrosine kinase. PMID:10880360

  3. RhoG regulates anoikis through a phosphatidylinositol 3-kinase-dependent mechanism

    SciTech Connect

    Yamaki, Nao; Negishi, Manabu; Katoh, Hironori . E-mail: hirokato@pharm.kyoto-u.ac.jp

    2007-08-01

    In normal epithelial cells, cell-matrix interaction is required for cell survival and proliferation, whereas disruption of this interaction causes epithelial cells to undergo apoptosis called anoikis. Here we show that the small GTPase RhoG plays an important role in the regulation of anoikis. HeLa cells are capable of anchorage-independent cell growth and acquire resistance to anoikis. We found that RNA interference-mediated knockdown of RhoG promoted anoikis in HeLa cells. Previous studies have shown that RhoG activates Rac1 and induces several cellular functions including promotion of cell migration through its effector ELMO and the ELMO-binding protein Dock180 that function as a Rac-specific guanine nucleotide exchange factor. However, RhoG-induced suppression of anoikis was independent of the ELMO- and Dock180-mediated activation of Rac1. On the other hand, the regulation of anoikis by RhoG required phosphatidylinositol 3-kinase (PI3K) activity, and constitutively active RhoG bound to the PI3K regulatory subunit p85{alpha} and induced the PI3K-dependent phosphorylation of Akt. Taken together, these results suggest that RhoG protects cells from apoptosis caused by the loss of anchorage through a PI3K-dependent mechanism, independent of its activation of Rac1.

  4. Cellular Notch responsiveness is defined by phosphoinositide 3-kinase-dependent signals

    PubMed Central

    Mckenzie, Grahame; Ward, George; Stallwood, Yvette; Briend, Emmanuel; Papadia, Sofia; Lennard, Andrew; Turner, Martin; Champion, Brian; Hardingham, Giles E

    2006-01-01

    Background Notch plays a wide-ranging role in controlling cell fate, differentiation and development. The PI3K-Akt pathway is a similarly conserved signalling pathway which regulates processes such as differentiation, proliferation and survival. Mice with disrupted Notch and PI3K signalling show phenotypic similarities during haematopoietic cell development, suggesting functional interaction between these pathways. Results We show that cellular responsiveness to Notch signals depends on the activity of the PI3K-Akt pathway in cells as diverse as CHO cells, primary T-cells and hippocampal neurons. Induction of the endogenous PI3K-Akt pathway in CHO cells (by the insulin pathway), in T-cells (via TCR activation) or in neurons (via TrKB activation) potentiates Notch-dependent responses. We propose that the PI3K-Akt pathway exerts its influence on Notch primarily via inhibition of GSK3-beta, a kinase known to phosphorylate and regulate Notch signals. Conclusion The PI3K-Akt pathway acts as a "gain control" for Notch signal responses. Since physiological levels of intracellular Notch are often low, coincidence with PI3K-activation may be crucial for induction of Notch-dependent responses. PMID:16507111

  5. Phosphoinositide 3-kinase: the key switch mechanism in insulin signalling.

    PubMed Central

    Shepherd, P R; Withers, D J; Siddle, K

    1998-01-01

    Insulin plays a key role in regulating a wide range of cellular processes. However, until recently little was known about the signalling pathways that are involved in linking the insulin receptor with downstream responses. It is now apparent that the activation of class 1a phosphoinositide 3-kinase (PI 3-kinase) is necessary and in some cases sufficient to elicit many of insulin's effects on glucose and lipid metabolism. The lipid products of PI 3-kinase act as both membrane anchors and allosteric regulators, serving to localize and activate downstream enzymes and their protein substrates. One of the major ways these lipid products of PI 3-kinase act in insulin signalling is by binding to pleckstrin homology (PH) domains of phosphoinositide-dependent protein kinase (PDK) and protein kinase B (PKB) and in the process regulating the phosphorylation of PKB by PDK. Using mechanisms such as this, PI 3-kinase is able to act as a molecular switch to regulate the activity of serine/threonine-specific kinase cascades important in mediating insulin's effects on endpoint responses. PMID:9677303

  6. The distinct roles of Ras and Rac in PI 3-kinase-dependent protrusion during EGF-stimulated cell migration.

    PubMed

    Yip, Shu-Chin; El-Sibai, Mirvat; Coniglio, Salvatore J; Mouneimne, Ghassan; Eddy, Robert J; Drees, Beth E; Neilsen, Paul O; Goswami, Sumanta; Symons, Marc; Condeelis, John S; Backer, Jonathan M

    2007-09-01

    Cell migration involves the localized extension of actin-rich protrusions, a process that requires Class I phosphoinositide 3-kinases (PI 3-kinases). Both Rac and Ras have been shown to regulate actin polymerization and activate PI 3-kinase. However, the coordination of Rac, Ras and PI 3-kinase activation during epidermal growth factor (EGF)-stimulated protrusion has not been analyzed. We examined PI 3-kinase-dependent protrusion in MTLn3 rat adenocarcinoma cells. EGF-stimulated phosphatidyl-inositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P(3)] levels showed a rapid and persistent response, as PI 3-kinase activity remained elevated up to 3 minutes. The activation kinetics of Ras, but not Rac, coincided with those of leading-edge PtdIns(3,4,5)P(3) production. Small interfering RNA (siRNA) knockdown of K-Ras but not Rac1 abolished PtdIns(3,4,5)P(3) production at the leading edge and inhibited EGF-stimulated protrusion. However, Rac1 knockdown did inhibit cell migration, because of the inhibition of focal adhesion formation in Rac1 siRNA-treated cells. Our data show that in EGF-stimulated MTLn3 carcinoma cells, Ras is required for both PtdIns(3,4,5)P(3) production and lamellipod extension, whereas Rac1 is required for formation of adhesive structures. These data suggest an unappreciated role for Ras during protrusion, and a crucial role for Rac in the stabilization of protrusions required for cell motility. PMID:17698922

  7. Mechanism for phosphoinositide selectivity and activation of TRPV1 ion channels

    PubMed Central

    Ufret-Vincenty, Carmen A.; Klein, Rebecca M.; Collins, Marcus D.; Rosasco, Mario G.; Martinez, Gilbert Q.

    2015-01-01

    Although PI(4,5)P2 is believed to play an essential role in regulating the activity of numerous ion channels and transporters, the mechanisms by which it does so are unknown. Here, we used the ability of the TRPV1 ion channel to discriminate between PI(4,5)P2 and PI(4)P to localize the region of TRPV1 sequence that interacts directly with the phosphoinositide. We identified a point mutation in the proximal C-terminal region after the TRP box, R721A, that inverted the selectivity of TRPV1. Although the R721A mutation produced only a 30% increase in the EC50 for activation by PI(4,5)P2, it decreased the EC50 for activation by PI(4)P by more than two orders of magnitude. We used chemically induced and voltage-activated phosphatases to determine that PI(4)P continued to support TRPV1 activity even after depletion of PI(4,5)P2 from the plasma membrane. Our data cannot be explained by a purely electrostatic mechanism for interaction between the phosphoinositide and the protein, similar to that of the MARCKS (myristoylated alanine-rich C kinase substrate) effector domain or the EGF receptor. Rather, conversion of a PI(4,5)P2-selective channel to a PI(4)P-selective channel indicates that a structured phosphoinositide-binding site mediates the regulation of TRPV1 activity and that the amino acid at position 721 likely interacts directly with the moiety at the 5? position of the phosphoinositide. PMID:25918361

  8. Deletion of the phosphoinositide 3-Kinase p110(gamma) gene attenuates murine atherosclerosis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Inflammatory cell activation by chemokines requires intracellular signaling through phosphoinositide 3-kinase (PI3-kinase) and the PI3-kinase-dependent protein serine/threonine kinase Akt. Atherosclerosis is a chronic inflammatory process driven by oxidatively modified (atherogenic) lipoproteins, ch...

  9. Sac1–Vps74 structure reveals a mechanism to terminate phosphoinositide signaling in the Golgi apparatus

    PubMed Central

    Cai, Yiying; Deng, Yongqiang; Horenkamp, Florian

    2014-01-01

    Sac1 is a phosphoinositide phosphatase of the endoplasmic reticulum and Golgi apparatus that controls organelle membrane composition principally via regulation of phosphatidylinositol 4-phosphate signaling. We present a characterization of the structure of the N-terminal portion of yeast Sac1, containing the conserved Sac1 homology domain, in complex with Vps74, a phosphatidylinositol 4-kinase effector and the orthologue of human GOLPH3. The interface involves the N-terminal subdomain of the Sac1 homology domain, within which mutations in the related Sac3/Fig4 phosphatase have been linked to Charcot–Marie–Tooth disorder CMT4J and amyotrophic lateral sclerosis. Disruption of the Sac1–Vps74 interface results in a broader distribution of phosphatidylinositol 4-phosphate within the Golgi apparatus and failure to maintain residence of a medial Golgi mannosyltransferase. The analysis prompts a revision of the membrane-docking mechanism for GOLPH3 family proteins and reveals how an effector of phosphoinositide signaling serves a dual function in signal termination. PMID:25113029

  10. Cholesterol stabilizes fluid phosphoinositide domains

    PubMed Central

    Jiang, Zhiping; Redfern, Roberta E.; Isler, Yasmin; Ross, Alonzo H.

    2014-01-01

    Local accumulation of phosphoinositides (PIPs) is an important factor for a broad range of cellular events including membrane trafficking and cell signaling. The negatively charged phosphoinositide headgroups can interact with cations or cationic proteins and this electrostatic interaction has been identified as the main phosphoinositide clustering mechanism. However, an increasing number of reports show that phosphoinositide-mediated signaling events are at least in some cases cholesterol dependent, suggesting other possible contributors to the segregation of phosphoinositides. Using fluorescence microscopy on giant unilamellar vesicles and monolayers at the air/water interface, we present data showing that cholesterol stabilizes fluid phosphoinositide-enriched phases. The interaction with cholesterol is observed for all investigated phosphoinositides (PI(4)P, PI(3,4)P2, PI(3,5)P2, PI(4,5)P2 and PI(3,4,5)P3) as well as phosphatidylinositol. We find that cholesterol is present in the phosphoinositide-enriched phase and that the resulting phase is fluid. Cholesterol derivatives modified at the hydroxyl group (cholestenone, cholesteryl ethyl ether) do not promote formation of phosphoinositide domains, suggesting an instrumental role of the cholesterol hydroxyl group in the observed cholesterol/phosphoinositide interaction. This leads to the hypothesis that cholesterol participates in an intermolecular hydrogen bond network formed among the phosphoinositide lipids. We had previously reported that the intra- and intermolecular hydrogen bond network between the phosphoinositide lipids leads to a reduction of the charge density at the phosphoinositide phosphomonoester groups (Kooijman et al. Biochemistry 48, (2009) 9360). We believe that cholesterol acts as a spacer between the phosphoinositide lipids, thereby reducing the electrostatic repulsion, while participating in the hydrogen bond network, leading to its further stabilization. To illustrate the effect of phosphoinositide segregation on protein binding, we show that binding of the tumor suppressor protein PTEN to PI(5)P and PI(4,5)P2 is enhanced in the presence of cholesterol. These results provide new insights into how phosphoinositides mediate important cellular events. PMID:24556334

  11. Activated macrophages in HIV encephalitis and a macaque model show increased [3H](R)-PK11195 binding in a PI3-kinase dependent manner

    PubMed Central

    Venneti, Sriram; Wang, Guoji; Wiley., Clayton A.

    2007-01-01

    HIV encephalitis (HIVE) is a neurodegenerative disease seen in approximately one in four terminally infected patients. Macaques infected with the simian immunodeficiency virus develop encephalitis (SIVE) very similar to the human disease. Neurodegeneration in both these conditions occurs from the effects of toxic viral proteins and neurotoxins derived from activated brain macrophages. Activated macrophages in the brain of macaques with SIVE can be labeled in vivo using positron emission tomography (PET) using PK11195, a ligand that binds the peripheral benzodiazepine receptor (PBR). However, the functional significance and mechanisms mediating increased PK11195 binding in activated brain macrophages are not known. Using post mortem tissues from macaques with SIVE and macrophages cell cultures activated with lipopolysaccaride (LPS), we show that [3H](R)-PK11195 binding is increased in activated macrophages. Increased [3H](R)-PK11195 binding in LPS activated macrophages was reversed by pharmacologically inhibiting class III phosphatidylinositol-3 kinase (PI3-kinase), but was not altered by inhibiting the mitogen-activated protein kinase (MAP-kinase) pathway. Our results suggest that activated macrophages in lentiviral encephalitis show increased [3H](R)-PK11195 binding in a PI3-kinase dependent fashion which may help elucidate the function of PBR in activated brain macrophages in HIVE and other neuroinflammatory diseases. PMID:17888571

  12. Oxidative stress stimulates skeletal muscle glucose uptake through a phosphatidylinositol 3-kinase-dependent pathway

    PubMed Central

    Higaki, Yasuki; Mikami, Toshio; Fujii, Nobuharu; Hirshman, Michael F.; Koyama, Katsuhiro; Seino, Tetsuya; Tanaka, Keitaro; Goodyear, Laurie J.

    2010-01-01

    We determined the acute effects of oxidative stress on glucose uptake and intracellular signaling in skeletal muscle by incubating muscles with reactive oxygen species (ROS). Xanthine oxidase (XO) is a superoxide-generating enzyme that increases ROS. Exposure of isolated rat extensor digitorum longus (EDL) muscles to Hx/XO (Hx/XO) for 20 min resulted in a dose-dependent increase in glucose uptake. To determine whether the mechanism leading to Hx/XO-stimulated glucose uptake is associated with the production of H2O2, EDL muscles from rats were preincubated with the H2O2 scavenger catalase or the superoxide scavenger superoxide dismutase (SOD) prior to incubation with Hx/XO. Catalase treatment, but not SOD, completely inhibited the increase in Hx/XO-stimulated 2-deoxyglucose (2-DG) uptake, suggesting that H2O2 is an intermediary leading to Hx/XO-stimulated glucose uptake with incubation. Direct H2O2 also resulted in a dose-dependent increase in 2-DG uptake in isolated EDL muscles, and the maximal increase was threefold over basal levels at a concentration of 600 ?mol/l H2O2. H2O2-stimulated 2-DG uptake was completely inhibited by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, but not the nitric oxide inhibitor NG-monomethyl-L-arginine. H2O2 stimulated the phosphorylation of Akt Ser473 (7-fold) and Thr308 (2-fold) in isolated EDL muscles. H2O2 at 600 ?mol/l had no effect on ATP concentrations and did not increase the activities of either the ?1 or ?2 catalytic isoforms of AMP-activated protein kinase. These results demonstrate that acute exposure of muscle to ROS is a potent stimulator of skeletal muscle glucose uptake and that this occurs through a PI3K-dependent mechanism. PMID:18303121

  13. Protein Kinase B Activation and Lamellipodium Formation Are Independent Phosphoinositide 3-Kinase-Mediated Events Differentially Regulated by Endogenous Ras

    PubMed Central

    van Weering, David H. J.; de Rooij, Johan; Marte, Barbara; Downward, Julian; Bos, Johannes L.; Burgering, Boudewijn M. T.

    1998-01-01

    Regulation of phosphoinositide 3-kinase (PI 3-kinase) can occur by binding of the regulatory p85 subunit to tyrosine-phosphorylated proteins and by binding of the p110 catalytic subunit to activated Ras. However, the way in which these regulatory mechanisms act to regulate PI 3-kinase in vivo is unclear. Here we show that several growth factors (basic fibroblast growth factor [bFGF], platelet-derived growth factor [PDGF], and epidermal growth factor [EGF; to activate an EGF receptor-Ret chimeric receptor]) all activate PI 3-kinase in vivo in the neuroectoderm-derived cell line SKF5. However, these growth factors differ in their ability to activate PI 3-kinase-dependent signaling. PDGF and EGF(Ret) treatment induced PI 3-kinase-dependent lamellipodium formation and protein kinase B (PKB) activation. In contrast, bFGF did not induce lamellipodium formation but activated PKB, albeit to a small extent. PDGF and EGF(Ret) stimulation resulted in binding of p85 to tyrosine-phosphorylated proteins and strong Ras activation. bFGF, however, induced only strong activation of Ras. In addition, while RasAsn17 abolished bFGF activation of PKB, PDGF- and EGF(Ret)-induced PKB activation was only partially inhibited and lamellipodium formation was unaffected. Interestingly, in contrast to activation of only endogenous Ras (bFGF), ectopic expression of activated Ras did result in lamellipodium formation. From this we conclude that, in vivo, p85 and Ras synergize to activate PI 3-kinase and that strong activation of only endogenous Ras exerts a small effect on PI 3-kinase activity, sufficient for PKB activation but not lamellipodium formation. This differential sensitivity to PI 3-kinase activation could be explained by our finding that PKB activation and lamellipodium formation are independent PI 3-kinase-induced events. PMID:9528752

  14. Differential PI 3-kinase dependence of early and late phases of recycling of the internalized AT1 angiotensin receptor

    PubMed Central

    Hunyady, László; Baukal, Albert J.; Gáborik, Zsuzsanna; Olivares-Reyes, Jesus A.; Bor, Márta; Szaszák, Márta; Lodge, Robert; Catt, Kevin J.; Balla, Tamas

    2002-01-01

    Agonist-induced endocytosis and processing of the G protein–coupled AT1 angiotensin II (Ang II) receptor (AT1R) was studied in HEK 293 cells expressing green fluorescent protein (GFP)– or hemagglutinin epitope–tagged forms of the receptor. After stimulation with Ang II, the receptor and its ligand colocalized with Rab5–GFP and Rab4–GFP in early endosomes, and subsequently with Rab11–GFP in pericentriolar recycling endosomes. Inhibition of phosphatidylinositol (PI) 3-kinase by wortmannin (WT) or LY294002 caused the formation of large endosomal vesicles of heterogeneous Rab composition, containing the ligand–receptor complex in their limiting membranes and in small associated vesicular structures. In contrast to Alexa®–transferrin, which was mainly found in small vesicles associated with the outside of large vesicles in WT-treated cells, rhodamine–Ang II was also segregated into small internal vesicles. In cells labeled with 125I-Ang II, WT treatment did not impair the rate of receptor endocytosis, but significantly reduced the initial phase of receptor recycling without affecting its slow component. Similarly, WT inhibited the early, but not the slow, component of the recovery of AT1R at the cell surface after termination of Ang II stimulation. These data indicate that internalized AT1 receptors are processed via vesicles that resemble multivesicular bodies, and recycle to the cell surface by a rapid PI 3-kinase–dependent recycling route, as well as by a slower pathway that is less sensitive to PI 3-kinase inhibitors. PMID:12070129

  15. Phosphoinositides as regulators of protein-chromatin interactions.

    PubMed

    Viiri, Keijo; Mäki, Markku; Lohi, Olli

    2012-05-01

    The molecular function of phospholipids in the nucleus has been only partially elucidated. The upsurge of epigenetic research has contributed to increased interest in nuclear phospholipids, such as phosphoinositides, and their involvement in gene transcription. However, the mechanisms by which phosphoinositides regulate transcription is still unknown at the molecular level. Certain phosphoinositide species can regulate protein-chromatin and protein-nucleic acid interactions, and specific nuclear target proteins link nuclear signaling lipids to gene expression. We propose that a phosphoinositide-mediated detachment of proteins from chromatin is a general biological mechanism that partly underlies the signaling effects of nuclear phosphoinositides. PMID:22550339

  16. Interferon-? Activates Transglutaminase 2 via a Phosphatidylinositol-3-Kinase-Dependent Pathway: Implications for Celiac Sprue TherapyS?

    PubMed Central

    DiRaimondo, Thomas R.; Klöck, Cornelius

    2012-01-01

    The mechanism for activation of extracellular transglutaminase 2 (TG2) in the small intestine remains a fundamental mystery in our understanding of celiac sprue pathogenesis. Using the T84 human enterocytic cell line, we show that interferon-? (IFN-?), the predominant cytokine secreted by gluten-reactive T cells in the celiac intestine, activates extracellular TG2 in a dose-dependent manner. IFN-? mediated activation of TG2 requires phosphatidylinositol-3-kinase (PI3K) activity, but is uninfluenced by a number of other kinases reported to be active in T84 cells. Pharmacological inhibition of PI3K in the presence of IFN-? prevents TG2 activation as well as the previously characterized increase in transepithelial permeability. Our findings therefore establish PI3K as an attractive target for celiac sprue therapy, a possibility that is underscored by the encouraging safety profiles of several PI3K inhibitors undergoing human clinical trials. PMID:22228808

  17. Phosphoinositides alter lipid bilayer properties

    PubMed Central

    Hobart, E. Ashley; Koeppe, Roger E.; Andersen, Olaf S.

    2013-01-01

    Phosphatidylinositol-4,5-bisphosphate (PIP2), which constitutes ?1% of the plasma membrane phospholipid, plays a key role in membrane-delimited signaling. PIP2 regulates structurally and functionally diverse membrane proteins, including voltage- and ligand-gated ion channels, inwardly rectifying ion channels, transporters, and receptors. In some cases, the regulation is known to involve specific lipid–protein interactions, but the mechanisms by which PIP2 regulates many of its various targets remain to be fully elucidated. Because many PIP2 targets are membrane-spanning proteins, we explored whether the phosphoinositides might alter bilayer physical properties such as curvature and elasticity, which would alter the equilibrium between membrane protein conformational states—and thereby protein function. Taking advantage of the gramicidin A (gA) channels’ sensitivity to changes in lipid bilayer properties, we used gA-based fluorescence quenching and single-channel assays to examine the effects of long-chain PIP2s (brain PIP2, which is predominantly 1-stearyl-2-arachidonyl-PIP2, and dioleoyl-PIP2) on bilayer properties. When premixed with dioleoyl-phosphocholine at 2 mol %, both long-chain PIP2s produced similar changes in gA channel function (bilayer properties); when applied through the aqueous solution, however, brain PIP2 was a more potent modifier than dioleoyl-PIP2. Given the widespread use of short-chain dioctanoyl-phosphoinositides, we also examined the effects of diC8-phosphoinositol (PI), PI(4,5)P2, PI(3,5)P2, PI(3,4)P2, and PI(3,4,5)P3. The diC8 phosphoinositides, except for PI(3,5)P2, altered bilayer properties with potencies that decreased with increasing head group charge. Nonphosphoinositide diC8 phospholipids generally were more potent bilayer modifiers than the polyphosphoinositides. These results show that physiological increases or decreases in plasma membrane PIP2 levels, as a result of activation of PI kinases or phosphatases, are likely to alter lipid bilayer properties, in addition to any other effects they may have. The results further show that exogenous PIP2, as well as structural analogues that differ in acyl chain length or phosphorylation state, alters lipid bilayer properties at the concentrations used in many cell physiological experiments. PMID:23712549

  18. Phosphoinositides alter lipid bilayer properties.

    PubMed

    Rusinova, Radda; Hobart, E Ashley; Koeppe, Roger E; Andersen, Olaf S

    2013-06-01

    Phosphatidylinositol-4,5-bisphosphate (PIP2), which constitutes ?1% of the plasma membrane phospholipid, plays a key role in membrane-delimited signaling. PIP2 regulates structurally and functionally diverse membrane proteins, including voltage- and ligand-gated ion channels, inwardly rectifying ion channels, transporters, and receptors. In some cases, the regulation is known to involve specific lipid-protein interactions, but the mechanisms by which PIP2 regulates many of its various targets remain to be fully elucidated. Because many PIP2 targets are membrane-spanning proteins, we explored whether the phosphoinositides might alter bilayer physical properties such as curvature and elasticity, which would alter the equilibrium between membrane protein conformational states-and thereby protein function. Taking advantage of the gramicidin A (gA) channels' sensitivity to changes in lipid bilayer properties, we used gA-based fluorescence quenching and single-channel assays to examine the effects of long-chain PIP2s (brain PIP2, which is predominantly 1-stearyl-2-arachidonyl-PIP2, and dioleoyl-PIP2) on bilayer properties. When premixed with dioleoyl-phosphocholine at 2 mol %, both long-chain PIP2s produced similar changes in gA channel function (bilayer properties); when applied through the aqueous solution, however, brain PIP2 was a more potent modifier than dioleoyl-PIP2. Given the widespread use of short-chain dioctanoyl-phosphoinositides, we also examined the effects of diC8-phosphoinositol (PI), PI(4,5)P2, PI(3,5)P2, PI(3,4)P2, and PI(3,4,5)P3. The diC8 phosphoinositides, except for PI(3,5)P2, altered bilayer properties with potencies that decreased with increasing head group charge. Nonphosphoinositide diC8 phospholipids generally were more potent bilayer modifiers than the polyphosphoinositides. These results show that physiological increases or decreases in plasma membrane PIP2 levels, as a result of activation of PI kinases or phosphatases, are likely to alter lipid bilayer properties, in addition to any other effects they may have. The results further show that exogenous PIP2, as well as structural analogues that differ in acyl chain length or phosphorylation state, alters lipid bilayer properties at the concentrations used in many cell physiological experiments. PMID:23712549

  19. Rho GTPases, phosphoinositides, and actin

    PubMed Central

    Croisé, Pauline; Estay-Ahumada, Catherine; Gasman, Stéphane; Ory, Stéphane

    2014-01-01

    Rho GTPases are well known regulators of the actin cytoskeleton that act by binding and activating actin nucleators. They are therefore involved in many actin-based processes, including cell migration, cell polarity, and membrane trafficking. With the identification of phosphoinositide kinases and phosphatases as potential binding partners or effectors, Rho GTPases also appear to participate in the regulation of phosphoinositide metabolism. Since both actin dynamics and phosphoinositide turnover affect the efficiency and the fidelity of vesicle transport between cell compartments, Rho GTPases have emerged as critical players in membrane trafficking. Rho GTPase activity, actin remodeling, and phosphoinositide metabolism need to be coordinated in both space and time to ensure the progression of vesicles along membrane trafficking pathways. Although most molecular pathways are still unclear, in this review, we will highlight recent advances made in our understanding of how Rho-dependent signaling pathways organize actin dynamics and phosphoinositides and how phosphoinositides potentially provide negative feedback to Rho GTPases during endocytosis, exocytosis and membrane exchange between intracellular compartments. PMID:24914539

  20. Enhancement of phototransduction g protein-effector interactions by phosphoinositides.

    PubMed

    He, Feng; Mao, Muling; Wensel, Theodore G

    2004-03-01

    Light responses in photoreceptor cells are mediated by the action of the G protein transducin (G(t)) on the effector enzyme cGMP phosphodiesterase (PDE6) at the surface of disk membranes. The enzymatic components needed for phosphoinositide-based signaling are known to be present in rod cells, but it has remained uncertain what role phosphoinositides play in vertebrate phototransduction. Reconstitution of PDE6 and activated G(alphat), on the surface of large unilamellar vesicles containing d-myo-phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)), stimulated PDE activity nearly 4-fold above the level observed with membranes containing no phosphoinositides, whereas G protein-independent activation by trypsin was unaffected by the presence of phosphoinositides. PDE activity was similarly stimulated by d-myo-phosphatidylinositol-3,4-bisphosphate and d-myo-phosphatidylinositol-4-phosphate (PI(4)P), but much less by d-myo-phosphatidylinositol-5-phosphate (PI(5)P) or d-myo-phosphatidylinositol-3,5-bisphosphate. Incubation of rod outer segment membranes with phosphoinositide-specific phospholipase C decreased G protein-stimulated activation of endogenous PDE6, but not trypsin-stimulated PDE activity. Binding experiments using phosphoinositide-containing vesicles revealed patterns of PDE6 binding and PDE6-enhanced G(alphat)-GTPgammaS binding, consistent with the activation profile PI(4,5)P(2) > PI(4)P > PI(5)P approximately control vesicles. These results suggest that enhancement of effector-G protein interactions represents a possible mechanism for modulation of phototransduction gain by changes in phosphoinositide levels, perhaps occurring in response to longterm changes in illumination or other environmental cues. PMID:14699118

  1. Phosphoinositides and host-pathogen interactions.

    PubMed

    Pizarro-Cerdá, Javier; Kühbacher, Andreas; Cossart, Pascale

    2015-06-01

    Phosphoinositides control key cellular processes including vesicular trafficking and actin polymerization. Intracellular bacterial pathogens manipulate phosphoinositide metabolism in order to promote their uptake by target cells and to direct in some cases the biogenesis of their replication compartments. In this chapter, we review the molecular strategies that major pathogens including Listeria, Mycobacterium, Shigella, Salmonella, Legionella and Yersinia use to hijack phosphoinositides during infection. This article is part of a Special Issue entitled Phosphoinositides. PMID:25241942

  2. Gold nanoparticle supported phospholipid membranes as a biomimetic biosensor platform for phosphoinositide signaling detection.

    PubMed

    Wen, Qian; Liu, Si-Jia; Tang, Li-Juan; Tang, Ying; Jiang, Jian-Hui

    2014-12-15

    Enzyme mediated phosphoinositide signaling plays important regulatory roles in diverse cellular processes and has close implication in human diseases. However, detection of phosphoinositide enzymes remains a challenge because of the difficulty in discriminating the phosphorylation patterns of phosphoinositide. Here we develop a novel enzyme-activated gold nanoparticles (AuNPs) assembly strategy as a homogeneous colorimetric biosensor for activity detection of phosphoinositide kinases and phosphatases. This strategy utilizes a biomimetic mechanism of phosphoinositide signaling, in which AuNP supported phospholipid membranes are constructed to mimic the cellular membrane substrate, and AuNPs modified with the pleckstrin homology (PH) domain of cytosolic proteins are designed for specific, multivalent recognition of phosphorylated phosphoinositides. This biomimetic strategy enables efficient enzymatic reactions of the substrate and highly selective detection of target enzyme. The biosensor is demonstrated for the detection of phosphoinositide 3-kinase (PI3K) and phosphatase with tensin homology (PTEN). The results revealed that it allows sensitive, rapid visual detection of the enzymes with pM detection limits and four-decade wide dynamic ranges, and is capable of detecting enzyme activities in complex cell lysate samples. This biosensor might provide a general biosensor platform for high-throughput detection of phosphoinositide enzymes with high sensitivity and selectivity in biomedical research and clinical diagnostics. PMID:24994507

  3. Plant phosphoinositide-specific phospholipase C

    PubMed Central

    Rupwate, Sunny D.; Rajasekharan, Ram

    2012-01-01

    Phosphoinositide-specific phospholipase C (PI-PLC) belongs to an important class of enzymes involved in signaling related to lipids. They hydrolyze a membrane-associated phospholipid, phosphatidylinositol-4,5-bisphosphate, to produce inositol-1,4,5-trisphosphate and diacylglycerol. The role of PI-PLC and the mechanism behind its functioning is well studied in animal system; however, mechanism of plant PI-PLC functioning remains largely obscure. Here, we attempted to summarize the understanding regarding plant PI-PLC mechanism of regulation, localization, and domain association. Using sedimentation based phospholipid binding assay and surface plasmon resonance spectroscopy, it was demonstrated that C2 domain of plant PI-PLC alone is capable of targeting membranes. Moreover, change in surface hydrophobicity upon calcium stimulus is the key element in targeting plant PI-PLC from soluble fractions to membranes. This property of altering surface hydrophobicity plays a pivot role in regulation of PI-PLC activity. PMID:22902702

  4. AMPA protects cultured neurons against glutamate excitotoxicity through a phosphatidylinositol 3-kinase-dependent activation in extracellular signal-regulated kinase to upregulate BDNF gene expression.

    PubMed

    Wu, Xuan; Zhu, Daming; Jiang, Xueying; Okagaki, Peter; Mearow, Karen; Zhu, Guanshan; McCall, Sherman; Banaudha, Krishna; Lipsky, Robert H; Marini, Ann M

    2004-08-01

    The signal transduction and molecular mechanisms underlying alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-mediated neuroprotection are unknown. In the present study, we determined a major AMPA receptor-mediated neuroprotective pathway. Exposure of cerebellar granule cells to AMPA (500 microM) + aniracetam (1 microM), a known blocker of AMPA receptor desensitization, evoked an accumulation of brain-derived neurotropic factor (BDNF) in the culture medium and enhanced TrkB-tyrosine phosphorylation following the release of BDNF. AMPA also activated the src-family tyrosine kinase, Lyn, and the downstream target of the phosphatidylinositol 3-kinase (PI3-K) pathway, Akt. Extracellular signal regulated kinase (ERK), a component of the mitogen-activated protein kinase (MAPK) pathway, was also activated. K252a, a selective inhibitor of neurotrophin signaling, blocked the AMPA-mediated neuroprotection. The involvement of BDNF release in protecting neurons by AMPA was confirmed using a BDNF-blocking antibody. AMPA-mediated neuroprotection is blocked by PP1, an inhibitor of src family kinases, LY294002, a PI3-K inhibitor, or U0126, a MAPK kinase (MEK) inhibitor. Neuroprotective concentrations of AMPA increased BDNF mRNA levels that was blocked by the AMPA receptor antagonist, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX). The increase in BDNF gene expression appeared to be the downstream target of the PI3-K-dependent activation of the MAPK cascade since MEK or the PI3-K inhibitor blocked the AMPA receptor-mediated increase in BDNF mRNA. Thus, AMPA receptors protect neurons through a mechanism involving BDNF release, TrkB receptor activation, and a signaling pathway involving a PI3-K dependent activation of MAPK that increases BDNF expression. PMID:15287886

  5. Insulin promotes Rip11 accumulation at the plasma membrane by inhibiting a dynamin- and PI3-kinase-dependent, but Akt-independent, internalisation event.

    PubMed

    Boal, Frédéric; Hodgson, Lorna R; Reed, Sam E; Yarwood, Sophie E; Just, Victoria J; Stephens, David J; McCaffrey, Mary W; Tavaré, Jeremy M

    2016-01-01

    Rip11 is a Rab11 effector protein that has been shown to be important in controlling the trafficking of several intracellular cargoes, including the fatty acid transporter FAT/CD36, V-ATPase and the glucose transporter GLUT4. We have previously demonstrated that Rip11 translocates to the plasma membrane in response to insulin and here we examine the basis of this regulated phenomenon in more detail. We show that Rip11 rapidly recycles between the cell interior and surface, and that the ability of insulin to increase the appearance of Rip11 at the cell surface involves an inhibition of Rip11 internalisation from the plasma membrane. By contrast the hormone has no effect on the rate of Rip11 translocation towards the plasma membrane. The ability of insulin to inhibit Rip11 internalisation requires dynamin and class I PI3-kinases, but is independent of the activation of the protein kinase Akt; characteristics which are very similar to the mechanism by which insulin inhibits GLUT4 endocytosis. PMID:26515129

  6. The anti-apoptotic effect of IGF-1 on tissue resident stem cells is mediated via PI3-kinase dependent secreted frizzled related protein 2 (Sfrp2) release

    SciTech Connect

    Gehmert, Sebastian; Sadat, Sanga; Song Yaohua; Yan Yasheng; Alt, Eckhard

    2008-07-11

    Previous studies suggest that IGF-1 may be used as an adjuvant to stem cell transfer in order to improve cell engraftment in ischemic tissue. In the current study, we investigated the effect of IGF-1 on serum deprivation and hypoxia induced stem cell apoptosis and the possible mechanisms involved. Exposure of adipose tissue derived stem cells (ASCs) to serum deprivation and hypoxia resulted in significant apoptosis in ASC which is partially prevented by IGF-1. IGF-1's anti-apoptotic effect was abolished in ASCs transfected with Sfrp2 siRNA but not by the control siRNA. Using Western blot analysis, we demonstrated that serum deprivation and hypoxia reduced the expression of nuclear {beta}-catenin, which is reversed by IGF-1. IGF-1's effect on {beta}-catenin expression was abolished by the presence of PI3-kinase inhibitor LY294002 or in ASCs transfected with Sfrp2 siRNA. These results suggest that IGF-1, through the release of the Sfrp2, contributes to cell survival by stabilizing {beta}-catenin.

  7. Insulin promotes Rip11 accumulation at the plasma membrane by inhibiting a dynamin- and PI3-kinase-dependent, but Akt-independent, internalisation event

    PubMed Central

    Boal, Frédéric; Hodgson, Lorna R.; Reed, Sam E.; Yarwood, Sophie E.; Just, Victoria J.; Stephens, David J.; McCaffrey, Mary W.; Tavaré, Jeremy M.

    2016-01-01

    Rip11 is a Rab11 effector protein that has been shown to be important in controlling the trafficking of several intracellular cargoes, including the fatty acid transporter FAT/CD36, V-ATPase and the glucose transporter GLUT4. We have previously demonstrated that Rip11 translocates to the plasma membrane in response to insulin and here we examine the basis of this regulated phenomenon in more detail. We show that Rip11 rapidly recycles between the cell interior and surface, and that the ability of insulin to increase the appearance of Rip11 at the cell surface involves an inhibition of Rip11 internalisation from the plasma membrane. By contrast the hormone has no effect on the rate of Rip11 translocation towards the plasma membrane. The ability of insulin to inhibit Rip11 internalisation requires dynamin and class I PI3-kinases, but is independent of the activation of the protein kinase Akt; characteristics which are very similar to the mechanism by which insulin inhibits GLUT4 endocytosis. PMID:26515129

  8. Phosphoinositide function in cytokinesis.

    PubMed

    Brill, Julie A; Wong, Raymond; Wilde, Andrew

    2011-11-22

    In systems as diverse as yeast, slime mold and animal cells, the levels and distribution of phosphatidylinositol phosphates (PIPs) must be strictly regulated for successful cell cleavage. The precise mechanism by which PIPs function in this process remains unknown. Recent experiments are beginning to shed light on the cellular pathways in which PIPs make key contributions during cytokinesis. In particular, PIPs promote proper actin cytoskeletal organization and direct membrane trafficking in dividing cells. Future research will uncover temporal and spatial regulation of the different PIPs, thus elucidating their role in cytoskeletal and membrane events that drive cell cleavage. PMID:22115464

  9. Serotonin-stimulated phosphoinositide turnover: mediation by the S2 binding site in rat cerebral cortex but not in subcortical regions

    SciTech Connect

    Conn, P.J.; Sanders-Bush, E.

    1985-07-01

    In rat cerebral cortex, serotonin (5-HT) stimulates phosphoinositide turnover with an EC50 of 1 microM in the presence of pargyline. The EC50 is 16-fold higher in the absence of pargyline. Selective S2 antagonists inhibit 5-HT-stimulated phosphoinositide turnover. Schild analysis of the blockade by ketanserin of the 5-HT effect gives an estimated Kd of ketanserin for the phosphoinositide-linked receptor of 11.7 nM, which agrees with the Kd (3.5 nM) of (/sup 3/H)ketanserin for the S2 site. Furthermore, MK-212, 5-HT and 5-fluorotryptamine stimulate phosphoinositide turnover with potencies that resemble their potencies at the S2 but not the S1 binding site. Of 11 agonists tested, the tryptamine derivatives tend to be more efficacious than the piperazine derivatives. The selective S1 agonist 8-hydroxy-2-(di-N-propylamino)tetralin is inactive at stimulating phosphoinositide turnover. No significant relationship exists between the regional distributions of 5-HT-stimulated phosphoinositide turnover and S2 binding sites. Furthermore, the S2 antagonist ketanserin is less potent and less efficacious in hippocampus and limbic forebrain than in cerebral cortex. These data suggest that 5-HT-stimulated phosphoinositide turnover is linked to the S2 binding site in rat cerebral cortex. However, 5-HT increases phosphoinositide turnover in subcortical regions by mechanisms other than stimulation of the S2 receptor.

  10. Analysis, regulation, and roles of endosomal phosphoinositides.

    PubMed

    Maffucci, Tania; Falasca, Marco

    2014-01-01

    Phosphoinositides (PIs) are minor lipid components of cellular membranes that play critical roles in membrane dynamics, trafficking, and cellular signaling. Among the seven naturally occurring PIs, the monophosphate phosphatidylinositol 3-phosphate (PtdIns3P) and the bisphosphate phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P2] have been mainly associated with endosomes and endosomal functions. Metabolic labeling and HPLC analysis revealed that a bulk of PtdIns3P is constitutively present in cells, making it the only detectable product of the enzymes phosphoinositide 3-kinases in unstimulated, normal cells. The use of specific tagged-PtdIns3P-binding domains later demonstrated that this constitutive PtdIns3P accumulates in endosomes where it critically regulates trafficking and membrane dynamics. PMID:24377918

  11. Decreased platelet phosphoinositide turnover and enhanced platelet activation in IDDM

    SciTech Connect

    Bastyr, E.J. 3d.; Kadrofske, M.M.; Dershimer, R.C.; Vinik, A.I. )

    1989-09-01

    Individuals with diabetes mellitus may have increased in vivo platelet activity. Abnormal platelet function could contribute to the increased incidence of vascular disease in diabetes mellitus. The biochemical mechanism(s) for platelet hyperactivation is unknown. We examined the hypothesis that platelet phosphoinositide turnover, a key signal-transducing mechanism involved in platelet activation, was abnormal in diabetic subjects. Platelets were harvested from 16 subjects with insulin-dependent diabetes mellitus (IDDM) and 19 healthy, nondiabetic control subjects of comparable age. Plasma beta-thromboglobulin (beta-TBG), a specific marker of platelet activity in vivo, was increased in IDDM (67.1 +/- 7.3 ng/ml) compared with control (41.0 +/- 6.0 ng/ml) subjects (P less than .005). (32P)orthophosphate (32Pi) incorporation into the individual phosphoinositides and phosphatidic acid (PA) reached isotopic equilibrium by 120 min for IDDM and control subjects. Specific activity (dpm 32P/micrograms phosphorus) of phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) was not different between IDDM and control subjects. Under these conditions, basal 32Pi incorporation into PIP2 and PIP but not phosphatidylinositol (PI) or PA was significantly lower in IDDM subjects. There was significantly decreased (32P)PIP2 and (32P)PIP hydrolysis and decreased (32P)PA formation in IDDM after platelet stimulation with 4 U/ml human thrombin. There were no differences in (32P)PI hydrolysis between the two groups. The mass of PIP2 was reduced (P less than .005) in the platelets from IDDM (0.71 +/- 0.23 nmol/10(9) platelets) compared with control (1.65 +/- 0.53 nmol/10(9) platelets) subjects. Similarly, PIP was lower (P less than .001) in IDDM (0.66 +/- 0.09 nmol/10(9) platelets) than in control (2.92 +/- 0.43 nmol/10(9) platelets) subjects.

  12. Analysis of the Phosphoinositide Composition of Subcellular Membrane Fractions.

    PubMed

    Sarkes, Deborah A; Rameh, Lucia E

    2016-01-01

    Phosphoinositides play critical roles in the transduction of extracellular signals through the plasma membrane and also in endomembrane events important for vesicle trafficking and organelle function (Di Paolo and De Camilli, Nature 443(7112):651-657, 2006). The response triggered by these lipids is heavily dependent on the microenvironment in which they are found. HPLC analysis of labeled phosphoinositides allows quantification of the levels of each phosphoinositide species relative to their precursor, phosphatidylinositol. When combined with subcellular fractionation techniques, this strategy allows measurement of the relative phosphoinositide composition of each membrane fraction or organelle and determination of the microenvironment in which each species is enriched. Here, we describe the steps to separate and quantify total or localized phosphoinositides from cultured cells. PMID:26552687

  13. The Receptor Binding Domain of Botulinum Neurotoxin Stereotype C Binds Phosphoinositides

    SciTech Connect

    Zhang, Yanfeng; Varnum, Susan M.

    2012-03-01

    Botulinum neurotoxins (BoNTs) are the most toxic proteins known for humans and animals with an extremely low LD50 of {approx} 1 ng/kg. BoNTs generally require a protein and a ganglioside on the cell membrane surface for binding, which is known as a 'dual receptor' mechanism for host intoxication. Recent studies have suggested that in addition to gangliosides, other membrane lipids such as phosphoinositides may be involved in the interactions with the receptor binding domain (HCR) of BoNTs for better membrane penetration. Here, using two independent lipid-binding assays, we tested the interactions of BoNT/C-HCR with lipids in vitro. BoNT/C-HCR was found to bind negatively charged phospholipids, preferentially phosphoinositides. Additional interactions to phosphoinositides may help BoNT/C bind membrane more tightly and transduct signals for subsequent steps of intoxication. Our results provide new insights into the mechanisms of host cell membrane recognition by BoNTs.

  14. HGF/c-Met signaling promotes liver progenitor cell migration and invasion by an epithelial-mesenchymal transition-independent, phosphatidyl inositol-3 kinase-dependent pathway in an in vitro model.

    PubMed

    Suárez-Causado, A; Caballero-Díaz, D; Bertrán, E; Roncero, C; Addante, A; García-Álvaro, M; Fernández, M; Herrera, B; Porras, A; Fabregat, I; Sánchez, A

    2015-10-01

    Oval cells constitute an interesting hepatic cell population. They contribute to sustain liver regeneration during chronic liver damage, but in doing this they can be target of malignant conversion and become tumor-initiating cells and drive hepatocarcinogenesis. The molecular mechanisms beneath either their pro-regenerative or pro-tumorigenic potential are still poorly understood. In this study, we have investigated the role of the HGF/c-Met pathway in regulation of oval cell migratory and invasive properties. Our results show that HGF induces c-Met-dependent oval cell migration both in normal culture conditions and after in vitro wounding. HGF-triggered migration involves F-actin cytoskeleton reorganization, which is also evidenced by activation of Rac1. Furthermore, HGF causes ZO-1 translocation from cell-cell contact sites to cytoplasm and its concomitant activation by phosphorylation. However, no loss of expression of cell-cell adhesion proteins, including E-cadherin, ZO-1 and Occludin-1, is observed. Additionally, migration does not lead to cell dispersal but to a characteristic organized pattern in rows, in turn associated with Golgi compaction, providing strong evidence of a morphogenic collective migration. Besides migration, HGF increases oval cell invasion through extracellular matrix, a process that requires PI3K activation and is at least partly mediated by expression and activation of metalloproteases. Altogether, our findings provide novel insights into the cellular and molecular mechanisms mediating the essential role of HGF/c-Met signaling during oval cell-mediated mouse liver regeneration. PMID:26001768

  15. Retroviruses Human Immunodeficiency Virus and Murine Leukemia Virus Are Enriched in Phosphoinositides? †

    PubMed Central

    Chan, Robin; Uchil, Pradeep D.; Jin, Jing; Shui, Guanghou; Ott, David E.; Mothes, Walther; Wenk, Markus R.

    2008-01-01

    Retroviruses acquire a lipid envelope during budding from the membrane of their hosts. Therefore, the composition of this envelope can provide important information about the budding process and its location. Here, we present mass spectrometry analysis of the lipid content of human immunodeficiency virus type 1 (HIV-1) and murine leukemia virus (MLV). The results of this comprehensive survey found that the overall lipid content of these viruses mostly matched that of the plasma membrane, which was considerably different from the total lipid content of the cells. However, several lipids are enriched in comparison to the composition of the plasma membrane: (i) cholesterol, ceramide, and GM3; and (ii) phosphoinositides, phosphorylated derivatives of phosphatidylinositol. Interestingly, microvesicles, which are similar in size to viruses and are also released from the cell periphery, lack phosphoinositides, suggesting a different budding mechanism/location for these particles than for retroviruses. One phosphoinositide, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], has been implicated in membrane binding by HIV Gag. Consistent with this observation, we found that PI(4,5)P2 was enriched in HIV-1 and that depleting this molecule in cells reduced HIV-1 budding. Analysis of mutant virions mapped the enrichment of PI(4,5)P2 to the matrix domain of HIV Gag. Overall, these results suggest that HIV-1 and other retroviruses bud from cholesterol-rich regions of the plasma membrane and exploit matrix/PI(4,5)P2 interactions for particle release from cells. PMID:18799574

  16. PITPs as Targets for Selectively Interfering With Phosphoinositide Signaling in Cells

    PubMed Central

    Nile, Aaron H.; Tripathi, Ashutosh; Yuan, Peihua; Mousley, Carl J.; Suresh, Sundari; Wallace, Iain Michael; Shah, Sweety D.; Pohlhaus, Denise Teotico; Temple, Brenda; Nislow, Corey; Giaever, Guri; Tropsha, Alexander; Davis, Ronald W.; St Onge, Robert P.; Bankaitis, Vytas A.

    2013-01-01

    Sec14-like phosphatidylinositol transfer proteins (PITPs) integrate diverse territories of intracellular lipid metabolism with stimulated phosphatidylinositol-4-phosphate production, and are discriminating portals for interrogating phosphoinositide signaling. Yet, neither Sec14-like PITPs, nor PITPs in general, have been exploited as targets for chemical inhibition for such purposes. Herein, we validate the first small molecule inhibitors (SMIs) of the yeast PITP Sec14. These SMIs are nitrophenyl(4-(2-methoxyphenyl)piperazin-1-yl)methanones (NPPMs), and are effective inhibitors in vitro and in vivo. We further establish Sec14 is the sole essential NPPM target in yeast, that NPPMs exhibit exquisite targeting specificities for Sec14 (relative to related Sec14-like PITPs), propose a mechanism for how NPPMs exert their inhibitory effects, and demonstrate NPPMs exhibit exquisite pathway selectivity in inhibiting phosphoinositide signaling in cells. These data deliver proof-of-concept that PITP-directed SMIs offer new and generally applicable avenues for intervening with phosphoinositide signaling pathways with selectivities superior to those afforded by contemporary lipid kinase-directed strategies. PMID:24292071

  17. Phosphoinositide 3-kinase accelerates necrotic cell death during hypoxia.

    PubMed Central

    Aki, T; Mizukami, Y; Oka, Y; Yamaguchi, K; Uemura, K; Fujimiya, T; Yoshida, K

    2001-01-01

    Using H9c2 cells derived from rat cardiomyocytes, we investigated the mechanism of cell death during hypoxia in the presence of serum and glucose. Hypoxic cell death is by necrosis and is accompanied by metabolic acidosis. Moreover, hypoxic cell death is inhibited by Hepes buffer as well as by 2-deoxyglucose, an inhibitor of glycolysis, indicating that metabolic acidosis should play an essential role in hypoxic injury. The involvement of phosphoinositide 3-kinase (PI 3-kinase), which is known to activate glucose metabolism, was examined using its inhibitor, LY290042, or adenovirus-mediated gene transfer. Hypoxic cell death was inhibited by LY294002 in a dose-dependent manner. Overexpression of dominant negative PI 3-kinase was found to reduce cell death, whereas wild-type PI 3-kinase enhanced it. Dominant negative PI 3-kinase also reduced glucose consumption and acidosis, but this was stimulated by wild-type PI 3-kinase. The data indicate that PI 3-kinase stimulates cell death by enhancing metabolic acidosis. LY294002 significantly reduced glucose uptake, showing that PI 3-kinase regulates glycolysis at the step of glucose transport. These findings indicate the pivotal role of glucose metabolism in hypoxic cell death, and reveal a novel death-promoting effect of PI 3-kinase during hypoxia, despite this enzyme being considered to be a survival-promoting factor. PMID:11513748

  18. Targeting phosphoinositide 3-kinase ? for allergic asthma.

    PubMed

    Rowan, Wendy C; Smith, Janet L; Affleck, Karen; Amour, Augustin

    2012-02-01

    Chronic inflammation in the lung has long been linked to the pathogenesis of asthma. Central to this airway inflammation is a T-cell response to allergens, with Th2 cytokines driving the differentiation, survival and function of the major inflammatory cells involved in the allergic cascade. PI3K? (phosphoinositide 3-kinase ?) is a lipid kinase, expressed predominantly in leucocytes, where it plays a critical role in immune receptor signalling. A selective PI3K? inhibitor is predicted to block T-cell activation in the lung, reducing the production of pro-inflammatory Th2 cytokines. PI3K? is also involved in B-cell and mast cell activation. Therefore the inhibition of PI3K? should dampen down the inflammatory cascade involved in the asthmatic response through a wide breadth of pharmacology. Current anti-inflammatory therapies, which are based on corticosteroids, are effective in controlling inflammation in mild asthmatics, but moderate/severe asthmatic patients remain poorly controlled, experiencing recurrent exacerbations. Corticosteroids have no effect on mast cell degranulation and do not act directly on B-cells, so, overall, a PI3K? inhibitor has the potential to deliver improvements in onset of action, efficacy and reduced exacerbations in moderate/severe asthmatics. Additionally, PI3K? inhibition is expected to block effects of Th17 cells, which are increasingly implicated in steroid-insensitive asthma. PMID:22260698

  19. Phosphoinositide metabolism and adrenergic receptors in astrocytes

    SciTech Connect

    Noble, E.P.; Ritchie, T.; de Vellis, J.

    1986-03-01

    Agonist-induced phosphoinositide (PI) breakdown functions as a signal generating system. Diacylglycerol, one breakdown product of phosphotidylinositol-4,5-diphosphate hydrolysis, can stimulate protein kinase C, whereas inositol triphosphate, the other product, has been proposed to be a second messenger for Ca/sup + +/ mobilization. Using purified astrocyte cultures from neonatal rat brain, the effects of adrenergic agonists and antagonists at 10/sup -5/ M were measured on PI breakdown. Astrocytes grown in culture were prelabeled with (/sup 3/H)inositol, and basal (/sup 3/H) inositol phosphate (IP/sub 1/) accumulation was measured in the presence of Li/sup +/. Epinephrine > norepinephrine (NE) were the most active stimulants of IP/sub 1/ production. The ..cap alpha../sub 1/ adrenoreceptor blockers, phentolamine and phenoxybenzamine, added alone had no effect on IP/sub 1/ production was reduced below basal levels. Propranolol partially blocked the effects of NE. Clonidine and isoproterenol, separately added, reduced IP/sub 1/ below basal levels and when added together diminished IP/sub 1/ accumulation even further. The role of adrenergic stimulation in the production of c-AMP.

  20. Analyzing Protein-Phosphoinositide Interactions with Liposome Flotation Assays.

    PubMed

    Busse, Ricarda A; Scacioc, Andreea; Schalk, Amanda M; Krick, Roswitha; Thumm, Michael; Kühnel, Karin

    2016-01-01

    Liposome flotation assays are a convenient tool to study protein-phosphoinositide interactions. Working with liposomes resembles physiological conditions more than protein-lipid overlay assays, which makes this method less prone to detect false positive interactions. However, liposome lipid composition must be well-considered in order to prevent nonspecific binding of the protein through electrostatic interactions with negatively charged lipids like phosphatidylserine. In this protocol we use the PROPPIN Hsv2 (homologous with swollen vacuole phenotype 2) as an example to demonstrate the influence of liposome lipid composition on binding and show how phosphoinositide binding specificities of a protein can be characterized with this method. PMID:26552682

  1. Arabidopsis AtPLC2 Is a Primary Phosphoinositide-Specific Phospholipase C in Phosphoinositide Metabolism and the Endoplasmic Reticulum Stress Response

    PubMed Central

    Kanehara, Kazue; Yu, Chao-Yuan; Cho, Yueh; Cheong, Wei-Fun; Torta, Federico; Shui, Guanghou; Wenk, Markus R; Nakamura, Yuki

    2015-01-01

    Abstract Phosphoinositides represent important lipid signals in the plant development and stress response. However, multiple isoforms of the phosphoinositide biosynthetic genes hamper our understanding of the pivotal enzymes in each step of the pathway as well as their roles in plant growth and development. Here, we report that phosphoinositide-specific phospholipase C2 (AtPLC2) is the primary phospholipase in phosphoinositide metabolism and is involved in seedling growth and the endoplasmic reticulum (ER) stress responses in Arabidopsis thaliana. Lipidomic profiling of multiple plc mutants showed that the plc2-1 mutant increased levels of its substrates phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate, suggesting that the major phosphoinositide metabolic pathway is impaired. AtPLC2 displayed a distinct tissue expression pattern and localized at the plasma membrane in different cell types, where phosphoinositide signaling occurs. The seedlings of plc2-1 mutant showed growth defect that was complemented by heterologous expression of AtPLC2, suggesting that phosphoinositide-specific phospholipase C activity borne by AtPLC2 is required for seedling growth. Moreover, the plc2-1 mutant showed hypersensitive response to ER stress as evidenced by changes in relevant phenotypes and gene expression profiles. Our results revealed the primary enzyme in phosphoinositide metabolism, its involvement in seedling growth and an emerging link between phosphoinositide and the ER stress response. PMID:26401841

  2. Different phosphoinositide 3-kinase isoforms mediate carrageenan nociception and inflammation.

    PubMed

    Pritchard, Rory A; Falk, Lovissa; Larsson, Mathilda; Leinders, Mathias; Sorkin, Linda S

    2016-01-01

    Phosphoinositide 3-kinases (PI3Ks) participate in signal transduction cascades that can directly activate and sensitize nociceptors and enhance pain transmission. They also play essential roles in chemotaxis and immune cell infiltration leading to inflammation. We wished to determine which PI3K isoforms were involved in each of these processes. Lightly anesthetized rats (isoflurane) were injected subcutaneously with carrageenan in their hind paws. This was preceded by a local injection of 1% DMSO vehicle or an isoform-specific antagonist to PI3K-? (compound 15-e), -? (TGX221), -? (Cal-101), or -? (AS252424). We measured changes in the mechanical pain threshold and spinal c-Fos expression (4 hours after injection) as indices of nociception. Paw volume, plasma extravasation (Evans blue, 0.3 hours after injection), and neutrophil (myeloperoxidase; 1 hour after injection) and macrophage (CD11b+; 4 hour after injection) infiltration into paw tissue were the measured inflammation endpoints. Only PI3K-? antagonist before treatment reduced the carrageenan-induced pain behavior and spinal expression of c-Fos (P ? 0.01). In contrast, pretreatment with PI3K-?, -?, and-? antagonists reduced early indices of inflammation. Plasma extravasation PI3K-? (P ? 0.05), -? (P ? 0.05), and -? (P ? 0.01), early (0-2 hour) edema -? (P ? 0.05), -? (P ? 0.001), and -? (P ? 0.05), and neutrophil infiltration (all P ? 0.001) were all reduced compared to vehicle pretreatment. Later (2-4 hour), edema and macrophage infiltration (P ? 0.05) were reduced by only the PI3K-? and -? isoform antagonists, with the PI3K-? antagonist having a greater effect on edema. PI3K-? antagonism was ineffective in all paradigms. These data indicate that pain and clinical inflammation are pharmacologically separable and may help to explain clinical conditions in which inflammation naturally wanes or goes into remission, but pain continues unabated. PMID:26313408

  3. Catalytic Domain of Phosphoinositide-specific Phospholipase C (PLC)

    E-print Network

    Williams, Roger L.

    Catalytic Domain of Phosphoinositide-specific Phospholipase C (PLC) MUTATIONAL ANALYSIS OF RESIDUES WITHIN THE ACTIVE SITE AND HYDROPHOBIC RIDGE OF PLC 1* (Received for publication, November 20, 1997 Institute, University of Dundee, Dundee DD1 4HN, United Kingdom Structural studies of phospholipase C 1 (PLC

  4. Sec14-nodulin proteins and the patterning of phosphoinositide landmarks for developmental control of membrane morphogenesis.

    PubMed

    Ghosh, Ratna; de Campos, Marília K F; Huang, Jin; Huh, Seong K; Orlowski, Adam; Yang, Yuan; Tripathi, Ashutosh; Nile, Aaron; Lee, Hsin-Chieh; Dynowski, Marek; Schäfer, Helen; Róg, Tomasz; Lete, Marta G; Ahyayauch, Hasna; Alonso, Alicia; Vattulainen, Ilpo; Igumenova, Tatyana I; Schaaf, Gabriel; Bankaitis, Vytas A

    2015-05-01

    Polarized membrane morphogenesis is a fundamental activity of eukaryotic cells. This process is essential for the biology of cells and tissues, and its execution demands exquisite temporal coordination of functionally diverse membrane signaling reactions with high spatial resolution. Moreover, mechanisms must exist to establish and preserve such organization in the face of randomizing forces that would diffuse it. Here we identify the conserved AtSfh1 Sec14-nodulin protein as a novel effector of phosphoinositide signaling in the extreme polarized membrane growth program exhibited by growing Arabidopsis root hairs. The data are consistent with Sec14-nodulin proteins controlling the lateral organization of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) landmarks for polarized membrane morphogenesis in plants. This patterning activity requires both the PtdIns(4,5)P2 binding and homo-oligomerization activities of the AtSfh1 nodulin domain and is an essential aspect of the polarity signaling program in root hairs. Finally, the data suggest a general principle for how the phosphoinositide signaling landscape is physically bit mapped so that eukaryotic cells are able to convert a membrane surface into a high-definition lipid-signaling screen. PMID:25739452

  5. The Skap-hom dimerization and PH domains comprise a 3'-phosphoinositide-gated molecular switch.

    PubMed

    Swanson, Kenneth D; Tang, Yong; Ceccarelli, Derek F; Poy, Florence; Sliwa, Jan P; Neel, Benjamin G; Eck, Michael J

    2008-11-21

    PH domains, by binding to phosphoinositides, often serve as membrane-targeting modules. Using crystallographic, biochemical, and cell biological approaches, we have uncovered a mechanism that the integrin-signaling adaptor Skap-hom uses to mediate cytoskeletal interactions. Skap-hom is a homodimer containing an N-terminal four-helix bundle dimerization domain, against which its two PH domains pack in a conformation incompatible with phosphoinositide binding. The isolated PH domains bind PI[3,4,5]P(3), and mutations targeting the dimerization domain or the PH domain's PI[3,4,5]P(3)-binding pocket prevent Skap-hom localization to ruffles. Targeting is retained when the PH domain is deleted or by combined mutation of the PI[3,4,5]P(3)-binding pocket and the PH/dimerization domain interface. Thus, the dimerization and PH domain form a PI[3,4,5]P(3)-responsive molecular switch that controls Skap-hom function. PMID:19026786

  6. Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides

    PubMed Central

    Borbiro, Istvan; Badheka, Doreen; Rohacs, Tibor

    2015-01-01

    Capsaicin is an activator of the heat-sensitive TRPV1 (transient receptor potential vanilloid 1) ion channels and has been used as a local analgesic. We found that activation of TRPV1 channels with capsaicin either in dorsal root ganglion neurons or in a heterologous expression system inhibited the mechanosensitive Piezo1 and Piezo2 channels by depleting phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its precursor PI(4)P from the plasma membrane through Ca2+-induced phospholipase C? (PLC?) activation. Experiments with chemically inducible phosphoinositide phosphatases and receptor-induced activation of PLC? indicated that inhibition of Piezo channels required depletion of both PI(4)P and PI(4,5)P2. The mechanically activated current amplitudes decreased substantially in the excised inside-out configuration, where the membrane patch containing Piezo1 channels is removed from the cell. PI(4,5)P2 and PI(4)P applied to these excised patches inhibited this decrease. Thus, we concluded that Piezo channel activity requires the presence of phosphoinositides, and the combined depletion of PI(4,5)P2 or PI(4)P reduces channel activity. In addition to revealing a role for distinct membrane lipids in mechanosensitive ion channel regulation, these data suggest that inhibition of Piezo2 channels may contribute to the analgesic effect of capsaicin. PMID:25670203

  7. Sec14-nodulin proteins and the patterning of phosphoinositide landmarks for developmental control of membrane morphogenesis

    PubMed Central

    Ghosh, Ratna; de Campos, Marília K. F.; Huang, Jin; Huh, Seong K.; Orlowski, Adam; Yang, Yuan; Tripathi, Ashutosh; Nile, Aaron; Lee, Hsin-Chieh; Dynowski, Marek; Schäfer, Helen; Róg, Tomasz; Lete, Marta G.; Ahyayauch, Hasna; Alonso, Alicia; Vattulainen, Ilpo; Igumenova, Tatyana I.; Schaaf, Gabriel; Bankaitis, Vytas A.

    2015-01-01

    Polarized membrane morphogenesis is a fundamental activity of eukaryotic cells. This process is essential for the biology of cells and tissues, and its execution demands exquisite temporal coordination of functionally diverse membrane signaling reactions with high spatial resolution. Moreover, mechanisms must exist to establish and preserve such organization in the face of randomizing forces that would diffuse it. Here we identify the conserved AtSfh1 Sec14-nodulin protein as a novel effector of phosphoinositide signaling in the extreme polarized membrane growth program exhibited by growing Arabidopsis root hairs. The data are consistent with Sec14-nodulin proteins controlling the lateral organization of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) landmarks for polarized membrane morphogenesis in plants. This patterning activity requires both the PtdIns(4,5)P2 binding and homo-oligomerization activities of the AtSfh1 nodulin domain and is an essential aspect of the polarity signaling program in root hairs. Finally, the data suggest a general principle for how the phosphoinositide signaling landscape is physically bit mapped so that eukaryotic cells are able to convert a membrane surface into a high-definition lipid-signaling screen. PMID:25739452

  8. Phosphoinositides: Tiny Lipids With Giant Impact on Cell Regulation

    PubMed Central

    2013-01-01

    Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease. PMID:23899561

  9. Kinetic analysis of receptor-activated phosphoinositide turnover

    PubMed Central

    Xu, Chang; Watras, James; Loew, Leslie M.

    2003-01-01

    We studied the bradykinin-induced changes in phosphoinositide composition of N1E-115 neuroblastoma cells using a combination of biochemistry, microscope imaging, and mathematical modeling. Phosphatidylinositol-4,5-bisphosphate (PIP2) decreased over the first 30 s, and then recovered over the following 2–3 min. However, the rate and amount of inositol-1,4,5-trisphosphate (InsP3) production were much greater than the rate or amount of PIP2 decline. A mathematical model of phosphoinositide turnover based on this data predicted that PIP2 synthesis is also stimulated by bradykinin, causing an early transient increase in its concentration. This was subsequently confirmed experimentally. Then, we used single-cell microscopy to further examine phosphoinositide turnover by following the translocation of the pleckstrin homology domain of PLC?1 fused to green fluorescent protein (PH-GFP). The observed time course could be simulated by incorporating binding of PIP2 and InsP3 to PH-GFP into the model that had been used to analyze the biochemistry. Furthermore, this analysis could help to resolve a controversy over whether the translocation of PH-GFP from membrane to cytosol is due to a decrease in PIP2 on the membrane or an increase in InsP3 in cytosol; by computationally clamping the concentrations of each of these compounds, the model shows how both contribute to the dynamics of probe translocation. PMID:12771127

  10. Eukaryotic virulence determinants utilize phosphoinositides at the ER and host cell surface

    PubMed Central

    Jiang, Rays H.Y.; Stahelin, Robert V.; Bhattacharjee, Souvik; Haldar, Kasturi

    2013-01-01

    Similar to bacteria, eukaryotic pathogens may also utilize common strategies of pathogenic secretion, as effector proteins from the oomycete Phytophthora infestans and virulence determinants from the human malaria parasite Plasmodium falciparum share a functionally equivalent host-cell targeting motif (RxLR-dEER in P. infestans and RxLxE/D/Q in P. falciparum). Here we summarize recent studies that reveal that the malarial motif may function differently than previously envisioned. Rather, binding the lipid phosphatidylinositol 3-phosphate [PI(3)P] is a critical step in accessing the host for both pathogens, but occurs in different locations. Nanomolar affinity for PI(3)P by these short amino acid motifs, suggests a new mechanism of phosphoinositide binding unexpectedly in secretory locations that has been exploited for virulence by diverse eukaryotic pathogens. PMID:23375057

  11. The nuclear phosphoinositide 3-kinase/AKT pathway: a new second messenger system.

    PubMed

    Neri, Luca M; Borgatti, Paola; Capitani, Silvano; Martelli, Alberto M

    2002-10-10

    Lipid second messengers, particularly those derived from the polyphosphoinositide cycle, play a pivotal role in several cell signaling networks. Phosphoinositide 3-kinases (PI3Ks) generate specific inositol lipids that have been implicated in a plethora of cell functions. One of the best-characterized targets of PI3K lipid products is the serine/threonine protein kinase Akt. Recent findings have implicated Akt in cancer progression because it stimulates cell proliferation and suppresses apoptosis. Evidence accumulated over the past 15 years has highlighted the presence of an autonomous nuclear inositol lipid metabolism, and suggests that lipid molecules are important components of signaling pathways operating within the nucleus. PI3Ks, their lipid products, and Akt have also been identified at the nuclear level. In this review, we shall summarize the most updated findings about these molecules in relationship with the nuclear compartment and provide an overview of the possible mechanisms by which they regulate important cell functions. PMID:12385889

  12. Identification of pleckstrin-homology-domain-containing proteins with novel phosphoinositide-binding specificities.

    PubMed Central

    Dowler, S; Currie , R A; Campbell , D G; Deak, M; Kular, G; Downes, C P; Alessi, D R

    2000-01-01

    The second messenger phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P(3)] is generated by the action of phosphoinositide 3-kinase (PI 3-kinase), and regulates a plethora of cellular processes. An approach for dissecting the mechanisms by which these processes are regulated is to identify proteins that interact specifically with PtdIns(3,4,5)P(3). The pleckstrin homology (PH) domain has become recognized as the specialized module used by many proteins to interact with PtdIns(3,4,5)P(3). Recent work has led to the identification of a putative phosphatidylinositol 3,4,5-trisphosphate-binding motif (PPBM) at the N-terminal regions of PH domains that interact with this lipid. We have searched expressed sequence tag databases for novel proteins containing PH domains possessing a PPBM. Surprisingly, many of the PH domains that we identified do not bind PtdIns(3,4,5)P(3), but instead possess unexpected and novel phosphoinositide-binding specificities in vitro. These include proteins possessing PH domains that interact specifically with PtdIns(3,4)P(2) [TAPP1 (tandem PH-domain-containing protein-1) and TAPP2], PtdIns4P [FAPP1 (phosphatidylinositol-four-phosphate adaptor protein-1)], PtdIns3P [PEPP1 (phosphatidylinositol-three-phosphate-binding PH-domain protein-1) and AtPH1] and PtdIns(3,5)P(2) (centaurin-beta2). We have also identified two related homologues of PEPP1, termed PEPP2 and PEPP3, that may also interact with PtdIns3P. This study lays the foundation for future work to establish the phospholipid-binding specificities of these proteins in vivo, and their physiological role(s). PMID:11001876

  13. VISUALIZIATION OF CELLULAR PHOSPHOINOSITIDE POOLS WITH GFP-FUSED PROTEIN-DOMAINS

    PubMed Central

    Balla, Tamas; Várnai, Péter

    2011-01-01

    This unit describes the method of following phosphoinositide dynamics in live cells. Inositol phospholipids have emerged as universal signaling molecules present in virtually every membrane of eukaryotic cells. Phosphoinositides are present only in tiny amounts compared to structural lipids but are metabolically very active as they are produced and degraded by the numerous inositide kinase and phosphatase enzymes. Phosphoinositides control the membrane-recruitment and activity of many protein signaling-complexes in specific membrane compartments and have been implicated in the regulation of a variety of signaling and trafficking pathways. It has been a challenge to develop methods that allow detection of phosphoinositides at the single cell level. The only available technique in live cell application is based on the use of the same protein domains selected by evolution to recognize cellular phosphoinositides. Some of these isolated protein modules when fused to fluorescent proteins can follow dynamic changes in phosphoinositides. While this technique can provide information on phosphoinositide dynamics in live cells with subcellular resolution and rapidly gained popularity, it also has several limitations that must be taken into account when interpreting the data. Here, we summarize the design and practical use of these constructs and also review important considerations for the interpretation of the data obtained by this technique. PMID:19283730

  14. Structural Comparisons of Class I phosphoinositide 3-kinases

    SciTech Connect

    Amzel, L.; Huang, C; Mandelker, D; Lengauer, C; Gabelli, S; Vogelstein, B

    2008-01-01

    Class I phosphoinositide 3-kinases (PI3Ks) are lipid kinases that regulate cell growth. One of these kinases, PI3Kalpha, is frequently mutated in diverse tumour types. The recently determined structure of PI3Kalpha reveals features that distinguish this enzyme from related lipid kinases. In addition, wild-type PI3Kgamma differs from PI3Kalpha by a substitution identical to a PI3Kalpha oncogenic mutant (His1047Arg) that might explain the differences in the enzymatic activities of the normal and mutant PI3Kalpha. Comparison of the PI3K structures also identified structural features that could potentially be exploited for the design of isoform-specific inhibitors.

  15. In vivo tracking of phosphoinositides in Drosophila photoreceptors.

    PubMed

    Hardie, Roger C; Liu, Che-Hsiung; Randall, Alexander S; Sengupta, Sukanya

    2015-12-01

    In order to monitor phosphoinositide turnover during phospholipase C (PLC)-mediated Drosophila phototransduction, fluorescently tagged lipid probes were expressed in photoreceptors and imaged both in dissociated cells, and in eyes of intact living flies. Of six probes tested, Tb(R332H) (a mutant of the Tubby protein pleckstrin homology domain) was judged the best reporter for phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P2], and the P4M domain from Legionella SidM for phosphatidylinositol 4-phosphate (PtdIns4P). Using accurately calibrated illumination, we found that only ?50% of PtdIns(4,5)P2 and very little PtdIns4P were depleted by full daylight intensities in wild-type flies, but both were severely depleted by ?100-fold dimmer intensities in mutants lacking Ca(2+)-permeable transient receptor potential (TRP) channels or protein kinase C (PKC). Resynthesis of PtdIns4P (t½ ?12?s) was faster than PtdIns(4,5)P2 (t½ ?40?s), but both were greatly slowed in mutants of DAG kinase (rdgA) or PtdIns transfer protein (rdgB). The results indicate that Ca(2+)- and PKC-dependent inhibition of PLC is required for enabling photoreceptors to maintain phosphoinositide levels despite high rates of hydrolysis by PLC, and suggest that phosphorylation of PtdIns4P to PtdIns(4,5)P2 is the rate-limiting step of the cycle. PMID:26483384

  16. Phosphoinositide Signaling Pathways in Nuclei Are Associated with Nuclear Speckles Containing Pre-mRNA Processing Factors

    PubMed Central

    Boronenkov, Igor V.; Loijens, Joost C.; Umeda, Masato; Anderson, Richard A.

    1998-01-01

    Phosphoinositide signal transduction pathways in nuclei use enzymes that are indistinguishable from their cytosolic analogues. We demonstrate that distinct phosphatidylinositol phosphate kinases (PIPKs), the type I and type II isoforms, are concentrated in nuclei of mammalian cells. The cytosolic and nuclear PIPKs display comparable activities toward the substrates phosphatidylinositol 4-phosphate and phosphatidylinositol 3-phosphate. Indirect immunofluorescence revealed that these kinases were associated with distinct subnuclear domains, identified as “nuclear speckles,” which also contained pre-mRNA processing factors. A pool of nuclear phosphatidylinositol bisphosphate (PIP2), the product of these kinases, was also detected at these same sites by monoclonal antibody staining. The localization of PIPKs and PIP2 to speckles is dynamic in that both PIPKs and PIP2 reorganize along with other speckle components upon inhibition of mRNA transcription. Because PIPKs have roles in the production of most phosphatidylinositol second messengers, these findings demonstrate that phosphatidylinositol signaling pathways are localized at nuclear speckles. Surprisingly, the PIPKs and PIP2 are not associated with invaginations of the nuclear envelope or any nuclear membrane structure. The putative absence of membranes at these sites suggests novel mechanisms for the generation of phosphoinositides within these structures. PMID:9843587

  17. Functional Anatomy of Phospholipid Binding And Regulation of Phosphoinositide Homeostasis By Proteins of the Sec14 Superfamily

    SciTech Connect

    Schaaf, G.; Ortlund, E.A.; Tyeryar, K.R.; Mousley, C.J.; Ile, K.E.; Garrett, T.A.; Ren, J.; Woolls, M.J.; Raetz, C.R.H.; Redinbo, M.R.; Bankaitis, V.A.

    2009-05-27

    Sec14, the major yeast phosphatidylinositol (PtdIns)/phosphatidylcholine (PtdCho) transfer protein, regulates essential interfaces between lipid metabolism and membrane trafficking from the trans-Golgi network (TGN). How Sec14 does so remains unclear. We report that Sec14 binds PtdIns and PtdCho at distinct (but overlapping) sites, and both PtdIns- and PtdCho-binding activities are essential Sec14 activities. We further show both activities must reside within the same molecule to reconstitute a functional Sec14 and for effective Sec14-mediated regulation of phosphoinositide homeostasis in vivo. This regulation is uncoupled from PtdIns-transfer activity and argues for an interfacial presentation mode for Sec14-mediated potentiation of PtdIns kinases. Such a regulatory role for Sec14 is a primary counter to action of the Kes1 sterol-binding protein that antagonizes PtdIns 4-OH kinase activity in vivo. Collectively, these findings outline functional mechanisms for the Sec14 superfamily and reveal additional layers of complexity for regulating phosphoinositide homeostasis in eukaryotes.

  18. The antiepileptic drug valproic acid and other medium-chain fatty acids acutely reduce phosphoinositide levels independently of inositol in Dictyostelium.

    PubMed

    Chang, Pishan; Orabi, Benoit; Deranieh, Rania M; Dham, Manik; Hoeller, Oliver; Shimshoni, Jakob A; Yagen, Boris; Bialer, Meir; Greenberg, Miriam L; Walker, Matthew C; Williams, Robin S B

    2012-01-01

    Valproic acid (VPA) is the most widely prescribed epilepsy treatment worldwide, but its mechanism of action remains unclear. Our previous work identified a previously unknown effect of VPA in reducing phosphoinositide production in the simple model Dictyostelium followed by the transfer of data to a mammalian synaptic release model. In our current study, we show that the reduction in phosphoinositide [PtdInsP (also known as PIP) and PtdInsP(2) (also known as PIP(2))] production caused by VPA is acute and dose dependent, and that this effect occurs independently of phosphatidylinositol 3-kinase (PI3K) activity, inositol recycling and inositol synthesis. In characterising the structural requirements for this effect, we also identify a family of medium-chain fatty acids that show increased efficacy compared with VPA. Within the group of active compounds is a little-studied group previously associated with seizure control, and analysis of two of these compounds (nonanoic acid and 4-methyloctanoic acid) shows around a threefold enhanced potency compared with VPA for protection in an in vitro acute rat seizure model. Together, our data show that VPA and a newly identified group of medium-chain fatty acids reduce phosphoinositide levels independently of inositol regulation, and suggest the reinvestigation of these compounds as treatments for epilepsy. PMID:21876211

  19. Phosphoinositide kinases and the synthesis of polyphosphoinositides in higher plant cells

    NASA Technical Reports Server (NTRS)

    Drobak, B. K.; Dewey, R. E.; Boss, W. F.; Davies, E. (Principal Investigator)

    1999-01-01

    Phosphoinositides are a family of inositol-containing phospholipids which are present in all eukaryotic cells. Although in most cells these lipids, with the exception of phosphatidylinositol, constitute only a very minor proportion of total cellular lipids, they have received immense attention by researchers in the past 15-20 years. This is due to the discovery that these lipids, rather than just having structural functions, play key roles in a wide range of important cellular processes. Much less is known about the plant phosphoinositides than about their mammalian counterparts. However, it has been established that a functional phosphoinositide system exists in plant cells and it is becoming increasingly clear that inositol-containing lipids are likely to play many important roles throughout the life of a plant. It is not our intention to give an exhaustive overview of all aspects of the field, but rather we focus on the phosphoinositide kinases responsible for the synthesis of all phosphorylated forms of phosphatidylinositol. Also, we mention some of the aspects of current phosphoinositide research which, in our opinion, are most likely to provide a suitable starting point for further research into the role of phosphoinositides in plants.

  20. Inositol Pentakisphosphate Isomers Bind PH Domains with Varying Specificity and Inhibit Phosphoinositide Interactions

    SciTech Connect

    S Jackson; S Al-Saigh; C Schultz; M Junop

    2011-12-31

    PH domains represent one of the most common domains in the human proteome. These domains are recognized as important mediators of protein-phosphoinositide and protein-protein interactions. Phosphoinositides are lipid components of the membrane that function as signaling molecules by targeting proteins to their sites of action. Phosphoinositide based signaling pathways govern a diverse range of important cellular processes including membrane remodeling, differentiation, proliferation and survival. Myo-Inositol phosphates are soluble signaling molecules that are structurally similar to the head groups of phosphoinositides. These molecules have been proposed to function, at least in part, by regulating PH domain-phosphoinositide interactions. Given the structural similarity of inositol phosphates we were interested in examining the specificity of PH domains towards the family of myo-inositol pentakisphosphate isomers. In work reported here we demonstrate that the C-terminal PH domain of pleckstrin possesses the specificity required to discriminate between different myo-inositol pentakisphosphate isomers. The structural basis for this specificity was determined using high-resolution crystal structures. Moreover, we show that while the PH domain of Grp1 does not possess this high degree of specificity, the PH domain of protein kinase B does. These results demonstrate that some PH domains possess enough specificity to discriminate between myo-inositol pentakisphosphate isomers allowing for these molecules to differentially regulate interactions with phosphoinositides. Furthermore, this work contributes to the growing body of evidence supporting myo-inositol phosphates as regulators of important PH domain-phosphoinositide interactions. Finally, in addition to expanding our knowledge of cellular signaling, these results provide a basis for developing tools to probe biological pathway.

  1. Oxysterol-binding proteins: sterol and phosphoinositide sensors coordinating transport, signaling and metabolism.

    PubMed

    Olkkonen, Vesa M; Li, Shiqian

    2013-10-01

    Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute a family of sterol and phosphoinositide binding proteins conserved in eukaryotes. The mechanisms of ORP function have remained incompletely understood. However, several ORPs are present at membrane contact sites and control the activity of enzymatic effectors or assembly of protein complexes, with impacts on signaling, vesicle transport, and lipid metabolism. An increasing number of protein interaction partners of ORPs have been identified, providing clues of their involvement in multiple aspects of cell regulation. The functions assigned for mammalian ORPs include coordination of sterol and sphingolipid metabolism and mitogenic signaling (OSBP), control of ER-late endosome (LE) contacts and LE motility (ORP1L), neutral lipid metabolism (ORP2), cell adhesion (ORP3), cholesterol eggress from LE (ORP5), macrophage lipid homeostasis, migration and high-density lipoprotein metabolism (ORP8), apolipoprotein B-100 secretion (ORP10), and adipogenesis (ORP11). The anti-proliferative ORPphilin compounds target OSBP and ORP4, revealing a function of ORPs in cell proliferation and survival. The Saccharomyces cerevisiae OSBP homologue (Osh) proteins execute multifaceted functions in sterol and sphingolipid homeostasis, post-Golgi vesicle transport, as well as phosphatidylinositol-4-phosphate and target of rapamycin complex 1 (TORC1) signaling. These observations identify ORPs as coordinators of lipid signals with an unforeseen variety of cellular processes. PMID:23830809

  2. Corneal cell survival in adenovirus type 19 infection requires phosphoinositide 3-kinase/Akt activation.

    PubMed

    Rajala, Maitreyi S; Rajala, Raju V S; Astley, Roger A; Butt, Amir L; Chodosh, James

    2005-10-01

    Adenovirus type 19 is a major cause of epidemic keratoconjunctivitis, the only ocular adenoviral infection associated with prolonged corneal inflammation. In this study, we investigated the role of phosphoinositide 3-kinase (PI3K) and Akt and their downstream targets in adenovirus infection, and here we report the novel finding that adenovirus type 19 utilizes the PI3K/Akt pathway to maintain corneal fibroblast viability in acute infection. We demonstrate phosphorylation of GSK-3beta and nuclear translocation of the p65 subunit of NF-kappaB, both downstream targets of the PI3K/Akt pathway, in adenovirus-infected corneal fibroblasts in a PI3K-dependent manner. Inhibition of PI3K had no effect on early viral gene expression, suggesting normal viral internalization, but pretreatment with the PI3K inhibitor LY294002 or overexpression of dominant negative Akt induced early cytopathic effect and caspase-mediated cell death in adenovirus-infected cells. Early cell death could be circumvented despite LY294002 by overexpression of constitutively active Akt. Furthermore, we show an interaction between cSrc and the p85 regulatory subunit of PI3K in infected cells through a phosphorylation-dependent mechanism. The results presented in this paper provide the first direct evidence that PI3K-mediated Akt activation in adenovirus-infected corneal cells may contribute to viral pathogenesis by the prolongation of cell viability. PMID:16160160

  3. New experimental trends for phosphoinositides research on ion transporter/channel regulation.

    PubMed

    Mori, Masayuki X; Inoue, Ryuji

    2014-01-01

    Phosphoinositides(4,5)-bisphosphates [PI(4,5)P2] critically controls membrane excitability, the disruption of which leads to pathophysiological states. PI(4,5)P2 plays a primary role in regulating the conduction and gating properties of ion channels/transporters, through electrostatic and hydrophobic interactions that allow direct associations. In recent years, the development of many molecular tools have brought deep insights into the mechanisms underlying PI(4,5)P2-mediated regulation. This review summarizes the methods currently available to manipulate the cell membrane PI(4,5)P2 level including pharmacological interventions as well as newly designed molecular tools. We concisely introduce materials and experimental designs suitable for the study of PI(4,5)P2-mediated regulation of ion-conducting molecules, in order to assist researchers who are interested in this area. It is our further hope that the knowledge introduced in this review will help to promote our understanding about the pathology of diseases such as cardiac arrhythmias, bipolar disorders, and Alzheimer's disease which are somehow associated with a disruption of PI(4,5)P2 metabolism. PMID:25367262

  4. Phosphoinositide regulation of inward rectifier potassium (Kir) channels

    PubMed Central

    Fürst, Oliver; Mondou, Benoit; D'Avanzo, Nazzareno

    2014-01-01

    Inward rectifier potassium (Kir) channels are integral membrane proteins charged with a key role in establishing the resting membrane potential of excitable cells through selective control of the permeation of K+ ions across cell membranes. In conjunction with secondary anionic phospholipids, members of this family are directly regulated by phosphoinositides (PIPs) in the absence of other proteins or downstream signaling pathways. Different Kir isoforms display distinct specificities for the activating PIPs but all eukaryotic Kir channels are activated by PI(4,5)P2. On the other hand, the bacterial KirBac1.1 channel is inhibited by PIPs. Recent crystal structures of eukaryotic Kir channels in apo and lipid bound forms reveal one specific binding site per subunit, formed at the interface of N- and C-terminal domains, just beyond the transmembrane segments and clearly involving some of the key residues previously identified as controlling PI(4,5)P2 sensitivity. Computational, biochemical, and biophysical approaches have attempted to address the energetic determinants of PIP binding and selectivity among Kir channel isoforms, as well as the conformational changes that trigger channel gating. Here we review our current understanding of the molecular determinants of PIP regulation of Kir channel activity, including in context with other lipid modulators, and provide further discussion on the key questions that remain to be answered. PMID:24409153

  5. Kappa opioid receptors stimulate phosphoinositide turnover in rat brain

    SciTech Connect

    Periyasamy, S.; Hoss, W. )

    1990-01-01

    The effects of various subtype-selective opioid agonists and antagonists on the phosphoinositide (PI) turnover response were investigated in the rat brain. The {kappa}-agonists U-50,488H and ketocyclazocine produced a concentration-dependent increase in the accumulation of IP's in hippocampal slices. The other {kappa}-agonists Dynorphin-A (1-13) amide, and its protected analog D(Ala){sup 2}-dynorphin-A (1-13) amide also produced a significant increase in the formation of ({sup 3}H)-IP's, whereas the {mu}-selective agonists (D-Ala{sup 2}-N-Me-Phe{sup 4}-Gly{sup 5}-ol)-enkephalin and morphine and the {delta}-selective agonist (D-Pen{sup 2,5})-enkephalin were ineffective. The increase in IP's formation elicited by U-50,488H was partially antagonized by naloxone and more completely antagonized by the {kappa}-selective antagonists nor-binaltorphimine and MR 2266. The formation of IP's induced by U-50,488H varies with the regions of the brain used, being highest in hippocampus and amygdala, and lowest in striatum and pons-medullar. The results indicate that brain {kappa}- but neither {mu}- nor {delta}- receptors are coupled to the PI turnover response.

  6. Targeting phosphoinositide 3-kinase ? for the treatment of respiratory diseases.

    PubMed

    Sriskantharajah, Srividya; Hamblin, Nicole; Worsley, Sally; Calver, Andrew R; Hessel, Edith M; Amour, Augustin

    2013-03-01

    Asthma and chronic obstructive pulmonary disease (COPD) are characterized in their pathogenesis by chronic inflammation in the airways. Phosphoinositide 3-kinase ? (PI3K?), a lipid kinase expressed predominantly in leukocytes, is thought to hold much promise as a therapeutic target for such inflammatory conditions. Of particular interest for the treatment of severe respiratory disease is the observation that inhibition of PI3K? may restore steroid effectiveness under conditions of oxidative stress. PI3K? inhibition may also prevent recruitment of inflammatory cells, including T lymphocytes and neutrophils, as well as the release of proinflammatory mediators, such as cytokines, chemokines, reactive oxygen species, and proteolytic enzymes. In addition, targeting the PI3K? pathway could reduce the incidence of pathogen-induced exacerbations by improving macrophage-mediated bacterial clearance. In this review, we discuss the potential and highlight the unknowns of targeting PI3K? for the treatment of respiratory disease, focusing on recent developments in the role of the PI3K? pathway in inflammatory cell types believed to be critical to the pathogenesis of COPD. PMID:23551101

  7. Ciliary Phosphoinositide Regulates Ciliary Protein Trafficking in Drosophila.

    PubMed

    Park, Jina; Lee, Nayoung; Kavoussi, Adriana; Seo, Jeong Taeg; Kim, Chul Hoon; Moon, Seok Jun

    2015-12-29

    Cilia are highly specialized antennae-like cellular organelles. Inositol polyphosphate 5-phosphatase E (INPP5E) converts PI(4,5)P2 into PI4P and is required for proper ciliary function. Although Inpp5e mutations are associated with ciliopathies in humans and mice, the precise molecular role INPP5E plays in cilia remains unclear. Here, we report that Drosophila INPP5E (dINPP5E) regulates ciliary protein trafficking by controlling the phosphoinositide composition of ciliary membranes. Mutations in dInpp5e lead to hearing deficits due to the mislocalization of dTULP and mechanotransduction channels, Inactive and NOMPC, in chordotonal cilia. Both loss of dINPP5E and ectopic expression of the phosphatidylinositol-4-phosphate 5-kinase Skittles increase PI(4,5)P2 levels in the ciliary base. The fact that Skittles expression phenocopies the dInpp5e mutants confirms a central role for PI(4,5)P2 in the regulation of dTULP, Inactive, and NOMPC localization. These data suggest that the spatial localization and levels of PI(4,5)P2 in ciliary membranes are important regulators of ciliary trafficking and function. PMID:26723017

  8. Receptor-coupled phosphoinositide hydrolysis in human retinal pigment epithelium.

    PubMed

    Feldman, E L; Randolph, A E; Johnston, G C; DelMonte, M A; Greene, D A

    1991-06-01

    Carbachol and histamine stimulated phosphoinositide (PPI) hydrolysis in cultured human retinal pigment epithelium (RPE), as reflected by an accumulation of 3H-inositol phosphates in the presence of 10 mM Li+. Carbachol increased PPI hydrolysis to greater than 600% of basal with an EC50 of 60 microM; stimulation was linear up to 60 min. This activation likely occurred via the M3 muscarinic cholinergic receptor based on the IC50 values for 4-diphenylacetoxy-N-methylpiperidine methiodide (0.47 nM), pirenzepine (280 nM), and 11-[[2-[(diethylamino)methyl]-1-piperidinyl]-acetyl]-5,11- dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one (1.4 microM). Carbachol-mediated PPI hydrolysis was decreased by 80% in the absence of extracellular Ca2+. Histamine stimulated PPI turnover in a linear manner by 180% with an EC50 of 20 microM by the H1 histaminergic receptor. Serotonin, glutamate, norepinephrine, and dopamine were inactive. In human RPE, the resting cytoplasmic Ca2+ concentration, as determined by fura-2 fluorescence, was 138 +/- 24 nM. On the addition of carbachol, there was a 180% increase in peak intracellular Ca2+; addition of histamine increased intracellular Ca2+ by 187%. These results suggest receptor-mediated, inositol lipid hydrolysis is coupled to intracellular Ca2+ flux in human RPE. PMID:1851211

  9. The role of phosphoinositide-regulated actin reorganization in chemotaxis and cell migration

    PubMed Central

    Wu, C-Y; Lin, M-W; Wu, D-C; Huang, Y-B; Huang, H-T; Chen, C-L

    2014-01-01

    Reorganization of the actin cytoskeleton is essential for cell motility and chemotaxis. Actin-binding proteins (ABPs) and membrane lipids, especially phosphoinositides PI(4,5)P2 and PI(3,4,5)P3 are involved in the regulation of this reorganization. At least 15 ABPs have been reported to interact with, or regulated by phosphoinositides (PIPs) whose synthesis is regulated by extracellular signals. Recent studies have uncovered several parallel intracellular signalling pathways that crosstalk in chemotaxing cells. Here, we review the roles of ABPs and phosphoinositides in chemotaxis and cell migration. Linked Articles This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24 PMID:25420930

  10. Decrease in platelet activating factor stimulated phosphoinositide turnover during storage of human platelets in plasma

    SciTech Connect

    Carter, M.G.; Shukla, S.D. )

    1987-05-01

    Human platelet concentrate from the American Red Cross Blood Center was stored at 24{degree}C in a shaker and aliquots were taken out at time intervals aseptically. Platelet activating factor (PAF) stimulated turnover of phosphoinositide (PPI) was monitored by assaying {sup 32}P incorporation into phosphoinositides using platelet rich plasma (PRP). Platelets in PRP were incubated with 1 {times} 10{sup {minus}7} M PAF at 37{degree}C with gentle shaking and after 5 min their lipids were extracted and analysed by TLC for {sup 32}P-phosphoinositides. The percent stimulation of {sup 32}P incorporation by PAF (over control) into PPI was approximately 250, 100, 60, 25 and 20 on days 1, 2, 3, 5 and 6, respectively. This indicated a dramatic decrease in PAF responsive turnover of platelet PPI during storage. These findings have important implications in relation to PAF receptor activity and viability of platelets at different periods of storage.

  11. Ca2+ Regulation of Trypanosoma brucei Phosphoinositide Phospholipase C

    PubMed Central

    King-Keller, Sharon; Moore, Christina A.; Docampo, Roberto

    2015-01-01

    We characterized a phosphoinositide phospholipase C (PI-PLC) from the procyclic form (PCF) of Trypanosoma brucei. The protein contains a domain organization characteristic of typical PI-PLCs, such as X and Y catalytic domains, an EF-hand calcium-binding motif, and a C2 domain, but it lacks a pleckstrin homology (PH) domain. In addition, the T. brucei PI-PLC (TbPI-PLC) contains an N-terminal myristoylation consensus sequence found only in trypanosomatid PI-PLCs. A peptide containing this N-terminal domain fused to green fluorescent protein (GFP) was targeted to the plasma membrane. TbPI-PLC enzymatic activity was stimulated by Ca2+ concentrations below the cytosolic levels in the parasite, suggesting that the enzyme is constitutively active. TbPI-PLC hydrolyzes both phosphatidylinositol (PI) and phosphatidylinositol 4,5-bisphosphate (PIP2), with a higher affinity for PIP2. We found that modification of a single amino acid in the EF-hand motif greatly affected the protein's Ca2+ sensitivity and substrate preference, demonstrating the role of this motif in Ca2+ regulation of TbPI-PLC. Endogenous TbPI-PLC localizes to intracellular vesicles and might be using an intracellular source of PIP2. Knockdown of TbPI-PLC expression by RNA interference (RNAi) did not result in growth inhibition, although enzymatic activity was still present in parasites, resulting in hydrolysis of PIP2 and a contribution to the inositol 1,4,5-trisphosphate (IP3)/diacylglycerol (DAG) pathway. PMID:25769297

  12. Rapamycin increases CCN2 expression of lung fibroblasts via phosphoinositide 3-kinase.

    PubMed

    Xu, Xuefeng; Dai, Huaping; Geng, Jing; Wan, Xuan; Huang, Xiaoxi; Li, Fei; Jiang, Dianhua; Wang, Chen

    2015-08-01

    Excessive production of connective tissue growth factor (CTGF, CCN2) and increased motor ability of the activated fibroblast phenotype contribute to the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, molecules and signal pathways regulating CCN2 expression and migration of lung fibroblasts are still elusive. We hypothesize that rapamycin, via binding and blocking mammalian target of rapamycin (mTOR) complex (mTORC), affects CCN2 expression and migration of lung fibroblasts in vitro. Primary normal and fibrotic human lung fibroblasts were isolated from lung tissues of three patients with primary spontaneous pneumothorax and three with IPF. Cells were incubated with regular medium, or medium containing rapamycin, human recombinant transforming growth factor (TGF)-?1, or both. CCN2 and tissue inhibitor of metalloproteinase (TIMP)-1 expression in cells or supernatant was detected. Wound healing and migration assay was used to measure the migratory potential. TGF-? type I receptor (T?RI)/Smad inhibitor, SB431542 and phosphoinositide 3-kinase (PI3K) inhibitor, LY294002 were used to determine rapamycin's mechanism of action. We demonstrated that rapamycin amplified basal or TGF-?1-induced CCN2 mRNA and protein expression in normal or fibrotic fibroblasts by Smad-independent but PI3K-dependent pathway. Additionally, rapamycin also enhanced TIMP-1 expression as indicated by ELISA. However, wound healing and migrating assay showed rapamycin did not affect the mobility of fibroblasts. Collectively, this study implies a significant fibrogenic induction activity of rapamycin by activating AKT and inducing CCN2 expression in vitro and provides the possible mechanisms for the in vivo findings which previously showed no antifibrotic effect of rapamycin on lung fibrosis. PMID:26192087

  13. Genome-Wide Analysis of the Phosphoinositide Kinome from Two Ciliates Reveals Novel Evolutionary Links for Phosphoinositide Kinases in Eukaryotic Cells

    PubMed Central

    Leondaritis, George; Siokos, John; Skaripa, Irini; Galanopoulou, Dia

    2013-01-01

    Background The complexity of phosphoinositide signaling in higher eukaryotes is partly due to expansion of specific families and types of phosphoinositide kinases (PIKs) that can generate all phosphoinositides via multiple routes. This is particularly evident in the PI3Ks and PIPKs, and it is considered an evolutionary trait associated with metazoan diversification. Yet, there are limited comprehensive studies on the PIK repertoire of free living unicellular organisms. Methodology/Principal Findings We undertook a genome-wide analysis of putative PIK genes in two free living ciliated cells, Tetrahymena and Paramecium. The Tetrahymena thermophila and Paramecium tetraurelia genomes were probed with representative kinases from all families and types. Putative homologs were verified by EST, microarray and deep RNA sequencing database searches and further characterized for domain structure, catalytic efficiency, expression patterns and phylogenetic relationships. In total, we identified and characterized 22 genes in the Tetrahymena thermophila genome and 62 highly homologues genes in Paramecium tetraurelia suggesting a tight evolutionary conservation in the ciliate lineage. Comparison to the kinome of fungi reveals a significant expansion of PIK genes in ciliates. Conclusions/Significance Our study highlights four important aspects concerning ciliate and other unicellular PIKs. First, ciliate-specific expansion of PI4KIII-like genes. Second, presence of class I PI3Ks which, at least in Tetrahymena, are associated with a metazoan-type machinery for PIP3 signaling. Third, expansion of divergent PIPK enzymes such as the recently described type IV transmembrane PIPKs. Fourth, presence of possible type II PIPKs and presumably inactive PIKs (hence, pseudo-PIKs) not previously described. Taken together, our results provide a solid framework for future investigation of the roles of PIKs in ciliates and indicate that novel functions and novel regulatory pathways of phosphoinositides may be more widespread than previously thought in unicellular organisms. PMID:24244373

  14. Genetic alterations of phosphoinositide 3-kinase subunit genes in human glioblastomas.

    PubMed

    Mizoguchi, Masahiro; Nutt, Catherine L; Mohapatra, Gayatry; Louis, David N

    2004-10-01

    Genetic alterations of PI3K (phosphoinositide 3-kinase) subunits have been documented in a number of tumor types, with increased PI3K activity linked to gene amplification and mutation of catalytic subunits, as well as mutations of regulatory subunits. Among high grade gliomas, activation of the PI3K-AKT signaling pathway through loss of PTEN function is common. We therefore investigated whether genetic alteration of class IA PI3Ks might provide a mechanism for deregulation of this pathway in glioblastomas. We studied a series of glioblastomas with FISH to assess copy number of catalytic subunits (PIK3CA and PIK3CD) and with PCR-SSCP to screen for somatic mutations of conserved regions of both catalytic and regulatory subunits. FISH revealed frequent balanced copy number increases of both PIK3CA and PIK3CD, and one case showed an extra copy limited to PIK3CA. One glioblastoma exhibited a 9-bp deletion that encompassed the exon-intron junction of exon 12 of PIK3R1, documenting for the first time a mutation within a PI3K regulatory subunit in human glioblastoma. This deletion would be predicted to yield a truncated protein that lacks the inhibitory domain, resulting in increased PI3K activity. Furthermore, the case with selected PIK3CA copy number gain and the case with a truncating PIK3R1 mutation both featured AKT activation without PTEN mutation. These results suggest that genetic alterations of class IA PI3K subunit genes can occasionally play a role in human glioblastoma by activating the PI3K-AKT signaling pathway independently of PTEN mutation. PMID:15605984

  15. Phosphoinositide 3-kinase at the crossroad between endocytosis and signaling of cytokine receptors

    PubMed Central

    Basquin, Cyril; Sauvonnet, Nathalie

    2013-01-01

    Class I phosphoinositide 3-kinase (PI3K) is a lipid kinase playing key roles in many signaling pathways regulating cell survival and growth. Besides its important role in signal transduction, PI3K is also involved in actin and membrane reorganization such as protrusion, adhesion, phagocytosis and macropinocytosis. Receptor-mediated endocytosis is initiated by plasma membrane reorganization creating buds that then mature to small vesicles. Whereas most of endocytic mechanisms involve actin polymerization, PI3K requirement has not been clearly investigated. Our study identifies class I PI3K as a key player in clathrin-independent endocytosis of the interleukin 2 receptor (IL-2R) in contrast to the clathrin-dependent entry of transferrin (Tf). IL-2R is a cytokine receptor, inducing several signaling cascades such as PI3K, that are essential for the immune response. We have shown previously that IL-2R can be internalized with or without IL-2 and this process requires dynamin, actin and their regulators cortactin, N-WASP, Rac1 and the kinases Pak. Our recent work reveals that PI3K regulates Rac1 during IL-2R uptake in two ways: via its catalytic activity (p110) and via its regulatory factor (p85). Indeed, the catalytic activity of PI3K is required for both constitutive and IL-2 induced uptake of cytokine receptors, in lymphocytes as well as in epithelial cells. Interestingly, Vav2, a Rac1 GTPase exchange factor (GEF) induced upon PI3K activation, is specifically involved and recruited during IL-2R uptake. The second action of PI3K is via its regulatory subunit, p85, which binds activated Rac1 and IL-2R; this interaction being enhanced upon IL-2 treatment. Thus, PI3K regulates both the activation of Rac1 and its recruitment during IL-2R endocytosis. Finally, our results identify a link between cytokine receptors signaling and clathrin-independent endocytosis. PMID:23986799

  16. Coordinated Expression of Phosphoinositide Metabolic Genes during Development and Aging of Human Dorsolateral Prefrontal Cortex

    PubMed Central

    Rapoport, Stanley I.; Primiani, Christopher T.; Chen, Chuck T.; Ahn, Kwangmi; Ryan, Veronica H.

    2015-01-01

    Background Phosphoinositides, lipid-signaling molecules, participate in diverse brain processes within a wide metabolic cascade. Hypothesis Gene transcriptional networks coordinately regulate the phosphoinositide cascade during human brain Development and Aging. Methods We used the public BrainCloud database for human dorsolateral prefrontal cortex to examine age-related expression levels of 49 phosphoinositide metabolic genes during Development (0 to 20+ years) and Aging (21+ years). Results We identified three groups of partially overlapping genes in each of the two intervals, with similar intergroup correlations despite marked phenotypic differences between Aging and Development. In each interval, ITPKB, PLCD1, PIK3R3, ISYNA1, IMPA2, INPPL1, PI4KB, and AKT1 are in Group 1, PIK3CB, PTEN, PIK3CA, and IMPA1 in Group 2, and SACM1L, PI3KR4, INPP5A, SYNJ1, and PLCB1 in Group 3. Ten of the genes change expression nonlinearly during Development, suggesting involvement in rapidly changing neuronal, glial and myelination events. Correlated transcription for some gene pairs likely is facilitated by colocalization on the same chromosome band. Conclusions Stable coordinated gene transcriptional networks regulate brain phosphoinositide metabolic pathways during human Development and Aging. PMID:26168237

  17. Original Paper Abstract: Phosphoinositide-specific phospholipase C (PI-PLC)

    E-print Network

    Bhattacharyya, Madan Kumar

    Original Paper Abstract: Phosphoinositide-specific phospholipase C (PI-PLC) hydrolyzes the membrane. DNA synthesis, a measure of cell growth, was significantly suppressed by the PI-PLC-specific inhibitor,5-pyrrolidinedione did not cause any suppression. Acti- vation of PI-PLC by MS salts increased DNA synthesis and abol

  18. IN VITRO ALUMINUM INHIBITION OF BRAIN PHOSPHOINOSITIDE METABOLISM:COMPARISON OF NEONATAL AND ADULTS RATS

    EPA Science Inventory

    Recent evidence indicates that the neurotoxic metal aluminum interferes with the phosphoinositide second messenger system in adult rats both in vitro and in vivo. e have examined the age-related effects of aluminum chloride (AlCl3) on receptor-stimulated inositol phosphate (IP) a...

  19. Effects of the Metabotropic Glutamate Receptor Antagonist MCPG on Phosphoinositide Turnover and Synaptic Plasticity in

    E-print Network

    Bear, Mark

    Effects of the Metabotropic Glutamate Receptor Antagonist MCPG on Phosphoinositide Turnover- servation that the developmental decline in glutamate-stimulated PI turnover is well correlated-aminocyclopentane-1,3-dicarboxylic acid, it fails to block PI turnover and changes in spike adaptation stimulated

  20. Phosphoinositides and Rho Proteins Conspire to Spatially Regulate Actin Polymerization in Motile Cells

    E-print Network

    Fournier, John J.F.

    cytoskeleton. I consider models of actin dynamics, Rho proteins and PIs in isolation based on known or observedPhosphoinositides and Rho Proteins Conspire to Spatially Regulate Actin Polymerization in Motile arthritis and metastatic cancer. Polymerization of the protein actin, one of the three proteins in a cell

  1. Structural and Mechanistic Comparison of Prokaryotic and Eukaryotic Phosphoinositide-specific

    E-print Network

    Williams, Roger L.

    Structural and Mechanistic Comparison of Prokaryotic and Eukaryotic Phosphoinositide phosphates and diacylglycerol (DAG). Whereas the eukaryotic PI-PLCs play a central role in most signal PI-PLCs consist of a single domain of 30 to 35 kDa, while the much larger eukaryotic enzymes (85

  2. Effects of mastoparan and related peptides on phosphoinositide breakdown in HL-60 cells and cell-free preparations.

    PubMed

    Gusovsky, F; Soergel, D G; Daly, J W

    1991-04-25

    In differentiated HL-60 cells the amphiphilic peptide mastoparan induces a dose-dependent stimulation of phosphoinositide breakdown with an EC50 value of 9 microM. Such stimulation can be markedly reduced by pretreatment of the cells with pertussis toxin (100 ng/ml, 2 h). In membranes obtained from differentiated HL-60 cells, guanine nucleotides stimulate the formation of IP2 and IP3. Calcium ions also induce phosphoinositide breakdown in this preparation independent of the presence of guanine nucleotides. In HL-60 cell membranes, mastoparan inhibited GTP gamma S-stimulation of phosphoinositide breakdown with an IC50 value of 3 microM. Such inhibitory activity of mastoparan also was present in membranes from cells pretreated with pertussis toxin. Calcium-induced stimulation of phosphoinositide breakdown was not significantly inhibited by mastoparan. The analogs mastoparan-X and polistes mastoparan had similar inhibitory activity, whereas the analog des-Ile1-Asn2-mastoparan was inactive. In permeabilized HL-60 cells mastoparan also inhibited phosphoinositide breakdown. Another amphiphilic peptide, melittin, was inactive in HL-60 intact cells, but similar to mastoparan, inhibited guanine nucleotide-induced phosphoinositide breakdown in HL-60 cell membranes and permeabilized cells. Thus, mastoparan peptides can stimulate phosphoinositide breakdown in intact HL-60 cells, probably through the interaction with a guanine nucleotide binding protein. In permeabilized cells and in cell membranes, mastoparan induces inhibition of guanine nucleotide-mediated phosphoinositide breakdown presumably through an interaction with an intracellular site. The inhibitory action of mastoparan and melittin is probably related to the amphiphilic character of these peptides. PMID:1655489

  3. D-3 phosphoinositides of the ciliate Tetrahymena: characterization and study of their regulatory role in lysosomal enzyme secretion.

    PubMed

    Leondaritis, George; Tiedtke, Arno; Galanopoulou, Dia

    2005-09-30

    Phosphatidylinositol 3-phosphate, PtdIns3P, is a phosphoinositide which is implicated in regulating membrane trafficking in both mammalian and yeast cells. It also serves as a precursor for the synthesis of phosphatidylinositol 3,5-bisphosphate, PtdIns3,5P2, a phosphoinositide, the exact functions of which remain unknown. In this report, we show that these two phosphoinositides are constitutive lipid components of the ciliate Tetrahymena. Using HPLC analysis, PtdIns3P and PtdIns3,5P2 were found to comprise 16% and 30-40% of their relevant phosphoinositide pools, respectively. Treatment of Tetrahymena cells with wortmannin (0.1-10 microM) resulted in the depletion of PtdIns3P and PtdIns3,5P2 without any effect on D-4 phosphoinositides. Wortmannin was further used for the investigation of D-3 phosphoinositide involvement in the regulation of lysosomal vesicular trafficking. Incubation of Tetrahymena cells with wortmannin resulted in enhanced secretion of two different lysosomal enzymes without any change in their total activities. Experiments performed with a T. thermophila secretion mutant strain verified that the wortmannin-induced secretion is specific and it is not due to a diversion of lysosomal enzymes to other secretory pathways. Moreover, experiments performed with a phagocytosis-deficient T. thermophila strain showed that a substantial fraction of wortmannin-induced secretion was dependent on the presence of functional phagosomes/phagolysosomes. PMID:16081170

  4. Corequirement of Specific Phosphoinositides and Small GTP-binding Protein Cdc42 in Inducing Actin Assembly in Xenopus Egg Extracts

    PubMed Central

    Le Ma; Cantley, Lewis C.; Janmey, Paul A.; Kirschner, Marc W.

    1998-01-01

    Both phosphoinositides and small GTP-binding proteins of the Rho family have been postulated to regulate actin assembly in cells. We have reconstituted actin assembly in response to these signals in Xenopus extracts and examined the relationship of these pathways. We have found that GTP?S stimulates actin assembly in the presence of endogenous membrane vesicles in low speed extracts. These membrane vesicles are required, but can be replaced by lipid vesicles prepared from purified phospholipids containing phosphoinositides. Vesicles containing phosphatidylinositol (4,5) bisphosphate or phosphatidylinositol (3,4,5) trisphosphate can induce actin assembly even in the absence of GTP?S. RhoGDI, a guanine-nucleotide dissociation inhibitor for the Rho family, inhibits phosphoinositide-induced actin assembly, suggesting the involvement of the Rho family small G proteins. Using various dominant mutants of these G proteins, we demonstrate the requirement of Cdc42 for phosphoinositide-induced actin assembly. Our results suggest that phosphoinositides may act to facilitate GTP exchange on Cdc42, as well as to anchor Cdc42 and actin nucleation activities. Hence, both phosphoinositides and Cdc42 are required to induce actin assembly in this cell-free system. PMID:9490725

  5. Purification of active HOPS complex reveals its affinities for phosphoinositides and the SNARE Vam7p

    PubMed Central

    Stroupe, Christopher; Collins, Kevin M; Fratti, Rutilio A; Wickner, William

    2006-01-01

    Coupling of Rab GTPase activation and SNARE complex assembly during membrane fusion is poorly understood. The homotypic fusion and vacuole protein sorting (HOPS) complex links these two processes: it is an effector for the vacuolar Rab GTPase Ypt7p and is required for vacuolar SNARE complex assembly. We now report that pure, active HOPS complex binds phosphoinositides and the PX domain of the vacuolar SNARE protein Vam7p. These binding interactions support HOPS complex association with the vacuole and explain its enrichment at the same microdomains on docked vacuoles as phosphoinositides, Ypt7p, Vam7p, and the other SNARE proteins. Concentration of the HOPS complex at these microdomains may be a key factor for coupling Rab GTPase activation to SNARE complex assembly. PMID:16601699

  6. Qualitative and quantitative characterization of protein-phosphoinositide interactions with liposome-based methods

    PubMed Central

    Busse, Ricarda A.; Scacioc, Andreea; Hernandez, Javier M.; Krick, Roswitha; Stephan, Milena; Janshoff, Andreas; Thumm, Michael; Kühnel, Karin

    2013-01-01

    We characterized phosphoinositide binding of the S. cerevisiae PROPPIN Hsv2 qualitatively with density flotation assays and quantitatively through isothermal titration calorimetry (ITC) measurements using liposomes. We discuss the design of these experiments and show with liposome flotation assays that Hsv2 binds with high specificity to both PtdIns3P and PtdIns(3,5)P2. We propose liposome flotation assays as a more accurate alternative to the commonly used PIP strips for the characterization of phosphoinositide-binding specificities of proteins. We further quantitatively characterized PtdIns3P binding of Hsv2 with ITC measurements and determined a dissociation constant of 0.67 µM and a stoichiometry of 2:1 for PtdIns3P binding to Hsv2. PtdIns3P is crucial for the biogenesis of autophagosomes and their precursors. Besides the PROPPINs there are other PtdIns3P binding proteins with a link to autophagy, which includes the FYVE-domain containing proteins ZFYVE1/DFCP1 and WDFY3/ALFY and the PX-domain containing proteins Atg20 and Snx4/Atg24. The methods described could be useful tools for the characterization of these and other phosphoinositide-binding proteins. PMID:23445924

  7. Interplay between phosphoinositide lipids and calcium signals at the leading edge of chemotaxing ameboid cells?

    PubMed Central

    Falke, Joseph J.; Ziemba, Brian P.

    2014-01-01

    The chemotactic migration of eukaryotic ameboid cells up concentration gradients is among the most advanced forms of cellular behavior. Chemotaxis is controlled by a complex network of signaling proteins bound to specific lipids on the cytoplasmic surface of the plasma membrane at the front of the cell, or the leading edge. The central lipid players in this leading edge signaling pathway include the phosphoinositides PI(4,5)P2 (PIP2) and PI(3,4,5)P3 (PIP3), both of which play multiple roles. The products of PI(4,5)P2 hydrolysis, diacylglycerol (DAG) and Ins(1,4,5)P3 (IP3), are also implicated as important players. Together, these leading edge phosphoinositides and their degradation products, in concert with a local Ca2+ signal, control the recruitment and activities of many peripheral membrane proteins that are crucial to the leading edge signaling network. The present critical review summarizes the current molecular understanding of chemotactic signaling at the leading edge, including newly discovered roles of phosphoinositide lipids and Ca2+, while highlighting key questions for future research. PMID:24451847

  8. Age-related changes in receptor-mediated phosphoinositide hydrolysis in various regions of rat brain

    SciTech Connect

    Mundy, W.; Tandon, P.; Tilson, H. ); Ali, S. )

    1991-01-01

    The effects of age on cholinergic markers and receptor-stimulated phosphoinositide hydrolysis was examined in the frontal cortex and striatum of male Fischer-344 rats. Choline acetyltransferase activity was decreased 27% in the striatum of aged rats compared to young controls. Muscarinic receptor density as measured by ({sup 3}H)-quinuclidinyl benzilate binding showed a similar 26% decrease in the striatum of aged rats. Phosphoinositide hydrolysis was measured by the release of inositol phosphate (IP) from tissue slices prelabeled with ({sup 3}H)myoinositol in response to carbachol, norepinephrine, and quisqualate. In the cortex, stimulated IP release was significantly greater in slices from aged rats compared to young rats for all three agonists. In contrast, stimulated IP release was significantly decreased in striatal slices from aged rats compared to young for all three agonists. These data indicate a differential effect of age on agonist-stimulated phosphoinositide hydrolysis in the cortex and striatum. The decreased responsiveness in the latter area may result from the age-related loss of postsynaptic receptors.

  9. Characterization of the muscarinic receptor subtype involved in phosphoinositide metabolism in bovine tracheal smooth muscle.

    PubMed Central

    Roffel, A. F.; Meurs, H.; Elzinga, C. R.; Zaagsma, J.

    1990-01-01

    1. The muscarinic receptor subtype involved in the methacholine-induced enhancement of phosphoinositide metabolism in bovine tracheal smooth muscle was identified by using the M2-selective antagonist AF-DX 116 and the M3-selective antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) methobromide, in addition to the M1-selective antagonist pirenzepine, in a classical Schild analysis. 2. All the antagonists shifted the methacholine dose-response curve to the right in a parallel and concentration-dependent fashion, yielding Schild plots with slopes not significantly different from unity. The pA2 values (6.94, 6.32 and 8.54 for pirenzepine, AF-DX 116 and 4-DAMP methobromide respectively) indicate that it is the M3 (smooth muscle/glandular), but not the M2 (cardiac) muscarinic receptor subtype, present in this tissue, that mediates phosphoinositide turnover, in accordance with our previous contractile studies. 3. The results provide additional evidence for the involvement of phosphoinositide turnover in the pharmacomechanical coupling between muscarinic receptor stimulation and contraction in (bovine tracheal) smooth muscle. PMID:2158372

  10. Specificity of Collybistin-Phosphoinositide Interactions: IMPACT OF THE INDIVIDUAL PROTEIN DOMAINS.

    PubMed

    Ludolphs, Michaela; Schneeberger, Daniela; Soykan, Tolga; Schäfer, Jonas; Papadopoulos, Theofilos; Brose, Nils; Schindelin, Hermann; Steinem, Claudia

    2016-01-01

    The regulatory protein collybistin (CB) recruits the receptor-scaffolding protein gephyrin to mammalian inhibitory glycinergic and GABAergic postsynaptic membranes in nerve cells. CB is tethered to the membrane via phosphoinositides. We developed an in vitro assay based on solid-supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine membranes doped with different phosphoinositides on silicon/silicon dioxide substrates to quantify the binding of various CB2 constructs using reflectometric interference spectroscopy. Based on adsorption isotherms, we obtained dissociation constants and binding capacities of the membranes. Our results show that full-length CB2 harboring the N-terminal Src homology 3 (SH3) domain (CB2SH3+) adopts a closed and autoinhibited conformation that largely prevents membrane binding. This autoinhibition is relieved upon introduction of the W24A/E262A mutation, which conformationally "opens" CB2SH3+ and allows the pleckstrin homology domain to properly bind lipids depending on the phosphoinositide species with a preference for phosphatidylinositol 3-monophosphate and phosphatidylinositol 4-monophosphate. This type of membrane tethering under the control of the release of the SH3 domain of CB is essential for regulating gephyrin clustering. PMID:26546675

  11. Phosphoinositide Kinase-3 Status Associated With Presence or Absence of Human Papillomavirus in Head and Neck Squamous Cell Carcinomas

    SciTech Connect

    Yarbrough, Wendell G. Whigham, Amy; Brown, Brandee; Roach, Michael; Slebos, Robbert

    2007-10-01

    Purpose: To investigate phosphoinositide kinase-3 (PI3K) activation in relation to human papillomavirus (HPV) status in head and neck squamous cell carcinoma (HNSCC). Methods and Materials: Gene expression microarray data were analyzed to determine differentially expressed genes between HPV(+) and HPV(-) HNSCC. PIK3CA gene expression was confirmed by quantitative reverse transcriptase-polymerase chain reaction in seven HPV(+) and seven HPV(-) primary HNSCCs. PIK3CA mutation status in three HPV(+) and nine HPV(-) cell lines was determined by polymerase chain reaction amplification of hot spot exons (1, 9, 20) followed by direct sequencing. Results: PIK3CA was overexpressed in HPV(+)-associated HNSCC compared with the expression in HPV(-) HNSCC. Activation of PIK3CA by mutation was found in 1 of the 12 tested HNSCC cell lines. Conclusion: Activation of PI3K by mutation of PIK3CA is rare in HNSCC cell lines and was not found in three HPV(+) cell lines. One mechanism by which HPV-associated HNSCC might activate PI3K is increased expression of PIK3CA.

  12. A phosphoinositide-binding cluster in cavin1 acts as a molecular sensor for cavin1 degradation.

    PubMed

    Tillu, Vikas A; Kovtun, Oleksiy; McMahon, Kerrie-Ann; Collins, Brett M; Parton, Robert G

    2015-10-15

    Caveolae are abundant surface organelles implicated in a range of cellular processes. Two classes of proteins work together to generate caveolae: integral membrane proteins termed caveolins and cytoplasmic coat proteins called cavins. Caveolae respond to membrane stress by releasing cavins into the cytosol. A crucial aspect of this model is tight regulation of cytosolic pools of cavin under resting conditions. We now show that a recently identified region of cavin1 that can bind phosphoinositide (PI) lipids is also a major site of ubiquitylation. Ubiquitylation of lysines within this site leads to rapid proteasomal degradation. In cells that lack caveolins and caveolae, cavin1 is cytosolic and rapidly degraded as compared with cells in which cavin1 is associated with caveolae. Membrane stretching causes caveolar disassembly, release of cavin complexes into the cytosol, and increased proteasomal degradation of wild-type cavin1 but not mutant cavin1 lacking the major ubiquitylation site. Release of cavin1 from caveolae thus leads to exposure of key lysine residues in the PI-binding region, acting as a trigger for cavin1 ubiquitylation and down-regulation. This mutually exclusive PI-binding/ubiquitylation mechanism may help maintain low levels of cytosolic cavin1 in resting cells, a prerequisite for cavins acting as signaling modules following release from caveolae. PMID:26269585

  13. The Protein Complex of Neurodegeneration-related Phosphoinositide Phosphatase Sac3 and ArPIKfyve Binds the Lewy Body-associated Synphilin-1, Preventing Its Aggregation.

    PubMed

    Ikonomov, Ognian C; Sbrissa, Diego; Compton, Lauren M; Kumar, Rita; Tisdale, Ellen J; Chen, Xuequn; Shisheva, Assia

    2015-11-20

    The 5-phosphoinositide phosphatase Sac3, in which loss-of-function mutations are linked to neurodegenerative disorders, forms a stable cytosolic complex with the scaffolding protein ArPIKfyve. The ArPIKfyve-Sac3 heterodimer interacts with the phosphoinositide 5-kinase PIKfyve in a ubiquitous ternary complex that couples PtdIns(3,5)P2 synthesis with turnover at endosomal membranes, thereby regulating the housekeeping endocytic transport in eukaryotes. Neuron-specific associations of the ArPIKfyve-Sac3 heterodimer, which may shed light on the neuropathological mechanisms triggered by Sac3 dysfunction, are unknown. Here we conducted mass spectrometry analysis for brain-derived interactors of ArPIKfyve-Sac3 and unraveled the ?-synuclein-interacting protein Synphilin-1 (Sph1) as a new component of the ArPIKfyve-Sac3 complex. Sph1, a predominantly neuronal protein that facilitates aggregation of ?-synuclein, is a major component of Lewy body inclusions in neurodegenerative ?-synucleinopathies. Modulations in ArPIKfyve/Sac3 protein levels by RNA silencing or overexpression in several mammalian cell lines, including human neuronal SH-SY5Y or primary mouse cortical neurons, revealed that the ArPIKfyve-Sac3 complex specifically altered the aggregation properties of Sph1-GFP. This effect required an active Sac3 phosphatase and proceeded through mechanisms that involved increased Sph1-GFP partitioning into the cytosol and removal of Sph1-GFP aggregates by basal autophagy but not by the proteasomal system. If uncoupled from ArPIKfyve elevation, overexpressed Sac3 readily aggregated, markedly enhancing the aggregation potential of Sph1-GFP. These data identify a novel role of the ArPIKfyve-Sac3 complex in the mechanisms controlling aggregate formation of Sph1 and suggest that Sac3 protein deficiency or overproduction may facilitate aggregation of aggregation-prone proteins, thereby precipitating the onset of multiple neuronal disorders. PMID:26405034

  14. Focal adhesion kinase phosphorylates the phosphatase and tensin homolog deleted on chromosome 10 under the control of p110? phosphoinositide-3 kinase.

    PubMed

    Tzenaki, Niki; Aivaliotis, Michalis; Papakonstanti, Evangelia A

    2015-12-01

    The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor protein is regulated by various mechanisms that are not fully understood. This includes regulation by Tyr phosphorylation by a mechanism that remains elusive. Here, we show that focal adhesion kinase (FAK) phosphorylates PTEN in vitro, in cell-free systems and in cells. Furthermore, by mass spectrometry, we identified Tyr336 on PTEN as being phosphorylated by FAK. Tyr336 phosphorylation increased phosphatase activity, protein-lipid interaction, and protein stability of PTEN. In cells, including primary mouse macrophages and human cancer cell lines, FAK was found to be negatively regulated by p110? phosphoinositide-3 kinase (PI3K), whereas the activation of FAK was positively regulated by RhoA-associated kinase (ROCK). Indeed, the phosphorylation of FAK was unexpectedly increased in macrophages derived from mice expressing kinase-dead p110?. Pharmacologic inactivation of RhoA/ROCK reduced the phosphorylation of FAK to normal levels in cells with genetically inactivated p110?. Likewise, pharmacologic inactivation of FAK reduced the phosphorylation of PTEN in cells expressing kinase-dead p110? and restored the functional defects of p110? inactivation, including Akt phosphorylation and cell proliferation. This work identifies FAK as a target of p110? PI3K that links RhoA with PTEN and establishes for the first time that PTEN is a substrate of FAK-mediated Tyr phosphorylation.-Tzenaki, N., Aivaliotis, M., Papakonstanti, E. A. Focal adhesion kinase phosphorylates the phosphatase and tensin homolog deleted on chromosome 10 under the control of p110? phosphoinositide-3 kinase. PMID:26251180

  15. Assessing the subcellular distribution of oncogenic phosphoinositide 3-kinase using microinjection into live cells

    PubMed Central

    Layton, Meredith J.; Rynkiewicz, Natalie K.; Ivetac, Ivan; Horan, Kristy A.; Mitchell, Christina A.; Phillips, Wayne A.

    2014-01-01

    Oncogenic mutations in PIK3CA lead to an increase in intrinsic phosphoinositide kinase activity, but it is thought that increased access of PI3K? (phosphoinositide 3-kinase ?) to its PM (plasma membrane) localized substrate is also required for increased levels of downstream PIP3/Akt [phosphoinositide-3,4,5-trisphosphate/also called PKB (protein kinase B)] signalling. We have studied the subcellular localization of wild-type and the two most common oncogenic mutants of PI3K? in cells maintained in growth media, and starved or stimulated cells using a novel method in which PI3K? is pre-formed as a 1:1 p110?:p85? complex in vitro then introduced into live cells by microinjection. Oncogenic E545K and H1047R mutants did not constitutively interact with membrane lipids in vitro or in cells maintained in 10% (v/v) FBS. Following stimulation of RTKs (receptor tyrosine kinases), microinjected PI3K? was recruited to the PM, but oncogenic forms of PI3K? were not recruited to the PM to a greater extent and did not reside at the PM longer than the wild-type PI3K?. Instead, the E545K mutant specifically bound activated Cdc42 in vitro and microinjection of E545K was associated with the formation of cellular protrusions, providing some preliminary evidence that changes in protein–protein interactions may play a role in the oncogenicity of the E545K mutant in addition to the well-known changes in lipid kinase activity. PMID:24597785

  16. Characterization of a plasma membrane-associated phosphoinositide-specific phospholipase C from soybean.

    PubMed

    Shi, J; Gonzales, R A; Bhattacharyya, M K

    1995-09-01

    Phosphoinositide-specific phospholipase C (PI-PLC) is a key signal transducing enzyme which generates the second messengers inositol trisphosphate and diacylglycerol in mammalian cells. A cDNA clone (PI-PLC1) encoding a phosphoinositide-specific phospholipase C was isolated from soybean by screening a cDNA expression library using an anti-(plasma membrane) serum. Genomic DNA gel blot analysis suggested that the corresponding gene is a member of a multigene family. The deduced amino acid sequence of the soybean PI-PLC1 isozyme contains the conserved X and Y regions, found in other PI-PLCs. It is closely related to mammalian delta-type PI-PLCs, Dictyostelium discoideum PI-PLC and yeast PI-PLC1 in terms of the arrangement of the conserved region. Unlike mammalian delta-type PI-PLCs and yeast PI-PLC1, the putative Ca(2+)-binding site of the soybean PI-PLC1 is located in the region spanning the X and Y domains, and the N-terminal region is truncated. FLAG epitope-tagged PI-PLC1 fusion protein purified from transgenic tobacco plants showed phosphoinositide-specific phospholipase C activity. Heterologous expression of the soybean PI-PLC1 cDNA in a yeast PI-PLC1 deletion mutant complemented the lethality phenotype of haploid PI-PLC1 disruptants. Immunoblot analysis of the cell fractions prepared from transgenic tobacco plants over-expressing the FLAG epitope-tagged PI-PLC1 fusion protein indicated that the protein encoded by the PI-PLC1 cDNA was localized in the cytosol and plasma membrane. PMID:7550376

  17. Epigallocatechin gallate (EGCG), a major component of green tea, is a dual phosphoinositide-3-kinase/mTOR inhibitor

    SciTech Connect

    Van Aller, Glenn S.; Carson, Jeff D.; Tang, Wei; Peng, Hao; Zhao, Lin; Copeland, Robert A.; Tummino, Peter J.; Luo, Lusong

    2011-03-11

    Research highlights: {yields} Epigallocatechin-3-gallate (EGCG) is an ATP-competitive inhibitor of PI3K and mTOR with Ki values around 300 nM. {yields} EGCG inhibits cell proliferation and AKT phosphorylation at Ser473 in MDA-MB-231and A549 cells. {yields} Molecular docking studies show that EGCG binds well to the PI3K kinase domain active site. {yields} These results suggest another important molecular mechanism for the anticancer activities of EGCG. -- Abstract: The PI3K signaling pathway is activated in a broad spectrum of human cancers, either directly by genetic mutation or indirectly via activation of receptor tyrosine kinases or inactivation of the PTEN tumor suppressor. The key nodes of this pathway have emerged as important therapeutic targets for the treatment of cancer. In this study, we show that (-)-epigallocatechin-3-gallate (EGCG), a major component of green tea, is an ATP-competitive inhibitor of both phosphoinositide-3-kinase (PI3K) and mammalian target of rapamycin (mTOR) with K{sub i} values of 380 and 320 nM respectively. The potency of EGCG against PI3K and mTOR is within physiologically relevant concentrations. In addition, EGCG inhibits cell proliferation and AKT phosphorylation at Ser473 in MDA-MB-231 and A549 cells. Molecular docking studies show that EGCG binds well to the PI3K kinase domain active site, agreeing with the finding that EGCG competes for ATP binding. Our results suggest another important molecular mechanism for the anticancer activities of EGCG.

  18. Spatial Regulation of Membrane Fusion Controlled by Modification of Phosphoinositides

    PubMed Central

    Dumas, Fabrice; Byrne, Richard D.; Vincent, Ben; Hobday, Tina M. C.; Poccia, Dominic L.; Larijani, Banafshé

    2010-01-01

    Membrane fusion plays a central role in many cell processes from vesicular transport to nuclear envelope reconstitution at mitosis but the mechanisms that underlie fusion of natural membranes are not well understood. Studies with synthetic membranes and theoretical considerations indicate that accumulation of lipids characterised by negative curvature such as diacylglycerol (DAG) facilitate fusion. However, the specific role of lipids in membrane fusion of natural membranes is not well established. Nuclear envelope (NE) assembly was used as a model for membrane fusion. A natural membrane population highly enriched in the enzyme and substrate needed to produce DAG has been isolated and is required for fusions leading to nuclear envelope formation, although it contributes only a small amount of the membrane eventually incorporated into the NE. It was postulated to initiate and regulate membrane fusion. Here we use a multidisciplinary approach including subcellular membrane purification, fluorescence spectroscopy and Förster resonance energy transfer (FRET)/two-photon fluorescence lifetime imaging microscopy (FLIM) to demonstrate that initiation of vesicle fusion arises from two unique sites where these vesicles bind to chromatin. Fusion is subsequently propagated to the endoplasmic reticulum-derived membranes that make up the bulk of the NE to ultimately enclose the chromatin. We show how initiation of multiple vesicle fusions can be controlled by localised production of DAG and propagated bidirectionally. Phospholipase C (PLC?), GTP hydrolysis and (phosphatidylinsositol-(4,5)-bisphosphate (PtdIns(4,5)P2) are required for the latter process. We discuss the general implications of membrane fusion regulation and spatial control utilising such a mechanism. PMID:20808914

  19. Endothelial epithelial sodium channel inhibition activates endothelial nitric oxide synthase via phosphoinositide 3-kinase/Akt in small-diameter mesenteric arteries.

    PubMed

    Pérez, Francisco R; Venegas, Fabiola; González, Magdalena; Andrés, Sergio; Vallejos, Catalina; Riquelme, Gloria; Sierralta, Jimena; Michea, Luis

    2009-06-01

    Recent studies have shown that the epithelial sodium channel (ENaC) is expressed in vascular tissue. However, the role that ENaC may play in the responses to vasoconstrictors and NO production has yet to be addressed. In this study, the contractile responses of perfused pressurized small-diameter rat mesenteric arteries to phenylephrine and serotonin were reduced by ENaC blockade with amiloride (75.1+/-3.2% and 16.9+/-2.3% of control values, respectively; P<0.01) that was dose dependent (EC(50)=88.9+/-1.6 nmol/L). Incubation with benzamil, another ENaC blocker, had similar effects. alpha, beta, and gamma ENaC were identified in small-diameter rat mesenteric arteries using RT-PCR and Western blot with specific antibodies. In situ hybridization and immunohistochemistry localized ENaC expression to the tunica media and endothelium of small-diameter rat mesenteric arteries. Patch-clamp experiments demonstrated that primary cultures of mesenteric artery endothelial cells expressed amiloride-sensitive sodium currents. Mechanical ablation of the endothelium or inhibition of eNOS with N(omega)-nitro-L-arginine inhibited the reduction in contractility caused by ENaC blockers. ENaC inhibitors increased eNOS phosphorylation (Ser 1177) and Akt phosphorylation (Ser 473). The presence of the phosphoinositide 3-kinase inhibitor LY294002 blunted Akt phosphorylation and eNOS phosphorylation and the decrease in the response to phenylephrine caused by blockers of ENaC, indicating that the phosphoinositide 3-kinase/Akt pathway was activated after ENaC inhibition. Finally, we observed that the effects of blockers of ENaC were flow dependent and that the vasodilatory response to shear stress was enhanced by ENaC blockade. Our results identify a previously unappreciated role for ENaC as a negative modulator of eNOS and NO production in resistance arteries. PMID:19398659

  20. Electrostatics of phosphoinositide bilayer membranes. Theoretical and experimental results.

    PubMed Central

    Langner, M; Cafiso, D; Marcelja, S; McLaughlin, S

    1990-01-01

    We made fluorescence, electron paramagnetic resonance (EPR), electrophoretic mobility, and ionizing electrode measurements to study the effect of the monovalent lipid phosphatidylinositol (PI) and the trivalent lipid phosphatidylinositol 4,5-bisphosphate (PIP2) on the electrostatic potential adjacent to bilayer membranes. When the membranes were formed from mixtures of PI and the zwitterionic lipid phosphatidylcholine (PC), the Gouy-Chapman-Stern (GCS) theory described adequately the dependence of potential on distance (0, 1, 2 nm) from the membrane, mole % negative lipid, and [KCI]. Furthermore, all EPR and fluorescence probes reported identical surface potentials with a PC/PI membrane. With PC/PIP2 membranes, however, the anionic (coion) probes reported less negative potentials than the cationic (counterion) probes; the deviations from the GCS theory were greater for the coions than the counterions. Discreteness-of-charge theories based on the Poisson-Boltzmann equation incorrectly predict that deviations from the GCS theory should be greater for counterions than for coions. We discuss a consistent statistical mechanical theory that takes into account three effects ignored in the GCS theory: the finite size of the ions in the double layer, the electrical interaction between pairs of ions (correlation effects), and the mobile discrete nature of the surface charges. This theory correctly predicts that deviations from GCS theory should be negligible for monovalent lipids, significant for trivalent lipids, and greater for coions than for counterions. PMID:2156577

  1. Measuring Activity of Phosphoinositide Lipid Kinases Using a Bioluminescent ADP-Detecting Assay.

    PubMed

    Tai, Andrew W; Vidugiriene, Jolanta

    2016-01-01

    Phosphatidylinositol (PI) and its phosphorylated derivatives, collectively called phosphoinositides, are important second messengers involved in a variety of cellular processes, including cell proliferation, apoptosis, metabolism, and migration. These derivatives are generated by a family of kinases called phosphoinositide lipid kinases (PIKs). Due to the central role of these kinases in signaling pathways, assays for measuring their activity are often used for drug development. Lipid kinase substrates are present in unique membrane environments in vivo and are insoluble in aqueous solutions. Therefore the most important consideration in developing successful lipid kinase assays is the physical state of lipid kinase substrates. Here we describe the preparation of lipid substrates for two major classes of lipid kinases, phosphatidylinositol 3-kinases (PI3Ks) and phosphatidylinositol 4-kinases (PI4Ks). Using PI4Ks as an example, we also provide a detailed protocol for small-scale kinase expression and affinity purification from transiently transfected mammalian cells. For measuring lipid kinase activity we apply a universal bioluminescent ADP detection approach. The approach is compatible with diverse lipid substrates and can be used as a single integrated platform for measuring all classes of lipid and protein kinases. PMID:26501903

  2. Modulation of Ciliary Phosphoinositide Content Regulates Trafficking and Sonic Hedgehog Signaling Output.

    PubMed

    Chávez, Marcelo; Ena, Sabrina; Van Sande, Jacqueline; de Kerchove d'Exaerde, Alban; Schurmans, Stéphane; Schiffmann, Serge N

    2015-08-10

    Ciliary transport is required for ciliogenesis, signal transduction, and trafficking of receptors to the primary cilium. Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) have been associated with ciliary dysfunction; however, its role in regulating ciliary phosphoinositides is unknown. Here we report that in neural stem cells, phosphatidylinositol 4-phosphate (PI4P) is found in high levels in cilia whereas phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) is not detectable. Upon INPP5E inactivation, PI(4,5)P2 accumulates at the ciliary tip whereas PI4P is depleted. This is accompanied by recruitment of the PI(4,5)P2-interacting protein TULP3 to the ciliary membrane, along with Gpr161. This results in an increased production of cAMP and a repression of the Shh transcription gene Gli1. Our results reveal the link between ciliary regulation of phosphoinositides by INPP5E and Shh regulation via ciliary trafficking of TULP3/Gpr161 and also provide mechanistic insight into ciliary alterations found in Joubert and MORM syndromes resulting from INPP5E mutations. PMID:26190144

  3. Yunis-Varón Syndrome Is Caused by Mutations in FIG4, Encoding a Phosphoinositide Phosphatase

    PubMed Central

    Campeau, Philippe M.; Lenk, Guy M.; Lu, James T.; Bae, Yangjin; Burrage, Lindsay; Turnpenny, Peter; Román Corona-Rivera, Jorge; Morandi, Lucia; Mora, Marina; Reutter, Heiko; Vulto-van Silfhout, Anneke T.; Faivre, Laurence; Haan, Eric; Gibbs, Richard A.; Meisler, Miriam H.; Lee, Brendan H.

    2013-01-01

    Yunis-Varón syndrome (YVS) is an autosomal-recessive disorder with cleidocranial dysplasia, digital anomalies, and severe neurological involvement. Enlarged vacuoles are found in neurons, muscle, and cartilage. By whole-exome sequencing, we identified frameshift and missense mutations of FIG4 in affected individuals from three unrelated families. FIG4 encodes a phosphoinositide phosphatase required for regulation of PI(3,5)P2 levels, and thus endosomal trafficking and autophagy. In a functional assay, both missense substitutions failed to correct the vacuolar phenotype of Fig4-null mouse fibroblasts. Homozygous Fig4-null mice exhibit features of YVS, including neurodegeneration and enlarged vacuoles in neurons. We demonstrate that Fig4-null mice also have small skeletons with reduced trabecular bone volume and cortical thickness and that cultured osteoblasts accumulate large vacuoles. Our findings demonstrate that homozygosity or compound heterozygosity for null mutations of FIG4 is responsible for YVS, the most severe known human phenotype caused by defective phosphoinositide metabolism. In contrast, in Charcot-Marie-Tooth disease type 4J (also caused by FIG4 mutations), one of the FIG4 alleles is hypomorphic and disease is limited to the peripheral nervous system. This genotype-phenotype correlation demonstrates that absence of FIG4 activity leads to central nervous system dysfunction and extensive skeletal anomalies. Our results describe a role for PI(3,5)P2 signaling in skeletal development and maintenance. PMID:23623387

  4. An N-terminal Amphipathic Helix Binds Phosphoinositides and Enhances Kalirin Sec14 Domain-mediated Membrane Interactions.

    PubMed

    Miller, Megan B; Vishwanatha, Kurutihalli S; Mains, Richard E; Eipper, Betty A

    2015-05-22

    Previous studies revealed an essential role for the lipid-binding Sec14 domain of kalirin (KalSec14), but its mechanism of action is not well understood. Because alternative promoter usage appends unique N-terminal peptides to the KalSec14 domain, we used biophysical, biochemical, and cell biological approaches to examine the two major products, bKalSec14 and cKalSec14. Promoter B encodes a charged, unstructured peptide, whereas promoter C encodes an amphipathic helix (Kal-C-helix). Both bKalSec14 and cKalSec14 interacted with lipids in PIP strip and liposome flotation assays, with significantly greater binding by cKalSec14 in both assays. Disruption of the hydrophobic face of the Kal-C-helix in cKalSec14KKED eliminated its increased liposome binding. Although cKalSec14 showed significantly reduced binding to liposomes lacking phosphatidylinositol phosphates or cholesterol, liposome binding by bKalSec14 and cKalSec14KKED was not affected. When expressed in AtT-20 cells, bKalSec14-GFP was diffusely localized, whereas cKalSec14-GFP localized to the trans-Golgi network and secretory granules. The amphipathic C-helix was sufficient for this localization. When AtT-20 cells were treated with a cell-permeant derivative of the Kal-C-helix (Kal-C-helix-Arg9), we observed increased secretion of a product stored in mature secretory granules, with no effect on basal secretion; a cell-permeant control peptide (Kal-C-helixKKED-Arg9) did not have this effect. Through its ability to control expression of a novel, phosphoinositide-binding amphipathic helix, Kalrn promoter usage is expected to affect function. PMID:25861993

  5. The Phosphoinositide 3-Kinase Regulatory Subunit p85  Can Exert Tumor Suppressor Properties through Negative Regulation of Growth Factor Signaling

    E-print Network

    Taniguchi, Cullen M.

    Phosphoinositide 3-kinase (PI3K) plays a critical role in tumorigenesis, and the PI3K p85 regulatory subunit exerts both positive and negative effects on signaling. Expression of Pik3r1, the gene encoding p85, is decreased ...

  6. A Lipid-modified Phosphoinositide-specific Phospholipase C (TcPI-PLC) Is Involved in Differentiation of Trypomastigotes to

    E-print Network

    Singer, Randall

    A Lipid-modified Phosphoinositide-specific Phospholipase C (TcPI-PLC) Is Involved C (PI- PLC) is an important component of the inositol phos- phate/diacylglycerol signaling pathway. A newly discov- ered Trypanosoma cruzi PI-PLC (TcPI-PLC) is lipid modified in its N terminus, targeted

  7. Akt phosphorylation and nuclear phosphoinositide association mediate mRNA export and cell proliferation activities by ALY.

    PubMed

    Okada, Masashi; Jang, Sang-Wuk; Ye, Keqiang

    2008-06-24

    Nuclear PI3K and its downstream effectors play essential roles in a variety of cellular activities including cell proliferation, survival, differentiation, and pre-mRNA splicing. Aly is a nuclear speckle protein implicated in mRNA export. Here we show that Aly is a physiological target of nuclear PI3K signaling, which regulates its subnuclear residency, cell proliferation, and mRNA export activities through nuclear Akt phosphorylation and phosphoinositide association. Nuclear Akt phosphorylates Aly on threonine-219, which is required for its interaction with Akt. Aly binds phosphoinositides, and this action is regulated by Akt-mediated phosphorylation. Phosphoinositide binding but not Akt phosphorylation dictates Aly's nuclear speckle residency. Depletion of Aly results in cell growth suppression and mRNA export reduction. Inhibition of Aly phosphorylation substantially decreases cell proliferation and mRNA export. Furthermore, disruption of phosphoinositide association with Aly also significantly reduces these activities. Thus, nuclear PI3K signaling mediates both cell proliferation and mRNA export functions of Aly. PMID:18562279

  8. The yeast VAP homolog Scs2p has a phosphoinositide-binding ability that is correlated with its activity

    SciTech Connect

    Kagiwada, Satoshi Hashimoto, Misa

    2007-12-28

    The yeast VAMP-associated protein (VAP) homolog Scs2p is an endoplasmic reticulum (ER)/nuclear membrane protein that binds to an FFAT (diphenylalanine in an acidic tract) motif found in various lipid-metabolic proteins, including Opi1p, a negative regulator of phospholipid biosynthesis. Here, we show that Scs2p is a novel phosphoinositide-binding protein that can bind to phosphatidylinositol monophosphates and bisphosphates in vitro. The phosphoinositide-binding domain was assigned to the N-terminal major sperm protein (MSP) domain which also contains the FFAT-binding domain. When several lysine residues in the MSP domain were substituted for alanine, the resulting mutant Scs2 proteins lost the phosphoinositide-binding ability and failed to complement the inositol auxotrophy of an scs2 deletion strain. However, the mutant proteins still localized in the ER/nuclear membrane, in a similar manner to wild-type Scs2p. These results suggest the possibility that Scs2p activity is regulated by phosphoinositides to coordinate phospholipid biosynthesis in response to changes in phospholipid composition.

  9. A Ternary Metal Binding Site in the C2 Domain of Phosphoinositide-Specific Phospholipase C-1,

    E-print Network

    Williams, Roger L.

    A Ternary Metal Binding Site in the C2 Domain of Phosphoinositide-Specific Phospholipase C-1, Lars. Binding of these metal ions is observed in the active site of the catalytic TIM barrel and in the calcium adjacent binding sites in the C2 domain were observed for calcium and the other metal/enzyme complexes

  10. Vasodilator-stimulated phosphoprotein (VASP) is phosphorylated on Ser157 by protein kinase C-dependent and -independent mechanisms in thrombin-stimulated human platelets

    PubMed Central

    Wentworth, James K. T.; Pula, Giordano; Poole, Alastair W.

    2005-01-01

    VASP (vasodilator-stimulated phosphoprotein) is an actin- and profilin-binding protein that is expressed in platelets at high levels and plays a major role in negatively regulating secretory and adhesive events in these cells. VASP is a major substrate for cAMP- and cGMP-regulated protein kinases and it has been shown to be directly phosphorylated on Ser157 by PKC (protein kinase C). In the present paper, we show that, in human platelets, VASP is phosphorylated by PKC on Ser157, but not Ser239, in response to phorbol ester stimulation, in a manner blocked by the PKC inhibitor BIM I (bisindolylmaleimide I). In response to thrombin, VASP was also phosphorylated on Ser157, but this response was only partially inhibited by BIM I, indicating PKC-dependent and -independent pathways to VASP phosphorylation by thrombin. Using inhibitors, we have ruled out the possibility that the PKC-independent pathway acts through guanylate cyclase generation of cGMP, or through a phosphoinositide 3-kinase-dependent kinase. Inhibition of Rho kinase, however, substantially reduced Ser157 VASP phosphorylation, and its effects were additive with BIM I. This implicates Rho kinase and PKC as the major kinases that phosphorylate VASP Ser157 in response to thrombin in platelets. PMID:16197368

  11. Homotypic vacuole fusion requires VTI11 and is regulated by phosphoinositides.

    PubMed

    Zheng, Jiameng; Han, Sang Won; Rodriguez-Welsh, Maria Fernanda; Rojas-Pierce, Marcela

    2014-06-01

    Most plant cells contain a large central vacuole that is essential to maintain cellular turgor. We report a new mutant allele of VTI11 that implicates the SNARE protein VTI11 in homotypic fusion of protein storage and lytic vacuoles. Fusion of the multiple vacuoles present in vti11 mutants could be induced by treatment with Wortmannin and LY294002, which are inhibitors of Phosphatidylinositol 3-Kinase (PI3K). We provide evidence that Phosphatidylinositol 3-Phosphate (PtdIns(3)P) regulates vacuole fusion in vti11 mutants, and that fusion of these vacuoles requires intact microtubules and actin filaments. Finally, we show that Wortmannin also induced the fusion of guard cell vacuoles in fava beans, where vacuoles are naturally fragmented after ABA-induced stomata closure. These results suggest a ubiquitous role of phosphoinositides in vacuole fusion, both during the development of the large central vacuole and during the dynamic vacuole remodeling that occurs as part of stomata movements. PMID:24569132

  12. Platelet alpha-2 adrenergic receptor-mediated phosphoinositide responses in endogenous depression

    SciTech Connect

    Mori, Hideki ); Koyama, Tsukasa; Yamashita, Itaru )

    1991-01-01

    We have previously indicated that epinephrine stimulates phosphoinositide (PI) hydrolysis by activating alpha-2 adrenergic receptors in human platelets. This method involves the measurement of the accumulation of ({sup 3}H)-inositol-1-phosphate (IP-1) as an index of Pl hydrolysis; lithium is added to inhibit the metabolism of IP-1, thus giving an enhanced signal. In the present study, we assessed the platelet alpha-2 adrenergic receptor-mediated PI responses in samples from 15 unmedicated patients with endogenous depression and 15 age- and sex-matched control subjects. The responses to epinephrine in the depressed patients were significantly higher than those of the controls, whereas the basal values did not differ significantly. These results support the hypothesis that platelet alpha-2 adrenergic receptors may be supersensitive in patients with endogenous depression.

  13. The Phosphoinositide Phosphatase Sac1 Is Required for Midline Axon Guidance

    PubMed Central

    Lee, Seongsoo; Kim, Sungdae; Nahm, Minyeop; Kim, Euijae; Kim, Tai-Il; Yoon, Jin Ho; Lee, Seungbok

    2011-01-01

    Sac1 phosphoinositide (PI) phosphatases are important regulators of PtdIns(4)P turnover at the ER, Golgi, and plasma membrane (PM) and are involved in diverse cellular processes including cytoskeletal organization and vesicular trafficking. Here, we present evidence that Sac1 regulates axon guidance in the embryonic CNS of Drosophila. Sac1 is expressed on three longitudinal axon tracts that are defined by the cell adhesion molecule Fasciclin II (Fas II). Mutations in the sac1 gene cause ectopic midline crossing of Fas II-positive axon tracts. This phenotype is rescued by neuronal expression of wild-type Sac1 but not by a catalytically-inactive mutant. Finally, sac1 displays dosage-sensitive genetic interactions with mutations in the genes that encode the midline repellent Slit and its axonal receptor Robo. Taken together, our results suggest that Sac1-mediated regulation of PIs is critical for Slit/Robo-dependent axon repulsion at the CNS midline. PMID:22042447

  14. Phosphoinositide hydrolysis in permeabilized SH-SY5Y human neuroblastoma cells is inhibited by mastoparan.

    PubMed

    Wojcikiewicz, R J; Nahorski, S R

    1989-04-24

    The effects of mastoparan on phospholipase C-catalysed phosphoinositide hydrolysis were examined in [3H]inositol-labelled human neuroblastoma SH-SY5Y cells. [3H]Inositol phosphate formation in intact cells was not altered by 20 microM mastoparan. In contrast, [3H]inositol phosphate formation in electrically permeabilized cells stimulated with guanosine 5'-[gamma-thio]triphosphate and/or carbachol was inhibited by mastoparan with half-maximal effects at approx. 3 microM. The peptide was much less effective in inhibiting stimulatory effects of Ca2+. Similar but less potent inhibitory effects were observed with the cations, neomycin and spermine, indicating that direct interaction of mastoparan with polyphosphoinositides might account for its inhibitory effects on inositol phosphate formation. PMID:2541020

  15. Phosphoinositide-signaling is one component of a robust plant defense response

    PubMed Central

    Hung, Chiu-Yueh; Aspesi Jr, Peter; Hunter, Melissa R.; Lomax, Aaron W.; Perera, Imara Y.

    2014-01-01

    The phosphoinositide pathway and inositol-1,4,5-triphosphate (InsP3) have been implicated in plant responses to many abiotic stresses; however, their role in response to biotic stress is not well characterized. In the current study, we show that both basal defense and systemic acquired resistance responses are affected in transgenic plants constitutively expressing the human type I inositol polyphosphate 5-phosphatase (InsP 5-ptase) which have greatly reduced InsP3 levels. Flagellin induced Ca2+-release as well as the expressions of some flg22 responsive genes were attenuated in the InsP 5-ptase plants. Furthermore, the InsP 5-ptase plants were more susceptible to virulent and avirulent strains of Pseudomonas syringae pv. tomato (Pst) DC3000. The InsP 5-ptase plants had lower basal salicylic acid (SA) levels and the induction of SAR in systemic leaves was reduced and delayed. Reciprocal exudate experiments showed that although the InsP 5-ptase plants produced equally effective molecules that could trigger PR-1 gene expression in wild type plants, exudates collected from either wild type or InsP 5-ptase plants triggered less PR-1 gene expression in InsP 5-ptase plants. Additionally, expression profiles indicated that several defense genes including PR-1, PR-2, PR-5, and AIG1 were basally down regulated in the InsP 5-ptase plants compared with wild type. Upon pathogen attack, expression of these genes was either not induced or showed delayed induction in systemic leaves. Our study shows that phosphoinositide signaling is one component of the plant defense network and is involved in both basal and systemic responses. The dampening of InsP3-mediated signaling affects Ca2+ release, modulates defense gene expression and compromises plant defense responses. PMID:24966862

  16. Distinctive changes in plasma membrane phosphoinositides underlie differential regulation of TRPV1 in nociceptive neurons.

    PubMed

    Lukacs, Viktor; Yudin, Yevgen; Hammond, Gerald R; Sharma, Esseim; Fukami, Kiyoko; Rohacs, Tibor

    2013-07-10

    Transient Receptor Potential Vanilloid 1 (TRPV1) is a polymodal, Ca(2+)-permeable cation channel crucial to regulation of nociceptor responsiveness. Sensitization of TRPV1 by G-protein coupled receptor (GPCR) agonists to its endogenous activators, such as low pH and noxious heat, is a key factor in hyperalgesia during tissue injury as well as pathological pain syndromes. Conversely, chronic pharmacological activation of TRPV1 by capsaicin leads to calcium influx-induced adaptation of the channel. Paradoxically, both conditions entail activation of phospholipase C (PLC) enzymes, which hydrolyze phosphoinositides. We found that in sensory neurons PLC? activation by bradykinin led to a moderate decrease in phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2), but no sustained change in the levels of its precursor PI(4)P. Preventing this selective decrease in PI(4,5)P2 inhibited TRPV1 sensitization, while selectively decreasing PI(4,5)P2 independently of PLC potentiated the sensitizing effect of protein kinase C (PKC) on the channel, thereby inducing increased TRPV1 responsiveness. Maximal pharmacological TRPV1 stimulation led to a robust decrease of both PI(4,5)P2 and its precursor PI(4)P in sensory neurons. Attenuating the decrease of either lipid significantly reduced desensitization, and simultaneous reduction of PI(4,5)P2 and PI(4)P independently of PLC inhibited TRPV1. We found that, on the mRNA level, the dominant highly Ca(2+)-sensitive PLC isoform in dorsal root ganglia is PLC?4. Capsaicin-induced desensitization of TRPV1 currents was significantly reduced, whereas capsaicin-induced nerve impulses in the skin-nerve preparation increased in mice lacking this isoform. We propose a comprehensive model in which differential changes in phosphoinositide levels mediated by distinct PLC isoforms result in opposing changes in TRPV1 activity. PMID:23843517

  17. Phosphoinositide 3-kinase/Akt pathway is involved in pingyangmycin?induced growth inhibition, apoptosis and reduction of invasive potential in EOMA mouse hemangioendothelioma cells.

    PubMed

    Peng, Li-Xia; Zhao, Ping; Zhao, Hong-Sheng; Pan, Er; Yang, Bin-Bin; Li, Qin

    2015-12-01

    Pingyangmycin (PYM), a glycopeptide antibiotic, has been recommended as a stand treatment for hemangioma. However, the underlying mechanisms of its anti?tumor effects have remained elusive. The purpose of the present study was to explore the effects of PYM on the biological behavior of the EOMA mouse hemangioendothelioma cell line and investigate the possible mechanisms. The effects of PYM on EOMA cell viability were determined by an MTT assay, apoptosis was evaluated by Annexin V/propidium iodide staining and flow cytometric analysis, and cell invasion ability was determined using a Transwell invasion assay. In order to investigate the underlying mechanism of action of PYM, the expression of angiogenic signaling proteins was determined by western blot analysis. PYM treatment (0.5?500 µg/ml) inhibited cell growth in a time- and dose?dependent manner. PYM at 100 µg/ml significantly induced apoptosis and reduced the invasive ability of EOMA cells. Effects of PYM on cell viability, apoptosis and invasion ability were completely blocked by co?treatment with phosphoinositide 3?kinase (PI3K) activator insulin?like growth factor?1 (IGF?1). Furthermore, treatment with PYM reduced the expression of PI3K and phosphorylated Akt. In conclusion, the present study indicated that the PI3K/Akt pathway is likely to be involved in the anti-cancer effects of PYM on EOMA cells. PMID:26498320

  18. Involvement of the phosphoinositide 3-kinase/Akt pathway in apoptosis induced by capsaicin in the human pancreatic cancer cell line PANC-1.

    PubMed

    Zhang, Jian-Hong; Lai, Fu-Ji; Chen, Hui; Luo, Jiang; Zhang, Ri-Yuan; Bu, He-Qi; Wang, Zhao-Hong; Lin, Hong-Hai; Lin, Sheng-Zhang

    2013-01-01

    Capsaicin, one of the major pungent ingredients found in red peppers, has been recently demonstrated to induce apoptosis in various malignant cell lines through an unclear mechanism. In this study, the effect of capsaicin on proliferation and apoptosis in the human pancreatic cancer cell line PANC-1 and its possible mechanism(s) of action were investigated. The results of a Cell Counting Kit-8 (CCK-8) assay revealed that capsaicin significantly decreased the viability of PANC-1 cells in a dose-dependent manner. Capsaicin induced G0/G1 phase cell cycle arrest and apoptosis in PANC-1 cells as demonstrated by a flow cytometric assessment. Caspase-3 expression at both the protein and mRNA level was promoted following capsaicin treatment. Furthermore, we revealed that phospho-PI3 Kinase p85 (Tyr458) and phospho-Akt (Ser473) in PANC-1 cells were downregulated in response to capsaicin. Moreover, capsaicin gavage significantly inhibited the growth of pancreatic cancer PANC-1 cell xenografts in athymic nude mice. An increased number of TUNEL-positive cells and cleaved caspase-3 were observed in capsaicin-treated mice. In vivo, capsaicin downregulated the expression of phospho-PI3 Kinase p85 (Tyr458) and phospho-Akt (Ser473). In conclusion, we have demonstrated that capsaicin is an inhibitor of growth of PANC-1 cells, and downregulation of the phosphoinositide 3-kinase/Akt pathway may be involved in capsaicin-induced apoptosis in vitro and in vivo. PMID:23255891

  19. Molecular cloning and characterization of a rice phosphoinositide-specic phospholipase C gene, OsPI-PLC1, that is activated

    E-print Network

    Goodman, Robert M.

    Molecular cloning and characterization of a rice phosphoinositide-speci¢c phospholipase C gene, OsPI-PLC-speci®c phospholipase C (OsPI-PLC1, Oryza sativa L. phosphoinositide-speci®c phospholipase C1). OsPI-PLC1 encodes a 599, characteristics of this class of enzymes. Expression of OsPI-PLC1 was induced by various chemical and biological

  20. Bipolar Plasma Membrane Distribution of Phosphoinositides and Their Requirement for Auxin-Mediated Cell Polarity and Patterning in Arabidopsis[W

    PubMed Central

    Tejos, Ricardo; Sauer, Michael; Vanneste, Steffen; Palacios-Gomez, Miriam; Li, Hongjiang; Heilmann, Mareike; van Wijk, Ringo; Vermeer, Joop E.M.; Heilmann, Ingo; Munnik, Teun; Friml, Ji?í

    2014-01-01

    Cell polarity manifested by asymmetric distribution of cargoes, such as receptors and transporters, within the plasma membrane (PM) is crucial for essential functions in multicellular organisms. In plants, cell polarity (re)establishment is intimately linked to patterning processes. Despite the importance of cell polarity, its underlying mechanisms are still largely unknown, including the definition and distinctiveness of the polar domains within the PM. Here, we show in Arabidopsis thaliana that the signaling membrane components, the phosphoinositides phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] as well as PtdIns4P 5-kinases mediating their interconversion, are specifically enriched at apical and basal polar plasma membrane domains. The PtdIns4P 5-kinases PIP5K1 and PIP5K2 are redundantly required for polar localization of specifically apical and basal cargoes, such as PIN-FORMED transporters for the plant hormone auxin. As a consequence of the polarity defects, instructive auxin gradients as well as embryonic and postembryonic patterning are severely compromised. Furthermore, auxin itself regulates PIP5K transcription and PtdIns4P and PtdIns(4,5)P2 levels, in particular their association with polar PM domains. Our results provide insight into the polar domain–delineating mechanisms in plant cells that depend on apical and basal distribution of membrane lipids and are essential for embryonic and postembryonic patterning. PMID:24876254

  1. Fucoidan inhibits the migration and proliferation of HT-29 human colon cancer cells via the phosphoinositide-3 kinase/Akt/mechanistic target of rapamycin pathways

    PubMed Central

    HAN, YONG-SEOK; LEE, JUN HEE; LEE, SANG HUN

    2015-01-01

    Fucoidan, a sulfated polysaccharide, has a variety of biological activities, including anti-cancer, anti-angiogenic and anti-inflammatory effects. However, the underlying mechanisms of fucoidan as an anti-cancer agent remain to be elucidated. The present study examined the anti-cancer effect of fucoidan on HT-29 human colon cancer cells. The cell growth of HT29 cells was significantly decreased following treatment with fucoidan (200 ?g/ml). In addition, fucoidan inhibited the migration of HT-29 cells by decreasing the expression levels of matrix metalloproteinase-2 in a dose-dependent manner (0–200 ?g/ml). The underlying mechanism of these inhibitory effects included the downregulation of phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) by treatment with fucoidan. Furthermore, fucoidan increased the expression of cleaved caspase-3 and decreased cancer sphere formation. The present study suggested that fucoidan exerts an anti-cancer effect on HT-29 human colon cancer cells by downregulating the PI3K-Akt-mTOR signaling pathway. Therefore, fucoidan may be a potential therapeutic reagent against the growth of human colon cancer cells. PMID:25998232

  2. Structural Basis for Different Phosphoinositide Specificities of the PX Domains of Sorting Nexins Regulating G-protein Signaling*

    PubMed Central

    Mas, Caroline; Norwood, Suzanne J.; Bugarcic, Andrea; Kinna, Genevieve; Leneva, Natalya; Kovtun, Oleksiy; Ghai, Rajesh; Ona Yanez, Lorena E.; Davis, Jasmine L.; Teasdale, Rohan D.; Collins, Brett M.

    2014-01-01

    Sorting nexins (SNXs) or phox homology (PX) domain containing proteins are central regulators of cell trafficking and signaling. A subfamily of PX domain proteins possesses two unique PX-associated domains, as well as a regulator of G protein-coupled receptor signaling (RGS) domain that attenuates G?s-coupled G protein-coupled receptor signaling. Here we delineate the structural organization of these RGS-PX proteins, revealing a protein family with a modular architecture that is conserved in all eukaryotes. The one exception to this is mammalian SNX19, which lacks the typical RGS structure but preserves all other domains. The PX domain is a sensor of membrane phosphoinositide lipids and we find that specific sequence alterations in the PX domains of the mammalian RGS-PX proteins, SNX13, SNX14, SNX19, and SNX25, confer differential phosphoinositide binding preferences. Although SNX13 and SNX19 PX domains bind the early endosomal lipid phosphatidylinositol 3-phosphate, SNX14 shows no membrane binding at all. Crystal structures of the SNX19 and SNX14 PX domains reveal key differences, with alterations in SNX14 leading to closure of the binding pocket to prevent phosphoinositide association. Our findings suggest a role for alternative membrane interactions in spatial control of RGS-PX proteins in cell signaling and trafficking. PMID:25148684

  3. Phosphoinositides and membrane curvature switch the mode of actin polymerization via selective recruitment of toca-1 and Snx9

    PubMed Central

    Gallop, Jennifer L.; Walrant, Astrid; Cantley, Lewis C.; Kirschner, Marc W.

    2013-01-01

    The membrane–cytosol interface is the major locus of control of actin polymerization. At this interface, phosphoinositides act as second messengers to recruit membrane-binding proteins. We show that curved membranes, but not flat ones, can use phosphatidylinositol 3-phosphate [PI(3)P] along with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] to stimulate actin polymerization. In this case, actin polymerization requires the small GTPase cell cycle division 42 (Cdc42), the nucleation-promoting factor neural Wiskott–Aldrich syndrome protein (N-WASP) and the actin nucleator the actin-related protein (Arp) 2/3 complex. In liposomes containing PI(4,5)P2 as the sole phosphoinositide, actin polymerization requires transducer of Cdc42 activation-1 (toca-1). In the presence of phosphatidylinositol 3-phosphate, polymerization is both more efficient and independent of toca-1. Under these conditions, sorting nexin 9 (Snx9) can be implicated as a specific adaptor that replaces toca-1 to mobilize neural Wiskott–Aldrich syndrome protein and the Arp2/3 complex. This switch in phosphoinositide and adaptor specificity for actin polymerization from membranes has implications for how different types of actin structures are generated at precise times and locations in the cell. PMID:23589871

  4. Ion channel regulation by phosphoinositides analyzed with VSPs—PI(4,5)P2 affinity, phosphoinositide selectivity, and PI(4,5)P2 pool accessibility

    PubMed Central

    Rjasanow, Alexandra; Leitner, Michael G.; Thallmair, Veronika; Halaszovich, Christian R.; Oliver, Dominik

    2015-01-01

    The activity of many proteins depends on the phosphoinositide (PI) content of the membrane. E.g., dynamic changes of the concentration of PI(4,5)P2 are cellular signals that regulate ion channels. The susceptibility of a channel to such dynamics depends on its affinity for PI(4,5)P2. Yet, measuring affinities for endogenous PIs has not been possible directly, but has relied largely on the response to soluble analogs, which may not quantitatively reflect binding to native lipids. Voltage-sensitive phosphatases (VSPs) turn over PI(4,5)P2 to PI(4)P when activated by depolarization. In combination with voltage-clamp electrophysiology VSPs are useful tools for rapid and reversible depletion of PI(4,5)P2. Because cellular PI(4,5)P2 is resynthesized rapidly, steady state PI(4,5)P2 changes with the degree of VSP activation and thus depends on membrane potential. Here we show that titration of endogenous PI(4,5)P2 with Ci-VSP allows for the quantification of relative PI(4,5)P2 affinities of ion channels. The sensitivity of inward rectifier and voltage-gated K+ channels to Ci-VSP allowed for comparison of PI(4,5)P2 affinities within and across channel subfamilies and detected changes of affinity in mutant channels. The results also reveal that VSPs are useful only for PI effectors with high binding specificity among PI isoforms, because PI(4,5)P2 depletion occurs at constant overall PI level. Thus, Kir6.2, a channel activated by PI(4,5)P2 and PI(4)P was insensitive to VSP. Surprisingly, despite comparable PI(4,5)P2 affinity as determined by Ci-VSP, the Kv7 and Kir channel families strongly differed in their sensitivity to receptor-mediated depletion of PI(4,5)P2. While Kv7 members were highly sensitive to activation of PLC by Gq-coupled receptors, Kir channels were insensitive even when PI(4,5)P2 affinity was lowered by mutation. We hypothesize that different channels may be associated with distinct pools of PI(4,5)P2 that differ in their accessibility to PLC and VSPs. PMID:26150791

  5. WNT16B is a new marker of cellular senescence that regulates p53 activity and the phosphoinositide 3-kinase/AKT pathway.

    PubMed

    Binet, Romuald; Ythier, Damien; Robles, Ana I; Collado, Manuel; Larrieu, Delphine; Fonti, Claire; Brambilla, Elisabeth; Brambilla, Christian; Serrano, Manuel; Harris, Curtis C; Pedeux, Rémy

    2009-12-15

    Senescence is a tumor suppression mechanism that is induced by several stimuli, including oncogenic signaling and telomere shortening, and controlled by the p53/p21(WAF1) signaling pathway. Recently, a critical role for secreted factors has emerged, suggesting that extracellular signals are necessary for the onset and maintenance of senescence. Conversely, factors secreted by senescent cells may promote tumor growth. By using expression profiling techniques, we searched for secreted factors that were overexpressed in fibroblasts undergoing replicative senescence. We identified WNT16B, a member of the WNT family of secreted proteins. We found that WNT16B is overexpressed in cells undergoing stress-induced premature senescence and oncogene-induced senescence in both MRC5 cell line and the in vivo murine model of K-Ras(V12)-induced senescence. By small interfering RNA experiments, we observed that both p53 and WNT16B are necessary for the onset of replicative senescence. WNT16B expression is required for the full transcriptional activation of p21(WAF1). Moreover, WNT16B regulates activation of the phosphoinositide 3-kinase (PI3K)/AKT pathway. Overall, we identified WNT16B as a new marker of senescence that regulates p53 activity and the PI3K/AKT pathway and is necessary for the onset of replicative senescence. PMID:19951988

  6. Osteopontin is a myosphere-derived secretory molecule that promotes angiogenic progenitor cell proliferation through the phosphoinositide 3-kinase/Akt pathway

    SciTech Connect

    Ogata, Takehiro; Ueyama, Tomomi . E-mail: tueyama@kuhp.kyoto-u.ac.jp; Nomura, Tetsuya; Asada, Satoshi; Tagawa, Masashi; Nakamura, Tomoyuki; Takahashi, Tomosaburo; Matsubara, Hiroaki; Oh, Hidemasa . E-mail: hidemasa@kuhp.kyoto-u.ac.jp

    2007-07-27

    We have reported that skeletal myosphere-derived progenitor cells (MDPCs) can differentiate into vascular cells, and that MDPC transplantation into cardiomyopathic hearts improves cardiac function. However, the autocrine/paracrine molecules and underlying mechanisms responsible for MDPC growth have not yet been determined. To explore the molecules enhancing the proliferation of MDPCs, we performed serial analysis of gene expression and signal sequence trap methods using RNA isolated from MDPCs. We identified osteopontin (OPN), a secretory molecule, as one of most abundant molecules expressed in MDPCs. OPN provided a proliferative effect for MDPCs. MDPCs treated with OPN showed Akt activation, and inhibition of the phosphoinositide 3-kinase (PI3K)/Akt pathway repressed the proliferative effect of OPN. Furthermore, OPN-pretreated MDPCs maintained their differentiation potential into endothelial and vascular smooth muscle cells. These findings indicate an important role of OPN as an autocrine/paracrine molecule in regulating the proliferative growth of muscle-derived angiogenic progenitor cells via the PI3K/Akt pathway.

  7. Phosphoinositide 3-kinase enables phagocytosis of large particles by terminating actin assembly through Rac/Cdc42 GTPase-activating proteins

    PubMed Central

    Schlam, Daniel; Bagshaw, Richard D.; Freeman, Spencer A.; Collins, Richard F.; Pawson, Tony; Fairn, Gregory D.; Grinstein, Sergio

    2015-01-01

    Phagocytosis is responsible for the elimination of particles of widely disparate sizes, from large fungi or effete cells to small bacteria. Though superficially similar, the molecular mechanisms involved differ: engulfment of large targets requires phosphoinositide 3-kinase (PI3K), while that of small ones does not. Here, we report that inactivation of Rac and Cdc42 at phagocytic cups is essential to complete internalization of large particles. Through a screen of 62 RhoGAP-family members, we demonstrate that ARHGAP12, ARHGAP25 and SH3BP1 are responsible for GTPase inactivation. Silencing these RhoGAPs impairs phagocytosis of large targets. The GAPs are recruited to large—but not small—phagocytic cups by products of PI3K, where they synergistically inactivate Rac and Cdc42. Remarkably, the prominent accumulation of phosphatidylinositol 3,4,5-trisphosphate characteristic of large-phagosome formation is less evident during phagocytosis of small targets, accounting for the contrasting RhoGAP distribution and the differential requirement for PI3K during phagocytosis of dissimilarly sized particles. PMID:26465210

  8. Phosphatidylinositol-3-kinase-dependent phosphorylation of SLP-76 by the lymphoma-associated ITK-SYK fusion-protein

    SciTech Connect

    Hussain, Alamdar; Department of Biosciences, COMSATS Institute of Information Technology, Chak Shazad Campus, Islamabad ; Faryal, Rani; Department of Biosciences, COMSATS Institute of Information Technology, Chak Shazad Campus, Islamabad ; Nore, Beston F.; Mohamed, Abdalla J.; Smith, C.I. Edvard

    2009-12-18

    Recurrent chromosomal translocations have long been implicated in various types of lymphomas and other malignancies. Novel recurrent t(5;9)(q33;q22) has been recently discovered in un-specified peripheral T-cell lymphoma. To elucidate the role of this translocation, the corresponding fusion construct encoding the N-terminal portion of the ITK kinase and the C-terminal catalytic region of the SYK kinase was generated. We herein show that the ITK-SYK fusion-protein is constitutively active. Moreover, we demonstrate that ITK-SYK is phosphorylated on key tyrosine residues and is capable of potently phosphorylating the related adapter proteins BLNK and SLP-76. In transiently transfected cells, SYK was phosphorylated at Y352 but not detectably at the activation-loop tyrosines Y525/Y526. In contrast, ITK-SYK was phosphorylated both at Y212 and the activation-loop tyrosines Y385/Y386, corresponding to Y352 and Y525/Y526 in SYK, respectively. In resting primary lymphocytes, ITK-SYK predominantly localizes to the cell surface. In addition, we demonstrate that following stimulation, the ITK-SYK fusion-protein in cell lines translocates to the cell membrane and, moreover, that this phenomenon as well as SLP-76 phosphorylation are blocked upon phosphatidylinositol-3-kinase (PI3-kinase) inhibition.

  9. Osteopontin stimulates gelsolin-associated phosphoinositide levels and phosphatidylinositol triphosphate-hydroxyl kinase.

    PubMed Central

    Chellaiah, M; Hruska, K

    1996-01-01

    Based on previous studies demonstrating activation of phosphatidylinositol 3-hydroxyl kinase (PI3-kinase) and stimulation of a change in cell shape, we examined the effect of osteopontin on the association of phospholipids with gelsolin, an actin-capping/severing protein. Osteopontin stimulated a rapid increase in phosphatidylinositol bisphosphate and phosphatidylinositol triphosphate levels associated with gelsolin in Triton-soluble fractions of cell lysates. The increased levels of phosphatidylinositol triphosphate associated with gelsolin were due to stimulation of PI3-kinase activity associated with gelsolin in the Triton-soluble fractions, and they were blocked by the PI3-kinase inhibitor wortmannin. Osteopontin stimulated translocation of PI3-kinase from the Triton-insoluble to Triton-soluble gelsolin. Osteopontin also decreased Triton-soluble gelsolin/actin complexes consistent with actin uncapping, and increased F-actin levels, which were also blocked by wortmannin. The osteopontin effects were mediated through binding to the alpha(v)beta 3 integrin. Taken together, our studies indicate that osteopontin/alpha(v)beta 3-mediated changes in gelsolin-associated phosphoinositide levels and PI3-kinase activity are related to stimulation of F-actin formation in osteoclasts. Images PMID:8744948

  10. Short-Form Ron Promotes Spontaneous Breast Cancer Metastasis through Interaction with Phosphoinositide 3-Kinase

    PubMed Central

    Liu, Xuemei; Zhao, Ling; DeRose, Yoko S.; Lin, Yi-Chun; Bieniasz, Magdalena; Eyob, Henok; Buys, Saundra S.; Neumayer, Leigh

    2011-01-01

    Receptor tyrosine kinases (RTKs) have been the subject of intense investigation due to their widespread deregulation in cancer and the prospect of developing targeted therapeutics against these proteins. The Ron RTK has been implicated in tumor aggressiveness and is a developing target for therapy, but its function in tumor progression and metastasis is not fully understood. We examined Ron activity in human breast cancers and found striking predominance of an activated Ron isoform known as short-form Ron (sfRon), whose function in breast tumors has not been explored. We found that sfRon plays a significant role in aggressiveness of breast cancer in vitro and in vivo. sfRon expression was sufficient to convert slow-growing, nonmetastatic tumors into rapidly growing tumors that spontaneously metastasized to liver and bones. Mechanistic studies revealed that sfRon promotes epithelial-mesenchymal transition, invasion, tumor growth, and metastasis through interaction with p85, the regulatory subunit of phosphoinositide 3-kinase (PI3K). Inhibition of PI3K activity, or introduction of a single mutation in the p85 docking site on sfRon, completely eliminated the ability of sfRon to promote tumor growth, invasion, and metastasis. These findings reveal sfRon as an important new player in breast cancer and validate Ron and PI3K as therapeutic targets in this disease. PMID:22207901

  11. Ablation of phosphoinositide-3-kinase class II alpha suppresses hepatoma cell proliferation

    SciTech Connect

    Ng, Stanley K.L.; Neo, Soek-Ying; Yap, Yann-Wan; Karuturi, R. Krishna Murthy; Loh, Evelyn S.L.; Liau, Kui-Hin; Ren, Ee-Chee; Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore

    2009-09-18

    Cancer such as hepatocellular carcinoma (HCC) is characterized by complex perturbations in multiple signaling pathways, including the phosphoinositide-3-kinase (PI3K/AKT) pathways. Herein we investigated the role of PI3K catalytic isoforms, particularly class II isoforms in HCC proliferation. Among the siRNAs tested against the eight known catalytic PI3K isoforms, specific ablation of class II PI3K alpha (PIK3C2{alpha}) was the most effective in impairing cell growth and this was accompanied by concomitant decrease in PIK3C2{alpha} mRNA and protein levels. Colony formation ability of cells deficient for PIK3C2{alpha} was markedly reduced and growth arrest was associated with increased caspase 3 levels. A small but significant difference in gene dosage and expression levels was detected between tumor and non-tumor tissues in a cohort of 19 HCC patients. Taken together, these data suggest for the first time that in addition to class I PI3Ks in cancer, class II PIK3C2{alpha} can modulate HCC cell growth.

  12. Cell Activation-Induced Phosphoinositide 3-Kinase Alpha/Beta Dimerization Regulates PTEN Activity

    PubMed Central

    Pérez-García, Vicente; Redondo-Muñoz, Javier; Kumar, Amit

    2014-01-01

    The phosphoinositide 3-kinase (PI3K)/PTEN (phosphatase and tensin homolog) pathway is one of the central routes that enhances cell survival, division, and migration, and it is frequently deregulated in cancer. PI3K catalyzes formation of phosphatidylinositol 3,4,5-triphosphate [PI(3,4,5)P3] after cell activation; PTEN subsequently reduces these lipids to basal levels. Activation of the ubiquitous p110? isoform precedes that of p110? at several points during the cell cycle. We studied the potential connections between p110? and p110? activation, and we show that cell stimulation promotes p110? and p110? association, demonstrating oligomerization of PI3K catalytic subunits within cells. Cell stimulation also promoted PTEN incorporation into this complex, which was necessary for PTEN activation. Our results show that PI3Ks dimerize in vivo and that PI3K and PTEN activities modulate each other in a complex that controls cell PI(3,4,5)P3 levels. PMID:24958106

  13. Nonenzymatic domains of Kalirin7 contribute to spine morphogenesis through interactions with phosphoinositides and Abl.

    PubMed

    Ma, Xin-Ming; Miller, Megan B; Vishwanatha, K S; Gross, Maegan J; Wang, Yanping; Abbott, Thomas; Lam, Tukiet T; Mains, Richard E; Eipper, Betty A

    2014-05-01

    Like several Rho GDP/GTP exchange factors (GEFs), Kalirin7 (Kal7) contains an N-terminal Sec14 domain and multiple spectrin repeats. A natural splice variant of Kalrn lacking the Sec14 domain and four spectrin repeats is unable to increase spine formation; our goal was to understand the function of the Sec14 and spectrin repeat domains. Kal7 lacking its Sec14 domain still increased spine formation, but the spines were short. Strikingly, Kal7 truncation mutants containing only the Sec14 domain and several spectrin repeats increased spine formation. The Sec14 domain bound phosphoinositides, a minor but crucial component of cellular membranes, and binding was increased by a phosphomimetic mutation. Expression of KalSec14-GFP in nonneuronal cells impaired receptor-mediated endocytosis, linking Kal7 to membrane trafficking. Consistent with genetic studies placing Abl, a non-receptor tyrosine kinase, and the Drosophila orthologue of Kalrn into the same signaling pathway, Abl1 phosphorylated two sites in the fourth spectrin repeat of Kalirin, increasing its sensitivity to calpain-mediated degradation. Treating cortical neurons of the wild-type mouse, but not the Kal7(KO) mouse, with an Abl inhibitor caused an increase in linear spine density. Phosphorylation of multiple sites in the N-terminal Sec14/spectrin region of Kal7 may allow coordination of the many signaling pathways contributing to spine morphogenesis. PMID:24600045

  14. Spatiotemporal model of a key step in endocytosis: SNX9 recruitment via phosphoinositides

    E-print Network

    Schöneberg, Johannes; Posor, York; Haucke, Volker; Noe, Frank

    2013-01-01

    Clathrin mediated endocytosis (CME) is an ubiquitous cellular pathway that regulates central aspects of cell physiology such as nutrient uptake, modulation of signal transduction, synaptic transmission and membrane turn-over. Endocytic vesicle formation depends on the timed production of specific phosphoinositides and their interactions with various endocytic proteins. Recently, it has been found that phosphatidylinositol-3,4-bisphosphate (PI(3,4)P2) produced by the class II phosphatidylinositol 3-kinase C2alpha plays a key role in the recruitment of the PX-BAR domain protein SNX9, which is proposed to play a role in the constriction of the endocytic vesicle neck [Posor et al, Nature 499, p233 (2013)]. Interestingly, SNX9 and its close paralog SNX18 are not fully specific to PI(3,4)P2 but can also bind other phospholipids, in particular to PI(4,5)P2, an abundant plasma membrane lipid required for the recruitment of many endocytic proteins. In order to understand the dynamical interplay between phospholipids a...

  15. Synaptojanin 1-linked phosphoinositide dyshomeostasis and cognitive deficits in mouse models of Down's syndrome

    PubMed Central

    Voronov, Sergey V.; Frere, Samuel G.; Giovedi, Silvia; Pollina, Elizabeth A.; Borel, Christelle; Zhang, Hong; Schmidt, Cecilia; Akeson, Ellen C.; Wenk, Markus R.; Cimasoni, Laurent; Arancio, Ottavio; Davisson, Muriel T.; Antonarakis, Stylianos E.; Gardiner, Katheleen; De Camilli, Pietro; Di Paolo, Gilbert

    2008-01-01

    Phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] is a signaling phospholipid implicated in a wide variety of cellular functions. At synapses, where normal PtdIns(4,5)P2 balance is required for proper neurotransmission, the phosphoinositide phosphatase synaptojanin 1 is a key regulator of its metabolism. The underlying gene, SYNJ1, maps to human chromosome 21 and is thus a candidate for involvement in Down's syndrome (DS), a complex disorder resulting from the overexpression of trisomic genes. Here, we show that PtdIns(4,5)P2 metabolism is altered in the brain of Ts65Dn mice, the most commonly used model of DS. This defect is rescued by restoring Synj1 to disomy in Ts65Dn mice and is recapitulated in transgenic mice overexpressing Synj1 from BAC constructs. These transgenic mice also exhibit deficits in performance of the Morris water maze task, suggesting that PtdIns(4,5)P2 dyshomeostasis caused by gene dosage imbalance for Synj1 may contribute to brain dysfunction and cognitive disabilities in DS. PMID:18591654

  16. The Basal Transcription Complex Component TAF3 Transduces Changes in Nuclear Phosphoinositides into Transcriptional Output

    PubMed Central

    Stijf-Bultsma, Yvette; Sommer, Lilly; Tauber, Maria; Baalbaki, Mai; Giardoglou, Panagiota; Jones, David R.; Gelato, Kathy A.; van Pelt, Jason; Shah, Zahid; Rahnamoun, Homa; Toma, Clara; Anderson, Karen E.; Hawkins, Philip; Lauberth, Shannon M.; Haramis, Anna-Pavlina G.; Hart, Daniel; Fischle, Wolfgang; Divecha, Nullin

    2015-01-01

    Summary Phosphoinositides (PI) are important signaling molecules in the nucleus that influence gene expression. However, if and how nuclear PI directly affects the transcriptional machinery is not known. We report that the lipid kinase PIP4K2B regulates nuclear PI5P and the expression of myogenic genes during myoblast differentiation. A targeted screen for PI interactors identified the PHD finger of TAF3, a TATA box binding protein-associated factor with important roles in transcription regulation, pluripotency, and differentiation. We show that the PI interaction site is distinct from the known H3K4me3 binding region of TAF3 and that PI binding modulates association of TAF3 with H3K4me3 in vitro and with chromatin in vivo. Analysis of TAF3 mutants indicates that TAF3 transduces PIP4K2B-mediated alterations in PI into changes in specific gene transcription. Our study reveals TAF3 as a direct target of nuclear PI and further illustrates the importance of basal transcription components as signal transducers. PMID:25866244

  17. Alpha-1 adrenergic receptor: Binding and phosphoinositide breakdown in human myometrium

    SciTech Connect

    Breuiller-Fouche, M.; Doualla-Bell Kotto Maka, F.; Geny, B.; Ferre, F. )

    1991-07-01

    Alpha-1 adrenergic receptors were examined in both inner and outer layers of human pregnant myometrium using radioligand binding of (3H)prazosin. (3H)prazosin bound rapidly and reversibly to a single class of high affinity binding sites in myometrial membrane preparations. Scatchard analysis gave similar values of equilibrium dissociation constants in both myometrial layers. In contrast, more alpha-1 adrenergic receptors were detected in the outer layer than in the inner layer. Antagonist inhibited (3H)prazosin binding with an order of potency of prazosin greater than phentolamine greater than idazoxan. Competition experiments have also revealed that a stable guanine nucleotide decreases the apparent affinity of norepinephrine for myometrial (3H)prazosin binding sites. The functional status of these alpha-1 adrenergic receptors was also assessed by measuring the norepinephrine-induced accumulation of inositol phosphates in myometrial tissue. Norepinephrine produced a concentration-dependent accumulation of inositol phosphates in both myometrial layers. However, norepinephrine-induced increases in inositol 1,4,5-triphosphate were only observed in the outer layer. These results indicate that alpha-1 adrenergic receptors in human myometrium at the end of pregnancy are linked to phosphoinositide hydrolysis and that this response occurs mainly in the outer layer.

  18. Requirement for Class II Phosphoinositide 3-Kinase C2? in Maintenance of Glomerular Structure and Function?

    PubMed Central

    Harris, David P.; Vogel, Peter; Wims, Marie; Moberg, Karen; Humphries, Juliane; Jhaver, Kanchan G.; DaCosta, Christopher M.; Shadoan, Melanie K.; Xu, Nianhua; Hansen, Gwenn M.; Balakrishnan, Sanjeevi; Domin, Jan; Powell, David R.; Oravecz, Tamas

    2011-01-01

    An early lesion in many kidney diseases is damage to podocytes, which are critical components of the glomerular filtration barrier. A number of proteins are essential for podocyte filtration function, but the signaling events contributing to development of nephrotic syndrome are not well defined. Here we show that class II phosphoinositide 3-kinase C2? (PI3KC2?) is expressed in podocytes and plays a critical role in maintaining normal renal homeostasis. PI3KC2?-deficient mice developed chronic renal failure and exhibited a range of kidney lesions, including glomerular crescent formation and renal tubule defects in early disease, which progressed to diffuse mesangial sclerosis, with reduced podocytes, widespread effacement of foot processes, and modest proteinuria. These findings were associated with altered expression of nephrin, synaptopodin, WT-1, and desmin, indicating that PI3KC2? deficiency specifically impacts podocyte morphology and function. Deposition of glomerular IgA was observed in knockout mice; importantly, however, the development of severe glomerulonephropathy preceded IgA production, indicating that nephropathy was not directly IgA mediated. PI3KC2? deficiency did not affect immune responses, and bone marrow transplantation studies also indicated that the glomerulonephropathy was not the direct consequence of an immune-mediated disease. Thus, PI3KC2? is critical for maintenance of normal glomerular structure and function by supporting normal podocyte function. PMID:20974805

  19. Expression and localization of the diacylglycerol kinase family and of phosphoinositide signaling molecules in adrenal gland.

    PubMed

    Hozumi, Yasukazu; Akimoto, Ryo; Suzuki, Akihito; Otani, Koichi; Watanabe, Masahiko; Goto, Kaoru

    2015-11-01

    Adrenal glands play a central role in the secretion of steroid hormones and catecholamines. Previous studies have revealed that molecules engaged in phosphoinositide (PI) turnover are expressed in the adrenal gland, suggesting the importance of PI signaling in adrenal signal transduction. Diacylglycerol kinase (DGK) catalyzes the phosphorylation of diacylglycerol (DG), a major second messenger in the PI signaling cascade. The DGK family is expressed in distinct patterns in endocrine organs at the mRNA and protein levels. Nevertheless, little is known about the characteristics and morphological aspects of DGKs in the adrenal gland. We have performed immunohistochemical analyses to investigate the expression and localization of DGK isozymes, together with PI signaling molecules, in the adrenal gland at the protein level. Our results show that the DGK family and a set of PI signaling molecules are expressed intensely in zona glomerulosa cells and medullary chromaffin cells in the adrenal gland. In adrenal cells, DGK? localizes to the Golgi complex, DGK? to the plasma membrane, and DGK? to the nucleus. These findings show the distinct expression and subcellular localization of DGK isozymes and PI signaling molecules in the adrenal gland, suggesting that each DGK isozyme has a role in signal transduction in adrenal cells, especially in the zona glomerulosa and medulla. PMID:26003177

  20. Interaction of aluminum ions with phosphoinositide metabolism in rat cerebral cortical membranes

    SciTech Connect

    Candura, S.M.; Castoldi, A.F.; Costa, L.G. Fondazione Clinica del Lavoro, Pavia ); Manzo, L. Fondazione Clinica del Lavoro, Pavia )

    1991-01-01

    Al, complexed with fluoride to form fluoroaluminate (AlF{sub 4}-), can activate the GTP-binding (G) proteins of the adenylate cyclase and retinal cyclic GMP phosphodiesterase systems. Since an involvement of G-proteins with cerebral phosphoinositide (PtdIns) metabolism has also been suggested, in this study the authors investigated the interaction of the stable GTP analogue GTP(S), Al salts and NaF with this system. In rat cerebral cortical membranes, GTP(S) dose-dependently stimulated ({sup 3}H)inositol phosphates (({sup 3}H)InsPs) accumulation. This effect was potentiated by carbachol and was partially prevented by the GTP-binding antagonist GDP(S), indicating that CNS muscarinic receptor activation is coupled to PtdIns hydrolysis via putative G-protein(s). GTP(S) stimulation was also inhibited by phorbol 12-myristate 13-acetate (PMA). Both Al salts and NaF mimicked the action of GTP(S) in stimulating PtdIns turnover. Their actions were highly synergistic. However, the stimulatory effects of AlCl{sub 3} and/or NaF were not potentiated by carbachol and were not inhibited by GDP(S) and PMA. In the nervous tissue, activation of PtdIns hydrolysis by Al may be mediated by activating a regulatory G-protein at a location distinct from the GTP-binding site or by a direct stimulation of phospholipase C.

  1. A Toxoplasma gondii phosphoinositide phospholipase C (TgPI-PLC) with high affinity for phosphatidylinositol

    PubMed Central

    Fang, Jianmin; Marchesini, Norma; Moreno, Silvia N. J.

    2005-01-01

    The Toxoplasma gondii phosphoinositide-specific phospholipase C gene (TgPI-PLC) was cloned, sequenced and expressed in Escherichia coli and its enzymatic characteristics were investigated. TgPI-PLC is present in the genome as a single-copy gene consisting of 22 exons interrupted by 21 introns, and encodes a polypeptide of 1097 amino acids with a predicted molecular mass of 121 kDa. In addition to the conserved catalytic X and Y domains, TgPI-PLC contains an apparent N-terminal PH domain, an EF hand motif and a C-terminal C2 domain. When compared with mammalian ?-type PI-PLC, TgPI-PLC has an additional extended N-terminus and two insertions in the region between the X and Y domains, with a 31–35% identity over the whole sequence. Recombinant TgPI-PLC, as well as the native enzyme obtained from crude membrane extracts of the parasite, was more active with phosphatidylinositol than with phosphatidylinositol 4,5-bisphosphate as substrate. Indirect immunofluorescence analysis using an affinity-purified antibody against TgPI-PLC revealed that this enzyme localizes in the plasma membrane of the parasites. PMID:16288600

  2. Phosphoinositides Play Differential Roles in Regulating Phototropin1- and Phototropin2-Mediated Chloroplast Movements in Arabidopsis

    PubMed Central

    Aggarwal, Chhavi; ?abuz, Justyna; Gabry?, Halina

    2013-01-01

    Phototropins are UVA/blue-light receptors involved in controlling the light-dependent physiological responses which serve to optimize the photosynthetic activity of plants and promote growth. The phototropin-induced phosphoinositide (PI) metabolism has been shown to be essential for stomatal opening and phototropism. However, the role of PIs in phototropin-induced chloroplast movements remains poorly understood. The aim of this work is to determine which PI species are involved in the control of chloroplast movements in Arabidopsis and the nature of their involvement. We present the effects of the inactivation of phospholipase C (PLC), PI3-kinase (PI3K) and PI4-kinase (PI4K) on chloroplast relocations in Arabidopsis. The inhibition of the phosphatidylinositol 4,5-bisphospahte [PI(4,5)P2]-PLC pathway, using neomycin and U73122, suppressed the phot2-mediated chloroplast accumulation and avoidance responses, without affecting movement responses controlled by phot1. On the other hand, PI3K and PI4K activities are more restricted to phot1- and phot2-induced weak-light responses. The inactivation of PI3K and PI4K by wortmannin and LY294002 severely affected the weak blue-light-activated accumulation response but had little effect on the strong blue-light-activated avoidance response. The inhibitory effect observed with PI metabolism inhibitors is, at least partly, due to a disturbance in Ca2+(c) signaling. Using the transgenic aequorin system, we show that the application of these inhibitors suppresses the blue-light-induced transient Ca2+(c) rise. These results demonstrate the importance of PIs in chloroplast movements, with the PI(4,5)P2-PLC pathway involved in phot2 signaling while PI3K and PI4K are required for the phot1- and phot2-induced accumulation response. Our results suggest that these PIs modulate cytosolic Ca2+ signaling during movements. PMID:23405144

  3. Changes in phosphoinositide turnover, Ca sup 2+ mobilization, and protein phosphorylation in platelets from NIDDM patients

    SciTech Connect

    Ishii, H.; Umeda, F.; Hashimoto, T.; Nawata, H. )

    1990-12-01

    Enhanced platelet functions have been demonstrated in patients with non-insulin-dependent diabetes mellitus (NIDDM). This study evaluated abnormalities in platelet signal transduction in diabetic patients, including turnover of phosphoinositides, mobilization of intracellular Ca2+, and phosphorylation of 20,000- and 47,000-Mr proteins (P20 and P47). Washed platelets were obtained from 6 patients with NIDDM whose platelet aggregation rates were abnormally elevated (DM-A group), 11 NIDDM patients with normal platelet aggregation rates (DM-B group), and 8 age-matched healthy control subjects. The mass and specific radioactivity of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol (PI), and phosphatidic acid (PA) in 32P-labeled platelets were not different among the three groups. Hydrolysis of PIP2, PIP, and PI; accumulation of PA; and phosphorylation of P20 in platelets stimulated by 0.05 U/ml thrombin were significantly increased in the DM-A group compared with the control or DM-B group. There was no difference in P47 phosphorylation among the three groups. On the contrary, P20 and P47 phosphorylation induced by 50 nM of 12-O-tetradecanoylphorbol-13-acetate, an activator of protein kinase C, was significantly decreased in the DM-A group. Additionally, the intracellular free Ca2+ concentration (( Ca2+)i) was measured with the fluorescent Ca2+ indicator fura 2. Although the basal (Ca2+)i value was similar in the three groups, the rise in (Ca2+)i induced by 0.05 U/ml thrombin in the presence and the absence of extracellular Ca2+ was significantly higher in the DM-A group than the other groups.

  4. Assembly and Molecular Architecture of the Phosphoinositide 3-Kinase p85? Homodimer.

    PubMed

    LoPiccolo, Jaclyn; Kim, Seung Joong; Shi, Yi; Wu, Bin; Wu, Haiyan; Chait, Brian T; Singer, Robert H; Sali, Andrej; Brenowitz, Michael; Bresnick, Anne R; Backer, Jonathan M

    2015-12-18

    Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that are activated by growth factor and G-protein-coupled receptors and propagate intracellular signals for growth, survival, proliferation, and metabolism. p85?, a modular protein consisting of five domains, binds and inhibits the enzymatic activity of class IA PI3K catalytic subunits. Here, we describe the structural states of the p85? dimer, based on data from in vivo and in vitro solution characterization. Our in vitro assembly and structural analyses have been enabled by the creation of cysteine-free p85? that is functionally equivalent to native p85?. Analytical ultracentrifugation studies showed that p85? undergoes rapidly reversible monomer-dimer assembly that is highly exothermic in nature. In addition to the documented SH3-PR1 dimerization interaction, we identified a second intermolecular interaction mediated by cSH2 domains at the C-terminal end of the polypeptide. We have demonstrated in vivo concentration-dependent dimerization of p85? using fluorescence fluctuation spectroscopy. Finally, we have defined solution conditions under which the protein is predominantly monomeric or dimeric, providing the basis for small angle x-ray scattering and chemical cross-linking structural analysis of the discrete dimer. These experimental data have been used for the integrative structure determination of the p85? dimer. Our study provides new insight into the structure and assembly of the p85? homodimer and suggests that this protein is a highly dynamic molecule whose conformational flexibility allows it to transiently associate with multiple binding proteins. PMID:26475863

  5. Targeting Phosphoinositide-3-Kinase-? with Theophylline Reverses Corticosteroid Insensitivity in Chronic Obstructive Pulmonary Disease

    PubMed Central

    To, Yasuo; Ito, Kazuhiro; Kizawa, Yasuo; Failla, Marco; Ito, Misako; Kusama, Tadashi; Elliott, W. Mark; Hogg, James C.; Adcock, Ian M.; Barnes, Peter J.

    2010-01-01

    Rationale: Patients with chronic obstructive pulmonary disease (COPD) show a poor response to corticosteroids. This has been linked to a reduction of histone deacetylase-2 as a result of oxidative stress and is reversed by theophylline. Objectives: To determine the role of phosphoinositide-3-kinase-delta (PI3K-?) on the development of corticosteroid insensitivity in COPD and under oxidative stress, and as a target for theophylline. Methods: Corticosteroid sensitivity was determined as the 50% inhibitory concentration of dexamethasone on tumor necrosis factor-?–induced interleukin-8 release in peripheral blood mononuclear cells from patients with COPD (n = 17) and compared with that of nonsmoking (n = 8) and smoking (n = 7) control subjects. The effect of theophylline and a selective PI3K-? inhibitor (IC87114) on restoration of corticosteroid sensitivity was confirmed in cigarette smoke–exposed mice. Measurements and Main Results: Peripheral blood mononuclear cells of COPD (50% inhibitory concentration of dexamethasone: 156.8 ± 32.6 nM) were less corticosteroid sensitive than those of nonsmoking (41.2 ± 10.5 nM; P = 0.018) and smoking control subjects (47.5 ± 19.6 nM; P = 0.031). Corticosteroid insensitivity and reduced histone deacetylase-2 activity after oxidative stress were reversed by a non-selective PI3K inhibitor (LY294002) and low concentrations of theophylline. Theophylline was a potent selective inhibitor of oxidant-activated PI3K-?, which was up-regulated in peripheral lung tissue of patients with COPD. Furthermore, cells with knock-down of PI3K-? failed to develop corticosteroid insensitivity with oxidative stress. Both theophylline and IC87114, combined with dexamethasone, inhibited corticosteroid-insensitive lung inflammation in cigarette–smoke-exposed mice in vivo. Conclusions: Inhibition of oxidative stress dependent PI3K-? activation by a selective inhibitor or theophylline provides a novel approach to reversing corticosteroid insensitivity in COPD. PMID:20224070

  6. The Phosphoinositide 3-Kinase Pathway in Human Cancer: Genetic Alterations and Therapeutic Implications

    PubMed Central

    Arcaro, Alexandre; Guerreiro, Ana S

    2007-01-01

    The phosphoinositide 3-kinase (PI3K) pathway is frequently activated in human cancer and represents an attractive target for therapies based on small molecule inhibitors. PI3K isoforms play an essential role in the signal transduction events activated by cell surface receptors including receptor tyrosine kinases (RTKs) and G-protein-coupled receptors (GPCRs). There are eight known PI3K isoforms in humans, which have been subdivided into three classes (I-III). Therefore PI3Ks show considerable diversity and it remains unclear which kinases in this family should be targeted in cancer. The class IA of PI3K comprises the p110?, p110? and p110? isoforms, which associate with activated RTKs. In human cancer, recent reports have described activating mutations in the PIK3CA gene encoding p110?, and inactivating mutations in the phosphatase and tensin homologue (PTEN) gene, a tumour suppressor and antagonist of the PI3K pathway. The PIK3CA mutations described in cancer constitutively activate p110? and, when expressed in cells drive oncogenic transformation. Moreover, these mutations cause the constitutive activation of downstream signaling molecules such as Akt/protein kinase B (PKB), mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (S6K) that is commonly observed in cancer cells. In addition to p110?, the other isoforms of the PI3K family may also play a role in human cancer, although their individual functions remain to be precisely identified. In this review we will discuss the evidence implicating individual PI3K isoforms in human cancer and their potential as drug targets in this context. PMID:19384426

  7. IQGAP Proteins Reveal an Atypical Phosphoinositide (aPI) Binding Domain with a Pseudo C2 Domain Fold

    SciTech Connect

    Dixon, Miles J.; Gray, Alexander; Schenning, Martijn; Agacan, Mark; Tempel, Wolfram; Tong, Yufeng; Nedyalkova, Lyudmila; Park, Hee-Won; Leslie, Nicholas R.; van Aalten, Daan M.F.; Downes, C. Peter; Batty, Ian H.

    2012-10-16

    Class I phosphoinositide (PI) 3-kinases act through effector proteins whose 3-PI selectivity is mediated by a limited repertoire of structurally defined, lipid recognition domains. We describe here the lipid preferences and crystal structure of a new class of PI binding modules exemplified by select IQGAPs (IQ motif containing GTPase-activating proteins) known to coordinate cellular signaling events and cytoskeletal dynamics. This module is defined by a C-terminal 105-107 amino acid region of which IQGAP1 and -2, but not IQGAP3, binds preferentially to phosphatidylinositol 3,4,5-trisphosphate (PtdInsP3). The binding affinity for PtdInsP3, together with other, secondary target-recognition characteristics, are comparable with those of the pleckstrin homology domain of cytohesin-3 (general receptor for phosphoinositides 1), an established PtdInsP3 effector protein. Importantly, the IQGAP1 C-terminal domain and the cytohesin-3 pleckstrin homology domain, each tagged with enhanced green fluorescent protein, were both re-localized from the cytosol to the cell periphery following the activation of PI 3-kinase in Swiss 3T3 fibroblasts, consistent with their common, selective recognition of endogenous 3-PI(s). The crystal structure of the C-terminal IQGAP2 PI binding module reveals unexpected topological similarity to an integral fold of C2 domains, including a putative basic binding pocket. We propose that this module integrates select IQGAP proteins with PI 3-kinase signaling and constitutes a novel, atypical phosphoinositide binding domain that may represent the first of a larger group, each perhaps structurally unique but collectively dissimilar from the known PI recognition modules.

  8. Class I Phosphoinositide 3-Kinase Exerts a Differential Role on Cell Survival and Cell Trafficking in Retina.

    PubMed

    Azadi, Seifollah; Brush, Richard S; Anderson, Robert E; Rajala, Raju V S

    2016-01-01

    Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that phosphorylates the 3'OH of the inositol ring of phosphoinositides. They are responsible for coordinating a diverse range of cell functions including proliferation, cell survival, degranulation, vesicular trafficking, and cell migration. The PI 3-kinases are grouped into three distinct classes: I, II, and III. Class III PI3K has been shown to be involved in intracellular protein trafficking, whereas class I PI3K is known to regulate cell survival following activation of cell surface receptors. However, studies from our laboratory and others have shown that class I PI3K may also be involved in photoreceptor protein trafficking. Therefore, to learn more about the role of class I and class III P13K in trafficking and to understand the impact of the lipid content of trafficking cargo vesicles, we developed a methodology to isolate trafficking vesicles from retinal tissue. PI3K class I and III proteins were enriched in our extracted trafficking vesicle fraction. Moreover, levels of ether phosphatidylethanolamine (PE) and ether phosphatidylcholine (PC) were significantly higher in the trafficking vesicle fraction than in total retina. These two lipid classes have been suggested to be involved with fusion/targeting of trafficking vesicles. PMID:26427433

  9. Pharmacologic Profiling of Phosphoinositide 3-Kinase Inhibitors as Mitigators of Ionizing Radiation–Induced Cell Death

    PubMed Central

    Sharlow, Elizabeth R.; Epperly, Michael W.; Lira, Ana; Leimgruber, Stephanie; Skoda, Erin M.; Wipf, Peter; Greenberger, Joel S.

    2013-01-01

    Ionizing radiation (IR) induces genotoxic stress that triggers adaptive cellular responses, such as activation of the phosphoinositide 3-kinase (PI3K)/Akt signaling cascade. Pluripotent cells are the most important population affected by IR because they are required for cellular replenishment. Despite the clear danger to large population centers, we still lack safe and effective therapies to abrogate the life-threatening effects of any accidental or intentional IR exposure. Therefore, we computationally analyzed the chemical structural similarity of previously published small molecules that, when given after IR, mitigate cell death and found a chemical cluster that was populated with PI3K inhibitors. Subsequently, we evaluated structurally diverse PI3K inhibitors. It is remarkable that 9 of 14 PI3K inhibitors mitigated ?IR-induced death in pluripotent NCCIT cells as measured by caspase 3/7 activation. A single intraperitoneal dose of LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], administered to mice at 4 or 24 hours, or PX-867 [(4S,4aR,5R,6aS,9aR,Z)-11-hydroxy-4-(methoxymethyl)-4a,6a-dimethyl-2,7,10-trioxo-1-(pyrrolidin-1-ylmethylene)-1,2,4,4a,5,6,6a,7,8,9,9a,10-dodecahydroindeno[4,5-H]isochromen-5-yl acetate (CID24798773)], administered 4 hours after a lethal dose of ?IR, statistically significantly (P < 0.02) enhanced in vivo survival. Because cell cycle checkpoints are important regulators of cell survival after IR, we examined cell cycle distribution in NCCIT cells after ?IR and PI3K inhibitor treatment. LY294002 and PX-867 treatment of nonirradiated cells produced a marked decrease in S phase cells with a concomitant increase in the G1 population. In irradiated cells, LY294002 and PX-867 treatment also decreased S phase and increased the G1 and G2 populations. Treatment with LY294002 or PX-867 decreased ?IR-induced DNA damage as measured by ?H2AX, suggesting reduced DNA damage. These results indicate pharmacologic inhibition of PI3K after IR abrogated cell death. PMID:24068833

  10. RNA interference-mediated knockdown of Aurora-B alters the metastatic behavior of A549 cells via modulation of the phosphoinositide 3-kinase/Akt signaling pathway

    PubMed Central

    ZHOU, LONG DIAN; XIONG, XU; LONG, XIN HUA; LIU, ZHI LI; HUANG, SHAN HU; ZHANG, WEI

    2014-01-01

    Accumulating evidence has revealed that an elevated expression level of Aurora-B is associated with metastasis in various types of malignant tumor. However, it is currently unclear whether this molecule is involved in non-small lung cancer (NSCLC) metastasis, and the molecular mechanisms associated with Aurora-B and metastasis remain unknown. In the present study, in order to investigate whether Aurora-B is involved in the development and metastasis of NSCLC, the Aurora-B protein expression in NSCLC tissues was detected by immunohistochemistry and its association with metastasis was analyzed. The results revealed that the expression levels of the Aurora-B protein in tissues obtained from NSCLC patients with lymph node metastasis were significantly higher than those without metastatic disease. Furthermore, the effect of Aurora-B inhibition on A549 cell migration and invasion, as well as the activity of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway was evaluated. Aurora-B was inhibited in the A549 cells using short hairpin RNA, and the cell migration and invasion rates were investigated using wound healing and Transwell invasion assays. In addition, the expression of the main proteins in the PI3K/Akt/nuclear factor-?B (NF-?B) signaling pathway, and matrix metalloproteinase (MMP)-2 and -9 were measured by western blot analysis. The results demonstrated that cell migration and invasion were decreased as a result of silencing Aurora-B. Furthermore, the activity of the PI3K/Akt/NF-?B signaling pathway and the expression of MMP-2 and -9 protein were suppressed by silencing Aurora-B. The results of the present study indicate that the knockdown of Aurora-B suppresses A549 cell invasion and migration via the inhibition of the PI3K/Akt signaling pathway in vitro and thus, targeting Aurora-B may present a potential treatment strategy for NSCLC. PMID:25295091

  11. In vivo regulation of phosphoinositide 3-kinase in retina through light-induced tyrosine phosphorylation of the insulin receptor beta-subunit.

    PubMed

    Rajala, Raju V S; McClellan, Mark E; Ash, John D; Anderson, Robert E

    2002-11-01

    Recently, we have shown that phosphoinositide 3-kinase (PI3K) in bovine rod outer segment (ROS) is activated in vitro by tyrosine phosphorylation of the C-terminal tail of the insulin receptor (Rajala, R. V. S., and Anderson, R. E. (2001) Invest. Ophthal. Vis. Sci. 42, 3110-3117). In this study, we have investigated the in vivo mechanism of PI3K activation in the rodent retina and report the novel finding that light stimulates tyrosine phosphorylation of the beta-subunit of the insulin receptor (IRbeta) in ROS membranes, which leads to the association of PI3K enzyme activity with IRbeta. Retinas from light- or dark-adapted mice and rats were homogenized and immunoprecipitated with antibodies against phosphotyrosine, IRbeta, or the p85 regulatory subunit of PI3K, and PI3K activity was measured using PI-4,5-P(2) as substrate. We observed a light-dependent increase in tyrosine phosphorylation of IRbeta and an increase in PI3K enzyme activity in isolated ROS and in anti-phosphotyrosine and anti-IRbeta immunoprecipitates of retinal homogenates. The light effect was localized to photoreceptor neurons and is independent of insulin secretion. Our results suggest that light induces tyrosine phosphorylation of IRbeta in outer segment membranes, which leads to the binding of p85 through its N-terminal Src homology 2 domain and the generation of PI-3,4,5-P(3). We suggest that the physiological role of this process may be to provide neuroprotection of the retina against light damage by activating proteins that protect against stress-induced apoptosis. PMID:12213821

  12. IgA Fc receptor (FcalphaR) cross-linking recruits tyrosine kinases, phosphoinositide kinases and serine/threonine kinases to glycolipid rafts.

    PubMed Central

    Lang, Mark L; Chen, Yih-Wen; Shen, Li; Gao, Hong; Lang, Gillian A; Wade, Terri K; Wade, William F

    2002-01-01

    The human IgA Fc receptor (FcalphaR, CD89) triggers several important physiological functions, including phagocytosis, NADPH oxidase activation and antigen presentation. Efforts are underway to delineate FcalphaR signal-transduction pathways that control these functions. In a previous study, we demonstrated that cross-linking of FcalphaR increased its partitioning into membrane glycolipid rafts and was accompanied by gamma-chain-dependent recruitment and phosphorylation of the tyrosine kinases Lck/Yes-related novel protein tyrosine kinase (Lyn) and Bruton's tyrosine kinase (Btk). Here we have performed a more extensive characterization of signalling effectors recruited to rafts on FcalphaR cross-linking. We demonstrate that in addition to tyrosine kinases Lyn and Btk, FcalphaR cross-linking also recruits B-lymphocyte kinase (Blk) and spleen tyrosine kinase (Syk) to rafts. We show recruitment of phosphoinositide kinases, including 3-phosphoinositide 3-kinase and phospholipase Cgamma2, and serine/threonine kinases such as protein kinase C (PKC) alpha, PKCepsilon, and protein kinase B (PKB) alpha. This suggests that lipid rafts serve as sites for FcalphaR-triggered recruitment of multiple classes of signalling effectors. We further demonstrate that tyrosine kinases and PKCalpha have a sustained association with rafts, whereas phosphoinositide 3-kinase and its downstream effectors have a transient association with rafts. This is consistent with temporally regulated divergence of FcalphaR signalling pathways in rafts. Furthermore, we suggest the spatial separation of signalling effectors by transport of phosphoinositide 3-kinase, phosphoinositide-dependent kinase 1, PKBalpha and PKCepsilon to endocytic compartments containing internalized FcalphaR. PMID:12023895

  13. Structure-Based Design of Potent and Selective 3-Phosphoinositide-Dependent Kinase-1 (PDK1) Inhibitors

    SciTech Connect

    Medina, Jesus R.; Becker, Christopher J.; Blackledge, Charles W.; Duquenne, Celine; Feng, Yanhong; Grant, Seth W.; Heerding, Dirk; Li, William H.; Miller, William H.; Romeril, Stuart P.; Scherzer, Daryl; Shu, Arthur; Bobko, Mark A.; Chadderton, Antony R.; Dumble, Melissa; Gardiner, Christine M.; Gilbert, Seth; Liu, Qi; Rabindran, Sridhar K.; Sudakin, Valery; Xiang, Hong; Brady, Pat G.; Campobasso, Nino; Ward, Paris; Axten, Jeffrey M.

    2014-10-02

    Phosphoinositide-dependent protein kinase-1(PDK1) is a master regulator of the AGC family of kinases and an integral component of the PI3K/AKT/mTOR pathway. As this pathway is among the most commonly deregulated across all cancers, a selective inhibitor of PDK1 might have utility as an anticancer agent. Herein we describe our lead optimization of compound 1 toward highly potent and selective PDK1 inhibitors via a structure-based design strategy. The most potent and selective inhibitors demonstrated submicromolar activity as measured by inhibition of phosphorylation of PDK1 substrates as well as antiproliferative activity against a subset of AML cell lines. In addition, reduction of phosphorylation of PDK1 substrates was demonstrated in vivo in mice bearing OCl-AML2 xenografts. These observations demonstrate the utility of these molecules as tools to further delineate the biology of PDK1 and the potential pharmacological uses of a PDK1 inhibitor.

  14. [The role of phosphoinositide-3-kinase in controlling the shape and directional movement in Physarum polycephalum plasmodium].

    PubMed

    Matveeva, N B; Be?lina, S I; Teplov, V A

    2008-01-01

    The influence of wortmannin and LY294002, specific inhibitors of phosphoinosite-3-kinase, on the shape, motile behavior, and chemotaxis toward glucose has been investigated in Physarum polycephalum plasmodium, a multinuclear amoeboid cell with the autooscillatory mode of motion. Both inhibitors were shown to cause a reduction of the plasmodium frontal edge and a decrease in the efficiency of mass transfer during migration. They also suppress chemotaxis toward glucose and eliminate characteristic changes in autooscillatory behavior normally observed in response to the treatment of the whole plasmodium with glucose. The manifestation of these effects depends on the inhibitor concentration, the duration of treatment, and the size of plasmodium. The involvement of phosphoinosite-3-kinase in creating the frontal edge and in controlling the chemotaxis of Physarum plasmodium suggests that the interrelation of polar shape and directional movement of amoeboid cells with the distribution of phosphoinositides in the plasma membrane has the universal nature. PMID:19137682

  15. Involvement of phosphatidylinositol 4,5-bisphosphate in phosphatidylserine exposure in platelets: use of a permeant phosphoinositide-binding peptide.

    PubMed

    Bucki, R; Janmey, P A; Vegners, R; Giraud, F; Sulpice, J C

    2001-12-25

    During platelet activation, phosphatidylserine (PS) exposure on the extracellular face of the plasma membrane is associated with increased procoagulant activity. PS externalization is generally attributed to an increase in intracellular Ca(2+). Various phospholipid transporters, such as specific scramblases or proteins from the family of multidrug resistance proteins, and cofactors such as phosphatidylinositol 4,5-bisphosphate (PIP2) have been proposed to participate in this process. In this study, we used a membrane-permeant polycationic peptide (RhB-QRLFQVKGRR), derived from the PIP2-binding site of gelsolin (GS 160-169) and linked to rhodamine B, to investigate the role of PIP2 in PS externalization in whole platelets. The peptide penetrated rapidly into the platelets, specifically bound to PIP2, and induced PS exposure to a similar extent as thrombin or collagen, but independently of changes in intracellular Ca(2+) or phosphoinositide 3-kinase activity. A pretreatment of platelets with quercetin, an inhibitor of phosphoinositide metabolism, drastically decreased PS exposure induced by agonists or peptide. In large unilamellar vesicles (LUVs), the presence of PIP2 was strictly required for the induction of scrambling of NBD-labeled phospholipids (PC and PS) by the peptide. In inside-out vesicles from erythrocytes (IOVs), the peptide also induced redistribution of PC and PS. Our data suggest that, in intact platelets, PIP2 acts as a target of polycationic effectors, including Ca(2+), to promote PS exposure. The use of a membrane-permeant and fluorescent peptide which binds to PIP2 is a promising tool to investigate the role of PIP2 in various cellular processes. PMID:11747452

  16. Shiga toxin type-2 (Stx2) induces glutamate release via phosphoinositide 3-kinase (PI3K) pathway in murine neurons

    PubMed Central

    Obata, Fumiko; Hippler, Lauren M.; Saha, Progyaparamita; Jandhyala, Dakshina M.; Latinovic, Olga S.

    2015-01-01

    Shiga toxin-producing Escherichia coli (STEC) can cause central nervous system (CNS) damage resulting in paralysis, seizures, and coma. The key STEC virulence factors associated with systemic illness resulting in CNS impairment are Shiga toxins (Stx). While neurons express the Stx receptor globotriaosylceramide (Gb3) in vivo, direct toxicity to neurons by Stx has not been studied. We used murine neonatal neuron cultures to study the interaction of Shiga toxin type 2 (Stx2) with cell surface expressed Gb3. Single molecule imaging three dimensional STochastic Optical Reconstruction Microscopy—Total Internal Reflection Fluorescence (3D STORM-TIRF) allowed visualization and quantification of Stx2-Gb3 interactions. Furthermore, we demonstrate that Stx2 increases neuronal cytosolic Ca2+, and NMDA-receptor inhibition blocks Stx2-induced Ca2+ influx, suggesting that Stx2-mediates glutamate release. Phosphoinositide 3-kinase (PI3K)-specific inhibition by Wortmannin reduces Stx2-induced intracellular Ca2+ indicating that the PI3K signaling pathway may be involved in Stx2-associated glutamate release, and that these pathways may contribute to CNS impairment associated with STEC infection. PMID:26236186

  17. Structural basis for UCN-01 (7-hydroxystaurosporine) specificity and PDK1 (3-phosphoinositide-dependent protein kinase-1) inhibition.

    PubMed Central

    Komander, David; Kular, Gursant S; Bain, Jennifer; Elliott, Matthew; Alessi, Dario R; Van Aalten, Daan M F

    2003-01-01

    PDK1 (3-phosphoinositide-dependent protein kinase-1) is a member of the AGC (cAMP-dependent, cGMP-dependent, protein kinase C) family of protein kinases, and has a key role in insulin and growth-factor signalling through phosphorylation and subsequent activation of a number of other AGC kinase family members, such as protein kinase B. The staurosporine derivative UCN-01 (7-hydroxystaurosporine) has been reported to be a potent inhibitor for PDK1, and is currently undergoing clinical trials for the treatment of cancer. Here, we report the crystal structures of staurosporine and UCN-01 in complex with the kinase domain of PDK1. We show that, although staurosporine and UCN-01 interact with the PDK1 active site in an overall similar manner, the UCN-01 7-hydroxy group, which is not present in staurosporine, generates direct and water-mediated hydrogen bonds with active-site residues. Inhibition data from UCN-01 tested against a panel of 29 different kinases show a different pattern of inhibition compared with staurosporine. We discuss how these differences in inhibition could be attributed to specific interactions with the additional 7-hydroxy group, as well as the size of the 7-hydroxy-group-binding pocket. This information could lead to opportunities for structure-based optimization of PDK1 inhibitors. PMID:12892559

  18. Apelin/APJ signaling promotes hypoxia-induced proliferation of endothelial progenitor cells via phosphoinositide-3 kinase/Akt signaling.

    PubMed

    Zhang, Jingchang; Liu, Qiming; Hu, Xinqun; Fang, Zhenfei; Huang, Feng; Tang, Liang; Zhou, Shenghua

    2015-09-01

    Endothelial progenitor cells (EPCs) can adhere to the endothelium at sites of hypoxia/ischemia and participate in the formation of novel vessels through differentiating into endothelial cells (ECs). Apelin is an endogenous ligand for the G protein?coupled receptor APJ, and apelin/APJ signaling has a role in cardiovascular function. The present study aimed to investigate the role of apelin/APJ signaling in the regulation of EPC proliferation under hypoxia. The results showed that hypoxia was able to induce EPC proliferation, accompanied with an upregulation of hypoxia?inducible factor (HIF)?1? as well as apelin/APJ signaling. Further investigation indicated that siRNA?mediated knockdown of apelin or APJ expression attenuated the hypoxia?induced proliferation of EPCs, suggesting that apelin/APJ signaling has an important role in hypoxia?induced EPC proliferation. Moreover, the phosphoinositide?3 kinase (PI3K)/Akt signaling pathway was found to be involved in the apelin/APJ?mediated EPC proliferation under hypoxia. Based on these findings, the present study suggested that hypoxia?induced upregulation of HIF?1? promotes the expression of apelin and APJ, which further activate the downstream PI3K/Akt signaling pathway, a key promoter of EPC proliferation. In conclusion, the present study highlighted the role of apelin/APJ in the regulation of EPC proliferation, and apelin/APJ may therefore serve as a potential target for the prevention of hypoxic ischemic injury. PMID:26018184

  19. Leukotriene D4 receptor-mediated hydrolysis of phosphoinositide and mobilization of calcium in sheep tracheal smooth muscle cells

    SciTech Connect

    Mong, S.; Miller, J.; Wu, H.L.; Crooke, S.T.

    1988-02-01

    A sheep tracheal smooth muscle primary culture cell system was developed to characterize leukotriene D4 (LTD4) receptor-mediated biochemical and pharmacological effects. (/sup 3/H)LTD4 binding to the enriched plasma membrane receptor was specific, stereoselective and saturable. LTE4 and high affinity receptor antagonists bound to the receptors with a rank-order potency that was expected from previous smooth muscle contraction studies. In the (/sup 3/H)myoinositol labeled cells, LTD4 and LTE4 induced phosphoinositide hydrolysis. The biosynthesis of (/sup 3/H)inositol-trisphosphate was rapid and the induction of biosynthesis of (/sup 3/H)inositol-monophosphate by LTs was stereoselective and specific and was inhibited specifically by a receptor antagonist, SKF 104353. In the fura-2 loaded smooth muscle cells, LTD4 and LTE4 induced transient intracellular Ca++ mobilization. The fura-2/Ca++ transient was stereoselective and specific and was inhibited by receptor antagonist, SKF 104353. These results suggest that the cultured sheep tracheal smooth muscle cells have plasma membrane receptors for LTD4. These receptors were coupled to a phospholipase C that, when activated by agonists, induced hydrolysis of inositol containing phospholipids. The hydrolysis products, e.g. diacylglycerol and inositol-trisphosphate, may serve as intracellular messengers that trigger or contribute to the contractile effect in sheep tracheal smooth muscle.

  20. Requirement for class II phosphoinositide 3-kinase C2alpha in maintenance of glomerular structure and function.

    PubMed

    Harris, David P; Vogel, Peter; Wims, Marie; Moberg, Karen; Humphries, Juliane; Jhaver, Kanchan G; DaCosta, Christopher M; Shadoan, Melanie K; Xu, Nianhua; Hansen, Gwenn M; Balakrishnan, Sanjeevi; Domin, Jan; Powell, David R; Oravecz, Tamas

    2011-01-01

    An early lesion in many kidney diseases is damage to podocytes, which are critical components of the glomerular filtration barrier. A number of proteins are essential for podocyte filtration function, but the signaling events contributing to development of nephrotic syndrome are not well defined. Here we show that class II phosphoinositide 3-kinase C2? (PI3KC2?) is expressed in podocytes and plays a critical role in maintaining normal renal homeostasis. PI3KC2?-deficient mice developed chronic renal failure and exhibited a range of kidney lesions, including glomerular crescent formation and renal tubule defects in early disease, which progressed to diffuse mesangial sclerosis, with reduced podocytes, widespread effacement of foot processes, and modest proteinuria. These findings were associated with altered expression of nephrin, synaptopodin, WT-1, and desmin, indicating that PI3KC2? deficiency specifically impacts podocyte morphology and function. Deposition of glomerular IgA was observed in knockout mice; importantly, however, the development of severe glomerulonephropathy preceded IgA production, indicating that nephropathy was not directly IgA mediated. PI3KC2? deficiency did not affect immune responses, and bone marrow transplantation studies also indicated that the glomerulonephropathy was not the direct consequence of an immune-mediated disease. Thus, PI3KC2? is critical for maintenance of normal glomerular structure and function by supporting normal podocyte function. PMID:20974805

  1. Role of calcium in phosphoinositide metabolism and inhibition of norepinephrine transport into synaptic vesicles by amphetamine analogs

    SciTech Connect

    Knepper, S.M.

    1985-01-01

    Norepinephrine-(NE) and calcium ionophore A23187-stimulated phosphoinositide (PIn) metabolism in rat brain slices was studied under varying calcium conditions. Tissue was labelled with /sup 3/H-myo-inositol and /sup 3/H-inositol phosphates (IPn), products of PIn metabolism were measured. In the absence of media calcium the response to NE was decreased while that to A23187 was little affected A23187 can release calcium from intracellular stores. Basal and stimulated accumulation of /sup 3/H-IPn was reversibly antagonized with EGTA by addition of calcium. Using calcium buffers, approximately 10/sup -7/ M free calcium was required to support hydrolysis. Free intracellular calcium is maintained at approximately this level. Thus calcium is required for PIn hydrolysis but appears to play a permissive role, basal levels being sufficient to support metabolism. Conformationally-defined (rigid) and -restricted (semi-rigid) analogs of the most stable conformations of amphetamine, antiperiplanar (exo) and gauche (endo), were utilized to probe the conformational requirements of vesicular NE transport. Analogs tested were 2-aminotetralin (2AT), 3-methyltetrahydroisoquinoline, anti- and syn-9-aminobenzobicyclo(2.2.1)heptene, and endo and exo conformers of 2-aminobenzobicyclo(2.2.1)heptene and 2-aminobenzobicyclo(2.2.2)octene.

  2. A method to control phosphoinositides and to analyze PTEN function in living cells using voltage sensitive phosphatases

    PubMed Central

    Mavrantoni, Angeliki; Thallmair, Veronika; Leitner, Michael G.; Schreiber, Daniela N.; Oliver, Dominik; Halaszovich, Christian R.

    2015-01-01

    Voltage sensitive phosphatases (VSPs), including engineered voltage sensitive PTEN, are excellent tools to rapidly and reversibly alter the phosphoinositide (PI) content of the plasma membrane in vivo and study the tumor suppressor PTEN. However, widespread adoption of these tools is hampered by the requirement for electrophysiological instrumentation to control the activity of VSPs. Additionally, monitoring and quantifying the PI changes in living cells requires sophisticated microscopy equipment and image analysis. Here we present methods that bypass these obstacles. First, we explore technically simple means for activation of VSPs via extracellularly applied agents or light. Secondly, we characterize methods to monitor PI(4,5)P2 and PI(3,4,5)P3 levels using fluorescence microscopy or photometry in conjunction with translocation or FRET based PI probes, respectively. We then demonstrate the application of these techniques by characterizing the effect of known PTEN mutations on its enzymatic activity, analyzing the effect of PTEN inhibitors, and detecting in real time rapid inhibition of protein kinase B following depletion of PI(3,4,5)P3. Thus, we established an approach that does not only allow for rapidly manipulating and monitoring PI(4,5)P2 and PI(3,4,5)P3 levels in a population of cells, but also facilitates the study of PTEN mutants and pharmacological targeting in mammalian cells. PMID:25873899

  3. Regulatory roles of phosphoinositides in membrane trafficking and their potential impact on cell-wall synthesis and re-modelling

    PubMed Central

    Krishnamoorthy, Praveen; Sanchez-Rodriguez, Clara; Heilmann, Ingo; Persson, Staffan

    2014-01-01

    Background Plant cell walls are complex matrices of carbohydrates and proteins that control cell morphology and provide protection and rigidity for the plant body. The construction and maintenance of this intricate system involves the delivery and recycling of its components through a precise balance of endomembrane trafficking, which is controlled by a plethora of cell signalling factors. Phosphoinositides (PIs) are one class of signalling molecules with diverse roles in vesicle trafficking and cytoskeleton structure across different kingdoms. Therefore, PIs may also play an important role in the assembly of plant cell walls. Scope The eukaryotic PI pathway is an intricate network of different lipids, which appear to be divided in different pools that can partake in vesicle trafficking or signalling. Most of our current understanding of how PIs function in cell metabolism comes from yeast and mammalian systems; however, in recent years significant progress has been made towards a better understanding of the plant PI system. This review examines the current state of knowledge of how PIs regulate vesicle trafficking and their potential influence on plant cell-wall architecture. It considers first how PIs are formed in plants and then examines their role in the control of vesicle trafficking. Interactions between PIs and the actin cytoskeleton and small GTPases are also discussed. Future challenges for research are suggested. PMID:24769536

  4. Acylation-dependent Export of Trypanosoma cruzi Phosphoinositide-specific Phospholipase C to the Outer Surface of Amastigotes*

    PubMed Central

    de Paulo Martins, Vicente; Okura, Michael; Maric, Danijela; Engman, David M.; Vieira, Mauricio; Docampo, Roberto; Moreno, Silvia N. J.

    2010-01-01

    Phosphoinositide phospholipase C (PI-PLC) plays an essential role in cell signaling. A unique Trypanosoma cruzi PI-PLC (TcPI-PLC) is lipid-modified in its N terminus and localizes to the plasma membrane of amastigotes. Here, we show that TcPI-PLC is located onto the extracellular phase of the plasma membrane of amastigotes and that its N-terminal 20 amino acids are necessary and sufficient to target the fused GFP to the outer surface of the parasite. Mutagenesis of the predicted acylated residues confirmed that myristoylation of a glycine residue in the 2nd position and acyl modification of a cysteine in the 4th but not in the 8th or 15th position of the coding sequence are required for correct plasma membrane localization in T. cruzi epimastigotes or amastigotes. Interestingly, mutagenesis of the cysteine at the 8th position increased its flagellar localization. When expressed as fusion constructs with GFP, the N-terminal 6 and 10 amino acids fused to GFP are predominantly located in the cytosol and concentrated in a compartment that co-localizes with a Golgi complex marker. The N-terminal 20 amino acids of TcPI-PLC associate with lipid rafts when dually acylated. Taken together, these results indicate that N-terminal acyl modifications serve as a molecular addressing system for sending TcPI-PLC to the outer surface of the cell. PMID:20647312

  5. Tangeretin sensitizes cisplatin-resistant human ovarian cancer cells through downregulation of phosphoinositide 3-kinase/Akt signaling pathway.

    PubMed

    Arafa, El-Shaimaa A; Zhu, Qianzheng; Barakat, Bassant M; Wani, Gulzar; Zhao, Qun; El-Mahdy, Mohamed A; Wani, Altaf A

    2009-12-01

    Combination of innocuous dietary components with anticancer drugs is an emerging new strategy for cancer chemotherapy to increase antitumor responses. Tangeretin is a citrus flavonoid known to inhibit cancer cell proliferation. Here, we show an enhanced response of A2780/CP70 and 2008/C13 cisplatin-resistant human ovarian cancer cells to various combination treatments of cisplatin and tangeretin. Pretreatment of cells with tangeretin before cisplatin treatment synergistically inhibited cancer cell proliferation. This combination was effective in activating apoptosis via caspase cascade as well as arresting cell cycle at G(2)-M phase. Moreover, phospho-Akt and its downstream substrates, e.g., NF-kappaB, phospho-GSK-3beta, and phospho-BAD, were downregulated upon tangeretin-cisplatin treatment. The tangeretin-cisplatin-induced apoptosis in A2780/CP70 cells was increased by phosphoinositide-3 kinase (PI3K) inhibition and siRNA-mediated Akt silencing, but reduced by overexpression of constitutively activated Akt and GSK-3beta inhibition. The overall results indicated that tangeretin exposure preconditions cisplatin-resistant human ovarian cancer cells for a conventional response to low-dose cisplatin-induced cell death occurring through downregulation of PI3K/Akt signaling pathway. Thus, effectiveness of tangeretin combinations, as a promising modality in the treatment of resistant cancers, warrants systematic clinical studies. PMID:19903849

  6. Phosphoinositide dependent protein kinase 1 is required for exercise-induced cardiac hypertrophy but not the associated mitochondrial adaptations.

    PubMed

    Noh, Junghyun; Wende, Adam R; Olsen, Curtis D; Kim, Bumjun; Bevins, Jack; Zhu, Yi; Zhang, Quan-Jiang; Riehle, Christian; Abel, E Dale

    2015-12-01

    Phosphoinositide-dependent protein kinase-1 (PDPK1) is an important mediator of phosphatidylinositol 3-kinase (PI3K) signaling. We previously reported that PI3K but not Akt signaling mediates the increase in mitochondrial oxidative capacity following physiological cardiac hypertrophy. To determine if PDPK1 regulates these metabolic adaptations we examined mice with cardiomyocyte-specific heterozygous knockout of PDPK1 (cPDPK1(+/-)) after 5 wk. exercise swim training. Akt phosphorylation at Thr308 increased by 43% in wildtype (WT) mice but not in cPDPK1(+/-) mice following exercise training. Ventricular contractile function was not different between WT and cPDPK1(+/-) mice at baseline. In addition, exercise did not influence ventricular function in WT or cPDPK1(+/-) mice. Heart weight normalized to tibia length ratios increased by 13.8% in WT mice (6.2±0.2 vs. 7.1±0.2, P=0.001), but not in cPDPK1(+/-) (6.2±0.3 vs. 6.5±0.2, P=0.20) mice after swim training. Diastolic LV dimension increased in WT mice (3.7±0.1 vs. 4.0±0.1mm, P=0.01) but not in cPDPK1(+/-) (3.8±0.1 vs. 3.7±0.1mm, P=0.56) following swim training. Maximal mitochondrial oxygen consumption (VADP, nmol/min/mg) using palmitoyl carnitine as a substrate was significantly increased in mice of all genotypes following swim training (WT: 13.6±0.6 vs.16.1±0.9, P=0.04; cPDPK1(+/-): 12.4±0.6 vs.15.9±1.2, P=0.04). These findings suggest that PDPK1 is required for exercise-induced cardiac hypertrophy but does not contribute to exercise-induced increases in mitochondrial function. PMID:26476238

  7. Up-regulation of phosphoinositide metabolism in tobacco cells constitutively expressing the human type I inositol polyphosphate 5-phosphatase

    NASA Technical Reports Server (NTRS)

    Perera, Imara Y.; Love, John; Heilmann, Ingo; Thompson, William F.; Boss, Wendy F.; Brown, C. S. (Principal Investigator)

    2002-01-01

    To evaluate the impact of suppressing inositol 1,4,5-trisphosphate (InsP(3)) in plants, tobacco (Nicotiana tabacum) cells were transformed with the human type I inositol polyphosphate 5-phosphatase (InsP 5-ptase), an enzyme which specifically hydrolyzes InsP(3). The transgenic cell lines showed a 12- to 25-fold increase in InsP 5-ptase activity in vitro and a 60% to 80% reduction in basal InsP(3) compared with wild-type cells. Stimulation with Mas-7, a synthetic analog of the wasp venom peptide mastoparan, resulted in an approximately 2-fold increase in InsP(3) in both wild-type and transgenic cells. However, even with stimulation, InsP(3) levels in the transgenic cells did not reach wild-type basal values, suggesting that InsP(3) signaling is compromised. Analysis of whole-cell lipids indicated that phosphatidylinositol 4,5-bisphosphate (PtdInsP(2)), the lipid precursor of InsP(3), was greatly reduced in the transgenic cells. In vitro assays of enzymes involved in PtdInsP(2) metabolism showed that the activity of the PtdInsP(2)-hydrolyzing enzyme phospholipase C was not significantly altered in the transgenic cells. In contrast, the activity of the plasma membrane PtdInsP 5 kinase was increased by approximately 3-fold in the transgenic cells. In vivo labeling studies revealed a greater incorporation of (32)P into PtdInsP(2) in the transgenic cells compared with the wild type, indicating that the rate of PtdInsP(2) synthesis was increased. These studies show that the constitutive expression of the human type I InsP 5-ptase in tobacco cells leads to an up-regulation of the phosphoinositide pathway and highlight the importance of PtdInsP(2) synthesis as a regulatory step in this system.

  8. Up-Regulation of Phosphoinositide Metabolism in Tobacco Cells Constitutively Expressing the Human Type I Inositol Polyphosphate 5-Phosphatase1

    PubMed Central

    Perera, Imara Y.; Love, John; Heilmann, Ingo; Thompson, William F.; Boss, Wendy F.

    2002-01-01

    To evaluate the impact of suppressing inositol 1,4,5-trisphosphate (InsP3) in plants, tobacco (Nicotiana tabacum) cells were transformed with the human type I inositol polyphosphate 5-phosphatase (InsP 5-ptase), an enzyme which specifically hydrolyzes InsP3. The transgenic cell lines showed a 12- to 25-fold increase in InsP 5-ptase activity in vitro and a 60% to 80% reduction in basal InsP3 compared with wild-type cells. Stimulation with Mas-7, a synthetic analog of the wasp venom peptide mastoparan, resulted in an approximately 2-fold increase in InsP3 in both wild-type and transgenic cells. However, even with stimulation, InsP3 levels in the transgenic cells did not reach wild-type basal values, suggesting that InsP3 signaling is compromised. Analysis of whole-cell lipids indicated that phosphatidylinositol 4,5-bisphosphate (PtdInsP2), the lipid precursor of InsP3, was greatly reduced in the transgenic cells. In vitro assays of enzymes involved in PtdInsP2 metabolism showed that the activity of the PtdInsP2-hydrolyzing enzyme phospholipase C was not significantly altered in the transgenic cells. In contrast, the activity of the plasma membrane PtdInsP 5 kinase was increased by approximately 3-fold in the transgenic cells. In vivo labeling studies revealed a greater incorporation of 32P into PtdInsP2 in the transgenic cells compared with the wild type, indicating that the rate of PtdInsP2 synthesis was increased. These studies show that the constitutive expression of the human type I InsP 5-ptase in tobacco cells leads to an up-regulation of the phosphoinositide pathway and highlight the importance of PtdInsP2 synthesis as a regulatory step in this system. PMID:12177493

  9. Regulation of PLC?2 by the electrostatic and mechanical properties of lipid bilayers.

    PubMed

    Arduin, Alessia; Gaffney, Piers R J; Ces, Oscar

    2015-01-01

    Phosphoinositide-specific phospholipase C (PLC) is an important family of enzymes constituting a junction between phosphoinositide lipid signaling and the trans-membrane signal transduction processes that are crucial to many living cells. However, the regulatory mechanism of PLC is not yet understood in detail. To address this issue, activity studies were carried out using lipid vesicles in a model system that was specifically designed to study protein-protein and lipid-protein interactions in concert. Evidence was found for a direct interaction between PLC and the GTPases that mediate phospholipase activation. Furthermore, for the first time, the relationships between PLC activity and substrate presentation in lipid vesicles of various sizes, as well as lipid composition and membrane mechanical properties, were analyzed. PLC activity was found to depend upon the electrostatic potential and the stored curvature elastic stress of the lipid membranes. PMID:26243281

  10. Regulation of PLC?2 by the electrostatic and mechanical properties of lipid bilayers

    PubMed Central

    Arduin, Alessia; Gaffney, Piers R. J.; Ces, Oscar

    2015-01-01

    Phosphoinositide-specific phospholipase C (PLC) is an important family of enzymes constituting a junction between phosphoinositide lipid signaling and the trans-membrane signal transduction processes that are crucial to many living cells. However, the regulatory mechanism of PLC is not yet understood in detail. To address this issue, activity studies were carried out using lipid vesicles in a model system that was specifically designed to study protein-protein and lipid-protein interactions in concert. Evidence was found for a direct interaction between PLC and the GTPases that mediate phospholipase activation. Furthermore, for the first time, the relationships between PLC activity and substrate presentation in lipid vesicles of various sizes, as well as lipid composition and membrane mechanical properties, were analyzed. PLC activity was found to depend upon the electrostatic potential and the stored curvature elastic stress of the lipid membranes. PMID:26243281

  11. Piperine inhibits type II phosphatidylinositol 4-kinases: a key component in phosphoinositides turnover.

    PubMed

    Bojjireddy, Naveen; Sinha, Ranjeet Kumar; Subrahmanyam, Gosukonda

    2014-08-01

    Piperine has been shown to have anti-inflammatory properties. The molecular mechanisms by which it mediates anti-inflammatory activities remain elusive. Type II phosphatidylinositol 4-kinase(s) are key components in Fc?RI receptor-mediated signaling leading to inflammatory mediators release in RBL-2H3 cells. The effects of piperine on IgE-mediated signaling and mast cell degranulation were investigated. Pretreatment of RBL-2H3 cells with piperine inhibited IgE-induced activation of type II PtdIns 4-kinase(s). In vitro lipid kinase assays showed piperine-inhibited type II PtdIns 4-kinase activity in a dose-dependent fashion with no effect on PtdIns 3-kinase activity. Concomitantly, pretreatment of RBL-2H3 cells with piperine also inhibited IgE-induced ?-hexosaminidase release in RBL-2H3 cells. These results suggest that type II PtdIns 4-kinases are part of piperine-mediated anti-inflammatory signaling mechanisms. PMID:24671493

  12. A phosphatidylinositol transfer protein integrates phosphoinositide signaling with lipid droplet metabolism to regulate a developmental program of nutrient stress–induced membrane biogenesis

    PubMed Central

    Ren, Jihui; Pei-Chen Lin, Coney; Pathak, Manish C.; Temple, Brenda R. S.; Nile, Aaron H.; Mousley, Carl J.; Duncan, Mara C.; Eckert, Debra M.; Leiker, Thomas J.; Ivanova, Pavlina T.; Myers, David S.; Murphy, Robert C.; Brown, H. Alex; Verdaasdonk, Jolien; Bloom, Kerry S.; Ortlund, Eric A.; Neiman, Aaron M.; Bankaitis, Vytas A.

    2014-01-01

    Lipid droplet (LD) utilization is an important cellular activity that regulates energy balance and release of lipid second messengers. Because fatty acids exhibit both beneficial and toxic properties, their release from LDs must be controlled. Here we demonstrate that yeast Sfh3, an unusual Sec14-like phosphatidylinositol transfer protein, is an LD-associated protein that inhibits lipid mobilization from these particles. We further document a complex biochemical diversification of LDs during sporulation in which Sfh3 and select other LD proteins redistribute into discrete LD subpopulations. The data show that Sfh3 modulates the efficiency with which a neutral lipid hydrolase-rich LD subclass is consumed during biogenesis of specialized membrane envelopes that package replicated haploid meiotic genomes. These results present novel insights into the interface between phosphoinositide signaling and developmental regulation of LD metabolism and unveil meiosis-specific aspects of Sfh3 (and phosphoinositide) biology that are invisible to contemporary haploid-centric cell biological, proteomic, and functional genomics approaches. PMID:24403601

  13. PI 3-kinase-dependent phosphorylation of Plk1–Ser99 promotes association with 14-3-3? and is required for metaphase–anaphase transition

    PubMed Central

    Kasahara, Kousuke; Goto, Hidemasa; Izawa, Ichiro; Kiyono, Tohru; Watanabe, Nobumoto; Elowe, Sabine; Nigg, Erich A; Inagaki, Masaki

    2013-01-01

    Polo-like kinase 1 (Plk1) controls multiple aspects of mitosis and is activated through its phosphorylation at Thr210. Here we identify Ser99 on Plk1 as a novel mitosis-specific phosphorylation site, which operates independently of Plk1–Thr210 phosphorylation. Plk1–Ser99 phosphorylation creates a docking site for 14-3-3?, and this interaction stimulates the catalytic activity of Plk1. Knockdown of 14-3-3? or replacement of wild-type (WT) Plk1 by a Ser99-phospho-blocking mutant leads to a prometaphase/metaphase-like arrest due to the activation of the spindle assembly checkpoint. Inhibition of phosphatidylinositol 3-kinase (PI3K) and Akt significantly reduces the level of Plk1–Ser99 phosphorylation and delays metaphase to anaphase transition. Plk1–Ser99 phosphorylation requires not only Akt activity but also protein(s) associated with Plk1 in a mitosis-specific manner. Therefore, mitotic Plk1 activity is regulated not only by Plk1–Thr210 phosphorylation, but also by Plk1 binding to 14-3-3? following Plk1–Ser99 phosphorylation downstream of the PI3K–Akt signalling pathway. This novel Plk1 activation pathway controls proper progression from metaphase to anaphase. PMID:23695676

  14. Requirement of phosphatidylinositol 3-kinase-dependent pathway and Src for Gas6-Axl mitogenic and survival activities in NIH 3T3 fibroblasts.

    PubMed Central

    Goruppi, S; Ruaro, E; Varnum, B; Schneider, C

    1997-01-01

    Gas6 is a secreted protein previously identified as the ligand of the Axl receptor tyrosine kinase. We have shown that Gas6 is able to induce cell cycle reentry of serum-starved NIH 3T3 cells and to efficiently prevent apoptosis after complete growth factor removal, a survival effect uncoupled from Gas6-induced mitogenesis. Here we report that the mitogenic effect of Gas6 requires phosphatidylinositol 3-kinase (PI3K) activity since it is abrogated both by the specific inhibitor wortmannin and by overexpression of the dominant negative P13K p85 subunit. Consistently, Gas6 activates the P13K downstream targets S6K and Akt, whose activation is abrogated by addition of wortmannin. Moreover, rapamycin treatment blocks Gas6-induced entry into the S phase of serum-starved NIH 3T3 cells. We also demonstrate the requirement of Src tyrosine kinase for Gas6 signalling since stable or transient expression of a catalytically inactive form of Src significantly inhibited Gas6-stimulated entry into the S phase. Accordingly, Gas6 addition to serum-starved NIH 3T3 cells causes activation of the intrinsic Src kinase activity. When specifically analyzed in a survival assay, these elements were found to be required for the survival effect of Gas6. Taken together, the evidence presented here identifies elements involved in the Gas6 transduction pathway that are responsible for its antiapoptotic effect and suggests that Src is involved in the events regulating cell survival. PMID:9234702

  15. Variation in the Phosphoinositide 3-Kinase Gamma Gene Affects Plasma HDL-Cholesterol without Modification of Metabolic or Inflammatory Markers

    PubMed Central

    Kächele, Martin; Hennige, Anita M.; Machann, Jürgen; Hieronimus, Anja; Lamprinou, Apostolia; Machicao, Fausto; Schick, Fritz; Fritsche, Andreas; Stefan, Norbert; Nürnberg, Bernd; Häring, Hans-Ulrich; Staiger, Harald

    2015-01-01

    Objective Phosphoinositide 3-kinase ? (PI3K?) is a G-protein-coupled receptor-activated lipid kinase mainly expressed in leukocytes and cells of the cardiovascular system. PI3K? plays an important signaling role in inflammatory processes. Since subclinical inflammation is a hallmark of atherosclerosis, obesity-related insulin resistance, and pancreatic ?-cell failure, we asked whether common genetic variation in the PI3K? gene (PIK3CG) contributes to body fat content/distribution, serum adipokine/cytokine concentrations, alterations in plasma lipid profiles, insulin sensitivity, insulin release, and glucose homeostasis. Study Design Using a tagging single nucleotide polymorphism (SNP) approach, we analyzed genotype-phenotype associations in 2,068 German subjects genotyped for 10 PIK3CG SNPs and characterized by oral glucose tolerance tests. In subgroups, data from hyperinsulinaemic-euglycaemic clamps, magnetic resonance spectroscopy of the liver, whole-body magnetic resonance imaging, and intravenous glucose tolerance tests were available, and peripheral blood mononuclear cells (PBMCs) were used for gene expression analysis. Results After appropriate adjustment, none of the PIK3CG tagging SNPs was significantly associated with body fat content/distribution, adipokine/cytokine concentrations, insulin sensitivity, insulin secretion, or blood glucose concentrations (p>0.0127, all; Bonferroni-corrected ?-level: 0.0051). However, six non-linked SNPs displayed at least nominal associations with plasma HDL-cholesterol concentrations, two of them (rs4288294 and rs116697954) reaching the level of study-wide significance (p = 0.0003 and p = 0.0004, respectively). More precisely, rs4288294 and rs116697954 influenced HDL2-, but not HDL3-, cholesterol. With respect to the SNPs’ in vivo functionality, rs4288294 was significantly associated with PIK3CG mRNA expression in PBMCs. Conclusions We could demonstrate that common genetic variation in the PIK3CG locus, possibly via altered PIK3CG gene expression, determines plasma HDL-cholesterol concentrations. Since HDL2-, but not HDL3-, cholesterol is influenced by PIK3CG variants, PI3K? may play a role in HDL clearance rather than in HDL biogenesis. Even though the molecular pathways connecting PI3K? and HDL metabolism remain to be further elucidated, this finding could add a novel aspect to the pathophysiological role of PI3K? in atherogenesis. PMID:26658747

  16. Inhibition of the phosphoinositide 3-kinase pathway decreases innate resistance to lipopolysaccharide toxicity in TLR4 deficient mice

    PubMed Central

    2014-01-01

    Background Upon lipopolysaccharide (LPS) stimulation, activation of both the Toll-like receptor 4 (TLR4) and phosphoinositide 3-kinase (PI3K) pathways serves to balance proinflammatory and anti-inflammatory responses. Although the antagonist to TLR4 represents an emerging promising target for the treatment of sepsis; however, the role of the PI3K pathway under TLR4-null conditions is not well understood. This goal of this study was to investigate the effect of inhibition of PI3K on innate resistance to LPS toxicity in a murine model. Results The overall survival of the cohorts receiving intraperitoneal injections of 100, 500, or 1000 ?g LPS from Escherichia coli serotype 026:B6 after 7 d was 100%, 10%, and 10%, respectively. In contrast, no mortality was noted after 500-?g LPS injection in Tlr4-/- mice. When the PI3K inhibitor LY294002 was injected (1 mg/25 g body weight) 1 h prior to the administration of LPS, the overall survival of the Tlr4-/- mice was 30%. In the Tlr4-/- mice, the LPS injection induced no NF-?B activation but an increased Akt phosphorylation in the lung and liver, when compared to that of the C57BL/6 mice. Injection of 500 ?g LPS led to a significant induction in O2- detected by electron paramagnetic resonance (EPR) spin trapping spectroscopy in the lung and liver at 3 and 6 h in C57BL/6 but not Tlr4-/- mice. Addition of LY294002 only significantly increased the O2- level in the lung and liver of the Tlr4-/- mice but not in the C57BL/6 mice following 500-?g LPS injection. In addition, the serum IL-1? and IL-2 levels were more elevated in C57BL/6 mice than in Tlr4-/- mice. Notably, IL-1? and IL-2 were significantly increased in Tlr4-/- mice but not in the C57BL/6 mice when the PI3K pathway was inhibited by LY294002 prior to LPS injection. Conclusions In this study, we demonstrate that innate resistance to LPS toxicity in Tlr4-/- mice is impaired by inhibition of the PI3K pathway, with a corresponding increase in mortality and production of tissue O2- and inflammatory cytokines. PMID:24618279

  17. Insulin facilitates repetitive spike firing in rat insular cortex via phosphoinositide 3-kinase but not mitogen activated protein kinase cascade.

    PubMed

    Takei, H; Fujita, S; Shirakawa, T; Koshikawa, N; Kobayashi, M

    2010-11-10

    The insular cortex (IC) processes gustatory and visceral information, which functionally correlate to feeding behavior. Insulin, a well-known hormone controlling glucose metabolism, is released by elevation of blood glucose concentration following feeding behavior. The IC expresses dense insulin receptors and receives projection from the hypothalamus, which monitors changes in glucose concentration. Therefore, it is likely that insulin modulates neural properties in the IC. However, little is known about the effects of insulin on electrophysiological properties of the neocortex including the IC. To explore the effects of insulin on subthreshold responses and action potential properties in the IC, intracellular recording with sharp glass electrodes was performed from IC pyramidal cells using slice preparations. Although application of insulin (100 nM) had little effect on the resting membrane potential, input resistance and rheobase, insulin significantly increased the frequency of repetitive spike firing in response to a long depolarizing current pulse injection: the slope of the frequency-current curve was increased from 23.7±2.3 Hz/nA to 29.5±3.4 Hz/nA. Insulin slightly decreased the action potential threshold without affecting the amplitude of medium-duration and slow afterhyperpolarization (sAHP) s. The insulin-induced facilitation of repetitive spike firing was dose-dependent and blocked by pre-application of 200 nM lavendustin A, a tyrosine kinase inhibitor. Moreover, when combined with 200 nM wortmannin, a phosphoinositide 3-kinase (PI3-K) inhibitor, or 500 nM deguelin, an inhibitor of protein kinase B (PKB/Akt) downstream of PI3-K, insulin failed to increase the frequency of repetitive spike firing. In contrast, co-application of insulin and (10 ?M) PD 98059, an inhibitor of mitogen activated protein kinase (MAPK), exerted facilitation of repetitive spike firing. These results suggest that acute insulin-induced facilitation of firing frequency is at least partially induced by hyperpolarizing effects on the action potential threshold, and that this facilitation is induced by activation of PI3-K but not MAPK cascade. PMID:20691771

  18. Sann-Joong-Kuey-Jian-Tang induces autophagy in HepG2 cells via regulation of the phosphoinositide-3 kinase/Akt/mammalian target of rapamycin and p38 mitogen-activated protein kinase pathways

    PubMed Central

    CHUANG, WAN-LING; SU, CHIN-CHENG; LIN, PING-YI; LIN, CHI-CHEN; CHEN, YAO-LI

    2015-01-01

    Sann-Joong-Kuey-Jian-Tang (SJKJT), a traditional Chinese medicine, was previously reported to induce autophagy and inhibit the proliferation of the human HepG2 hepatocellular carcinoma cell line via an extrinsic pathway. In the present study, the effects of SJKJT-induced autophagy and the cytotoxic mechanisms mediating these effects were investigated in HepG2 cells. The cytotoxicity of SJKJT in the HepG2 cells was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The results demonstrated that the half-maximal inhibitory concentration of SJKJT was 2.91 mg/ml at 24 h, 1.64 mg/ml at 48 h and 1.26 mg/ml at 72 h. The results of confocal fluorescence microscopy indicated that SJKJT resulted in the accumulation of green fluorescent protein-LC3 and vacuolation of the cytoplasm. Flow cytometric analysis revealed the accumulation of acidic vesicular organelles. Furthermore, western blot analysis, used to determine the expression levels of autophagy-associated proteins, demonstrated that the HepG2 cells treated with SJKJT exhibited LC3B-I/LC3B-II conversion, increased expression levels of Beclin, Atg-3 and Atg-5 and reduced expression levels of p62 and decreased signaling of the phosphoinositide-3 kinase/Akt/mammalian target of rapamycin and the p38 mitogen-activated protein kinase pathways. Taken together, these findings may assist in the development of novel chemotherapeutic agents for the treatment of malignant types of liver cancer. PMID:25847489

  19. Sphingosine 1-phosphate stimulation of the p42/p44 mitogen-activated protein kinase pathway in airway smooth muscle. Role of endothelial differentiation gene 1, c-Src tyrosine kinase and phosphoinositide 3-kinase.

    PubMed Central

    Rakhit, S; Conway, A M; Tate, R; Bower, T; Pyne, N J; Pyne, S

    1999-01-01

    We report here that cultured airway smooth muscle cells contain transcripts of endothelial differentiation gene 1 (EDG-1), a prototypical orphan Gi-coupled receptor whose natural ligand is sphingosine 1-phosphate (S1P). This is consistent with data that showed that S1P activated both c-Src and p42/p44 mitogen-activated protein kinase (p42/p44 MAPK) in a pertussis toxin (PTX)-sensitive manner in these cells. An essential role for c-Src was confirmed by using the c-Src inhibitor, PP1, which markedly decreased p42/p44 MAPK activation. We have also shown that phosphoinositide 3-kinase (PI-3K) inhibitors (wortmannin and LY294002) decreased p42/p44 MAPK activation. An essential role for PI-3K was supported by experiments that showed that PI-3K activity was increased in Grb-2 immunoprecipitates from S1P-stimulated cells. Significantly, Grb-2 associated PI-3K activity was decreased by pretreatment of cells with PTX. Finally, we have shown that the co-stimulation of cells with platelet-derived growth factor (PDGF) and S1P (which failed to stimulate DNA synthesis) elicited a larger p42/p44 MAPK activation over a 30 min stimulation compared with each agonist alone. This was associated with a S1P-dependent increase in PDGF-stimulated DNA synthesis. These results demonstrate that S1P activates c-Src and Grb-2-PI-3K (intermediates in the p42/p44 MAPK cascade) via a PTX-sensitive mechanism. This action of S1P is consistent with the stimulation of EDG-1 receptors. S1P might also function as a co-mitogen with PDGF, producing a more robust activation of a common permissive signal transduction pathway linked to DNA synthesis. PMID:10051434

  20. Anti-tumor peptide AP25 decreases cyclin D1 expression and inhibits MGC-803 proliferation via phospho-extracellular signal-regulated kinase-, Src-, c-Jun N-terminal kinase- and phosphoinositide 3-kinase-associated pathways.

    PubMed

    Hu, Jialiang; Cheng, Tao; Zhang, Lijun; Sun, Beicheng; Deng, Lei; Xu, Hanmei

    2015-09-01

    The anti-tumor peptide AP25 is a prototype integrin antagonist, which exhibits anti?angiogenic and anti?tumor activity. The molecular mechanisms by which AP25 inhibits the growth of the MGC?803 gastric carcinoma cell line were investigated in the present study. K?ras specific RNA interference by lentiviral infection was successfully induced in MGC?803 cells [MGC?803 short hairpin (sh)RNA group] and the expression levels of K?ras, phosphorylated extracellular signal?regulated kinase (p-ERK) and cyclin D1 were observed to be markedly decreased. By contrast, AP25 caused cell cycle arrest of intact MGC?803 cells and decreased p?ERK and cyclin D1 expression levels. Of note, 0.4?3.2 µM AP25 no longer inhibited MGC?803 shRNA growth, indicating that AP25, at such concentrations, exerts its effect mainly through the Ras/Raf/mitogen-activated protein kinase kinase/ERK pathway, whereas at 25 µM, AP25 was able to inhibit MGC?803 shRNA growth. Chemical inhibitors of Src, c?Jun N?terminal kinase (JNK) and phosphoinositide 3?kinase (PI3K) were used to confirm that 25 µM AP25 inhibited growth of cells in the MGC?803 shRNA group and activated intracellular signaling pathways with Src, JNK and PI3K as key enzymes. In conclusion, the present study revealed the signal transduction pathways activated by AP25 at low (0.4?3.2 µM) or high (25 µM) concentrations. It also confirmed that integrins, when interacting with the freely moving ligand AP25 instead of immobilized extracellular matrix glycoproteins, are able to initiate cell signaling via similar pathways as in the latter case but with a reversed effect, to inhibit cell growth. PMID:26063313

  1. Phosphoinositide signalling in nuclei of Friend cells: DMSO-induced differentiation reduces the association of phosphatidylinositol-transfer protein with the nucleus.

    PubMed

    Rubbini, S; Cocco, L; Manzoli, L; Lutterman, J; Billi, A M; Matteucci, A; Wirtz, K W

    1997-01-13

    Friend erythroleukemia cells have a nuclear phosphoinositide cycle which is related to both mitogen-stimulated cell growth and erythorid differentiation. Because of the important role of the phosphatidylinositol-transfer protein (PI-TP) in phosphatidylinositol 4,5-bisphosphate (PtdInsP2) synthesis, we have analysed nuclei isolated from Friend cells for the presence of PI-TP. By Western Blotting it was demonstrated that both intact nuclei and nuclei deprived of the outer membrane contained the PI-TP alpha isoform. Upon induction of erythroid differentiation by DMSO, the amount of nuclear PI-TP alpha was greatly diminished. As shown previously, under these same conditions, nuclear phospholipase C beta1 (PLC beta1) is down-regulated as well. PMID:9016771

  2. Targeted Inhibition of Phosphoinositide 3-Kinase/Mammalian Target of Rapamycin Sensitizes Pancreatic Cancer Cells to Doxorubicin without Exacerbating Cardiac Toxicity.

    PubMed

    Durrant, David E; Das, Anindita; Dyer, Samya; Tavallai, Seyedmehrad; Dent, Paul; Kukreja, Rakesh C

    2015-09-01

    Pancreatic cancer has the lowest 5-year survival rate of all major cancers despite decades of effort to design and implement novel, more effective treatment options. In this study, we tested whether the dual phosphoinositide 3-kinase/mechanistic target of rapamycin inhibitor BEZ235 (BEZ) potentiates the antitumor effects of doxorubicin (DOX) against pancreatic cancer. Cotreatment of BEZ235 with DOX resulted in dose-dependent inhibition of the phosphoinositide 3-kinase/mechanistic target of rapamycin survival pathway, which corresponded with an increase in poly ADP ribose polymerase cleavage. Moreover, BEZ cotreatment significantly improved the effects of DOX toward both cell viability and cell death in part through reduced Bcl-2 expression and increased expression of the shorter, more cytotoxic forms of BIM. BEZ also facilitated intracellular accumulation of DOX, which led to enhanced DNA damage and reactive oxygen species generation. Furthermore, BEZ in combination with gemcitabine reduced MiaPaca2 cell proliferation but failed to increase reactive oxygen species generation or BIM expression, resulting in reduced necrosis and apoptosis. Treatment with BEZ and DOX in mice bearing tumor xenographs significantly repressed tumor growth as compared with BEZ, DOX, or gemcitabine. Additionally, in contrast to the enhanced expression seen in MiaPaca2 cells, BEZ and DOX cotreatment reduced BIM expression in H9C2 cardiomyocytes. Also, the Bcl-2/Bax ratio was increased, which was associated with a reduction in cell death. In vivo echocardiography showed decreased cardiac function with DOX treatment, which was not improved by combination treatment with BEZ. Thus, we propose that combining BEZ with DOX would be a better option for patients than current standard of care by providing a more effective tumor response without the associated increase in toxicity. PMID:26101222

  3. Autophosphorylation of serine 608 in the p85 regulatory subunit of wild type or cancer-associated mutants of phosphoinositide 3-kinase does not affect its lipid kinase activity

    PubMed Central

    2012-01-01

    Background The ?-isoform of the Type 1A Phosphoinositide 3-kinases (PI3K?) has protein kinase activity as well as phosphoinositide lipid kinase activity. The best described substrate for its protein kinase activity is its regulatory subunit, p85?, which becomes phosphorylated on Serine 608. Phosphorylation of Serine 608 has been reported to down-regulate its lipid kinase activity. Results We have assessed whether oncogenic mutants of PI3K?, which have up-regulated lipid kinase activity, have altered levels of Serine 608 phosphorylation compared to wild type PI3K?, and whether differential phosphorylation of Serine 608 contributes to increased activity of oncogenic forms of PI3K? with point mutations in the helical or the kinase domains. Despite markedly increased lipid kinase activity, protein kinase activity was not altered in oncogenic compared to wild type forms of PI3K?. By manipulating levels of phosphorylation of Serine 608 in vitro, we found no evidence that the protein kinase activity of PI3K? affects its phosphoinositide lipid kinase activity in either wild-type or oncogenic mutants of PI3K?. Conclusions Phosphorylation of p85? S608 is not a significant regulator of wild-type or oncogenic PI3K? lipid kinase activity. PMID:23270540

  4. Phosphatidic acid and phosphoinositides facilitate liposome association of Yas3p and potentiate derepression of ARE1 (alkane-responsive element one)-mediated transcription control.

    PubMed

    Kobayashi, Satoshi; Hirakawa, Kiyoshi; Horiuchi, Hiroyuki; Fukuda, Ryouichi; Ohta, Akinori

    2013-12-01

    In the n-alkane assimilating yeast Yarrowia lipolytica, the expression of ALK1, encoding a cytochrome P450 that catalyzes terminal mono-oxygenation of n-alkanes, is induced by n-alkanes. The transcription of ALK1 is regulated by a heterocomplex that comprises the basic helix-loop-helix transcription activators, Yas1p and Yas2p, and binds to alkane-responsive element 1 (ARE1) in the ALK1 promoter. An Opi1 family transcription repressor, Yas3p, represses transcription by binding to Yas2p. Yas3p localizes in the nucleus when Y. lipolytica is grown on glucose but localizes to the endoplasmic reticulum (ER) upon the addition of n-alkanes. In this study, we showed that recombinant Yas3p binds to the acidic phospholipids, phosphatidic acid (PA) and phosphoinositides (PIPs), in vitro. The ARE1-mediated transcription was enhanced in vivo in mutants defective in an ortholog of the Saccharomyces cerevisiae gene PAH1, encoding PA phosphatase, and in an ortholog of SAC1, encoding PIP phosphatase in the ER. Truncation mutation analyses for Yas3p revealed two regions that bound to PA and PIPs. These results suggest that the interaction with acidic phospholipids is important for the n-alkane-induced association of Yas3p with the ER membrane. PMID:24120453

  5. Ca2+ influx and phosphoinositide signalling are essential for the establishment and maintenance of cell polarity in monospores from the red alga Porphyra yezoensis

    PubMed Central

    Saga, Naotsune; Mikami, Koji

    2009-01-01

    The asymmetrical distribution of F-actin directed by cell polarity has been observed during the migration of monospores from the red alga Porphyra yezoensis. The significance of Ca2+ influx and phosphoinositide signalling during the formation of cell polarity in migrating monospores was analysed pharmacologically. The results indicate that the inhibition of the establishment of cell polarity, as judged by the ability of F-actin to localize asymmetrically, cell wall synthesis, and development into germlings, occurred when monospores were treated with inhibitors of the Ca2+ permeable channel, phospholipase C (PLC), diacylglycerol kinase, and inositol-1,4,5-trisphosphate receptor. Moreover, it was also found that light triggered the establishment of cell polarity via photosynthetic activity but not its direction, indicating that the Ca2+ influx and PLC activation required for the establishment of cell polarity are light dependent. By contrast, inhibition of phospholipase D (PLD) prevented the migration of monospores but not the asymmetrical localization of F-actin. Taken together, these findings suggest that there is functional diversity between the PLC and PLD signalling systems in terms of the formation of cell polarity; the former being critical for the light-dependent establishment of cell polarity and the latter playing a role in the maintenance of established cell polarity. PMID:19531546

  6. [CANCER RESEARCH 60, 35043513, July 1, 2000] A Direct Linkage between the Phosphoinositide 3-Kinase-AKT Signaling Pathway

    E-print Network

    Yin, Peng

    is a potent immunosuppressive drug and investigational anticancer agent, the major mechanism of action committed to enter S-phase of the cell cycle after release from drug-induced G1 arrest (1 interest in the possi- bility that this drug might be a useful cancer chemotherapeutic agent. Indeed

  7. CD40 ligand exhibits a direct antiviral effect on Herpes Simplex Virus type-1 infection via a PI3K-dependent, autophagy-independent mechanism.

    PubMed

    Vlahava, Virginia-Maria; Eliopoulos, Aristides G; Sourvinos, George

    2015-06-01

    The interaction between CD40 and its ligand, CD40L/CD154, is crucial for the efficient initiation and regulation of immune responses against viruses. Herpes Simplex Virus type-1 (HSV-1) is a neurotropic virus capable of manipulating host responses and exploiting host proteins to establish productive infection. Herein we have examined the impact of CD40L-mediated CD40 activation on HSV-1 replication in U2OS cells stably expressing the CD40 receptor. Treatment of these cells with CD40L significantly reduced the HSV-1 progeny virus compared to non-treated cells. The activation of CD40 signaling did not affect the binding of HSV-1 virions on the cell surface but rather delayed the translocation of VP16 to the nucleus, affecting all stages of viral life cycle. Using pharmacological inhibitors and RNAi we show that inhibition of PI3 kinase but not autophagy reverses the effects of CD40L on HSV-1 replication. Collectively, these data demonstrate that CD40 activation exerts a direct inhibitory effect on HSV-1, initiating from the very early stages of the infection by exploiting PI3 kinase-dependent but autophagy-independent mechanisms. PMID:25765994

  8. Neurotransmitter-specific profiles of inositol phosphates in rat brain cortex: relation to the mode of receptor activation of phosphoinositide phospholipase C.

    PubMed

    Sarri, E; Picatoste, F; Claro, E

    1995-01-01

    Phosphoinositide breakdown, as stimulated by six different neurotransmitter receptor agonists (carbachol, serotonin, norepinephrine, trans-(+/-)-aminocyclopentyl-1,3-dicarboxylic acid, endothelin-1 and histamine), has been studied in rat brain cortical slices. The accumulation was monitored of total 3H-inositol phosphates (InsPs) and [3H]CDP-diacylglycerol (CDP-DAG) in [3H]inositol or [3H]cytidine-prelabeled tissue, respectively, and the profile of the major InsPs was quantified as the index log [(inositol 4-monophosphate + inositol 1,4-bisphosphate)/inositol 1-monophosphate]. The efficacy of the six agonists to stimulate the accumulation of CDP-DAG, relative to that of InsPs, was not constant, which revealed varying degrees of defective recycling of DAG to CDP-DAG. The value of the index for the profile of InsPs was not constant either but was characteristic of each agonist. Both parameters (ratio of efficacies CDP-DAG/InsPs and InsPs profile) were not independent and defined two groups of agonists as follows: group a, carbachol and serotonin, with balanced CDP-DAG and InsPs responses, and Ins1P prevailing against inositol 4-monophosphate + inositol 1,4-bisphosphate and group b, norepinephrine, trans-(+/-)-aminocyclopentyl-1,3-dicarboxylic acid, endothelin-1 and histamine, with weak CDP-DAG responses and high accumulation of inositol 4-monophosphate + inositol 1,4-bisphosphate compared with that of inositol 1-monophosphate. In a membrane preparation from brain cortex, only agonists in group a stimulated phospholipase C in the presence of guanosine 5'-O-(3-thiotriphosphate) and in a receptor antagonist-sensitive fashion, which indicated that brain cortical alpha-1, H1, endothelin and glutamate metabotropic receptors stimulate phospholipase C indirectly.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7815367

  9. Insulin and insulin-like growth factor-1 can modulate the phosphoinositide-3-kinase/Akt/FoxO1 pathway in SZ95 sebocytes in vitro.

    PubMed

    Mirdamadi, Yasaman; Thielitz, Anja; Wiede, Antje; Goihl, Alexander; Papakonstantinou, Eleni; Hartig, Roland; Zouboulis, Christos C; Reinhold, Dirk; Simeoni, Luca; Bommhardt, Ursula; Quist, Sven; Gollnick, Harald

    2015-11-01

    A recent hypothesis suggests that a high glycaemic load diet-associated increase of insulin-like growth factor-1 (IGF-1) and insulin may promote acne by reducing nuclear localization of the forkhead box-O1 (FoxO1) transcription factor via activation of the phosphoinositide-3-kinase (PI3K)/Akt pathway. Using SZ95 sebocytes as a model, we investigated the effect of the most important insulinotropic western dietary factors, IGF-1 and insulin on acne. SZ95 sebocytes were stimulated with different concentrations of IGF-1 and insulin (0.001, 0.01, 0.1 and 1 ?M) for 15 to 120 min ± PI3K inhibitor LY294002 (50 ?M). Cytoplasmic and nuclear protein expression of p-Akt and p-FoxO1 as well as FoxO transcriptional activity was analysed. In addition, the proliferation and differentiation of sebocytes and their TLR2/4 expression were determined. We found that high concentrations of IGF-1 and insulin differentially stimulate the PI3K/Akt/FoxO1 pathway by an early up-regulation of cytoplasmic p-Akt and delayed up-regulation of p-FoxO1 resulting in FoxO1 shift to the cytoplasm and the reduction of FoxO transcriptional activity, physiological serum concentration had no effect. IGF-1 at concentrations of 0.1 and 1 ?M significantly reduced proliferation but increased differentiation of sebocytes to a greater extent than insulin (0.1 and 1 ?M), but up-regulated TLR2/4 expression to comparable extent. These data provide the first in vitro evidence that FoxO1 principally might be involved in the regulation of growth-factor-stimulatory effects on sebaceous lipogenesis and inflammation in the pathological condition of acne. However, the in vivo significance under physiological conditions remains to be elucidated. PMID:26257240

  10. Phosphoinositide 3-Kinases Upregulate System xc? via Eukaryotic Initiation Factor 2? and Activating Transcription Factor 4?–?A Pathway Active in Glioblastomas and Epilepsy

    PubMed Central

    Baxter, Paul; Kassubek, Rebecca; Albrecht, Philipp; Van Liefferinge, Joeri; Westhoff, Mike-Andrew; Halatsch, Marc-Eric; Karpel-Massler, Georg; Meakin, Paul J.; Hayes, John D.; Aronica, Eleonora; Smolders, Ilse; Ludolph, Albert C.; Methner, Axel; Conrad, Marcus; Massie, Ann; Hardingham, Giles E.

    2014-01-01

    Abstract Aims: Phosphoinositide 3-kinases (PI3Ks) relay growth factor signaling and mediate cytoprotection and cell growth. The cystine/glutamate antiporter system xc? imports cystine while exporting glutamate, thereby promoting glutathione synthesis while increasing extracellular cerebral glutamate. The aim of this study was to analyze the pathway through which growth factor and PI3K signaling induce the cystine/glutamate antiporter system xc? and to demonstrate its biological significance for neuroprotection, cell growth, and epilepsy. Results: PI3Ks induce system xc? through glycogen synthase kinase 3? (GSK-3?) inhibition, general control non-derepressible-2-mediated eukaryotic initiation factor 2? phosphorylation, and the subsequent translational up-regulation of activating transcription factor 4. This pathway is essential for PI3Ks to modulate oxidative stress resistance of nerve cells and insulin-induced growth in fibroblasts. Moreover, the pathway is active in human glioblastoma cells. In addition, it is induced in primary cortical neurons in response to robust neuronal activity and in hippocampi from patients with temporal lobe epilepsy. Innovation: Our findings further extend the concepts of how growth factors and PI3Ks induce neuroprotection and cell growth by adding a new branch to the signaling network downstream of GSK-3?, which, ultimately, leads to the induction of the cystine/glutamate antiporter system xc?. Importantly, the induction of this pathway by neuronal activity and in epileptic hippocampi points to a potential role in epilepsy. Conclusion: PI3K-regulated system xc? activity is not only involved in the stress resistance of neuronal cells and in cell growth by increasing the cysteine supply and glutathione synthesis, but also plays a role in the pathophysiology of tumor- and non-tumor-associated epilepsy by up-regulating extracellular cerebral glutamate. Antioxid. Redox Signal. 20: 2907–2922. PMID:24219064

  11. Histone deacetylase 3 expression correlates with vasculogenic mimicry through the phosphoinositide3-kinase / ERK–MMP–laminin5?2 signaling pathway

    PubMed Central

    Liu, Xiao; Wang, Ji-Hui; Li, Shun; Li, Lin-Lin; Huang, Min; Zhang, Yong-Hong; Liu, Yang; Yang, Yuan-Tao; Ding, Rui; Ke, Yi-Quan

    2015-01-01

    Vasculogenic mimicry (VM) refers to the process by which highly aggressive tumor cells mimic endothelial cells to form vessel-like structures that aid in supplying enough nutrients to rapidly growing tumors. Histone deacetylases (HDACs) regulate the expression and activity of numerous molecules involved in cancer initiation and progression. Notably, HDAC3 is overexpressed in the majority of carcinomas. However, thus far, no data are available to support the role of HDAC3 in VM. In this study, we subjected glioma specimens to immunohistochemical and histochemical double-staining methods and found that VM and HDAC3 expression were related to the pathological grade of gliomas. The presence of VM correlated with HDAC3 expression in glioma tissues. The formation of tubular structures, as determined by the tube formation assay to evaluate VM, was impaired in U87MG cells when transfected by siRNA or treated with an HDAC3 inhibitor. Importantly, the expression of VM-related molecules such as MMP-2/14 and laminin5?2 was also affected when HDAC3 expression was altered. Furthermore, U87MG cells were treated with a phosphoinositide 3-kinase (PI3K) inhibitor or/and ERK inhibitor and found that the PI3K and ERK signaling pathways play key roles in VM; whereas, in VM, the two signaling pathways did not act upstream or downstream from each other. Taken together, our findings showed that HDAC3 contributed to VM in gliomas, possibly through the PI3K/ERK–MMPs–laminin5?2 signaling pathway, which could potentially be a novel therapeutic target for gliomas. PMID:25940092

  12. Platelet activation by bacterial phospholipase C involves phosphoinositide turnover and phosphorylation of 47,000 dalton but not 20,000 dalton protein

    SciTech Connect

    Huzoor-Akbar; Anwer, K.

    1986-05-01

    This study was conducted to examine the role of phosphoinositides (PIns) and phosphorylation of 47,000 dalton (P47) and 20,000 dalton (P20) proteins in platelet activation by bacterial phospholipase C (PLC). PLC induced serotonin secretion (SS) and platelet aggregation (PA) in a concentration dependent manner. PLC (0.02 U/ml) caused phosphorylation of P47 in a time dependent manner (27% at 0.5 min to 378% at 7 min). PLC did not induce more than 15% phosphorylation of P20 by 7 min. Aspirin (500 ..mu..M) blocked phosphorylation of P20 but did not inhibit SS, PA or phosphorylation of P47. PLC (0.04 U/ml) decreased radioactivity (cpm) in /sup 32/P labeled phosphatidylinositol (PI), PI-4,5-bis-PO4 (PIP2) and PI-4-PO4 (PIP) by 20%, 12% and 7.5% respectively at 15 sec. The level of PI but not that of PIP2 returned to base line in 3 min. PIP level increased above control values within one min. PLC increased phosphatidic acid level (75% at 0.5 min. to 1545% at 3 min). In other experiments PLC produced diacylglycerol (DAG) in a time and concentration dependent manner. However, no DAG was detectable in the first 60 sec. These data suggest that: (a) PIns turnover and phosphorylation of P47 but not that of P20 is involved in platelet activation by PLC; and (b) DAG production from outer membrane phospholipids is not a prerequisite for platelet activation by PLC.

  13. Synergistic inhibition of colon carcinoma cell growth by Hedgehog-Gli1 inhibitor arsenic trioxide and phosphoinositide 3-kinase inhibitor LY294002

    PubMed Central

    Cai, Xinyi; Yu, Kun; Zhang, Lijuan; Li, Yunfeng; Li, Qiang; Yang, Zhibin; Shen, Tao; Duan, Lincan; Xiong, Wei; Wang, Weiya

    2015-01-01

    The Hedgehog (Hh) signaling pathway not only plays important roles in embryogenesis and adult tissue homeostasis, but also in tumorigenesis. Aberrant Hh pathway activation has been reported in a variety of malignant tumors including colon carcinoma. Here, we sought to investigate the regulation of the Hh pathway transcription factor Gli1 by arsenic trioxide and phosphoinositide 3-kinase (PI3K) inhibitor LY294002 in colon carcinoma cells. We transfected cells with siGli1 and observed a significant reduction of Gli1 expression in HCT116 and HT29 cells, which was confirmed by quantitative real-time polymerase chain reaction and Western blots. Knocking down endogenous Gli1 reduced colon carcinoma cell viability through inducing cell apoptosis. Similarly, knocking down Gli2 using short interfering RNA impaired colon carcinoma cell growth in vitro. To elucidate the regulation of Gli1 expression, we found that both Gli inhibitor arsenic trioxide and PI3K inhibitor LY294002 significantly reduced Gli1 protein expression and colon carcinoma cell proliferation. Arsenic trioxide treatment also reduced Gli1 downstream target gene expression, such as Bcl2 and CCND1. More importantly, the inhibition of Hedgehog-Gli1 by arsenic trioxide showed synergistic anticancer effect with the PI3K inhibitor LY294002 in colon carcinoma cells. Our findings suggest that the Hh pathway transcription factor Gli1 is involved in the regulation of colon carcinoma cell viability. Inhibition of Hedgehog-Gli1 expression by arsenic trioxide and PI3K inhibitor synergistically reduces colon cancer cell proliferation, indicating that they could be used as an effective anti-colon cancer combination therapy. PMID:25945059

  14. The Na+/H+ Exchanger-3 (NHE3) Activity Requires Ezrin Binding to Phosphoinositide and Its Phosphorylation.

    PubMed

    Babich, Victor; Di Sole, Francesca

    2015-01-01

    Na+/H+ exchanger-3 (NHE3) plays an essential role in maintaining sodium and fluid homeostasis in the intestine and kidney epithelium. Thus, NHE3 is highly regulated and its function depends on binding to multiple regulatory proteins. Ezrin complexed with NHE3 affects its activity via not well-defined mechanisms. This study investigates mechanisms by which ezrin regulates NHE3 activity in epithelial Opossum Kidney cells. Ezrin is activated sequentially by phosphatidylinositol-4,5-bisphosphate (PIP2) binding and phosphorylation of threonine 567. Expression of ezrin lacking PIP2 binding sites inhibited NHE3 activity (-40%) indicating that ezrin binding to PIP2 is required for preserving NHE3 activity. Expression of a phosphomimetic ezrin mutated at the PIP2 binding region was sufficient not only to reverse NHE3 activity to control levels but also to increase its activity (+80%) similar to that of the expression of ezrin carrying the phosphomimetic mutation alone. Calcineurin Homologous Protein-1 (CHP1) is part, with ezrin, of the NHE3 regulatory complex. CHP1-mediated activation of NHE3 activity was blocked by expression of an ezrin variant that could not be phosphorylated but not by an ezrin variant unable to bind PIP2. Thus, for NHE3 activity under baseline conditions not only ezrin phosphorylation, but also ezrin spatial-temporal targeting on the plasma membrane via PIP2 binding is required; however, phosphorylation of ezrin appears to overcome the control of NHE3 transport. CHP1 action on NHE3 activity is not contingent on ezrin binding to PIP2 but rather on ezrin phosphorylation. These findings are important in understanding the interrelation and dynamics of a CHP1-ezrin-NHE3 regulatory complex. PMID:26042733

  15. Alpha 1-adrenergic receptor-mediated phosphoinositide hydrolysis and prostaglandin E2 formation in Madin-Darby canine kidney cells. Possible parallel activation of phospholipase C and phospholipase A2

    SciTech Connect

    Slivka, S.R.; Insel, P.A.

    1987-03-25

    alpha 1-Adrenergic receptors mediate two effects on phospholipid metabolism in Madin-Darby canine kidney (MDCK-D1) cells: hydrolysis of phosphoinositides and arachidonic acid release with generation of prostaglandin E2 (PGE2). The similarity in concentration dependence for the agonist (-)-epinephrine in eliciting these two responses implies that they are mediated by a single population of alpha 1-adrenergic receptors. However, we find that the kinetics of the two responses are quite different, PGE2 production occurring more rapidly and transiently than the hydrolysis of phosphoinositides. The antibiotic neomycin selectively decreases alpha 1-receptor-mediated phosphatidylinositol 4,5-bisphosphate hydrolysis without decreasing alpha 1-receptor-mediated arachidonic acid release and PGE2 generation. In addition, receptor-mediated inositol trisphosphate formation is independent of extracellular calcium, whereas release of labeled arachidonic acid is largely calcium-dependent. Moreover, based on studies obtained with labeled arachidonic acid, receptor-mediated generation of arachidonic acid cannot be accounted for by breakdown of phosphatidylinositol monophosphate, phosphatidylinositol bisphosphate, or phosphatidic acid. Further studies indicate that epinephrine produces changes in formation or turnover of several classes of membrane phospholipids in MDCK cells. We conclude that alpha 1-adrenergic receptors in MDCK cells appear to regulate phospholipid metabolism by the parallel activation of phospholipase C and phospholipase A2. This parallel activation of phospholipases contrasts with models described in other systems which imply sequential activation of phospholipase C and diacylglycerol lipase or phospholipase A2.

  16. Identification of a Proline-Rich Sequence in the CD2 Cytoplasmic Domain Critical for Regulation of Integrin-Mediated Adhesion and Activation of Phosphoinositide 3-Kinase

    PubMed Central

    Kivens, Wendy J.; Hunt, Stephen W.; Mobley, James L.; Zell, Traci; Dell, Cheryl L.; Bierer, Barbara E.; Shimizu, Yoji

    1998-01-01

    The CD2 molecule is one of several lymphocyte receptors that rapidly initiates signaling events regulating integrin-mediated cell adhesion. CD2 stimulation of resting human T cells results within minutes in an increase in ?1-integrin-mediated adhesion to fibronectin. We have utilized the HL60 cell line to map critical residues within the CD2 cytoplasmic domain involved in CD2 regulation of integrin function. A panel of CD2 cytoplasmic domain mutants was constructed and analyzed for their ability to upregulate integrin-mediated adhesion to fibronectin. Mutations in the CD2 cytoplasmic domain implicated in CD2-mediated interleukin-2 production or CD2 avidity do not affect CD2 regulation of integrin activity. A proline-rich sequence, K-G-P-P-L-P (amino acids 299 to 305), is essential for CD2-mediated regulation of ?1 integrin activity. CD2-induced increases in ?1 integrin activity could be blocked by two phosphoinositide 3-kinase (PI 3-K) inhibitors or by overexpression of a dominant negative form of the p85 subunit of PI 3-K. In addition, CD2 cytoplasmic domain mutations that abrogate CD2-induced increases in integrin-mediated adhesion also ablate CD2-induced increases in PI 3-K enzymatic activity. Surprisingly, CD2 cytoplasmic domain mutations that inhibit CD2 regulation of adhesion do not affect the constitutive association of the p85 subunit of PI 3-K association with CD2. Mutation of the proline residues in the K-G-P-P-L-P motif to alanines prevented CD2-mediated activation of integrin function and PI 3-K activity but not mitogen-activated protein (MAP) kinase activity. Furthermore, the MEK inhibitor PD 098059 blocked CD2-mediated activation of MAP kinase but had no effect on CD2-induced adhesion. These studies identify a proline-rich sequence in CD2 critical for PI 3-K-dependent regulation of ?1 integrin adhesion by CD2. In addition, these studies suggest that CD2-mediated activation of MAP kinase is not involved in CD2 regulation of integrin adhesion. PMID:9710614

  17. Cellular and Molecular Mechanisms of Chronic Kidney Disease with Diabetes Mellitus and Cardiovascular Diseases as Its Comorbidities

    PubMed Central

    Gajjala, Prathibha Reddy; Sanati, Maryam; Jankowski, Joachim

    2015-01-01

    Chronic kidney disease (CKD), diabetes mellitus (DM), and cardiovascular diseases (CVD) are complex disorders of partly unknown genesis and mostly known progression factors. CVD and DM are the risk factors of CKD and are strongly intertwined since DM can lead to both CKD and/or CVD, and CVD can lead to kidney disease. In recent years, our knowledge of CKD, DM, and CVD has been expanded and several important experimental, clinical, and epidemiological associations have been reported. The tight cellular and molecular interactions between the renal, diabetic, and cardiovascular systems in acute or chronic disease settings are becoming increasingly evident. However, the (patho-) physiological basis of the interactions of CKD, DM, and CVD with involvement of multiple endogenous and environmental factors is highly complex and our knowledge is still at its infancy. Not only single pathways and mediators of progression of these diseases have to be considered in these processes but also the mutual interactions of these factors are essential. The recent advances in proteomics and integrative analysis technologies have allowed rapid progress in analyzing complex disorders and clearly show the opportunity for new efficient and specific therapies. More than a dozen pathways have been identified so far, including hyperactivity of the renin–angiotensin (RAS)–aldosterone system, osmotic sodium retention, endothelial dysfunction, dyslipidemia, RAS/RAF/extracellular-signal-regulated kinase pathway, modification of the purinergic system, phosphatidylinositol 3-kinase (PI 3-kinase)-dependent signaling pathways, and inflammation, all leading to histomorphological alterations of the kidney and vessels of diabetic and non-diabetic patients. Since a better understanding of the common cellular and molecular mechanisms of these diseases may be a key to successful identification of new therapeutic targets, we review in this paper the current literature about cellular and molecular mechanisms of CKD. PMID:26217336

  18. PTEN function: how normal cells control it and tumour cells lose it

    PubMed Central

    2004-01-01

    The PTEN (phosphatase and tensin homologue deleted on chromosome 10) tumour suppressor is a PI (phosphoinositide) 3-phosphatase that can inhibit cellular proliferation, survival and growth by inactivating PI 3-kinase-dependent signalling. It also suppresses cellular motility through mechanisms that may be partially independent of phosphatase activity. PTEN is one of the most commonly lost tumour suppressors in human cancer, and its deregulation is also implicated in several other diseases. Here we discuss recent developments in our understanding of how the cellular activity of PTEN is regulated, and the closely related question of how this activity is lost in tumours. Cellular PTEN function appears to be regulated by controlling both the expression of the enzyme and also its activity through mechanisms including oxidation and phosphorylation-based control of non-substrate membrane binding. Therefore mutation of PTEN in tumours disrupts not only the catalytic function of PTEN, but also its regulatory aspects. However, although mutation of PTEN is uncommon in many human tumour types, loss of PTEN expression seems to be more frequent. It is currently unclear how these tumours lose PTEN expression in the absence of mutation, and while some data implicate other potential tumour suppressors and oncogenes in this process, this area seems likely to be a key focus of future research. PMID:15193142

  19. Shear stress stimulates phosphorylation of eNOS at Ser(635) by a protein kinase A-dependent mechanism

    NASA Technical Reports Server (NTRS)

    Boo, Yong Chool; Hwang, Jinah; Sykes, Michelle; Michell, Belinda J.; Kemp, Bruce E.; Lum, Hazel; Jo, Hanjoong

    2002-01-01

    Shear stress stimulates nitric oxide (NO) production by phosphorylating endothelial NO synthase (eNOS) at Ser(1179) in a phosphoinositide-3-kinase (PI3K)- and protein kinase A (PKA)-dependent manner. The eNOS has additional potential phosphorylation sites, including Ser(116), Thr(497), and Ser(635). Here, we studied these potential phosphorylation sites in response to shear, vascular endothelial growth factor (VEGF), and 8-bromocAMP (8-BRcAMP) in bovine aortic endothelial cells (BAEC). All three stimuli induced phosphorylation of eNOS at Ser(635), which was consistently slower than that at Ser(1179). Thr(497) was rapidly dephosphorylated by 8-BRcAMP but not by shear and VEGF. None of the stimuli phosphorylated Ser(116). Whereas shear-stimulated Ser(635) phosphorylation was not affected by phosphoinositide-3-kinase inhibitors wortmannin and LY-294002, it was blocked by either treating the cells with a PKA inhibitor H89 or infecting them with a recombinant adenovirus-expressing PKA inhibitor. These results suggest that shear stress stimulates eNOS by two different mechanisms: 1) PKA- and PI3K-dependent and 2) PKA-dependent but PI3K-independent pathways. Phosphorylation of Ser(635) may play an important role in chronic regulation of eNOS in response to mechanical and humoral stimuli.

  20. AKT is translocated to the mitochondria during etoposide-induced apoptosis of HeLa cells.

    PubMed

    Park, Byoungduck; Je, Young-Tae; Chun, Kwang-Hoon

    2015-11-01

    Akt, or protein kinase B, is a key serine-threonine kinase, which exerts anti-apoptotic effects and promotes cell proliferation in response to various stimuli. Recently, however, it was demonstrated that Akt exhibits a proapoptotic role in certain contexts. During etoposide?induced apoptosis of HeLa cells, Akt enhances the interaction of second mitochondria?derived activator of caspases/direct IAP binding protein with low pI (Smac/DIABLO) and X?linked inhibitor of apoptosis protein by phosphorylating Smac at serine 67, and thus promotes apoptosis. However, the detailed mechanisms underlying Akt regulation in etoposide?mediated apoptosis remain to be determined. The present study investigated whether etoposide triggers the translocation of Akt into the mitochondria. It was found that Akt activity was increased and sustained during apoptosis triggered by etoposide in HeLa cells. During apoptosis, Akt was translocated from the cytoplasm into the mitochondria in a phosphoinositide 3?kinase-dependent manner at the early and late stages of apoptosis. Concomitantly, the depletion of Akt in the nuclear fraction was observed after etoposide treatment from analysis of confocal microscopy. The results suggest that etoposide?stimulated Akt is translocated into the mitochondria, thereby possibly enhancing its interaction with Smac and promoting apoptosis in HeLa cells. These results indicate that Akt may be a promising candidate for a pro-apoptotic approach in cancer treatment. PMID:26458825

  1. Oleanolic acid induces relaxation and calcium-independent release of endothelium-derived nitric oxide

    PubMed Central

    Rodriguez-Rodriguez, R; Stankevicius, E; Herrera, M D; Østergaard, L; Andersen, M R; Ruiz-Gutierrez, V; Simonsen, U

    2008-01-01

    Background and purpose: The present study investigated the mechanisms by which oleanolic acid, a component of olive oil, increases release of nitric oxide (NO). Experimental approach: Measurements of isometric tension, NO concentration, or endothelial cell calcium were made in rat isolated mesenteric arteries. Immunoblotting for endothelial NOS (eNOS) and Akt kinase were performed in primary cultures of human umbilical vein endothelial cells (HUVECs). Key results: Oleanolic acid (3–30??M) evoked endothelium-dependent relaxations in noradrenaline-contracted rat superior and small mesenteric arteries. In rat superior mesenteric arteries, oleanolic acid induced simultaneous increases in NO concentration and relaxation, and these responses were inhibited by an inhibitor of NOS, asymmetric dimethyl-L-arginine (300??M) and by the NO scavenger, oxyhaemoglobin (10??M). Oleanolic acid-evoked NO increases were not reduced in Ca2+-free solution and in the presence of an inhibitor of endoplasmic reticulum calcium-ATPase, thapsigargin (1??M). Oleanolic acid evoked relaxation without changes in endothelial cell calcium, but decreased smooth muscle calcium in arterial segments. Oleanolic acid failed to increase calcium in HUVECs, but increased time-dependently phosphorylation of Akt kinase at Serine473 (Akt-Ser473) and eNOS at Serine1177 (eNOS-Ser1177), which was attenuated by inhibitors of phosphoinositide-3-kinase. Conclusions and implications: This study provides direct evidence that a component of olive oil, oleanolic acid, activated endothelium-dependent release of NO and decreased smooth muscle cell calcium followed by relaxation. The oleanolic acid-evoked endothelium-derived NO release was independent of endothelial cell calcium and involved phosphoinositide-3-kinase-dependent phosphorylation of Akt-Ser473 followed by phosphorylation of eNOS-Ser1177. PMID:18622409

  2. Paclitaxel induces calcium oscillations via an inositol 1,4,5-trisphosphate receptor and neuronal calcium sensor 1-dependent mechanism

    PubMed Central

    Boehmerle, Wolfgang; Splittgerber, Ute; Lazarus, Michael B.; McKenzie, Kathleen M.; Johnston, David G.; Austin, David J.; Ehrlich, Barbara E.

    2006-01-01

    Taxol (Paclitaxel) is an important natural product for the treatment of solid tumors. Despite a well documented tubulin-stabilizing effect, many side effects of taxol therapy cannot be explained by cytoskeletal mechanisms. In the present study submicromolar concentrations of taxol, mimicking concentrations found in patients, induced cytosolic calcium (Ca2+) oscillations in a human neuronal cell line. These oscillations were independent of extracellular and mitochondrial Ca2+ but dependent on intact signaling via the phosphoinositide signaling pathway. We identified a taxol binding protein, neuronal Ca2+ sensor 1 (NCS-1), a Ca2+ binding protein that interacts with the inositol 1,4,5-trisphosphate receptor from a human brain cDNA phage display library. Taxol increased binding of NCS-1 to the inositol 1,4,5-trisphosphate receptor. Short hairpin RNA-mediated knockdown of NCS-1 in the same cell line abrogated the response to taxol but not to other agonists stimulating the phosphoinositide signaling pathway. These findings are important for studies involving taxol as a research tool in cell biology and may help to devise new strategies for the management of side effects induced by taxol therapy. PMID:17114292

  3. Different inhibition of G??-stimulated class IB phosphoinositide 3-kinase (PI3K) variants by a monoclonal antibody. Specific function of p101 as a G??-dependent regulator of PI3K? enzymatic activity.

    PubMed

    Shymanets, Aliaksei; Prajwal; Vadas, Oscar; Czupalla, Cornelia; LoPiccolo, Jaclyn; Brenowitz, Michael; Ghigo, Alessandra; Hirsch, Emilio; Krause, Eberhard; Wetzker, Reinhard; Williams, Roger L; Harteneck, Christian; Nürnberg, Bernd

    2015-07-01

    Class IB phosphoinositide 3-kinases ? (PI3K?) are second-messenger-generating enzymes downstream of signalling cascades triggered by G-protein-coupled receptors (GPCRs). PI3K? variants have one catalytic p110? subunit that can form two different heterodimers by binding to one of a pair of non-catalytic subunits, p87 or p101. Growing experimental data argue for a different regulation of p87-p110? and p101-p110? allowing integration into distinct signalling pathways. Pharmacological tools enabling distinct modulation of the two variants are missing. The ability of an anti-p110? monoclonal antibody [mAb(A)p110?] to block PI3K? enzymatic activity attracted us to characterize this tool in detail using purified proteins. In order to get insight into the antibody-p110? interface, hydrogen-deuterium exchange coupled to MS (HDX-MS) measurements were performed demonstrating binding of the monoclonal antibody to the C2 domain in p110?, which was accompanied by conformational changes in the helical domain harbouring the G??-binding site. We then studied the modulation of phospholipid vesicles association of PI3K? by the antibody. p87-p110? showed a significantly reduced G??-mediated phospholipid recruitment as compared with p101-p110?. Concomitantly, in the presence of mAb(A)p110?, G?? did not bind to p87-p110?. These data correlated with the ability of the antibody to block G??-stimulated lipid kinase activity of p87-p110? 30-fold more potently than p101-p110?. Our data argue for differential regulatory functions of the non-catalytic subunits and a specific G??-dependent regulation of p101 in PI3K? activation. In this scenario, we consider the antibody as a valuable tool to dissect the distinct roles of the two PI3K? variants downstream of GPCRs. PMID:26173259

  4. Hyaluronan Activates Cell Motility of v-Src-transformed Cells via Ras-Mitogen–activated Protein Kinase and Phosphoinositide 3-Kinase-Akt in a Tumor-specific Manner

    PubMed Central

    Sohara, Yasuyoshi; Ishiguro, Naoki; Machida, Kazuya; Kurata, Hisashi; Thant, Aye Aye; Senga, Takeshi; Matsuda, Satoru; Kimata, Koji; Iwata, Hisashi; Hamaguchi, Michinari

    2001-01-01

    We investigated the production of hyaluronan (HA) and its effect on cell motility in cells expressing the v-src mutants. Transformation of 3Y1 by v-src virtually activated HA secretion, whereas G2A v-src, a nonmyristoylated form of v-src defective in cell transformation, had no effect. In cells expressing the temperature-sensitive mutant of v-Src, HA secretion was temperature dependent. In addition, HA as small as 1 nM, on the other side, activated cell motility in a tumor-specific manner. HA treatment strongly activated the motility of v-Src–transformed 3Y1, whereas it showed no effect on 3Y1- and 3Y1-expressing G2A v-src. HA-dependent cell locomotion was strongly blocked by either expression of dominant-negative Ras or treatment with a Ras farnesyltransferase inhibitor. Similarly, both the MEK1 inhibitor and the kinase inhibitor clearly inhibited HA-dependent cell locomotion. In contrast, cells transformed with an active MEK1 did not respond to the HA. Finally, an anti-CD44–neutralizing antibody could block the activation of cell motility by HA as well as the HA-dependent phosphorylation of mitogen-activated protein kinase and Akt. Taken together, these results suggest that simultaneous activation of the Ras-mitogen-activated protein kinase pathway and the phosphoinositide 3-kinase pathway by the HA-CD44 interaction is required for the activation of HA-dependent cell locomotion in v-Src–transformed cells. PMID:11408591

  5. The Vr-PLC3 gene encodes a putative plasma membrane-localized phosphoinositide-specific phospholipase C whose expression is induced by abiotic stress in mung bean (Vigna radiata L.).

    PubMed

    Kim, Yun Ju; Kim, Jee Eun; Lee, Jae-Hoon; Lee, Myoung Hui; Jung, Ho Won; Bahk, Young Yil; Hwang, Byung Kook; Hwang, Inhwan; Kim, Woo Taek

    2004-01-01

    Phosphoinositide-specific phospholipase C (PI-PLC) catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate to generate inositol 1,4,5-trisphosphate and diacylglycerol, both of which act as secondary messengers in animal cells. In this report, we identified in Vigna radiata L. (mung bean) three distinct partial cDNAs (pVr-PLC1, pVr-PLC2, and pVr-PLC3), which encode forms of putative PI-PLC. All three Vr-PLC genes were transcriptionally active and displayed unique patterns of expression. The Vr-PLC1 and Vr-PLC2 transcripts were constitutively expressed to varying degrees in every tissue of mung bean plants examined. In contrast, the Vr-PLC3 mRNA level was very low under normal growth conditions and was rapidly induced in an abscisic acid-independent manner under environmental stress conditions (drought and high salinity). An isolated genomic clone, about 8.2 kb in length, showed that Vr-PLC1 and Vr-PLC3 are in tandem array in the mung bean genome. The predicted primary sequence of Vr-PLC3 (M(r)=67.4 kDa) is reminiscent of the delta-isoform of animal enzymes which contain core sequences found in typical PI-PLCs, such as the catalytic domain comprising X and Y motifs, a lipid-binding C2 domain, and the less conserved EF-hand domain. Results of in vivo targeting experiment using a green fluorescent protein (GFP) showed that the GFP-Vr-PLC3 fusion protein was localized primarily to the plasma membrane of the Arabidopsis protoplast. The C2 domain was essential for Vr-PLC3 to be targeted to the plasma membrane. The possible biological functions of stress-responsive Vr-PLC3 in mung bean plants are discussed. PMID:14706839

  6. REGULATION OF CA2+ ENTRY BY INOSITOL LIPIDS IN MAMMALIAN CELLS BY MULTIPLE MECHANISMS

    PubMed Central

    Balla, Tamas

    2009-01-01

    Increased phosphoinositide turnover was first identified as an early signal transduction event initiated by cell surface receptors that were linked to calcium signaling. Subsequently, the generation of inositol 1,4,5-trisphosphate by phosphoinositide-specific phospholipase C enzymes was defined as the major link between inositide turnover and the cytosolic Ca2+ rise in response to external stimulation. However, in the last decades, phosphoinositides have been emerging as major regulatory lipids involved in virtually every membrane-associated signaling process. Phosphoinositides regulate both the activity and the trafficking of almost all ion channels and transporters contributing to the maintenance of the ionic gradients that are essential for the proper functioning of all eukaryotic cells. Here we summarize the various means by which phosphoinositides affect ion channel functions with special emphasis on Ca2+ signaling and outline the principles that govern the highly compartmentalized roles of these regulatory lipids. PMID:19395084

  7. Guanylyl cyclase/natriuretic peptide receptor-A signaling antagonizes phosphoinositide hydrolysis, Ca2+ release, and activation of protein kinase C

    PubMed Central

    Pandey, Kailash N.

    2014-01-01

    Thus far, three related natriuretic peptides (NPs) and three distinct sub-types of cognate NP receptors have been identified and characterized based on the specific ligand binding affinities, guanylyl cyclase activity, and generation of intracellular cGMP. Atrial and brain natriuretic peptides (ANP and BNP) specifically bind and activate guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA), and C-type natriuretic peptide (CNP) shows specificity to activate guanylyl cyclase/natriuretic peptide receptor-B (GC-B/NPRB). All three NPs bind to natriuretic peptide receptor-C (NPRC), which is also known as clearance or silent receptor. The NPRA is considered the principal biologically active receptor of NP family; however, the molecular signaling mechanisms of NP receptors are not well understood. The activation of NPRA and NPRB produces the intracellular second messenger cGMP, which serves as the major signaling molecule of all three NPs. The activation of NPRB in response to CNP also produces the intracellular cGMP; however, at lower magnitude than that of NPRA, which is activated by ANP and BNP. In addition to enhanced accumulation of intracellular cGMP in response to all three NPs, the levels of cAMP, Ca2+ and inositol triphosphate (IP3) have also been reported to be altered in different cells and tissue types. Interestingly, ANP has been found to lower the concentrations of cAMP, Ca2+, and IP3; however, NPRC has been proposed to increase the levels of these metabolic signaling molecules. The mechanistic studies of decreased and/or increased levels of cAMP, Ca2+, and IP3 in response to NPs and their receptors have not yet been clearly established. This review focuses on the signaling mechanisms of ANP/NPRA and their biological effects involving an increased level of intracellular accumulation of cGMP and a decreased level of cAMP, Ca2+, and IP3 in different cells and tissue systems. PMID:25202235

  8. Investigation of molecular mechanisms and regulatory pathways of pro-angiogenic nanorods

    NASA Astrophysics Data System (ADS)

    Nethi, Susheel Kumar; Veeriah, Vimal; Barui, Ayan Kumar; Rajendran, Saranya; Mattapally, Saidulu; Misra, Sanjay; Chatterjee, Suvro; Patra, Chitta Ranjan

    2015-05-01

    Angiogenesis, a process involving the growth of new blood vessels from the pre-existing vasculature, plays a crucial role in various pathophysiological conditions. We have previously demonstrated that europium hydroxide [EuIII(OH)3] nanorods (EHNs) exhibit pro-angiogenic properties through the generation of reactive oxygen species (ROS) and mitogen activated protein kinase (MAPK) activation. Considering the enormous implication of angiogenesis in cardiovascular diseases (CVDs) and cancer, it is essential to understand in-depth molecular mechanisms and signaling pathways in order to develop the most efficient and effective alternative treatment strategy for CVDs. However, the exact underlying mechanism and cascade signaling pathways behind the pro-angiogenic properties exhibited by EHNs still remain unclear. Herein, we report for the first time that the hydrogen peroxide (H2O2), a redox signaling molecule, generated by these EHNs activates the endothelial nitric oxide synthase (eNOS) that promotes the nitric oxide (NO) production in a PI3K (phosphoinositide 3-kinase)/Akt dependent manner, eventually triggering angiogenesis. We intensely believe that the investigation and understanding of the in-depth molecular mechanism and signaling pathways of EHNs induced angiogenesis will help us in developing an effective alternative treatment strategy for cardiovascular related and ischemic diseases where angiogenesis plays an important role.Angiogenesis, a process involving the growth of new blood vessels from the pre-existing vasculature, plays a crucial role in various pathophysiological conditions. We have previously demonstrated that europium hydroxide [EuIII(OH)3] nanorods (EHNs) exhibit pro-angiogenic properties through the generation of reactive oxygen species (ROS) and mitogen activated protein kinase (MAPK) activation. Considering the enormous implication of angiogenesis in cardiovascular diseases (CVDs) and cancer, it is essential to understand in-depth molecular mechanisms and signaling pathways in order to develop the most efficient and effective alternative treatment strategy for CVDs. However, the exact underlying mechanism and cascade signaling pathways behind the pro-angiogenic properties exhibited by EHNs still remain unclear. Herein, we report for the first time that the hydrogen peroxide (H2O2), a redox signaling molecule, generated by these EHNs activates the endothelial nitric oxide synthase (eNOS) that promotes the nitric oxide (NO) production in a PI3K (phosphoinositide 3-kinase)/Akt dependent manner, eventually triggering angiogenesis. We intensely believe that the investigation and understanding of the in-depth molecular mechanism and signaling pathways of EHNs induced angiogenesis will help us in developing an effective alternative treatment strategy for cardiovascular related and ischemic diseases where angiogenesis plays an important role. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01327e

  9. The phosphoinositide 3-kinase/Akt-signal pathway mediates proliferation and secretory function of hepatic sinusoidal endothelial cells in rats after partial hepatectomy

    SciTech Connect

    Chen Ping . E-mail: chenping@263.net; Zhang Lin; Ding Jiming; Zhu Jin; Li Ying; Duan Shigang; Yan Hongtao; Huan Yongwei; Dong Jiahong

    2006-04-14

    Objective: To investigate the role of AKT signaling pathway in hepatic sinusoidal endothelial cells (SECs) early after partial hepatectomy in rats and the regulatory mechanisms involved. Methods: The animal model of 70% hepatectomy was made. Hepatic SECs were isolated and cultured according to Braet et al.'s method with some modifications. The cultured hepatic SECs were divided into two groups: 70% partial hepatectomy groups and LY294002 group (LY). We observed the expressions of AKT and NF-{kappa}B in cultured hepatic SECs by Western blot, measured the levels of NO, NOs, IL-6, and HGF in the supernatants of hepatic SEC cultures and [{sup 3}H]thymidine incorporation, and analyzed cell cycle of cultured hepatic SECs by flow cytometer. The relationship of the Akt pathway with secretions and proliferation of hepatic SECs after partial hepatectomy was probed. Results: The levels of Akt protein expression increased significantly after partial hepatectomy in OG group and with a peak at 24 h post operation. Meanwhile, there was a markedly increase in phosphorylated Akt protein during 2-72 h after operation. But the expression and activity of Akt protein did not change significantly after partial hepatectomy in the LY group. So, partial hepatectomy can marked induce Akt expression and result in rapid and marked phosphorylation of Akt from 2 to 72 h thereafter. The changes of NF-{kappa}B expression in cultured hepatic SECs were similar to those of Akt expression after operation. The concentrations of HGF and IL-6 in the supernatants of cultured hepatic SECs were relatively low in the LY group, and were markedly increased after partial hepatectomy, with a peak at 24 h in the OG group. There were significant differences between the OG and LY groups at 6 and 24 h (P < 0.05). Both NO and NOS secretion was increased in the OG group compared to the LY group within 24 h after partial hepatectomy. But the secretion of NO and NOS was increased more markedly in the LY group than that in the OG beyond 24 h. These findings suggest that the secretion of the cytokines by hepatic SECs is mediated by Akt signaling. Akt signaling pathway in relationship with proliferation of hepatic SECs and suppression of apoptosis. In OG group, the hepatic SECs in S and G2/M obviously increased. The proliferative index of hepatic SECs in OG group had significant differences with that in LY group at 6, 24, and 72 h, P < 0.05. Meanwhile, the cells of apoptosis in OG group were very low, and the cells in LY group gradually increased. Conclusions: These results suggest that AKT signaling pathway plays a crucial role in mediating proliferating and secreted signals in hepatic SECs. AKT has been suggested to play a pivotal role in early liver regeneration involved in the induction of secreted cytokines and proliferation of hepatic SECs.

  10. Plasma membrane nanoporation as a possible mechanism behind infrared excitation of cells

    NASA Astrophysics Data System (ADS)

    Beier, Hope T.; Tolstykh, Gleb P.; Musick, Joshua D.; Thomas, Robert J.; Ibey, Bennett L.

    2014-12-01

    Objective. Short infrared (IR) laser pulses have been used to stimulate action potentials in neurons both in vivo and in vitro. However, the mechanism(s) underlying this phenomenon has remained elusive. In vitro studies have found that pulsed IR exposure generates a nearly instant change in capacitance in the plasma membrane, characterized by inward rectification, a common feature in pore-forming exposures, such as electrical pulses and acoustic shock waves. Based on this similarity, we hypothesize that the mechanism of IR stimulation is the formation of short-lived nanopores in the plasma membrane. These transient, small-diameter pores allow the influx of extracellular ions that lead to action potential generation, possibly through activation of secondary messenger pathways or depolarization of the cell membrane resulting in activation of voltage-gated ion channels. Approach. A variety of fluorescent markers are used to observe the cell response to IR stimulation to monitor for effects indicative of nanoporation in other modalities. Main results. We observe rapid, transient rises in intracellular Ca2+, influx of YO-PRO-1 and propidium iodide into the cell signifying membrane permeabilization, cellular blebbing and swelling, and activation of the intracellular phosphoinositides lipid signaling pathway. Significance. This conclusion better explains the experimental observations and limitations of IR-induced neurological stimulation and represents a distinct theoretical shift in the understanding of the mechanism of IR-induced stimulation.

  11. Puzzling Mechanisms

    ERIC Educational Resources Information Center

    van Deventer, M. Oskar

    2009-01-01

    The basis of a good mechanical puzzle is often a puzzling mechanism. This article will introduce some new puzzling mechanisms, like two knots that engage like gears, a chain whose links can be interchanged, and flat gears that do not come apart. It illustrates how puzzling mechanisms can be transformed into real mechanical puzzles, e.g., by…

  12. Bohmian Mechanics

    E-print Network

    Detlef Duerr; Sheldon Goldstein; Roderich Tumulka; Nino Zanghi

    2009-03-15

    Bohmian mechanics is a theory about point particles moving along trajectories. It has the property that in a world governed by Bohmian mechanics, observers see the same statistics for experimental results as predicted by quantum mechanics. Bohmian mechanics thus provides an explanation of quantum mechanics. Moreover, the Bohmian trajectories are defined in a non-conspiratorial way by a few simple laws.

  13. Impairments in hepatocyte phosphoinositide metabolism in endotoxemia.

    PubMed

    Rodriguez de Turco, E; Spitzer, J A

    1987-08-01

    The status of phospholipid metabolism and inositol lipids-mediated transmembrane signaling in rat hepatocytes was analyzed during chronic, nonlethal endotoxemia. Rats were infused intravenously (IV) with Escherichia coli endotoxin (ET) via subcutaneously implanted osmotic pumps at a rate of 0.1 mg/100 g bw/day. The experiments were performed after 30 hours of ET or sterile saline (NaCl) infusion, in hepatocytes prelabelled "in vitro" with 32P (15 microCi/mL) and further stimulated with vasopressin (VP, 0.23 mumol/L). Similar experiments were done with food-restricted animals, whose food intake was matched with the voluntary intake of ET-infused rats. Uptake of 32P label into phosphatidic acid (PA), phosphatidylinositol 4-phosphate (PIP), and phosphatidylinositol 4,5-bisphosphate (PIP2) occurs rapidly in cells from pair-fed, saline and ET-infused animals, and reaches a plateau between 60 and 80 minutes of incubation. Labeling of phosphatidylinositol (PI), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) proceeds linearly after a ten-minute lag period for PI and 20 minutes for the two other lipids. The nutritional state greatly affects the distribution of 32P uptake into lipids, resulting in very low labeling of PA and PI and a high labeling of poly-PI as compared with control (taken from untreated rats) cells. In ET-v saline-infused rats, the labeling of PI and PE was depressed concomitantly with a proportional increase in the labeling of PIP and PC. The ability of VP to induce polyphosphoinositide (poly-PI) degradation in hepatocytes from saline-infused animals was similar to that observed in control cells.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3037237

  14. Bohmian mechanics contradicts quantum mechanics

    E-print Network

    Neumaier, Arnold

    Bohmian mechanics contradicts quantum mechanics Arnold Neumaier Institut fur Mathematik, Universit and quantum mechanics predict values of opposite sign for certain time correlations. The discrepancy can no loophole for claiming that Bohmian mechanics reproduces all predictions of quantum mechanics exactly

  15. & Mechanical Engineering

    E-print Network

    Zhou, Chongwu

    as continuum and particulate uid mechanics, ight mechanics, propulsion, novel microelectromechanical systems > Develop new devices including satellites, aircraft and rocket components > Improve the safety of existing Materials Flight Mechanics & Propulsion Biomechanics Microscale Devices LEARN MORE: viterbi.usc.edu/ame #12

  16. Cellular Mechanisms of Gravitropic Response in Higher Plants

    NASA Astrophysics Data System (ADS)

    Medvedev, Sergei; Smolikova, Galina; Pozhvanov, Gregory; Suslov, Dmitry

    The evolutionary success of land plants in adaptation to the vectorial environmental factors was based mainly on the development of polarity systems. In result, normal plant ontogenesis is based on the positional information. Polarity is a tool by which the developing plant organs and tissues are mapped and the specific three-dimensional structure of the organism is created. It is due to their polar organization plants are able to orient themselves relative to the gravity vector and different vectorial cues, and to respond adequately to various stimuli. Gravitation is one of the most important polarized environmental factor that guides the development of plant organisms in space. Every plant can "estimate" its position relative to the gravity vector and correct it, if necessary, by means of polarized growth. The direction and the magnitude of gravitational stimulus are constant during the whole plant ontogenesis. The key plant response to the action of gravity is gravitropism, i.e. the directed growth of organs with respect to the gravity vector. This response is a very convenient model to study the mechanisms of plant orientation in space. The present report is focused on the main cellular mechanisms responsible for graviropic bending in higher plants. These mechanisms and structures include electric polarization of plant cells, Ca ({2+) }gradients, cytoskeleton, G-proteins, phosphoinositides and the machinery responsible for asymmetric auxin distribution. Those mechanisms tightly interact demonstrating some hierarchy and multiple feedbacks. The Ca (2+) gradients provide the primary physiological basis of polarity in plant cells. Calcium ions influence on the bioelectric potentials, the organization of actin cytoskeleton, the activity of Ca (2+) -binding proteins and Ca (2+) -dependent protein kinases. Protein kinases modulate transcription factors activity thereby regulating the gene expression and switching the developmental programs. Actin cytoskeleton affects the molecular machinery of polar auxin transport. It results in the changes of auxin gradients in plant organs and tissues, which modulate all cellular mechanisms of polarity via multiple feedback loops. The understanding of the mechanisms of plant organism orientation relative to the gravity vector will allow us to develop efficient technologies for plant growing in microgravity conditions at orbital space stations and during long piloted space flights. This work was supported by the grant of Russian Foundation for Basic Research (N 14-04-01-624) and by the grant of St.-Petersburg State University (N 1.38.233.2014).

  17. Automotive Mechanics.

    ERIC Educational Resources Information Center

    Linder, Ralph C.; And Others

    This curriculum guide, which was validated by vocational teachers and mechanics in the field, describes the competencies needed by entry-level automotive mechanics. This guide lists 15 competencies; for each competency, various tasks with their performance objective, student learning experiences, suggested instructional techniques, instructional…

  18. Grasping Mechanism

    NASA Technical Reports Server (NTRS)

    Myers, W. Neil; Forbes, John C.

    1987-01-01

    Grasping mechanism captures and locks onto rodlike handle without being precisely aligned with it initially. Mechanism includes two faceplates and three rotatable fingers meshing odd finger between two members of opposite finger pair. Power for fingers supplied by motor powered via harmonic drive reduces speed and increases torque by factor of 160.

  19. Cytoskeletal Mechanics

    NASA Astrophysics Data System (ADS)

    Mofrad, Mohammad R. K.; Kamm, Roger D.

    2006-10-01

    1. Introduction and the biological basis for cell mechanics Mohammad R. K. Mofrad and Roger Kamm; 2. Experimental measurements of intracellular mechanics Paul Janmey and Christoph Schmidt; 3. The cytoskeleton as a soft glassy material Jeffrey Fredberg and Ben Fabry; 4. Continuum elastic or viscoelastic models for the cell Mohammad R. K. Mofrad, Helene Karcher and Roger Kamm; 5. Multiphasic models of cell mechanics Farshid Guuilak, Mansoor A. Haider, Lori A. Setton, Tod A. Laursen and Frank P. T. Baaijens; 6. Models of cytoskeletal mechanics based on tensegrity Dimitrije Stamenovic; 7. Cells, gels and mechanics Gerald H. Pollack; 8. Polymer-based models of cytoskeletal networks F. C. MacKintosh; 9. Cell dynamics and the actin cytoskeleton James L. McGrath and C. Forbes Dewey, Jr; 10. Active cellular motion: continuum theories and models Marc Herant and Micah Dembo; 11. Summary Mohammad R. K. Mofrad and Roger Kamm.

  20. Cytoskeletal Mechanics

    NASA Astrophysics Data System (ADS)

    Mofrad, Mohammad R. K.; Kamm, Roger D.

    2011-08-01

    1. Introduction and the biological basis for cell mechanics Mohammad R. K. Mofrad and Roger Kamm; 2. Experimental measurements of intracellular mechanics Paul Janmey and Christoph Schmidt; 3. The cytoskeleton as a soft glassy material Jeffrey Fredberg and Ben Fabry; 4. Continuum elastic or viscoelastic models for the cell Mohammad R. K. Mofrad, Helene Karcher and Roger Kamm; 5. Multiphasic models of cell mechanics Farshid Guuilak, Mansoor A. Haider, Lori A. Setton, Tod A. Laursen and Frank P. T. Baaijens; 6. Models of cytoskeletal mechanics based on tensegrity Dimitrije Stamenovic; 7. Cells, gels and mechanics Gerald H. Pollack; 8. Polymer-based models of cytoskeletal networks F. C. MacKintosh; 9. Cell dynamics and the actin cytoskeleton James L. McGrath and C. Forbes Dewey, Jr; 10. Active cellular motion: continuum theories and models Marc Herant and Micah Dembo; 11. Summary Mohammad R. K. Mofrad and Roger Kamm.

  1. Mural propagation of descending vasa recta responses to mechanical stimulation.

    PubMed

    Zhang, Zhong; Payne, Kristie; Cao, Chunhua; Pallone, Thomas L

    2013-08-01

    To investigate the responses of descending vasa recta (DVR) to deformation of the abluminal surface, we devised an automated method that controls duration and frequency of stimulation by utilizing a stream of buffer from a micropipette. During stimulation at one end of the vessel, fluorescent responses from fluo4 or bis[1,3-dibutylbarbituric acid-(5)] trimethineoxonol [DiBAC?(3)], indicating cytoplasmic calcium ([Ca²?]CYT) or membrane potential, respectively, were recorded from distant cells. Alternately, membrane potential was recorded from DVR pericytes by nystatin whole cell patch-clamp. Mechanical stimulation elicited reversible [Ca²?)]CYT responses that increased with frequency. Individual pericyte responses along the vessel were initiated within a fraction of a second of one another. Those responses were inhibited by gap junction blockade with 18 ?-glycyrrhetinic acid (100 ?M) or phosphoinositide 3 kinase inhibition with 2-morpholin-4-yl-8-phenylchromen-4-one (50 ?M). [Ca²?]CYT responses were blocked by removal of extracellular Ca²? or L-type voltage-gated channel blockade with nifedipine (10 ?M). At concentrations selective for the T-type channel blockade, mibefradil (100 nM) was ineffective. During mechanostimulation, pericytes rapidly depolarized, as documented with either DiBAC4(3) fluorescence or patch-clamp recording. Single stimuli yielded depolarizations of 22.5 ± 2.2 mV while repetitive stimuli at 0.1 Hz depolarized pericytes by 44.2 ± 4.0 mV. We conclude that DVR are mechanosensitive and that rapid transmission of signals along the vessel axis requires participation of gap junctions, L-type Ca²? channels, and pericyte depolarization. PMID:23698119

  2. Mechanical memory

    DOEpatents

    Gilkey, Jeffrey C. (Albuquerque, NM); Duesterhaus, Michelle A. (Albuquerque, NM); Peter, Frank J. (Albuquerque, NM); Renn, Rosemarie A. (Alburquerque, NM); Baker, Michael S. (Albuquerque, NM)

    2006-08-15

    A first-in-first-out (FIFO) microelectromechanical memory apparatus (also termed a mechanical memory) is disclosed. The mechanical memory utilizes a plurality of memory cells, with each memory cell having a beam which can be bowed in either of two directions of curvature to indicate two different logic states for that memory cell. The memory cells can be arranged around a wheel which operates as a clocking actuator to serially shift data from one memory cell to the next. The mechanical memory can be formed using conventional surface micromachining, and can be formed as either a nonvolatile memory or as a volatile memory.

  3. Mechanical memory

    DOEpatents

    Gilkey, Jeffrey C. (Albuquerque, NM); Duesterhaus, Michelle A. (Albuquerque, NM); Peter, Frank J. (Albuquerque, NM); Renn, Rosemarie A. (Albuquerque, NM); Baker, Michael S. (Albuquerque, NM)

    2006-05-16

    A first-in-first-out (FIFO) microelectromechanical memory apparatus (also termed a mechanical memory) is disclosed. The mechanical memory utilizes a plurality of memory cells, with each memory cell having a beam which can be bowed in either of two directions of curvature to indicate two different logic states for that memory cell. The memory cells can be arranged around a wheel which operates as a clocking actuator to serially shift data from one memory cell to the next. The mechanical memory can be formed using conventional surface micromachining, and can be formed as either a nonvolatile memory or as a volatile memory.

  4. Mechanisms of Cardiovascular Homeostasis and Pathophysiology?- From Gene Expression, Signal Transduction to Cellular Communication.

    PubMed

    Akazawa, Hiroshi

    2015-11-25

    During embryogenesis, progenitor cells are specified and differentiated into mature cardiomyocytes. Soon after birth, the ability of cardiomyocytes to proliferate is strongly restrained, and thereafter, they grow in size without cell division. Under pathological conditions, cardiomyocytes show adaptive and maladaptive responses through complex intracellular signaling pathways and cross-talking networks of intercellular and inter-tissue communications, but ultimately, they become dysfunctional and undergo cell death or degeneration. Cardiovascular diseases remain the most prevalent, costly, disabling, and deadly medical conditions. To develop novel therapies for them, it is important to elucidate the underlying mechanisms that govern gene expression, signal transduction to cellular communication. In this review article for the 2014 SATO Memorial Award, an approach to uncover molecular and cellular pathophysiology is summarized, focusing on homeobox transcription factor Nkx2-5 in the transcriptional regulation of the cardiac gene program, 3-phosphoinositide-dependent kinase-1, in the regulation of postnatal cardiomyocyte growth, survival, and function, angiotensin II type 1 receptor in the development of pathological hypertrophy and remodeling, and mast cell infiltration in the pathogenesis of atrial remodeling and fibrillation. (Circ J 2015; 79: 2529-2536). PMID:26538467

  5. Rhizobium nod factor signaling. Evidence for a g protein-mediated transduction mechanism

    PubMed Central

    Pingret, JL; Journet, EP; Barker, DG

    1998-01-01

    Rhizobium nodulation (Nod) factors are lipochitooligosaccharide signals that elicit key symbiotic developmental responses in the host legume root. In this study, we have investigated Nod factor signal transduction in the Medicago root epidermis by using a pharmacological approach in conjunction with transgenic plants expressing the Nod factor-responsive reporter construct pMtENOD12-GUS. Evidence for the participation of heterotrimeric G proteins in Nod factor signaling has come from three complementary observations: (1) the amphiphilic peptides mastoparan and Mas7, known G protein agonists, are able to mimic Nod factor-induced epidermal MtENOD12 expression; (2) growth of plants in nodulation-inhibiting conditions (10 mM NH4NO3) leads to a dramatic reduction in both Nod factor- and mastoparan-elicited gene expression; and (3) bacterial pertussis toxin, a well-characterized G protein antagonist, blocks the activities of both the Nod factor and mastoparan. In addition, we have found that antagonists that interfere with phospholipase C activity (neomycin and U73122) and Ca2+ influx/release (EGTA, La3+, and ruthenium red) block Nod factor/mastoparan activity. Taken together, these results are consistent with a Nod factor signal transduction mechanism involving G protein mediation coupled to the activation of both phosphoinositide and Ca2+ second messenger pathways. PMID:9596628

  6. Mechanisms of Hypoxic Up-Regulation of Versican Gene Expression in Macrophages

    PubMed Central

    Sotoodehnejadnematalahi, Fattah; Staples, Karl J.; Chrysanthou, Elvina; Pearson, Helen; Ziegler-Heitbrock, Loems; Burke, Bernard

    2015-01-01

    Hypoxia is a hallmark of many pathological tissues. Macrophages accumulate in hypoxic sites and up-regulate a range of hypoxia-inducible genes. The matrix proteoglycan versican has been identified as one such gene, but the mechanisms responsible for hypoxic induction are not fully characterised. Here we investigate the up-regulation of versican by hypoxia in primary human monocyte-derived macrophages (HMDM), and, intriguingly, show that versican mRNA is up-regulated much more highly (>600 fold) by long term hypoxia (5 days) than by 1 day of hypoxia (48 fold). We report that versican mRNA decay rates are not affected by hypoxia, demonstrating that hypoxic induction of versican mRNA is mediated by increased transcription. Deletion analysis of the promoter identified two regions required for high level promoter activity of luciferase reporter constructs in human macrophages. The hypoxia-inducible transcription factor HIF-1 has previously been implicated as a key potential regulator of versican expression in hypoxia, however our data suggest that HIF-1 up-regulation is unlikely to be principally responsible for the high levels of induction observed in HMDM. Treatment of HMDM with two distinct specific inhibitors of Phosphoinositide 3-kinase (PI3K), LY290042 and wortmannin, significantly reduced induction of versican mRNA by hypoxia and provides evidence of a role for PI3K in hypoxic up-regulation of versican expression. PMID:26057378

  7. Fault mechanics

    SciTech Connect

    Segall, P. )

    1991-01-01

    Recent observational, experimental, and theoretical modeling studies of fault mechanics are discussed in a critical review of U.S. research from the period 1987-1990. Topics examined include interseismic strain accumulation, coseismic deformation, postseismic deformation, and the earthquake cycle; long-term deformation; fault friction and the instability mechanism; pore pressure and normal stress effects; instability models; strain measurements prior to earthquakes; stochastic modeling of earthquakes; and deep-focus earthquakes. Maps, graphs, and a comprehensive bibliography are provided. 220 refs.

  8. Computational mechanics

    SciTech Connect

    Goudreau, G.L.

    1993-03-01

    The Computational Mechanics thrust area sponsors research into the underlying solid, structural and fluid mechanics and heat transfer necessary for the development of state-of-the-art general purpose computational software. The scale of computational capability spans office workstations, departmental computer servers, and Cray-class supercomputers. The DYNA, NIKE, and TOPAZ codes have achieved world fame through our broad collaborators program, in addition to their strong support of on-going Lawrence Livermore National Laboratory (LLNL) programs. Several technology transfer initiatives have been based on these established codes, teaming LLNL analysts and researchers with counterparts in industry, extending code capability to specific industrial interests of casting, metalforming, and automobile crash dynamics. The next-generation solid/structural mechanics code, ParaDyn, is targeted toward massively parallel computers, which will extend performance from gigaflop to teraflop power. Our work for FY-92 is described in the following eight articles: (1) Solution Strategies: New Approaches for Strongly Nonlinear Quasistatic Problems Using DYNA3D; (2) Enhanced Enforcement of Mechanical Contact: The Method of Augmented Lagrangians; (3) ParaDyn: New Generation Solid/Structural Mechanics Codes for Massively Parallel Processors; (4) Composite Damage Modeling; (5) HYDRA: A Parallel/Vector Flow Solver for Three-Dimensional, Transient, Incompressible Viscous How; (6) Development and Testing of the TRIM3D Radiation Heat Transfer Code; (7) A Methodology for Calculating the Seismic Response of Critical Structures; and (8) Reinforced Concrete Damage Modeling.

  9. Turntable mechanism

    NASA Technical Reports Server (NTRS)

    Myers, William Neill (inventor)

    1993-01-01

    In vacuum plasma spraying a turntable must be provided which not only makes it possible to rotate and tilt a heavy workpiece, but to operate at vacuum plasma temperatures to do so. In the vacuum plasma coating of large parts such as combustion chambers of rocket engines, the workpiece must not only be rotated, but it must be tilted. Hence, the turntable must be capable not only of supporting heavy parts, but of angulating such heavy workpieces. And this must be done without drive means failure due to extremely high temperatures under which the turntable mechanism is operated. A turntable mechanism is provided which is capable of operating under such conditions. For cooling the turntable drive mechanism, internal cooling means are included.

  10. Computational mechanics

    SciTech Connect

    Raboin, P J

    1998-01-01

    The Computational Mechanics thrust area is a vital and growing facet of the Mechanical Engineering Department at Lawrence Livermore National Laboratory (LLNL). This work supports the development of computational analysis tools in the areas of structural mechanics and heat transfer. Over 75 analysts depend on thrust area-supported software running on a variety of computing platforms to meet the demands of LLNL programs. Interactions with the Department of Defense (DOD) High Performance Computing and Modernization Program and the Defense Special Weapons Agency are of special importance as they support our ParaDyn project in its development of new parallel capabilities for DYNA3D. Working with DOD customers has been invaluable to driving this technology in directions mutually beneficial to the Department of Energy. Other projects associated with the Computational Mechanics thrust area include work with the Partnership for a New Generation Vehicle (PNGV) for ''Springback Predictability'' and with the Federal Aviation Administration (FAA) for the ''Development of Methodologies for Evaluating Containment and Mitigation of Uncontained Engine Debris.'' In this report for FY-97, there are five articles detailing three code development activities and two projects that synthesized new code capabilities with new analytic research in damage/failure and biomechanics. The article this year are: (1) Energy- and Momentum-Conserving Rigid-Body Contact for NIKE3D and DYNA3D; (2) Computational Modeling of Prosthetics: A New Approach to Implant Design; (3) Characterization of Laser-Induced Mechanical Failure Damage of Optical Components; (4) Parallel Algorithm Research for Solid Mechanics Applications Using Finite Element Analysis; and (5) An Accurate One-Step Elasto-Plasticity Algorithm for Shell Elements in DYNA3D.

  11. Soil mechanics

    NASA Technical Reports Server (NTRS)

    Mitchell, J. K.; Carrier, W. D., III; Houston, W. N.; Scott, R. F.; Bromwell, L. G.; Durgunoglu, H. T.; Hovland, H. J.; Treadwell, D. D.; Costes, N. C.

    1972-01-01

    Preliminary results are presented of an investigation of the physical and mechanical properties of lunar soil on the Descartes slopes, and the Cayley Plains in the vicinity of the LM for Apollo 16. The soil mechanics data were derived form (1) crew commentary and debriefings, (2) television, (3) lunar surface photography, (4) performance data and observations of interactions between soil and lunar roving vehicle, (5) drive-tube and deep drill samples, (6) sample characteristics, and (7) measurements using the SRP. The general characteristics, stratigraphy and variability are described along with the core samples, penetrometer test results, density, porosity and strength.

  12. Automotive Mechanics.

    ERIC Educational Resources Information Center

    Brown, Desmond

    This curriculum guide provides materials for a competency-based course in automotive mechanics at the secondary level. The curriculum design uses the curriculum infused model for the teaching of basic skills as part of vocational education and demonstrates the relationship of vocationally related skills to communication, mathematics, and science…

  13. Mechanical Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 33 units to consider for use in a tech prep competency profile for the occupation of mechanical technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific occupation and would…

  14. Cratering mechanics

    NASA Technical Reports Server (NTRS)

    Ivanov, B. A.

    1986-01-01

    Main concepts and theoretical models which are used for studying the mechanics of cratering are discussed. Numerical two-dimensional calculations are made of explosions near a surface and high-speed impact. Models are given for the motion of a medium during cratering. Data from laboratory modeling are given. The effect of gravitational force and scales of cratering phenomena is analyzed.

  15. Mechanical Drafting.

    ERIC Educational Resources Information Center

    McClain, Gerald R.

    This publication, the third in a series on drafting, is intended to strengthen students' competence in the specialized field of mechanical drafting. The text consists of instructional materials for both teacher and students, written in terms of student performance using measurable objectives. The course includes 11 units. Each instructional unit…

  16. Compliant mechanisms 

    E-print Network

    Venkataraghavan, Janarthanan T

    2001-01-01

    at the cost of making the system very bulky and complex. With the advent of new polymers, the possibility of building joint-free mechanisms that fulfil the requirements of adaptation has increased. Based on this approach, a Magneto Active Polymer (MAP...

  17. Classical Mechanics

    NASA Astrophysics Data System (ADS)

    Chow, Tai L.

    1995-05-01

    Bring Classical Mechanics To Life With a Realistic Software Simulation! You can enhance the thorough coverage of Chow's Classical Mechanics with a hands-on, real-world experience! John Wiley & Sons, Inc. is proud to announce a new computer simulation for classical mechanics. Developed by the Consortium for Upper-Level Physics Software (CUPS), this simulation offers complex, often realistic calculations of models of various physical systems. Classical Mechanics Simulations (54881-2) is the perfect complement to Chow's text. Like all of the CUPS simulations, it is remarkably easy to use, yet sophisticated enough for explorations of new ideas. Other Important Features Include: * Six powerful simulations include: The Motion Generator, Rotation of Three-Dimensional Objects, Coupled Oscillators, Anharmonic Oscillators, Gravitational Orbits, and Collisions * Pascal source code for all programs is supplied and a number of exercises suggest specific ways the programs can be modified. * Simulations usually include graphical (often animated) displays. The entire CUPS simulation series consists of nine book/software simulations which comprise most of the undergraduate physics major's curriculum.

  18. Fluid Mechanics.

    ERIC Educational Resources Information Center

    Drazin, Philip

    1987-01-01

    Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)

  19. Multiple mutations and bypass mechanisms can contribute to development of acquired resistance to MET inhibitors.

    PubMed

    Qi, Jie; McTigue, Michele A; Rogers, Andrew; Lifshits, Eugene; Christensen, James G; Jänne, Pasi A; Engelman, Jeffrey A

    2011-02-01

    Therapies targeting receptor tyrosine kinases have shown efficacy in molecularly defined subsets of cancers. Unfortunately, cancers invariably develop resistance, and overcoming or preventing resistance will ultimately be key to unleashing their full therapeutic potential. In this study, we examined how cancers become resistant to MET inhibitors, a class of drugs currently under clinical development. We utilized the highly sensitive gastric carcinoma cell line, SNU638, and two related MET inhibitors PHA-665752 and PF-2341066. To our surprise, we observed at least two mechanisms of resistance that arose simultaneously. Both resulted in maintenance of downstream PI3K (phosphoinositide 3-kinase)-AKT and MEK (MAP/ERK kinase)-ERK signaling in the presence of inhibitor. One mechanism, observed by modeling resistance both in vitro and in vivo, involved the acquisition of a mutation in the MET activation loop (Y1230). Structural analysis indicates that this mutation destabilizes the autoinhibitory conformation of MET and abrogates an important aromatic stacking interaction with the inhibitor. The other cause of resistance was activation of the epidermal growth factor receptor (EGFR) pathway due to increased expression of transforming growth factor ?. Activation of EGFR bypassed the need for MET signaling to activate downstream signaling in these cells. This resistance could be overcome by combined EGFR and MET inhibition. Thus, therapeutic strategies that combine MET inhibitors capable of inhibiting Y1230 mutant MET in combination with anti-EGFR-based therapies may enhance clinical benefit for patients with MET-addicted cancers. Importantly, these results also underscore the notion that a single cancer can simultaneously develop resistance induced by several mechanisms and highlight the daunting challenges associated with preventing or overcoming resistance. PMID:21266357

  20. Multiple Mutations and Bypass Mechanisms Can Contribute to Development of Acquired Resistance to MET Inhibitors

    PubMed Central

    Qi, Jie; McTigue, Michele A.; Rogers, Andrew; Lifshits, Eugene; Christensen, James G.; Jänne, Pasi A.; Engelman, Jeffrey A.

    2011-01-01

    Therapies targeting receptor tyrosine kinases have shown efficacy in molecularly defined subsets of cancers. Unfortunately, cancers invariably develop resistance, and overcoming or preventing resistance will ultimately be key to unleashing their full therapeutic potential. In this study, we examined how cancers become resistant to MET inhibitors, a class of drugs currently under clinical development. We utilized the highly sensitive gastric carcinoma cell line, SNU638, and two related MET inhibitors PHA-665752 and PF-2341066. To our surprise, we observed at least two mechanisms of resistance that arose simultaneously. Both resulted in maintenance of downstream PI3K (phosphoinositide 3-kinase)-AKT and MEK (MAP/ERK kinase)-ERK signaling in the presence of inhibitor. One mechanism, observed by modeling resistance both in vitro and in vivo, involved the acquisition of a mutation in the MET activation loop (Y1230). Structural analysis indicates that this mutation destabilizes the autoinhibitory conformation of MET and abrogates an important aromatic stacking interaction with the inhibitor. The other cause of resistance was activation of the epidermal growth factor receptor (EGFR) pathway due to increased expression of transforming growth factor ?. Activation of EGFR bypassed the need for MET signaling to activate downstream signaling in these cells. This resistance could be overcome by combined EGFR and MET inhibition. Thus, therapeutic strategies that combine MET inhibitors capable of inhibiting Y1230 mutant MET in combination with anti-EGFR–based therapies may enhance clinical benefit for patients with MET-addicted cancers. Importantly, these results also underscore the notion that a single cancer can simultaneously develop resistance induced by several mechanisms and highlight the daunting challenges associated with preventing or overcoming resistance. PMID:21266357

  1. MECHANICAL ENGINEERING What is Mechanical

    E-print Network

    , development, and manufacture of gas turbine and other aircraft engines; design and construction of electrical aircraft and automotive to consumer products and building equipment. In these jobs, mechanical engineers design products, machines, and processes for manufacturing. They analyze, test, and develop

  2. Mechanical capacitor

    NASA Technical Reports Server (NTRS)

    Kirk, J. A.; Studer, P. A.; Evans, H. E.

    1976-01-01

    A new energy storage system (the mechanical capacitor), using a spokeless magnetically levitated composite ring rotor, is described and design formulas for sizing the components are presented. This new system is configured around a permanent magnet (flux biased) suspension which has active servo control in the radial direction and passive control in the axial direction. The storage ring is used as a moving rotor and electronic commutation of the stationary armature coils is proposed. There is no mechanical contact with the rotating spokeless ring; therefore, long life and near zero rundown losses are projected. A 7-kW h system is sized to demonstrate feasibility. A literature review of flywheel energy storage systems is also presented and general formulas are developed for comparing rotor geometries.

  3. Biofluid Mechanics

    NASA Astrophysics Data System (ADS)

    Oertel, Herbert

    In contrast to the topics discussed in previous chapters, biofluid mechanics is concerned with flows that are influenced by flexible biological surfaces. We distinguish between flows past living bodies in air or in water, such as bird flight or the swimming of fish, and internal flows, such as the closed blood circulation of living beings. In the previous millions of years, evolution has developed crawling, running, swimming, gliding, and flying as methods of motion of living beings, depending on their size and weight.

  4. Mechanical Engineering ME 3720 FLUID MECHANICS

    E-print Network

    Panchagnula, Mahesh

    Mechanical Engineering ME 3720 FLUID MECHANICS Pre-requisite: ME 2330 Co-requisite: ME 3210) to develop an understanding of the physical mechanisms and the mathematical models of fluid mechanics of fluid mechanics problems in engineering practice. The basic principles of fluid mechanics

  5. Information Mechanics

    E-print Network

    John L. Haller Jr

    2015-01-29

    I hypothesize the unification of action and entropy and suggest an interpretation where this hypothesis is able to reconcile the Bohemian and Copenhagen interpretations of quantum mechanics. I explore the hypothesis implications to the discretization of space; both for a particle and for the vacuum itself. I argue the second law of thermodynamics is the justification for the principle of least action. Similarities with the spin networks of quantum loop gravity are found and the exact simplified area of the network is given. An experiment to test the theory is suggested. I conclude with comments on the non-local interpretation of nature.

  6. Cellular and molecular mechanisms of HGF/Met in the cardiovascular system.

    PubMed

    Gallo, Simona; Sala, Valentina; Gatti, Stefano; Crepaldi, Tiziana

    2015-12-01

    Met tyrosine kinase receptor, also known as c-Met, is the HGF (hepatocyte growth factor) receptor. The HGF/Met pathway has a prominent role in cardiovascular remodelling after tissue injury. The present review provides a synopsis of the cellular and molecular mechanisms underlying the effects of HGF/Met in the heart and blood vessels. In vivo, HGF/Met function is particularly important for the protection of the heart in response to both acute and chronic insults, including ischaemic injury and doxorubicin-induced cardiotoxicity. Accordingly, conditional deletion of Met in cardiomyocytes results in impaired organ defence against oxidative stress. After ischaemic injury, activation of Met provides strong anti-apoptotic stimuli for cardiomyocytes through PI3K (phosphoinositide 3-kinase)/Akt and MAPK (mitogen-activated protein kinase) cascades. Recently, we found that HGF/Met is also important for autophagy regulation in cardiomyocytes via the mTOR (mammalian target of rapamycin) pathway. HGF/Met induces proliferation and migration of endothelial cells through Rac1 (Ras-related C3 botulinum toxin substrate 1) activation. In fibroblasts, HGF/Met antagonizes the actions of TGF?1 (transforming growth factor ?1) and AngII (angiotensin II), thus preventing fibrosis. Moreover, HGF/Met influences the inflammatory response of macrophages and the immune response of dendritic cells, indicating its protective function against atherosclerotic and autoimmune diseases. The HGF/Met axis also plays an important role in regulating self-renewal and myocardial regeneration through the enhancement of cardiac progenitor cells. HGF/Met has beneficial effects against myocardial infarction and endothelial dysfunction: the cellular and molecular mechanisms underlying repair function in the heart and blood vessels are common and include pro-angiogenic, anti-inflammatory and anti-fibrotic actions. Thus administration of HGF or HGF mimetics may represent a promising therapeutic agent for the treatment of both coronary and peripheral artery disease. PMID:26561593

  7. quantum mechanics

    PubMed Central

    Bender, Carl M; DeKieviet, Maarten; Klevansky, S. P.

    2013-01-01

    -symmetric quantum mechanics (PTQM) has become a hot area of research and investigation. Since its beginnings in 1998, there have been over 1000 published papers and more than 15 international conferences entirely devoted to this research topic. Originally, PTQM was studied at a highly mathematical level and the techniques of complex variables, asymptotics, differential equations and perturbation theory were used to understand the subtleties associated with the analytic continuation of eigenvalue problems. However, as experiments on -symmetric physical systems have been performed, a simple and beautiful physical picture has emerged, and a -symmetric system can be understood as one that has a balanced loss and gain. Furthermore, the phase transition can now be understood intuitively without resorting to sophisticated mathe- matics. Research on PTQM is following two different paths: at a fundamental level, physicists are attempting to understand the underlying mathematical structure of these theories with the long-range objective of applying the techniques of PTQM to understanding some of the outstanding problems in physics today, such as the nature of the Higgs particle, the properties of dark matter, the matter–antimatter asymmetry in the universe, neutrino oscillations and the cosmological constant; at an applied level, new kinds of -synthetic materials are being developed, and the phase transition is being observed in many physical contexts, such as lasers, optical wave guides, microwave cavities, superconducting wires and electronic circuits. The purpose of this Theme Issue is to acquaint the reader with the latest developments in PTQM. The articles in this volume are written in the style of mini-reviews and address diverse areas of the emerging and exciting new area of -symmetric quantum mechanics. PMID:23509390

  8. Cyberspatial mechanics.

    PubMed

    Bayne, Jay S

    2008-06-01

    In support of a generalization of systems theory, this paper introduces a new approach in modeling complex distributed systems. It offers an analytic framework for describing the behavior of interactive cyberphysical systems (CPSs), which are networked stationary or mobile information systems responsible for the real-time governance of physical processes whose behaviors unfold in cyberspace. The framework is predicated on a cyberspace-time reference model comprising three spatial dimensions plus time. The spatial domains include geospatial, infospatial, and sociospatial references, the latter describing relationships among sovereign enterprises (rational agents) that choose voluntarily to organize and interoperate for individual and mutual benefit through geospatial (physical) and infospatial (logical) transactions. Of particular relevance to CPSs are notions of timeliness and value, particularly as they relate to the real-time governance of physical processes and engagements with other cooperating CPS. Our overarching interest, as with celestial mechanics, is in the formation and evolution of clusters of cyberspatial objects and the federated systems they form. PMID:18558529

  9. Windmill mechanism

    SciTech Connect

    Yang, W. H.

    1985-07-23

    An improved windmill mechanism for adjusting the position of a wind responsive assembly in relation to wind is disclosed. The preferred embodiment comprises a fabric sail mounted on the end of an arm which extends from a power output shaft. A torque sensor is disposed on the arm to sense the torque contribution through that arm to the power output shaft in response to wind acting upon the fabric sail on that arm. The position of the fabric sail is adjusted on the arm by means of a control processor which controls a trim-motor and a magnetic brake. The control processor receives the torque signal provided from the sensor and provides adjustment of the fabric sail in accordance with the torque signal. The control operates to position the sail in a running mode over the semi-circular path segment of rotation of the arm which has a leeward component of motion. It is also effective to position the sail to tacking modes at the beginning and ending of the semi-circular path segment and the flutter mode in the middle of that segment which has a windward component of motion. The control is also effective to automatically adjust for changes in the prevailing wind direction. The sails are supported on flexible mast elements which provide automatic feathering of the sails in response to wind gusts and high wind velocities.

  10. FTY720 and two novel butterfly derivatives exert a general anti-inflammatory potential by reducing immune cell adhesion to endothelial cells through activation of S1P3 and phosphoinositide 3-kinase.

    PubMed

    Imeri, Faik; Blanchard, Olivier; Jenni, Aurelio; Schwalm, Stephanie; Wünsche, Christin; Zivkovic, Aleksandra; Stark, Holger; Pfeilschifter, Josef; Huwiler, Andrea

    2015-12-01

    Sphingosine-1-phosphate (S1P) is a key lipid regulator of a variety of cellular responses including cell proliferation and survival, cell migration, and inflammatory reactions. Here, we investigated the effect of S1P receptor activation on immune cell adhesion to endothelial cells under inflammatory conditions. We show that S1P reduces both tumor necrosis factor (TNF)-?- and lipopolysaccharide (LPS)-stimulated adhesion of Jurkat and U937 cells to an endothelial monolayer. The reducing effect of S1P was reversed by the S1P1+3 antagonist VPC23019 but not by the S1P1 antagonist W146. Additionally, knockdown of S1P3, but not S1P1, by short hairpin RNA (shRNA) abolished the reducing effect of S1P, suggesting the involvement of S1P3. A suppression of immune cell adhesion was also seen with the immunomodulatory drug FTY720 and two novel butterfly derivatives ST-968 and ST-1071. On the molecular level, S1P and all FTY720 derivatives reduced the mRNA expression of LPS- and TNF-?-induced adhesion molecules including ICAM-1, VCAM-1, E-selectin, and CD44 which was reversed by the PI3K inhibitor LY294002, but not by the MEK inhibitor U0126.In summary, our data demonstrate a novel molecular mechanism by which S1P, FTY720, and two novel butterfly derivatives acted anti-inflammatory that is by suppressing gene transcription of various endothelial adhesion molecules and thereby preventing adhesion of immune cells to endothelial cells and subsequent extravasation. PMID:26267293

  11. Mechanical Design

    SciTech Connect

    Shook, Richard; /Marquette U. /SLAC

    2010-08-25

    The particle beam of the SXR (soft x-ray) beam line in the LCLS (Linac Coherent Light Source) has a high intensity in order to penetrate through samples at the atomic level. However, the intensity is so high that many experiments fail because of severe damage. To correct this issue, attenuators are put into the beam line to reduce this intensity to a level suitable for experimentation. Attenuation is defined as 'the gradual loss in intensity of any flux through a medium' by [1]. It is found that Beryllium and Boron Carbide can survive the intensity of the beam. At very thin films, both of these materials work very well as filters for reducing the beam intensity. Using a total of 12 filters, the first 9 being made of Beryllium and the rest made of Boron Carbide, the beam's energy range of photons can be attenuated between 800 eV and 9000 eV. The design of the filters allows attenuation for different beam intensities so that experiments can obtain different intensities from the beam if desired. The step of attenuation varies, but is relative to the thickness of the filter as a power function of 2. A relationship for this is f(n) = x{sub 0}2{sup n} where n is the step of attenuation desired and x{sub 0} is the initial thickness of the material. To allow for this desired variation, a mechanism must be designed within the test chamber. This is visualized using a 3D computer aided design modeling tool known as Solid Edge.

  12. Phospholipase A{sub 2} is involved in the mechanism of activation of neutrophils by polychlorinated biphenyls

    SciTech Connect

    Tithof, P.K.; Schiamberg, E.; Ganey, P.E.; Peters-Golden, M.

    1996-01-01

    Aroclor 1242, a mixture of polychlorinated biphenyls (PCBs), activates neutrophils to produce superoxide anion (O{sub 2}{sup {minus}}) by a mechanism that involves phospholipase C-dependent hydrolysis of membrane phosphoinositides; however, subsequent signal transduction mechanisms are unknown. This study determines whether phospholipase A{sub 2}-dependent release of arachidonic acid is involved in PCB-induced O{sub 2}{sup {minus}} production. O{sub 2}{sup {minus}} production was measured in vitro in glycogen-elicited, rat neutrophils in the presence and absence of the inhibitors of phospholipase A{sub 2}: quinacrine, 4-bromophenacyl bromide (BPB), and manoalide. All three agents significantly decreased the amount of O{sub 2}{sup {minus}} detected during stimulation of neutrophils with Aroclor 1242. Similar inhibition occurred when neutrophils were activated with the classical stimuli, formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate. The effects of BPB and manoalide were not a result of cytotoxicity or other nonspecific effects. Significant release of {sup 3}H-arachidonic acid preceded O{sub 2}{sup {minus}} production in neutrophils stimulated with Aroclor 1242 or fMLP. Manoalide, at a concentration that abolished O{sub 2}{sup {minus}} production, also inhibited the release of {sup 3}H-arachidonate. Aspirin, zileuton, or WEB 2086 did not affect Aroclor 1242-induced O{sub 2}{sup {minus}} production, suggesting that eicosanoids and platelet-activating factor are not needed for neutrophil activation by PCBs. Activation of phos-pholipase A{sub 2} and O{sub 2}{sup {minus}} production do not appear to involve the Ah receptor. These data suggest that Aroclor 1242 stimulates neutrophils to produce O{sub 2}{sup {minus}} by a mechanism that involves phospholipase A{sub 2}-dependent release of arachiodonic acid. 49 refs., 6 figs., 2 tabs.

  13. Fc gamma R(CD16) interaction with ligand induces Ca2+ mobilization and phosphoinositide turnover in human natural killer cells. Role of Ca2+ in Fc gamma R(CD16)-induced transcription and expression of lymphokine genes

    PubMed Central

    1989-01-01

    In this study, we present evidence that interaction of Fc gamma R(CD16) with ligands (immune complexes or anti-CD16 antibodies) induces a rapid rise in [Ca2+]i and fast production of both inositol 1,4,5 triphosphate (IP3) and IP4 in homogeneous NK cell preparations. Part of the initial [Ca2+]i rise observed upon stimulation of NK cells with either anti- CD16 antibodies alone or after their crosslinking at the cell membrane depends on Ca2+ mobilization from intracellular stores, but sustained [Ca2+]i levels are maintained, after the initial spike, through influx of extracellular Ca2+. The [Ca2+]i rise is mediated, at least in part, by increases in IP3 after receptor-induced hydrolysis of membrane polyphosphoinositides (PPI). The role of extracellular Ca2+ in Fc gamma R(CD16)-dependent induction of lymphokine gene expression has been tested by evaluating production, mRNA accumulation and transcription of IFN-gamma and TNF in NK cells stimulated with Fc gamma R(CD16) ligands and/or rIL-2 in the presence of EGTA. Under these conditions, accumulation and transcription of both IFN-gamma and TNF mRNA induced by CD16 ligands, but not that induced by rIL-2, is completely abolished and neither cytokine can be detected at significant levels in the supernatant fluids of cells so treated. These data confirm that NK cell activation by specific ligands occurs through mechanisms distinct from those induced by IL-2, and indicate that extracellular Ca2+ represents a stringent requirement for cytokine production induced in NK cells through specific (Fc gamma R) stimulation. Our data also indicate that the [Ca2+]i rise induced upon Fc gamma R(CD16) crosslinking, though necessary, is not sufficient per se to induce activation of lymphokine genes, compatible with the hypothesis that Fc gamma R(CD16) crosslinking generates additional transducing signals that synergize with IL-2 to maximally activate NK cells. PMID:2536067

  14. Relative contribution of phosphoinositides and phosphatidylcholine hydrolysis to the actions of carbamylcholine, thyrotropin (TSH), and phorbol esters on dog thyroid slices: regulation of cytidine monophosphate-phosphatidic acid accumulation and phospholipase-D activity. I. Actions of carbamylcholine, calcium ionophores, and TSH.

    PubMed

    Lejeune, C; Mockel, J; Dumont, J E

    1994-12-01

    The actions of carbamylcholine (Cchol), the ionophores A23187 and thapsigargin, and TSH on [3H]cytidine monophosphate-phosphatidic acid ([3H]CAMP-PA) accumulation were studied in prelabeled dog thyroid slices to evaluate phosphatidic acid (PA) generation and inositol recycling by phosphatidylinositol (PtdIns) synthesis. The effects of the same agonists were also measured on phosphatidylbutanol generation in [3H]palmitate- or [3H]myristate-prelabeled slices to assess the activity of phospholipase-D (PLD) and on the effluxes of myo-[3H]inositol and [3H]choline induced by these agents from prelabeled slices. Cchol (10(-6)-10(-4) M) increased inositol phosphate (InsP) generation, with no change in inositol efflux, and contracted the intracellular inositol pool. This suggests a stimulation of PtdIns synthesis as well as hydrolysis. The muscarinic agonist provoked a dramatic accumulation of CMP-PA in the presence of lithium chloride (10 mM), which suggests that when InsP hydrolysis is inhibited, inositol limits the rate of CMP-PA incorporation into PtdIns. Cchol also increased phosphatidylbutanol formation. The latter two actions of Cchol were reproduced by A23187 (10(-5) M) and thapsigargin (2 x 10(-6) M) and were inhibited by calphostin-C, an inhibitor of the regulatory site of protein kinase-C. Cchol also induced increased free choline efflux, with a decreased choline phosphate relative content of the medium. TSH (10 mU/ml) stimulated free inositol efflux and induced a slight and proportional increase in [3H]inositol incorporation in phosphoinositides and InsP. The hormone also increased PA and CMP-PA accumulation exclusively in the presence of the PA phosphatase inhibitor propranolol (10(-4) M), but had no detectable action on PLD activity. None of these effects of TSH was reproduced by forskolin or potentiated by lithium chloride (10 mM). The data demonstrate the existence in thyroid tissue of a PLD-hydrolyzing phosphatidylcholine that was stimulated by Cchol and increased intracellular Ca2+, but not by TSH. The results obtained, besides confirming that TSH does not stimulate PtdInsP2-PLC or affect phosphatidylcholine hydrolysis, suggest that the hormone, instead, stimulates de novo PtdIns synthesis and/or inositol transport. The physiological relevance of these actions of Cchol, increased intracellular Ca2+, and TSH in thyroid metabolism could be related to their divergent effects on thyroid cell metabolism. PMID:7988436

  15. Molecular mechanism of apoptosis induction in skin cancer cells by the centipedegrass extract

    PubMed Central

    2013-01-01

    Background Centipedegrass extract (CGE) is mainly composed of maysin and its derivatives, which are recognized internationally as natural compounds. Compared to other flavonoids, maysin has a unique structure in that mannose is bound to the flavonoid backbone. CGE exhibits some biological properties in that it can function as an anti-oxidant, anti-inflammatory, anti-adipogenic, and insecticidal. Whether CGE has other biological functions, such as anti-cancer activity, is unknown. Methods B16F1 (mouse) and SKMEL-5 (human) cells were treated with CGE, and their subsequent survival was determined using MTT assay. We performed a cell cycle analysis using propidium iodide (PI), and detected apoptosis using double staining with annexin V-FITC/PI. In addition, we examined mitochondrial membrane potentials using flow cytometry, as well as signaling mechanisms with an immunoblotting analysis. Results CGE inhibited skin cancer cell growth by arresting the cell cycle in the G2/M phase, and increased both early and late apoptotic cell populations without affecting normal cells. Furthermore, we observed mitochondrial transmembrane depolarization, increased cytochrome-c release, caspase-3 and caspase-7 activation, and increased poly ADP-ribose polymerase degradation. CGE also downregulated activation of p-AKT, p-glycogen synthase kinase-3? (GSK-3?), and p-BAD in a time-dependent manner. LY294002 inhibition of phosphoinositide 3-kinase (PI3K) significantly sensitized skin cancer cells, which led to an increase in CGE-induced apoptosis. Conclusions CGE controlled skin cancer cell growth by inhibiting the PI3K/AKT/GSK-3? signaling pathway and activating the effector caspases. This study is the first to demonstrate anti-cancer properties for CGE, and that CGE may be an effective therapeutic agent for treating skin cancer. PMID:24325618

  16. Distinct Mechanisms for Induction and Tolerance Regulate the Immediate Early Genes Encoding Interleukin 1? and Tumor Necrosis Factor ?

    PubMed Central

    Adamik, Juraj; Wang, Kent Z. Q.; Unlu, Sebnem; Su, An-Jey A.; Tannahill, Gillian M.; Galson, Deborah L.; O’Neill, Luke A.; Auron, Philip E.

    2013-01-01

    Interleukin-1? and Tumor Necrosis Factor ? play related, but distinct, roles in immunity and disease. Our study revealed major mechanistic distinctions in the Toll-like receptor (TLR) signaling-dependent induction for the rapidly expressed genes (IL1B and TNF) coding for these two cytokines. Prior to induction, TNF exhibited pre-bound TATA Binding Protein (TBP) and paused RNA Polymerase II (Pol II), hallmarks of poised immediate-early (IE) genes. In contrast, unstimulated IL1B displayed very low levels of both TBP and paused Pol II, requiring the lineage-specific Spi-1/PU.1 (Spi1) transcription factor as an anchor for induction-dependent interaction with two TLR-activated transcription factors, C/EBP? and NF-?B. Activation and DNA binding of these two pre-expressed factors resulted in de novo recruitment of TBP and Pol II to IL1B in concert with a permissive state for elongation mediated by the recruitment of elongation factor P-TEFb. This Spi1-dependent mechanism for IL1B transcription, which is unique for a rapidly-induced/poised IE gene, was more dependent upon P-TEFb than was the case for the TNF gene. Furthermore, the dependence on phosphoinositide 3-kinase for P-TEFb recruitment to IL1B paralleled a greater sensitivity to the metabolic state of the cell and a lower sensitivity to the phenomenon of endotoxin tolerance than was evident for TNF. Such differences in induction mechanisms argue against the prevailing paradigm that all IE genes possess paused Pol II and may further delineate the specific roles played by each of these rapidly expressed immune modulators. PMID:23936458

  17. Phosphoinositide metabolism and metabolism-contraction coupling in rabbit aorta

    SciTech Connect

    Coburn, R.F.; Baron, C.; Papadopoulos, M.T. )

    1988-12-01

    The authors tested a hypothesis that metabolism-contraction coupling in vascular smooth muscle is controlled by the rate of delivery of energy to ATP-dependent reactions in the inositol phospholipid transduction system that generate second messengers exerting control on smooth muscle force. Rabbit aorta was contracted by norepinephrine (NOR) under conditions of normoxia and hypoxia, and changes in inositol phospholipid pool sizes and metabolic flux rates (J{sub F}) were determined. J{sub F} was determined by labeling free cytosolic myo-inositol by incubation of unstimulated muscle with myo-({sup 3}H)inositol and then measuring rates of incorporation of this isotope into inositol phospholipids and inositol phosphates when the muscle was activated by NOR. J{sub F} measured during maintenance of NOR-induced force was markedly inhibited during hypoxia to 40-50% of that determined during normoxia; rates of increases in inositol phosphate radioactivities were similarly depressed during NOR activation under hypoxia. The hypoxia-induced decrease in J{sub F} was associated with four- to fivefold increase in phosphatidylinositol 4-phosphate (PIP) total pool size, suggesting PIP kinase was inhibited and rate limiting. These data suggest that activation of inositol phospholipid metabolism, which generates inositol 1,4,5-trisphosphate (IP{sub 3}) and diacylglycerol, is blunted under conditions where aerobic energy production is inhibited. Data are consistent with rate-limiting effects of decreased ATP delivery, or decreased phosphate potential, on PIP kinase and reactions that control resynthesis of phosphatidylinositol.

  18. JournalofCellScience ERK and phosphoinositide 3-kinase temporally

    E-print Network

    Amaya, Enrique

    to draw the epithelium and connective tissue forward together in a `purse-string-like' fashion (Martin recovery of tissue integrity and homeostasis, which is vital for survival. Tissue movement in embryonic in a complex tissue setting, namely embryonic wound healing. Key words: ERK, PI3K, Wound healing, Rho GTPases

  19. Role of phospholipase C? in physiological phosphoinositide signaling networks

    PubMed Central

    Smrcka, Alan V.; Brown, Joan Heller; Holz, George G.

    2012-01-01

    Receptor-initiated phospholipase C activation and generation of IP3 and DAG are important common triggers for a diversity of signal transduction processes in many cell types. Contributing to this diversity is the existence and differential cellular and subcellular distribution of distinct phospholipase C isoforms with distinct regulatory prop- erties. The recently identified PLC? enzyme is an isoform that is uniquely regulated by multiple upstream signals including ras-family GTP binding proteins as well as heterotrimeric G-proteins. In this review we will consider the well documented biochemical regulation of this isoform in the context of cell and whole animal physiology and in the context of other G protein-regulated PLC isoforms. These studies together reveal a surprisingly wide range of unexpected functions for PLC? in cellular signaling, physiology and disease. PMID:22286105

  20. Analysis of plasma membrane phosphoinositides from fusogenic carrot cells

    SciTech Connect

    Wheeler, J.J.; Boss, W.F.

    1987-04-01

    Phosphatidylinositol monophosphate (PIP) and phosphatidylinositol bisphosphate (PIP/sub 2/) were found to be associated with the plasma membrane-rich fractions isolated by aqueous polymer two-phase partitioning from fusogenic cells. They represented at least 5% and 0.7% of the total inositol-labeled lipids in the plasma membrane-rich fractions, respectively, and were present in a ratio of about 7:1 (PIP:PIP/sub 2/). In addition, two unidentified inositol-labeled compounds, which together were approximately 3% of the inositol-labeled lipids, were found predominantly in the plasma membrane-rich fractions and migrated between PIP/sub 2/ and PIP. The R/sub f/s of these compounds were approximately 0.31 and 0.34 in the solvent system CHCl/sub 3/:MeOH:15N NH/sub 4/OH:H/sub 2/O (90:90:7:22) using LK5 plates presoaked in 1% potassium oxalate. These compounds incorporated /sup 32/P/sub i/, (/sup 3/H)inositol and were hydrolyzed in mild base. These data suggested that they were glycero-phospholipids. Although the compounds did not comigrate with lysoPIP obtained from bovine brain (R/sub f/ approx. 0.35), when endogenous PIP was hydrolyzed to lysoPIP, the breakdown product migrated in the region of the unidentified inositol lipids.

  1. Phosphoinositide 3-kinase: a critical signalling event in pulmonary cells

    E-print Network

    2000-06-08

    they also seem to exert a critical influence on the malignant phenotype of small cell lung cancer. PI-3K isoforms and their downstream targets thus provide novel therapeutic targets for intervention in a broad spectrum of respiratory diseases....

  2. Reusable Mechanical Pin Puller

    NASA Technical Reports Server (NTRS)

    Ngo, Son; Farley, Rodger; Devine, ED

    1991-01-01

    Reusable mechanical pin puller relatively simple spring-loaded trigger mechanism. Designed to save money and increase safety as substitute for costly and potentially dangerous pyrotechnic pin pullers used in development and testing of deployment mechanisms.

  3. Mechanical, Industrial & Manufacturing

    E-print Network

    Balasubramanian, Ravi

    Mechanical, Industrial & Manufacturing Engineering (MIME) COLLEGE OF ENGINEERING FY2013 Oregon graduate degrees (MS, MEng, PhD) in mechanical engineering, industrial engineering, and materials science. We offer bachelor's degrees in mechanical, industrial, manufacturing, and energy systems engineering

  4. STUDENTHANDBOOK Mechanical Engineering

    E-print Network

    Fainman, Yeshaiahu

    (Secondary): knowledge of attitude determination and control, space structures, orbital mechanics, and rocket2013-2014 STUDENTHANDBOOK Mechanical Engineering Aerospace Engineering Environmental Engineering Engineering Science #12;2 | P a g e Welcome to the Mechanical and Aerospace Engineering Department

  5. Mechanical systems: A compilation

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A compilation of several mechanized systems is presented. The articles are contained in three sections: robotics, industrial mechanical systems, including several on linear and rotary systems and lastly mechanical control systems, such as brakes and clutches.

  6. Regulation of osteoclasts by membrane-derived lipid mediators.

    PubMed

    Oikawa, Tsukasa; Kuroda, Yukiko; Matsuo, Koichi

    2013-09-01

    Osteoclasts are bone-resorbing cells of monocytic origin. An imbalance between bone formation and resorption can lead to osteoporosis or osteopetrosis. Osteoclastogenesis is triggered by RANKL- and IP3-induced Ca(2+) influx followed by activation of NFATc1, a master transcription factor for osteoclastogenic gene regulation. During differentiation, osteoclasts undergo cytoskeletal remodeling to migrate and attach to the bone surface. Simultaneously, they fuse with each other to form multinucleated cells. These processes require PI3-kinase-dependent cytoskeletal protein activation to initiate cytoskeletal remodeling, resulting in the formation of circumferential podosomes and fusion-competent protrusions. In multinucleated osteoclasts, circumferential podosomes mature into stabilized actin rings, which enables the formation of a ruffled border where intensive membrane trafficking is executed. Membrane lipids, especially phosphoinositides, are key signaling molecules that regulate osteoclast morphology and act as second messengers and docking sites for multiple important effectors. We examine the critical roles of phosphoinositides in the signaling cascades that regulate osteoclast functions. PMID:23296124

  7. Defense Mechanisms: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    This bibliography includes studies of defense mechanisms, in general, and studies of multiple mechanisms. Defense mechanisms, briefly and simply defined, are the unconscious ego defendants against unpleasure, threat, or anxiety. Sigmund Freud deserves the clinical credit for studying many mechanisms and introducing them in professional literature.…

  8. Quantum Mechanics + Open Systems

    E-print Network

    Steinhoff, Heinz-Jürgen

    Quantum Mechanics + Open Systems = Thermodynamics ? Jochen Gemmer T¨ubingen, 09.02.2006 #12., World Scientific) #12;Fundamental Law or Emergent Description? Quantum Mechanics i t = (- 2 2m + V or Emergent Description? Quantum Mechanics i t = (- 2 2m + V ) "Heisenberg Cut" Classical Mechanics: m d2

  9. The inhibitory mechanism of crude saponin fraction from Korean Red Ginseng in collagen-induced platelet aggregation

    PubMed Central

    Jeon, Bo Ra; Kim, Su Jung; Hong, Seung Bok; Park, Hwa-Jin; Cho, Jae Youl; Rhee, Man Hee

    2015-01-01

    Background Korean Red Ginseng has been used as a traditional oriental medicine to treat illness and to promote health for several thousand years in Eastern Asia. It is widely accepted that ginseng saponins, ginsenosides, are the major active ingredients responsible for Korean Red Ginseng’s therapeutic activity against many kinds of illness. Although the crude saponin fraction (CSF) displayed antiplatelet activity, the molecular mechanism of its action remains to be elucidated. Methods The platelet aggregation was induced by collagen, the ligand of integrin ?II?I and glycoprotein VI. The crude saponin’s effects on granule secretion [e.g., calcium ion mobilization and adenosine triphosphate (ATP) release] were determined. The activation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated protein kinase 1/2 (ERK1/2), c-Jun N-terminal kinases (JNKs), and p38 MAPK, and phosphoinositide 3-kinase (PI3K)/Akt was analyzed by immunoblotting. In addition, the activation of integrin ?IIb?III was examined by fluorocytometry. Results CSF strongly inhibited collagen-induced platelet aggregation and ATP release in a concentration-dependent manner. It also markedly suppressed [Ca2+]i mobilization in collagen-stimulated platelets. Immunoblotting assay revealed that CSF significantly suppressed ERK1/2, p38, JNK, PI3K, Akt, and mitogen-activated protein kinase kinase 1/2 phosphorylation. In addition, our fraction strongly inhibited the fibrinogen binding to integrin ?IIb?3. Conclusion Our present data suggest that CSF may have a strong antiplatelet property and it can be considered as a candidate with therapeutic potential for the treatment of cardiovascular disorders involving abnormal platelet function. PMID:26199561

  10. Internal pipe attachment mechanism

    DOEpatents

    Bast, R.M.; Chesnut, D.A.; Henning, C.D.; Lennon, J.P.; Pastrnak, J.W.; Smith, J.A.

    1994-12-13

    An attachment mechanism is described for repairing or extending fluid carrying pipes, casings, conduits, etc. utilizing one-way motion of spring tempered fingers to provide a mechanical connection between the attachment mechanism and the pipe. The spring tempered fingers flex to permit insertion into a pipe to a desired insertion depth. The mechanical connection is accomplished by reversing the insertion motion and the mechanical leverage in the fingers forces them outwardly against the inner wall of the pipe. A seal is generated by crushing a sealing assembly by the action of setting the mechanical connection. 6 figures.

  11. Potential mechanisms of action of lithium in bipolar disorder. Current understanding.

    PubMed

    Malhi, Gin S; Tanious, Michelle; Das, Pritha; Coulston, Carissa M; Berk, Michael

    2013-02-01

    Lithium has been used for over half a century for the treatment of bipolar disorder as the archetypal mood stabilizer, and has a wealth of empirical evidence supporting its efficacy in this role. Despite this, the specific mechanisms by which lithium exerts its mood-stabilizing effects are not well understood. Given the inherently complex nature of the pathophysiology of bipolar disorder, this paper aims to capture what is known about the actions of lithium ranging from macroscopic changes in mood, cognition and brain structure, to its effects at the microscopic level on neurotransmission and intracellular and molecular pathways. A comprehensive literature search of databases including MEDLINE, EMBASE and PsycINFO was conducted using relevant keywords and the findings from the literature were then reviewed and synthesized. Numerous studies report that lithium is effective in the treatment of acute mania and for the long-term maintenance of mood and prophylaxis; in comparison, evidence for its efficacy in depression is modest. However, lithium possesses unique anti-suicidal properties that set it apart from other agents. With respect to cognition, studies suggest that lithium may reduce cognitive decline in patients; however, these findings require further investigation using both neuropsychological and functional neuroimaging probes. Interestingly, lithium appears to preserve or increase the volume of brain structures involved in emotional regulation such as the prefrontal cortex, hippocampus and amygdala, possibly reflecting its neuroprotective effects. At a neuronal level, lithium reduces excitatory (dopamine and glutamate) but increases inhibitory (GABA) neurotransmission; however, these broad effects are underpinned by complex neurotransmitter systems that strive to achieve homeostasis by way of compensatory changes. For example, at an intracellular and molecular level, lithium targets second-messenger systems that further modulate neurotransmission. For instance, the effects of lithium on the adenyl cyclase and phospho-inositide pathways, as well as protein kinase C, may serve to dampen excessive excitatory neurotransmission. In addition to these many putative mechanisms, it has also been proposed that the neuroprotective effects of lithium are key to its therapeutic actions. In this regard, lithium has been shown to reduce the oxidative stress that occurs with multiple episodes of mania and depression. Further, it increases protective proteins such as brain-derived neurotrophic factor and B-cell lymphoma 2, and reduces apoptotic processes through inhibition of glycogen synthase kinase 3 and autophagy. Overall, it is clear that the processes which underpin the therapeutic actions of lithium are sophisticated and most likely inter-related. PMID:23371914

  12. Central neural mechanisms governing postural cardiovascular mechanisms

    NASA Technical Reports Server (NTRS)

    Reis, D. J.

    1976-01-01

    The results of the vestibular apparatus and cerebellum in orthostatic reflex control are summarized. Mechanisms within the brain which govern circulation reflexes and the consequences of disturbances in their function are also included.

  13. Section II--Mechanisms Mechanisms of Succession

    E-print Network

    del Moral, Roger

    of Mount St. Helens was initiated by disturbances whose in- tensity and severity varied profoundly in space of successional mechanisms. This figure has evolved from early studies on Mount St. Helens (del Moral 1993

  14. Ninteenth Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The proceedings of the 19th Aerospace Mechanisms Symposium are reported. Technological areas covered include space lubrication, bearings, aerodynamic devices, spacecraft/Shuttle latches, deployment, positioning, and pointing. Devices for spacecraft docking and manipulator and teleoperator mechanisms are also described.

  15. Learning in quantum mechanics

    NASA Astrophysics Data System (ADS)

    Gardner, David E.

    This thesis describes qualitative research conducted to understand the problems students have when learning quantum mechanics. It differs from previous studies on educational issues associated with quantum mechanics in that I have examined the difficulties from the students' perspective. Three questions guided this research: What are the experiences of students learning quantum mechanics? What conceptual difficulties do students have with quantum mechanics? and, How do students approach learning quantum mechanics? From these questions, two themes emerged. First, students do not consider the quantum mechanical concepts of wave-particle duality or the uncertainty principle to be important sources of difficulties for them. Second, many of the difficulties students encounter are not related to conceptual understanding of specific topics, but stem from a mindset that is incongruent with the nature and structure of quantum mechanics. The implications for teaching are that the nature and structure of quantum mechanics should be emphasized and be an explicit part of instruction.

  16. Mechanical Properties of Polymers.

    ERIC Educational Resources Information Center

    Aklonis, J. J.

    1981-01-01

    Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

  17. Department of Mechanical & Aerospace

    E-print Network

    Zhigilei, Leonid V.

    in mechanics, electrical theory, kinematics, thermodynamics, fluid mechanics, heat transfer and materials basic and applied research in advanced aerospace technologies, conducting unique experiments with faculty in their advanced laboratories and to complete dissertation work. Undergraduate students

  18. Missing Mechanism Information

    ERIC Educational Resources Information Center

    Tryon, Warren W.

    2009-01-01

    The first recommendation Kazdin made for advancing the psychotherapy research knowledge base, improving patient care, and reducing the gulf between research and practice was to study the mechanisms of therapeutic change. He noted, "The study of mechanisms of change has received the least attention even though understanding mechanisms may well be…

  19. Basic Engineer Equipment Mechanic.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    This student guide, one of a series of correspondence training courses designed to improve the job performance of members of the Marine Corps, deals with the skills needed by basic engineer equipment mechanics. Addressed in the four individual units of the course are the following topics: mechanics and their tools (mechanics, hand tools, and power…

  20. Mechanical & Aerospace Engineering

    E-print Network

    Mechanical & Aerospace Engineering Strategic Plan 2014-2018 College of Engineering, Architecture & Technology #12;Mechanical and Aerospace Engineering at Oklahoma State University was organized as Mechanical to the advancement of science and tech- nology on a national and international scale. And outreach through technology

  1. Mechanical Engineering David Sumner

    E-print Network

    Saskatchewan, University of

    ME 251 Engineering Analysis I RCM 300 Effective Professional Communication #12;ME Program ­ 3rd YearMechanical Engineering David Sumner david.sumner@usask.ca #12;Mechanical Engineering? · Design, production and use of mechanical systems that control and transform energy · Focused on engineering systems

  2. Introduction to Quantum Mechanics

    E-print Network

    Eduardo J. S. Villaseñor

    2008-04-23

    The purpose of this contribution is to give a very brief introduction to Quantum Mechanics for an audience of mathematicians. I will follow Segal's approach to Quantum Mechanics paying special attention to algebraic issues. The usual representation of Quantum Mechanics on Hilbert spaces is also discussed.

  3. Triple seesaw mechanism

    E-print Network

    D. Cogollo; H. Diniz; C. A. de S. Pires

    2010-02-09

    On fitting the type II seesaw mechanism into the type I seesaw mechanism, we obtain a formula to the neutrino masses which get suppressed by high-scale $M^3$ in its denominator. As a result, light neutrinos are naturally obtained with new physics at TeV scale. As interesting consequence, the mechanism may be directly probed at the LHC by directly producing the TeV states intrinsic of the mechanism. We show that the 3-3-1 model with right-handed neutrinos realizes naturally such seesaw mechanism.

  4. Mechanical seal assembly

    DOEpatents

    Kotlyar, Oleg M. (Salt Lake City, UT)

    2001-01-01

    An improved mechanical seal assembly is provided for sealing rotating shafts with respect to their shaft housings, wherein the rotating shafts are subject to substantial axial vibrations. The mechanical seal assembly generally includes a rotating sealing ring fixed to the shaft, a non-rotating sealing ring adjacent to and in close contact with the rotating sealing ring for forming an annular seal about the shaft, and a mechanical diode element that applies a biasing force to the non-rotating sealing ring by means of hemispherical joint. The alignment of the mechanical diode with respect to the sealing rings is maintained by a series of linear bearings positioned axially along a desired length of the mechanical diode. Alternative embodiments include mechanical or hydraulic amplification components for amplifying axial displacement of the non-rotating sealing ring and transferring it to the mechanical diode.

  5. Mechanical seal assembly

    DOEpatents

    Kotlyar, Oleg M. (Salt Lake City, UT)

    2002-01-01

    An improved mechanical seal assembly is provided for sealing rotating shafts with respect to their shaft housings, wherein the rotating shafts are subject to substantial axial vibrations. The mechanical seal assembly generally includes a rotating sealing ring fixed to the shaft, a non-rotating sealing ring adjacent to and in close contact with the rotating sealing ring for forming an annular seal about the shaft, and a mechanical diode element that applies a biasing force to the non-rotating sealing ring by means of hemispherical joint. The alignment of the mechanical diode with respect to the sealing rings is maintained by a series of linear bearings positioned axially along a desired length of the mechanical diode. Alternative embodiments include mechanical or hydraulic amplification components for amplifying axial displacement of the non-rotating sealing ring and transfering it to the mechanical diode.

  6. Respiratory mechanics in mechanically ventilated patients.

    PubMed

    Hess, Dean R

    2014-11-01

    Respiratory mechanics refers to the expression of lung function through measures of pressure and flow. From these measurements, a variety of derived indices can be determined, such as volume, compliance, resistance, and work of breathing. Plateau pressure is a measure of end-inspiratory distending pressure. It has become increasingly appreciated that end-inspiratory transpulmonary pressure (stress) might be a better indicator of the potential for lung injury than plateau pressure alone. This has resulted in a resurgence of interest in the use of esophageal manometry in mechanically ventilated patients. End-expiratory transpulmonary pressure might also be useful to guide the setting of PEEP to counterbalance the collapsing effects of the chest wall. The shape of the pressure-time curve might also be useful to guide the setting of PEEP (stress index). This has focused interest in the roles of stress and strain to assess the potential for lung injury during mechanical ventilation. This paper covers both basic and advanced respiratory mechanics during mechanical ventilation. PMID:25336536

  7. Fractional Classical Mechanics

    E-print Network

    Nick Laskin

    2013-02-03

    Fractional classical mechanics has been introduced and developed as a classical counterpart of the fractional quantum mechanics. Lagrange, Hamilton and Hamilton-Jacobi frameworks have been implemented for the fractional classical mechanics. The Lagrangian of fractional classical mechanics has been introduced, and equation of motion has been obtained. Fractional oscillator model has been launched and solved in 1D case. A new equation for the period of oscillations of fractional classical oscillator has been found. The interplay between the energy dependency of the period of classical oscillations and the non-equidistant distribution of the energy levels for fractional quantum oscillator has been discussed. We discuss as well, the relationships between new equations of fractional classical mechanics and the well-known fundamental equations of classical mechanics.

  8. Auto Mechanics: Auto Mechanic Service Specialist (Lubrication).

    ERIC Educational Resources Information Center

    Hoover, Virgil

    The unit of individualized learning activities is designed to provide training in the job skill, lubrication, for the prospective auto mechanic service specialist. The materials in the unit are divided into two sections. The developmental, or preliminary phase, for use by the instructor, includes brief descriptions of the job and of the student…

  9. From linear mechanics to nonlinear mechanics

    NASA Technical Reports Server (NTRS)

    Loeb, Julian

    1955-01-01

    Consideration is given to the techniques used in telecommunication where a nonlinear system (the modulator) results in a linear transposition of a signal. It is then shown that a similar method permits linearization of electromechanical devices or nonlinear mechanical devices. A sweep function plays the same role as the carrier wave in radio-electricity. The linearizations of certain nonlinear functionals are presented.

  10. Testing Nonassociative Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Bojowald, Martin; Brahma, Suddhasattwa; Büyükçam, Umut

    2015-11-01

    The familiar concepts of state vectors and operators in quantum mechanics rely on associative products of observables. However, these notions do not apply to some exotic systems such as magnetic monopoles, which have long been known to lead to nonassociative algebras. Their quantum physics has remained obscure. This Letter presents the first derivation of potentially testable physical results in nonassociative quantum mechanics, based on effective potentials. They imply new effects which cannot be mimicked in usual quantum mechanics with standard magnetic fields.

  11. Space Mechanisms Technology Workshop

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B. (Editor)

    2002-01-01

    The Mechanical Components Branch at NASA Glenn Research Center hosted a workshop on Tuesday, May 14, 2002, to discuss space mechanisms technology. The theme for this workshop was 'Working in the Cold,' a focus on space mechanisms that must operate at low temperatures. We define 'cold' as below -60C (210 K), such as would be found near the equator of Mars. However, we are also concerned with much colder temperatures such as in permanently dark craters of the Moon (about 40 K).

  12. Positioning Mechanism For Hoisting

    NASA Technical Reports Server (NTRS)

    Marlin, John D., III; Moore, Barry J.; Myers, Robert I.

    1992-01-01

    Mechanism positions large, heavy objects in container for lifting out by hoist, crane, or winch. Handles objects gently and ensures they are lifted cleanly away in vertical direction without bumping container. Developed for lifting offset pieces of solid-propellant core out of rocket motor through its propellant port. Similar specialized mechanisms can be developed to lift other specially shaped, specially contained heavy objects. Track in base of mechanism guides each trunnion and piece to which attached to middle as hydraulic rods extend. When mechanism lifted, tilted pieces swing inward and come to rest on energy-absorbing paddle.

  13. Structural Mechanics & Solid Mechanics A finite element toolbox to MATLAB

    E-print Network

    Ehrhardt, Matthias

    Structural Mechanics & Solid Mechanics Department of Mechanics and Materials CALFEM A finite.3 Copyright © 1999 by Structural Mechanics, LTH, Sweden. Printed by JABE Offset, Lund, Sweden. ISRN LUTVDG/TVSM--99/9001--SE (1-265) ISSN 0281-6679 Department of Mechanics and Materials Structural Mechanics #12;The

  14. Quantum Mechanics From the Cradle?

    ERIC Educational Resources Information Center

    Martin, John L.

    1974-01-01

    States that the major problem in learning quantum mechanics is often the student's ignorance of classical mechanics and that one conceptual hurdle in quantum mechanics is its statistical nature, in contrast to the determinism of classical mechanics. (MLH)

  15. Discrete dark matter mechanism

    E-print Network

    E. Peinado

    2012-10-25

    We present the Discrete Dark Matter mechanism (DDM) which consist on the stability of the dark matter from a spontaneous breaking of a flavor symmetry group into one of its subgroups. Here we present the inclusion of the quarks on this mechanism promoting the quarks to transform non-trivial under the flavor group.

  16. Mechanical Engineering & Thermal Group

    E-print Network

    Mojzsis, Stephen J.

    /electronics implementations · One-time and extended life mechanisms · Spacecraft structures · Thermal control design of detector, payload, and spacecraft systems · Mechanical static, dynamic, and thermal/optical integrated and thermal vacuum qualification testing of payloads. The LASP ME & Thermal Group is available to provide

  17. Building Wings Mechanical Engineering

    E-print Network

    Provancher, William

    Building Wings Mechanical Engineering Objective · Introduce students to the theory of Conservation Description #12;Airplanes are engineered to generate lift. Lift is a mechanical force generated by a solid of a wing design before spending the money to create a full-size wing. This particular engineering lesson

  18. INJECTION WELL MECHANICAL INTEGRITY

    EPA Science Inventory

    EPA's underground injection control regulations require that all injection wells demonstrate mechanical integrity. The regulations state that an injection well has mechanical integrity if (1) there is no significant leak in the casing, tubing or packer and (2) there is no signifi...

  19. Seesaw mechanism and leptogenesis

    E-print Network

    D. Falcone

    2006-12-05

    A brief overview of the phenomenology related to the seesaw mechanism and the baryogenesis via leptogenesis is presented. In particular, it is explained how large but not maximal lepton mixing can be achieved within the type II seesaw mechanism. Moreover, the consequences for leptogenesis are explored, including flavor effects.

  20. The Clementine mechanisms

    NASA Technical Reports Server (NTRS)

    Purdy, William; Hurley, Michael

    1995-01-01

    The Clementine spacecraft was developed under the 'faster, better, cheaper' theme. The constraints of a low budget coupled with an unusually tight schedule forced many departures from the normal spacecraft development methods. This paper discusses technical lessons learned about several of the mechanisms on the Clementine spacecraft as well as managerial lessons learned for the entire mechanisms subsystem. A quick overview of the Clementine mission is included; the mission schedule and environment during the mechanisms releases and deployment are highlighted. This paper then describes the entire mechanisms subsystem. The design and test approach and key philosophies for a fast-track program are discussed during the description of the mechanisms subsystem. The mechanism subsystem included a marman clamp separation system, a separation nut separation system, a solar panel deployment and pointing system, a high gain antenna feed deployment system, and two separate sensor cover systems. Each mechanism is briefly discussed. Additional technical discussion is given on the marman clamp design, the sensor cover designs, and the design and testing practices for systems driven by heated actuators (specifically paraffin actuators and frangibolts). All of the other mechanisms were of conventional designs and will receive less emphasis. Lessons learned are discussed throughout the paper as they applied to the systems being discussed. Since there is information on many different systems, this paper is organized so that information on a particular topic can be quickly referenced.

  1. Geometrization of Quantum Mechanics

    E-print Network

    J. F. Carinena; J. Clemente-Gallardo; G. Marmo

    2007-03-23

    We show that it is possible to represent various descriptions of Quantum Mechanics in geometrical terms. In particular we start with the space of observables and use the momentum map associated with the unitary group to provide an unified geometrical description for the different pictures of Quantum Mechanics. This construction provides an alternative to the usual GNS construction for pure states.

  2. Safety Critical Mechanisms

    NASA Technical Reports Server (NTRS)

    Robertson, Brandan

    2008-01-01

    Spaceflight mechanisms have a reputation for being difficult to develop and operate successfully. This reputation is well earned. Many circumstances conspire to make this so: the environments in which the mechanisms are used are extremely severe, there is usually limited or no maintenance opportunity available during operation due to this environment, the environments are difficult to replicate accurately on the ground, the expense of the mechanism development makes it impractical to build and test many units for long periods of time before use, mechanisms tend to be highly specialized and not prone to interchangeability or off-the-shelf use, they can generate and store a lot of energy, and the nature of mechanisms themselves, as a combination of structures, electronics, etc. designed to accomplish specific dynamic performance, makes them very complex and subject to many unpredictable interactions of many types. In addition to their complexities, mechanism are often counted upon to provide critical vehicle functions that can result in catastrophic events should the functions not be performed. It is for this reason that mechanisms are frequently subjected to special scrutiny in safety processes. However, a failure tolerant approach, along with good design and development practices and detailed design reviews, can be developed to allow such notoriously troublesome mechanisms to be utilized confidently in safety-critical applications.

  3. Ann Wagner, Mechanical Engineer.

    ERIC Educational Resources Information Center

    Bennett, Betsy K.

    1996-01-01

    Presents a profile of Ann Wagner, a mechanical engineer at the Goddard Space Flight Center in Maryland, and her job responsibilities there. Also includes a brief history of mechanical engineering as well as a sample graph and data activity sheet with answers. (AIM)

  4. Engineer Equipment Mechanic.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on engineer equipment mechanics is designed to advance the professional competence of privates through sergeants as equipment mechanics, Military Occupation Specialty 1341, and is adaptable for nonmilitary instruction. Introductory materials include…

  5. Time in quantum mechanics 

    E-print Network

    Chapin, Kimberly R.

    1997-01-01

    The role of time in quantum mechanics has been and is still very controversial. The purpose of this paper was to explore the historical interpretation of time in quantum mechanics, to determine the current status of this problem-L and to investigate...

  6. Department of Mechanical and

    E-print Network

    Huang, Jianwei

    in the souvenir publication of the Department of Mechanical and Automation Engineering of The Chinese University of Mechanical and Automation Engineering have also played a significant part in equipping businesses and industries in Hong Kong to meet the challenges of new advancements in modernization and automation worldwide

  7. Elmer Electro-Mechanics

    NASA Astrophysics Data System (ADS)

    Martín-Fleitas, J. M.; Maldonado, M.; García-Vargas, M. L.; Cavaller-Marqués, L.

    2005-12-01

    ELMER is a multi-purpose Camera&Spectrograph in the optical range for the GTC. ELMERs electro-mechanical design was based in well known, straightforward and reliable solutions, hence each mechanism is based in a wheel driven by a pre-loaded worm gear transmission, except focusing of the focal plane on the CCD which is based in a translation stage. All mechanisms are driven by the same stepper motor type with an incremental encoder, being commanded each one by a local control unit. After integration, an intensive campaign was carried out at factory for testing the functionality and performances of each mechanism. We present the electro-mechanical design of ELMER and the resulting performance after factory tests.

  8. Magnetic capture docking mechanism

    NASA Technical Reports Server (NTRS)

    Howard, Nathan (Inventor); Nguyen, Hai D. (Inventor)

    2010-01-01

    A mechanism uses a magnetic field to dock a satellite to a host vehicle. A docking component of the mechanism residing on the host vehicle has a magnet that is used to induce a coupled magnetic field with a docking component of the mechanism residing on the satellite. An alignment guide axially aligns the docking component of the satellite with the docking component of the host device dependent on the coupled magnetic field. Rotational alignment guides are used to rotationally align the docking component of the satellite with the docking component of the host device. A ball-lock mechanism is used to mechanically secure the docking component of the host vehicle and the docking component of the satellite.

  9. Mechanical code comparator

    DOEpatents

    Peter, Frank J. (Albuquerque, NM); Dalton, Larry J. (Bernalillo, NM); Plummer, David W. (Albuquerque, NM)

    2002-01-01

    A new class of mechanical code comparators is described which have broad potential for application in safety, surety, and security applications. These devices can be implemented as micro-scale electromechanical systems that isolate a secure or otherwise controlled device until an access code is entered. This access code is converted into a series of mechanical inputs to the mechanical code comparator, which compares the access code to a pre-input combination, entered previously into the mechanical code comparator by an operator at the system security control point. These devices provide extremely high levels of robust security. Being totally mechanical in operation, an access control system properly based on such devices cannot be circumvented by software attack alone.

  10. Effects of orexin A on glucose metabolism in human hepatocellular carcinoma in vitro via PI3K/Akt/mTOR-dependent and -independent mechanism.

    PubMed

    Liu, Yuanyuan; Zhao, Yuyan; Guo, Lei

    2016-01-15

    Orexins are hypothalamic neuropeptides that regulate food intake, energy homeostasis, reward system and sleep/wakefulness states. The purpose of this study was to investigate the effects of orexin A on glucose metabolism in human hepatocellular carcinoma cell line, Hep3B, and determine the possible mechanisms. Hep3B cells were incubated with different concentrations of orexin A (10(-9)-10(-7) M) in vitro in the presence or absence of the orexin receptor 1 (OX1R) inhibitor (SB334867), Akt inhibitor (PF-04691502) and mammalian target of rapamycin (mTOR) inhibitor (temsirolimus). Subsequently, OX1R protein expression, glucose transporter 1 (GLUT1) expression, glucose uptake, the mRNA expression of lactate dehydrogenase (LDHA), pyruvate dehydrogenase kinase 1 (PDK1) and pyruvate dehydrogenase B (PDHB), lactate generation and mitochondrial pyruvate dehydrogenase (PDH) enzyme activity were measured. The activity of phosphoinositide 3-kinase (PI3K)/Akt/mTOR signaling was also determined. OX1R was expressed in hepatoma tissues and Hep3B cells. Stimulation of the Hep3B cells with orexin A resulted in a dose-dependent increase of GLUT1 expression and glucose uptake, which was associated with the activation of PI3K/Akt/mTOR pathway. Further, orexin A increased PDHB expression and PDH enzyme activity, decreased LDHA, PDK1 mRNA levels and lactate generation independent of PI3K/Akt/mTOR pathway. Our results demonstrated that orexin A directed the cellular metabolism towards mitochondrial glucose oxidation rather than glycolysis. These findings provide functional evidence of the metabolic actions of orexin A in hepatocellular carcinoma cells. PMID:26549689

  11. The Mechanisms of Involuntary Attention

    ERIC Educational Resources Information Center

    Prinzmetal, William; Ha, Ruby; Khani, Aniss

    2010-01-01

    We tested 3 mechanisms of involuntary attention: (1) a perceptual enhancement mechanism, (2) a response-decision mechanism, and (3) a serial-search mechanism. Experiment 1 used a response deadline technique to compare the perceptual enhancement and the decision mechanisms and found evidence consistent with the decision mechanism. Experiment 2 used…

  12. Overview of Bohmian Mechanics

    E-print Network

    Xavier Oriols; Jordi Mompart

    2013-01-09

    This chapter provides a comprehensive overview of the Bohmian formulation of quantum mechanics. It starts with a historical review of the difficulties found by Louis de Broglie, David Bohm, and John S. Bell to convince the scientific community about the validity and utility of Bohmian mechanics. Then, a formal explanation of Bohmian mechanics for nonrelativistic, single-particle quantum systems is presented. The generalization to many-particle systems, where the exchange interaction and the spin play an important role, is also presented. After that, the measurement process in Bohmian mechanics is discussed. It is emphasized that Bohmian mechanics exactly reproduces the mean value and temporal and spatial correlations obtained from the standard, that is the Copenhagen or orthodox, formulation. The ontological characteristics of Bohmian mechanics provide a description of measurements as another type of interaction without the need for introducing the wave function collapse. Several solved problems are presented at the end of the chapter, giving additional mathematical support to some particular issues. A detailed description of computational algorithms to obtain Bohmian trajectories from the numerical solution of the Schrodinger or the Hamilton-Jacobi equations are presented in an appendix. The motivation of this chapter is twofold: first, as a didactic introduction to Bohmian formalism, which is used in the subsequent chapters, and second, as a self-contained summary for any newcomer interested in using Bohmian mechanics in his or her daily research activity.

  13. Actin Mechanics and Fragmentation.

    PubMed

    De La Cruz, Enrique M; Gardel, Margaret L

    2015-07-10

    Cell physiological processes require the regulation and coordination of both mechanical and dynamical properties of the actin cytoskeleton. Here we review recent advances in understanding the mechanical properties and stability of actin filaments and how these properties are manifested at larger (network) length scales. We discuss how forces can influence local biochemical interactions, resulting in the formation of mechanically sensitive dynamic steady states. Understanding the regulation of such force-activated chemistries and dynamic steady states reflects an important challenge for future work that will provide valuable insights as to how the actin cytoskeleton engenders mechanoresponsiveness of living cells. PMID:25957404

  14. Is quantum mechanics exact?

    SciTech Connect

    Kapustin, Anton

    2013-06-15

    We formulate physically motivated axioms for a physical theory which for systems with a finite number of degrees of freedom uniquely lead to quantum mechanics as the only nontrivial consistent theory. Complex numbers and the existence of the Planck constant common to all systems arise naturally in this approach. The axioms are divided into two groups covering kinematics and basic measurement theory, respectively. We show that even if the second group of axioms is dropped, there are no deformations of quantum mechanics which preserve the kinematic axioms. Thus, any theory going beyond quantum mechanics must represent a radical departure from the usual a priori assumptions about the laws of nature.

  15. Rotary mechanical latch

    DOEpatents

    Spletzer, Barry L.; Martinez, Michael A.; Marron, Lisa C.

    2012-11-13

    A rotary mechanical latch for positive latching and unlatching of a rotary device with a latchable rotating assembly having a latching gear that can be driven to latched and unlatched states by a drive mechanism such as an electric motor. A cam arm affixed to the latching gear interfaces with leading and trailing latch cams affixed to a flange within the drive mechanism. The interaction of the cam arm with leading and trailing latch cams prevents rotation of the rotating assembly by external forces such as those due to vibration or tampering.

  16. Central mechanisms of itch.

    PubMed

    Mochizuki, Hideki; Kakigi, Ryusuke

    2015-09-01

    Itch is a complex sensory and emotional experience. Functional brain imaging studies have been performed to identify brain regions associated with this complex experience, and these studies reported that several brain regions are activated by itch stimuli. The possible roles of these regions in itch perception and difference in cerebral mechanism between healthy subjects and chronic itch patients are discussed in this review article. Additionally, the central itch modulation system and cerebral mechanisms of contagious itch, pleasurable sensation evoked by scratching have also been investigated in previous brain imaging studies. We also discuss how these studies advance our understanding of these mechanisms. PMID:25534483

  17. Electronic door locking mechanism

    DOEpatents

    Williams, G.L.; Kirby, P.G.

    1997-10-21

    The invention is a motorized linkage for engaging a thumb piece in a door mechanism. The device has an exterior lock assembly with a small battery cell and combination lock. Proper entry by a user of a security code allows the battery to operate a small motor within the exterior lock assembly. The small motor manipulates a cam-plunger which moves an actuator pin into a thumb piece. The user applies a force on to the thumb piece. This force is transmitted by the thumb piece to a latch engagement mechanism by the actuator pin. The latch engagement mechanism operates the door latch. 6 figs.

  18. Electronic door locking mechanism

    DOEpatents

    Williams, Gary Lin (428 E. Third Ave., Kennewick, WA 99336); Kirby, Patrick Gerald (1010 W. Fifteenth Pl., Kennewick, WA 99337)

    1997-01-01

    The invention is a motorized linkage for engaging a thumb piece in a door mechanism. The device has an exterior lock assembly with a small battery cell and combination lock. Proper entry by a user of a security code allows the battery to operate a small motor within the exterior lock assembly. The small motor manipulates a cam-plunger which moves an actuator pin into a thumb piece. The user applies a force on to the thumb piece. This force is transmitted by the thumb piece to a latch engagement mechanism by the actuator pin. The latch engagement mechanism operates the door latch.

  19. Understand mechanical seals

    SciTech Connect

    Godse, A.G.

    1995-04-01

    Most pump failures (about 70%) are attributed to malfunctioning mechanical seals. Rotating machinery consists primarily of centrifugal pumps. The regular revision of the API standard on pumps and the increasing role of environmental regulations bring mechanical seals into sharp focus for centrifugal pumps. A integrated process plant brings a variety of influences into the selection process: end user; process consultant; engineering and construction contractors and pump/seal manufacturer. The paper discusses seal selection, understanding the seal mechanism, vapor pressure, forces acting on the seal faces and the concept of balance ratio, importance of PV curves, types of seals, heat balance, flushing plans, materials of construction, and other factors.

  20. Quantum Mechanics Without Observers

    E-print Network

    W. H. Sulis

    2013-03-03

    The measurement problem and the role of observers have plagued quantum mechanics since its conception. Attempts to resolve these have introduced anthropomorphic or non-realist notions into physics. A shift of perspective based upon process theory and utilizing methods from combinatorial games, interpolation theory and complex systems theory results in a novel realist version of quantum mechanics incorporating quasi-local, nondeterministic hidden variables that are compatible with the no-hidden variable theorems and relativistic invariance, and reproduce the standard results of quantum mechanics to a high degree of accuracy without invoking observers.

  1. Advanced Mechanics. Mathematical Introduction

    E-print Network

    G. Giachetta; L. Mangiarotti; G. Sardanashvily

    2010-01-20

    Classical non-relativistic mechanics in a general setting of time-dependent transformations and reference frame changes is formulated in the terms of fibre bundles over the time-axis R. Connections on fibre bundles are the main ingredient in this formulation of mechanics which thus is covariant under reference frame transformations. The basic notions of a non-relativistic reference frame, a relative velocity, a free motion equation, a relative acceleration, an external force are formulated. Newtonian, Lagrangian, Hamiltonian mechanical systems and the relations between them are defined. Lagrangian and Hamiltonian conservation laws are considered.

  2. The orbital mechanics of flight mechanics

    NASA Technical Reports Server (NTRS)

    Dunning, R. S.

    1973-01-01

    A reference handbook on modern dynamic orbit theory is presented. Starting from the most basic inverse-square law, the law of gravity for a sphere is developed, and the motion of point masses under the influence of a sphere is considered. The reentry theory and the orbital theory are discussed along with the relative motion between two bodies in orbit about the same planet. Relative-motion equations, rectangular coordinates, and the mechanics of simple rigid bodies under the influence of a gravity gradient field are also discussed.

  3. Essays on mechanism design

    E-print Network

    Balestrieri, Filippo

    2008-01-01

    This thesis is a collection of three essays on mechanism design. In Chapter 1, we consider a general Informed Principal Problem in the context of procurement. Both the potential suppliers and the buyer hold some private ...

  4. Biorepair mechanisms and longevity.

    PubMed

    Weale, Robert A

    2004-05-01

    The purpose of the study was to find out whether a link could be established between hypothetical biological repair mechanisms, their decay, and longevity. Human biological functions (biomarkers) can be classified accordingly as their generally linear age-related decline starts at birth or in adulthood ( approximately 1% per annum), or occurs at a rate of less than approximately 0.5% per annum Sums of exponentially declining functions representing the decline of repair mechanisms are fitted to the averages of each of the above groups. The time constants of the mechanisms are lowest for those ceasing normal function at the age of approximately 35-40 years, i.e., approximately at twice the maximal age at which puberty is reached. An extrapolation of the overall loss of the mechanisms, postulated to account for the declining biomarkers, is, at present, such as to reach zero in the twelfth decade of life. PMID:15123754

  5. Failure mechanisms in MEMS.

    SciTech Connect

    Walraven, Jeremy Allen

    2003-07-01

    MEMS components by their very nature have different and unique failure mechanisms than their macroscopic counterparts. This paper discusses failure mechanisms observed in various MEMS components and technologies. MEMS devices fabricated using bulk and surface micromachining process technologies are emphasized. MEMS devices offer uniqueness in their application, fabrication, and functionality. Their uniqueness creates various failure mechanisms not typically found in their bulk or IC counterparts. In ICs, electrical precautions are taken to mitigate failure. In MEMS, both electrical and mechanical precautions must be enacted to reduce the risk of failure and increased reliability. Unlike ICs, many MEMS components are designed to interact with their environment, making the fabrication, testing, and packaging processes critical for the success of the device.

  6. Boosted Statistical Mechanics

    NASA Astrophysics Data System (ADS)

    Testa, Massimo

    2015-08-01

    Starting with the basic principles of Relativistic Quantum Mechanics, we give a rigorous, but completely elementary proof of the relation between fundamental observables of a statistical system, when measured within two inertial reference frames, related by a Lorentz transformation.

  7. Mechanics in medicine

    E-print Network

    Bao, Gang

    Over decades, the theoretical and applied mechanics community has developed sophisticated approaches for analysing the behaviour of complex engineering systems. Most of these approaches have targeted systems in the ...

  8. Boosted Statistical Mechanics

    E-print Network

    Massimo Testa

    2015-07-30

    Based on the fundamental principles of Relativistic Quantum Mechanics, we give a rigorous, but completely elementary, proof of the relation between fundamental observables of a statistical system when measured relatively to two inertial reference frames, connected by a Lorentz transformation.

  9. MECHANISMS OF PESTICIDE DEGRADATION

    EPA Science Inventory

    This research project was initiated with the overall objective of determining (1) the chemical structures of toxic components of toxaphene, (2) to study anaerobic metabolism to degrade toxaphene and other pesticides, and (3) to understand toxic action mechanism of chlordimeform. ...

  10. Space Mechanisms Technology Workshop

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B. (Editor)

    2001-01-01

    The Mechanical Components Branch at NASA Glenn Research Center hosted a workshop to discuss the state of drive systems technology needed for space exploration. The Workshop was held Thursday, November 2, 2000. About 70 space mechanisms experts shared their experiences from working in this field and considered technology development that will be needed to support future space exploration in the next 10 to 30 years.

  11. Ultrasound—biophysics mechanisms

    PubMed Central

    O'Brien, William D.

    2007-01-01

    Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk studies focus on issues related to the effects of ultrasound on biological materials. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for image production and risk assessment. Relative to the bioeffect or risk studies, that is, the biophysical mechanisms by which ultrasound affects biological materials, ultrasound-induced bioeffects are generally separated into thermal and nonthermal mechanisms. Ultrasonic dosimetry is concerned with the quantitative determination of ultrasonic energy interaction with biological materials. Whenever ultrasonic energy is propagated into an attenuating material such as tissue, the amplitude of the wave decreases with distance. This attenuation is due to either absorption or scattering. Absorption is a mechanism that represents that portion of ultrasonic wave that is converted into heat, and scattering can be thought of as that portion of the wave, which changes direction. Because the medium can absorb energy to produce heat, a temperature rise may occur as long as the rate of heat production is greater than the rate of heat removal. Current interest with thermally mediated ultrasound-induced bioeffects has focused on the thermal isoeffect concept. The non-thermal mechanism that has received the most attention is acoustically generated cavitation wherein ultrasonic energy by cavitation bubbles is concentrated. Acoustic cavitation, in a broad sense, refers to ultrasonically induced bubble activity occurring in a biological material that contains pre-existing gaseous inclusions. Cavitation-related mechanisms include radiation force, microstreaming, shock waves, free radicals, microjets and strain. It is more challenging to deduce the causes of mechanical effects in tissues that do not contain gas bodies. These ultrasonic biophysics mechanisms will be discussed in the context of diagnostic ultrasound exposure risk concerns. PMID:16934858

  12. Phase Field Fracture Mechanics.

    SciTech Connect

    Robertson, Brett Anthony

    2015-11-01

    For this assignment, a newer technique of fracture mechanics using a phase field approach, will be examined and compared with experimental data for a bend test and a tension test. The software being used is Sierra Solid Mechanics, an implicit/explicit finite element code developed at Sandia National Labs in Albuquerque, New Mexico. The bend test experimental data was also obtained at Sandia Labs while the tension test data was found in a report online from Purdue University.

  13. MECH 386 INDUSTRIAL FLUID MECHANICS INDUSTRIAL FLUID MECHANICS

    E-print Network

    Phani, A. Srikantha

    MECH 386 ­ INDUSTRIAL FLUID MECHANICS 1 INDUSTRIAL FLUID MECHANICS MECH 386 Contact information Dr This course is an introduction to industrial fluid mechanics. According to J. C. R. Hunt (a famous fluid mechanics specialist): "industrial fluid mechanics broadly covers those aspects of the design, manufacture

  14. Nuclear Mechanics in Cancer

    PubMed Central

    Denais, Celine; Lammerding, Jan

    2015-01-01

    Despite decades of research, cancer metastasis remains an incompletely understood process that is as complex as it is devastating. In recent years, there has been an increasing push to investigate the biomechanical aspects of tumorigenesis, complementing the research on genetic and biochemical changes. In contrast to the high genetic variability encountered in cancer cells, almost all metastatic cells are subject to the same physical constraints as they leave the primary tumor, invade surrounding tissues, transit through the circulatory system, and finally infiltrate new tissues. Advances in live cell imaging and other biophysical techniques, including measurements of subcellular mechanics, have yielded stunning new insights into the physics of cancer cells. While much of this research has been focused on the mechanics of the cytoskeleton and the cellular microenvironment, it is now emerging that the mechanical properties of the cell nucleus and its connection to the cytoskeleton may play a major role in cancer metastasis, as deformation of the large and stiff nucleus presents a substantial obstacle during the passage through the dense interstitial space and narrow capillaries. Here, we present an overview of the molecular components that govern the mechanical properties of the nucleus and we discuss how changes in nuclear structure and composition observed in many cancers can modulate nuclear mechanics and promote metastatic processes. Improved insights into this interplay between nuclear mechanics and metastatic progression may have powerful implications in cancer diagnostics and therapy and may reveal novel therapeutic targets for pharmacological inhibition of cancer cell invasion. PMID:24563360

  15. Docking mechanism for spacecraft

    NASA Technical Reports Server (NTRS)

    Lange, Gregory A. (inventor); Mcmanamen, John P. (inventor); Schliesing, John A. (inventor)

    1989-01-01

    A system is presented for docking a space vehicle to a space station where a connecting tunnel for in-flight transfer of personnel is required. Cooperable coupling mechanisms include docking rings on the space vehicle and space station. The space station is provided with a tunnel structure, a retraction mechanism, and a docking ring. The vehicle coupling mechanism is designed to capture the station coupling mechanism, arrest relative spacecraft motions while limiting loads to acceptable levels, and then realign the spacecraft for final docking and tunnel interconnection. The docking ring of the space vehicle coupling mechanism is supported by linear attentuator actuator devices, each of which is controlled by a control system which receives loading information signals and attenuator stroke information signals from each device and supplies output signals for controlling its linear actuation to attenuate impact loading or to realign the spacecraft for final docking and tunnel interconnection. The retraction mechanism is used to draw the spacecraft together after initial contact and coupling. Tunnel trunnions, cooperative with the latches on the space vehicle constitute the primary structural tie between the spacecraft in final docked configuration.

  16. Wear and Tear - Mechanical

    NASA Technical Reports Server (NTRS)

    Swanson, Theodore

    2008-01-01

    The focus of this chapter is on the long term wear and tear, or aging, of the mechanical subsystem of a spacecraft. The mechanical subsystem is herein considered to be the primary support structure (as in a skeleton or exoskeleton) upon which all other spacecraft systems rest, and the associated mechanisms. Mechanisms are devices which have some component that moves at least once, in response to some type of passive or active control system. For the structure, aging may proceed as a gradual degradation of mechanical properties and/or function, possibly leading to complete structural failure over an extended period of time. However, over the 50 years of the Space Age such failures appear to be unusual. In contrast, failures for mechanisms are much more frequent and may have a very serious effect on mission performance. Just as on Earth, all moving devices are subject to normal (and possibly accelerated) degradation from mechanical wear due to loss or breakdown of lubricant, misalignment, temperature cycling effects, improper design/selection of materials, fatigue, and a variety of other effects. In space, such environmental factors as severe temperature swings (possibly 100's of degrees C while going in and out of direct solar exposure), hard vacuum, micrometeoroids, wear from operation in a dusty or contaminated environment, and materials degradation from radiation can be much worse. In addition, there are some ground handling issues such as humidity, long term storage, and ground transport which may be of concern. This chapter addresses the elements of the mechanical subsystem subject to wear, and identifies possible causes. The potential impact of such degradation is addressed, albeit with the recognition that the impact of such wear often depends on when it occurs and on what specific components. Most structural elements of the mechanical system typically are conservatively designed (often to a safety factor of greater than approximately 1.25 on yield for unmanned spacecraft) but do not have backup structure due to the added mass this would impose, and also due to the fact that structural elements can be accurately modeled mathematically and in test. Critical mechanisms or devices may have backups, or alternate work-arounds, since characterization of these systems in a 1g environment is less accurate than structure, and repair in-space is often impossible.

  17. Incremental Mechanism Design Vincent Conitzer

    E-print Network

    Incremental Mechanism Design Vincent Conitzer Duke University Department of Computer Science@cs.cmu.edu Abstract Mechanism design has traditionally focused almost exclusively on the design of truthful mechanisms mechanisms exist; 2. truthful mechanisms are unable to take advantage of the fact that com- putationally

  18. Conventional mechanical ventilation

    PubMed Central

    Tobias, Joseph D.

    2010-01-01

    The provision of mechanical ventilation for the support of infants and children with respiratory failure or insufficiency is one of the most common techniques that are performed in the Pediatric Intensive Care Unit (PICU). Despite its widespread application in the PICUs of the 21st century, before the 1930s, respiratory failure was uniformly fatal due to the lack of equipment and techniques for airway management and ventilatory support. The operating rooms of the 1950s and 1960s provided the arena for the development of the manual skills and the refinement of the equipment needed for airway management, which subsequently led to the more widespread use of endotracheal intubation thereby ushering in the era of positive pressure ventilation. Although there seems to be an ever increasing complexity in the techniques of mechanical ventilation, its successful use in the PICU should be guided by the basic principles of gas exchange and the physiology of respiratory function. With an understanding of these key concepts and the use of basic concepts of mechanical ventilation, this technique can be successfully applied in both the PICU and the operating room. This article reviews the basic physiology of gas exchange, principles of pulmonary physiology, and the concepts of mechanical ventilation to provide an overview of the knowledge required for the provision of conventional mechanical ventilation in various clinical arenas. PMID:20927268

  19. Waldyr Muniz Oliva Geometric Mechanics

    E-print Network

    Natário, José

    Waldyr Muniz Oliva Geometric Mechanics February 1, 2002 Springer Berlin Heidelberg New mechanics : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 51 4.1 Galilean space-time structure and Newton equations . . . . . . . . 51 4.2 Critical remarks on Newtonian mechanics

  20. The scar mechanism revisited

    E-print Network

    F. Borondo; D. A. Wisniacki; E. G. Vergini; R. M. Benito

    2007-12-20

    Unstable periodic orbits are known to originate scars on some eigenfunctions of classically chaotic systems through recurrences causing that some part of an initial distribution of quantum probability in its vicinity returns periodically close to the initial point. In the energy domain, these recurrences are seen to accumulate quantum density along the orbit by a constructive interference mechanism when the appropriate quantization (on the action of the scarring orbit) is fulfilled. Other quantized phase space circuits, such as those defined by homoclinic tori, are also important in the coherent transport of quantum density in chaotic systems. The relationship of this secondary quantum transport mechanism with the standard mechanism for scarring is here discussed and analyzed.

  1. Dissipative and quantum mechanics

    E-print Network

    Roumen Tsekov

    2015-06-08

    Three existing interpretations of quantum mechanics, given by Heisenberg, Bohm and Madelung, are examined to describe dissipative quantum systems as well. It is found that the Madelung quantum hydrodynamics is the only correct approach. A new stochastic reinterpretation of the quantum mechanics is proposed, which represents the microscopic face of the Madelung hydrodynamics. The main idea is that the vacuum fluctuates permanently, which explains the probabilistic character of the quantum mechanics. Thus, it is an objective theory independent of the human beings and their measurements. The effect of the thermal fluctuations in the surrounding is also accounted for via a heuristic Langevin equation with two random forces. Some statistical characteristics of these quantum and thermal noises are determined by reproducing known results for the system phase-space dynamics.

  2. Fracture mechanics expert system

    NASA Technical Reports Server (NTRS)

    Powers, E.; Elfer, N.; Casadaban, C.

    1992-01-01

    Attention is given to fracture mechanics, an analytical method used extensively in the National Space Transportation System to conservatively predict the remaining service life of an article when a flaw or a material defect is detected. These analyses are performed on hardware containing material defects that have been detected by various nondestructive inspection techniques. An expert system being developed to streamline the process so that hardware dispositions may be obtained in a timely and consistent manner is discussed. The expert system reduces the potential for errors due to the manual transcription between the various software programs involved in completing a fracture mechanics analysis. NEXPERT Object, the expert system development shell selected for this purpose, allows the various software programs used in fracture mechanics analyses to be accessed and manipulated from the same platform.

  3. Mechanisms of epigenetic inheritance.

    PubMed

    Martin, Cyrus; Zhang, Yi

    2007-06-01

    The mechanisms by which stable gene expression patterns are inherited during cell division are not well understood. Chromatin is subject to a number of covalent modifications and it is generally believed that the transfer of these modifications between cell generations plays a critical role in inheritance, though how this occurs is a matter of debate. In one proposed model, replication of chromatin in a semi-conservative fashion would allow 'template reading' and 'writing' mechanisms to copy modifications from old histones to new histones. Conversely, if chromatin is replicated in a conservative fashion, then other mechanisms, such as the replacement and/or modification of histones during transcription, may mediate the replication of these modifications. Finally, several recent studies suggest that the faithful replication of DNA methylation patterns may be used to propagate histone modifications associated with gene silencing. PMID:17466502

  4. Graphene Statistical Mechanics

    NASA Astrophysics Data System (ADS)

    Bowick, Mark; Kosmrlj, Andrej; Nelson, David; Sknepnek, Rastko

    2015-03-01

    Graphene provides an ideal system to test the statistical mechanics of thermally fluctuating elastic membranes. The high Young's modulus of graphene means that thermal fluctuations over even small length scales significantly stiffen the renormalized bending rigidity. We study the effect of thermal fluctuations on graphene ribbons of width W and length L, pinned at one end, via coarse-grained Molecular Dynamics simulations and compare with analytic predictions of the scaling of width-averaged root-mean-squared height fluctuations as a function of distance along the ribbon. Scaling collapse as a function of W and L also allows us to extract the scaling exponent eta governing the long-wavelength stiffening of the bending rigidity. A full understanding of the geometry-dependent mechanical properties of graphene, including arrays of cuts, may allow the design of a variety of modular elements with desired mechanical properties starting from pure graphene alone. Supported by NSF grant DMR-1435794

  5. Grassmann Matrix Quantum Mechanics

    E-print Network

    Anninos, Dionysios; Monten, Ruben

    2015-01-01

    We explore quantum mechanical theories whose fundamental degrees of freedom are rectangular matrices with Grassmann valued matrix elements. We study particular models where the low energy sector can be described in terms of a bosonic Hermitian matrix quantum mechanics. We describe the classical curved phase space that emerges in the low energy sector. The phase space lives on a compact Kahler manifold parameterized by a complex matrix, of the type discovered some time ago by Berezin. The emergence of a semiclassical bosonic matrix quantum mechanics at low energies requires that the original Grassmann matrices be in the long rectangular limit. We discuss possible holographic interpretations of such matrix models which, by construction, are endowed with a finite dimensional Hilbert space.

  6. Antimutagenesis and anticarcinogenesis mechanisms

    SciTech Connect

    Shankel, D.M.; Hartmann, P.E.; Hollaender, A.; Kada, T.

    1986-01-01

    This book discusses information regarding: carcinogens and anticarcinogens; cancer and free radicals; alteration of mutagenic potentials by peroxidase, catalase, and superoxide dismutase; effects of vitamins C and E on carcinogen formation and action and relationship to human cancer; interception of toxic agents/mutagens/carcinogens; avoidance of errors after DNA damage; molecular mechanism of adaptive response to alkylating agents; genetic analyses of the roles of UmuDC and MucAB in mutagenesis; mechanisms of spontaneous mutagenesis; inducible cellular responses to DNA damage in mammalian cells; multiple inducible cytochromes P-450 in yeast; mechanisms of carcinogenicity and anticarcinogenicity - role of dietary components; the concentration of bile acids in the fecal stream as a risk factor for colon cancer; dietary promoters nad antipromoters; a mutagen is a mutagen, not necessarily a carcinogen; genetic aspects of cancer epidemiology; inhibitors of mutagenesis and their relevance to carcinogenesis; and population consequences of mutagenesis and antimutagenesis.

  7. Grassmann Matrix Quantum Mechanics

    E-print Network

    Dionysios Anninos; Frederik Denef; Ruben Monten

    2015-12-11

    We explore quantum mechanical theories whose fundamental degrees of freedom are rectangular matrices with Grassmann valued matrix elements. We study particular models where the low energy sector can be described in terms of a bosonic Hermitian matrix quantum mechanics. We describe the classical curved phase space that emerges in the low energy sector. The phase space lives on a compact Kahler manifold parameterized by a complex matrix, of the type discovered some time ago by Berezin. The emergence of a semiclassical bosonic matrix quantum mechanics at low energies requires that the original Grassmann matrices be in the long rectangular limit. We discuss possible holographic interpretations of such matrix models which, by construction, are endowed with a finite dimensional Hilbert space.

  8. Particulate erosion mechanisms

    NASA Technical Reports Server (NTRS)

    Veerabhadrarao, P.; Buckley, D. H.

    1983-01-01

    Particulate damage and erosion of ductile metals are today plaguing design and field engineers in diverse fields of engineering and technology. It was found that too many models and theories were proposed leading to much speculation from debris analysis and failure mechanism postulations. Most theories of solid particle erosion are based on material removal models which do not fully represent the actual physical processes of material removal. The various mechanisms proposed thus far are: melting, low-cycle fatigue, extrusion, delamination, shear localization, adhesive material transfer, etc. The experimental data on different materials highlighting the observed failure modes of the deformation and cutting wear processes using optical and scanning electron microscopy are presented. The most important mechanisms proved from the experimental observations of the specimens exposed to both spherical and angular particles are addressed, and the validity of the earlier theories discussed. Both the initial stages of damage and advanced stages of erosion were studied to gain a fundamental understanding of the process.

  9. [Bone metabolism: molecular mechanisms].

    PubMed

    Neumann, E; Schett, G

    2007-07-01

    In order to accommodate individual load, the skeletal system is in a continual state of change. Bone metabolism guarantees optimal bone structure. The osteoblasts are responsible for the synthesis and the osteoclasts for resorption of the bone. A finely adjusted interplay between molecular mechanisms leads, via cytokines, hormones and growth factors, to an homeostasis in bone metabolism. Disturbances of this process lead via increased bone resorption to osteoporosis, and via increased synthesis to osteopetrosis. This contribution describes the known molecular mechanisms in this remodelling process. PMID:17562055

  10. Advanced mechanisms for robotics

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1991-01-01

    An overview of applied research and development at the Goddard Space Flight Center (GSFC) on mechanisms and collision avoidance skin for robots is presented. The work on robot end effectors is outlined, followed by a brief discussion of robot-friendly payload latching mechanisms and compliant joints. This is followed by discussions of the collision avoidance/management skin and the GSFC research on magnetorestrictive direct drive motors. A new project, the artificial muscle, is introduced. Each of the devices is described sufficiently to permit a basic understanding of its purpose, capabilities, and operating fundamentals. The implications for commercialization are discussed.

  11. Mechanical Harvesting of Corn. 

    E-print Network

    Sorenson, J. W. (Jerome Wallace); Smith, H. P. (Harris Pearson)

    1948-01-01

    STATION R. D. LEWIS, Director ' College Station, Texas BULLETIN 706 OCTOBER 1948 Mechanical Harvesting of Corn H. P. SMITH and J. W. SORENSON, JR. Department of Agricultural Engineering LlBRARY Atricaltr~ial &$J~he~i~ai CallcgoofTexas Collbge... Statign, Toxes THE TEXAS AGRICULTURAL AND MECHANICAL COLLEGE SYSTEM GIBB GILCHRIST, Chancellor P9-1048-6500-L180 [Blank Page in Original Bulletin] Preface 1~x2s farmers annually plant from 4% to 5 million acres of corn, from which they harvest about...

  12. Mechanics of amoeboid motion

    SciTech Connect

    Dembo, M.

    1986-01-01

    The reactive flow model is a putative description of amoeboid cytoplasm based on the formalism of multifield fluid mechanics. We show by direct numerical computations that the reactive flow model is able to account for various phenomena observed in dissociated cytoplasm and/or in vitro contractile networks. These phenomena include states of relaxation or mechanical equilibrium, as well as transitions between such states, by processes of expansion or contraction. Simulations also indicate the existence of states of chaotic or turbulent cytoplasmic streaming. Finally, simulations yield steady states of coherent motion similar to motions observed in cytoplasm dissociated from the giant amoeba, Chaos carolinensis.

  13. Optically Defined Mechanical Geometry

    E-print Network

    Barasheed, Abeer Z; Sankey, Jack C

    2015-01-01

    In the field of optomechanics, radiation forces have provided a particularly high level of control over the frequency and dissipation of mechanical elements. Here we propose a class of optomechanical systems in which light exerts a profound influence over two other fundamental parameters: geometry and mass. By applying an optical trap to one lattice site of an extended phononic crystal, we show it is possible to create a tunable, localized mechanical mode. Owing to light's simultaneous and constructive coupling with the structure's continuum of modes, we estimate that a trap intensity at the level of a single photon should be capable of producing a measurable effect within a realistic, chip-scale device.

  14. Soil mechanics experiment

    NASA Technical Reports Server (NTRS)

    Mitchell, J. K.; Bromwell, L. G.; Carrier, W. D., III; Costes, N. C.; Houston, W. N.; Scott, R. F.

    1972-01-01

    The Apollo 15 soil-mechanics experiment has offered greater opportunity for study of the mechanical properties of the lunar soil than previous missions, not only because of the extended lunar-surface stay time and enhanced mobility provided by the lunar roving vehicle (rover), but also because four new data sources were available for the first time. These sources were: (1) the self-recording penetrometer (SRP), (2) new, larger diameter, thin-walled core tubes, (3) the rover, and (4) the Apollo lunar-surface drill (ALSD). These data sources have provided the best bases for quantitative analyses thus far available in the Apollo Program.

  15. Dual Quantum Mechanics

    E-print Network

    W. Chagas-Filho

    2009-05-11

    We point out a possible complementation of the basic equations of quantum mechanics in the presence of gravity. This complementation is suggested by the well-known fact that quantum mechanics can be equivalently formulated in the position or in the momentum representation. As a way to support this complementation, starting from the action that describes conformal gravity in the world-line formalism, we show that there are duality transformations that relate the dynamics in the presence of position dependent vector and tensor fields to the dynamics in the presence of momentum dependent vector and tensor fields.

  16. Geometrical Mechanics on algebroids

    E-print Network

    K. Grabowska; J. Grabowski; P. Urba?ski

    2006-05-03

    A natural geometric framework is proposed, based on ideas of W. M. Tulczyjew, for constructions of dynamics on general algebroids. One obtains formalisms similar to the Lagrangian and the Hamiltonian ones. In contrast with recently studied concepts of Analytical Mechanics on Lie algebroids, this approach requires much less than the presence of a Lie algebroid structure on a vector bundle, but it still reproduces the main features of the Analytical Mechanics, like the Euler-Lagrange-type equations, the correspondence between the Lagrangian and Hamiltonian functions (Legendre transform) in the hyperregular cases, and a version of the Noether Theorem. Besides, the constructions seem to be more natural and simpler.

  17. Noncommutative quantum mechanics

    NASA Astrophysics Data System (ADS)

    Gamboa, J.; Loewe, M.; Rojas, J. C.

    2001-09-01

    A general noncommutative quantum mechanical system in a central potential V=V(r) in two dimensions is considered. The spectrum is bounded from below and, for large values of the anticommutative parameter ?, we find an explicit expression for the eigenvalues. In fact, any quantum mechanical system with these characteristics is equivalent to a commutative one in such a way that the interaction V(r) is replaced by V=V(HHO,Lz), where HHO is the Hamiltonian of the two-dimensional harmonic oscillator and Lz is the z component of the angular momentum. For other finite values of ? the model can be solved by using perturbation theory.

  18. Mechanical Properties of Aerogels

    NASA Technical Reports Server (NTRS)

    Parmenter, Kelly E.; Milstein, Frederick

    1995-01-01

    Aerogels are extremely low density solids that are characterized by a high porosity and pore sizes on the order of nanometers. Their low thermal conductivity and sometimes transparent appearance make them desirable for applications such as insulation in cryogenic vessels and between double paned glass in solar architecture. An understanding of the mechanical properties of aerogels is necessary before aerogels can be used in load bearing applications. In the present study, the mechanical behavior of various types of fiber-reinforced silica aerogels was investigated with hardness, compression, tension and shear tests. Particular attention was paid to the effects of processing parameters, testing conditions, storage environment, and age on the aerogels' mechanical response. The results indicate that the addition of fibers to the aerogel matrix generally resulted in softer, weaker materials with smaller elastic moduli. Furthermore, the testing environment significantly affected compression results. Tests in ethanol show an appreciable amount of scatter, and are not consistent with results for tests in air. In fact, the compression specimens appeared to crack and begin to dissolve upon exposure to the ethanol solution. This is consistent with the inherent hydrophobic nature of these aerogels. In addition, the aging process affected the aerogels' mechanical behavior by increasing their compressive strength and elastic moduli while decreasing their strain at fracture. However, desiccation of the specimens did not appreciably affect the mechanical properties, even though it reduced the aerogel density by removing trapped moisture. Finally, tension and shear test results indicate that the shear strength of the aerogels exceeds the tensile strength. This is consistent with the response of brittle materials. Future work should concentrate on mechanical testing at cryogenic temperatures, and should involve more extensive tensile tests. Moreover, before the mechanical response of reinforced aerogels can be fully understood, more tests of unreinforced aerogels are necessary. Unreinforced aerogels are of particular use because their birefringent nature allows for visual determination of stress fields during mechanical testing. The success of any future tests depends on the availability of a large supply of quality specimens with well-documented preparation and storage histories.

  19. Reconstructing the Antikythera Mechanism

    NASA Astrophysics Data System (ADS)

    Freeth, Tony

    The Antikythera Mechanism is a geared astronomical calculating machine from ancient Greece. The extraordinary nature of this device has become even more apparent in recent years as a result of research under the aegis of the Antikythera Mechanism Research Project (AMRP) - an international collaboration of scientists, historians, museum staff, engineers, and imaging specialists. Though many questions still remain, we may now be close to reconstructing the complete machine. As a technological artifact, it is unique in the ancient world. Its brilliant design conception means that it is a landmark in the history of science and technology.

  20. Nonlinear Solid Mechanics SOLID MECHANICS AND ITS APPLICATIONS

    E-print Network

    Nonlinear Solid Mechanics #12;SOLID MECHANICS AND ITS APPLICATIONS Volume 160 Series Editors: G and Scope of the Series The fundamental questions arising in mechanics are: Why?, How?, and How much and insight in answering these questions on the subject of mechanics as it relates to solids. The scope

  1. Mechanical Systems and Libraries.

    ERIC Educational Resources Information Center

    Dubin, Fred

    1987-01-01

    Discusses the following aspects of the design of mechanical and electrical systems to meet the various requirements of libraries: (1) library planning teams; (2) raised floors; (3) lighting considerations; (4) air quality; (5) acoustics; and (6) climate controls. The importance of adaptability to meet future needs is stressed. (MES)

  2. Higgs Mechanism for Gravitons

    E-print Network

    Ichiro Oda

    2010-04-05

    Just like the vector gauge bosons in the gauge theories, it is now known that gravitons acquire mass in the process of spontaneous symmetry breaking of diffeomorphisms through the condensation of scalar fields. The point is that we should find the gravitational Higgs mechanism such that it results in massive gravity in a flat Minkowski space-time without non-unitary propagating modes. This is usually achieved by including higher-derivative terms in scalars and tuning the cosmological constant to be a negative value in a proper way. Recently, a similar but different gravitational Higgs mechanism has been advocated by Chamseddine and Mukhanov where one can relax the negative cosmological constant to zero or positive one. In this work, we investigate why the non-unitary ghost mode decouples from physical Hilbert space in a general space-time dimension. Moreover, we generalize the model to possess an arbitrary potential and clarify under what conditions the general model exhibits the gravitational Higgs mechanism. By searching for solutions to the conditions, we arrive at two classes of potentials exhibiting gravitational Higgs mechanism. One class includes the model by Chamseddine and Mukhanov in a specific case while the other is completely a new model.

  3. Horticultural Mechanics Competencies

    ERIC Educational Resources Information Center

    Shipley, W. Edward

    1974-01-01

    Ornamental horticulture teachers and managers of ornamental horticulture businesses were surveyed to determine which agricultural mechanics knowledges and skills are needed for entry-level employment in nursery, greenhouse, turf, and landscape management, which are common to the four areas, and the appropriate grade level at which they should be…

  4. ANEUPLOIDY: ETIOLOGY AND MECHANISMS

    EPA Science Inventory

    The 'Symposium on Aneuploidy: Etiology and Mechanisms' was held from March 25-29, 1985. This Symposium developed as a consequence of the concern of the Environmental Protection Agency with the support of the National Institute of Environmental Health Sciences about human exposure...

  5. Gravitational Spin Mechanics

    NASA Astrophysics Data System (ADS)

    Tocci, Joseph

    2009-05-01

    In high gravitational situations, such as blackholes, spin-state mechanic undergo changes. The orthogonal basis which spin-state information is emended in becomes deformed along its path to the singularity. At this point the spin-state information is lost in both stationary and spinning blackhole cases.

  6. Paper Boats Mechanical Engineering

    E-print Network

    Provancher, William

    Paper Boats Mechanical Engineering Objective · This lesson teaches students about the physics with designing boats? · How can the best boat be constructed from butcher paper and duct tape? Time Required time) · Testing the boats in the swimming pool (1 class period) Assessments · Students will be graded

  7. Construction Mechanic 1 & C.

    ERIC Educational Resources Information Center

    Seitz, Thomas E.

    This Rate Training Manual and Nonresident Career Course (RTM/NRCC) form a self-study package that will enable Naval Construction Mechanics First and Chief to fulfill the requirements of their rating. (Persons holding these ratings direct and coordinate efforts of individuals and crews in maintaining, repairing, and overhauling automotive,…

  8. Modernizing Mechanical Services.

    ERIC Educational Resources Information Center

    Rutgers, Norman L.

    Some of the problems of renovating school buildings and in particular the modernization of mechanical services in existing facilities are discussed. According to school management publications, approximately 42 per cent of our elementary and 59 per cent of our secondary schools are 15 years old or older. School plants, which were built 12 to 15…

  9. Mechanisms of triboluminescence.

    PubMed

    Lin, S H; Wutz, D; Ho, Z Z; Eyring, H

    1980-03-01

    The purpose of this paper has been to develop the theoretical treatment of the triboexcitation mechanisms due to the electric field effect and the pressure effect and to show how to analyze the triboluminescent spectra to determine the external factors that affect or induce the triboluminescence. PMID:16592782

  10. Mechanisms of triboluminescence

    PubMed Central

    Lin, S. H.; Wutz, D.; Ho, Z. Z.; Eyring, H.

    1980-01-01

    The purpose of this paper has been to develop the theoretical treatment of the triboexcitation mechanisms due to the electric field effect and the pressure effect and to show how to analyze the triboluminescent spectra to determine the external factors that affect or induce the triboluminescence. PMID:16592782

  11. Turboprop Propulsion Mechanic.

    ERIC Educational Resources Information Center

    Chanute AFB Technical Training Center, IL.

    This instructional package consists of a plan of instruction, glossary, and student handouts and exercises for use in training Air Force personnel to become turboprop propulsion mechanics. Addressed in the individual lessons of the course are the following: common hand tools, hardware, measuring devices, and safety wiring; aircraft and engine…

  12. Auto Mechanics Supplementary Units.

    ERIC Educational Resources Information Center

    Donovan, Roger; Smith, Sam

    This document contains supplemental materials for special needs high school students intended to facilitate their mainstreaming in regular auto mechanics courses. Teacher's materials precede the materials for students and include general notes for the instructor, suggestions, 18 references, a class progress chart, a questionnaire on the usefulness…

  13. Mechanical and Aerospace Engineering

    E-print Network

    Mechanical and Aerospace Engineering seminar Plasma Actuators for Aerodynamic Flow Control Abstract Plasma actuators have become very popular in aerodynamic flow control research over the last in plasma actuators is motivated by the potential for simple construction, lack of moving parts, low power

  14. Diesel Mechanics: Fundamentals.

    ERIC Educational Resources Information Center

    Foutes, William; And Others

    This publication is the first in a series of three texts for a diesel mechanics curriculum. Its purpose is to teach the basic concepts related to employment in a diesel trade. Six sections contain 29 units. Each instructional unit includes some or all of these basic components: unit and specific (performance) objectives, suggested activities for…

  15. Formic Acid Mechanical,

    E-print Network

    Lee, Tonghun

    Formic Acid Fire Ant Starch Mechanical, Industrial Chemical, Petroleum Biological What Do and engineering. Products will range from starch, to polylactic acid, to corn fiber, to motor fuels. Progressive systems. Fire ants make formic acid. U of I researchers are developing fuel cells that use formic acid (1

  16. Metrics for Auto Mechanics.

    ERIC Educational Resources Information Center

    Cooper, Gloria S., Ed.; Magisos, Joel H., Ed.

    Designed to meet the job-related metric measurement needs of auto mechanics students, this instructional package is one of four for the transportation occupations cluster, part of a set of 55 packages for metric instruction in different occupations. The package is intended for students who already know the occupational terminology, measurement…

  17. Truck Mechanic Apprentice Training.

    ERIC Educational Resources Information Center

    Cernota, Henry R.

    A study was conducted to identify the current needs of truck mechanic apprenticeship training programs, the problems experienced in these programs, and possible solutions to these problems. Research data was collected by the following methods: A questionnaire was completed by operating and maintenance people in the trucking industry in the Chicago…

  18. Cerebellar learning mechanisms.

    PubMed

    Freeman, John H

    2015-09-24

    The mechanisms underlying cerebellar learning are reviewed with an emphasis on old arguments and new perspectives on eyeblink conditioning. Eyeblink conditioning has been used for decades a model system for elucidating cerebellar learning mechanisms. The standard model of the mechanisms underlying eyeblink conditioning is that there two synaptic plasticity processes within the cerebellum that are necessary for acquisition of the conditioned response: (1) long-term depression (LTD) at parallel fiber-Purkinje cell synapses and (2) long-term potentiation (LTP) at mossy fiber-interpositus nucleus synapses. Additional Purkinje cell plasticity mechanisms may also contribute to eyeblink conditioning including LTP, excitability, and entrainment of deep nucleus activity. Recent analyses of the sensory input pathways necessary for eyeblink conditioning indicate that the cerebellum regulates its inputs to facilitate learning and maintain plasticity. Cerebellar learning during eyeblink conditioning is therefore a dynamic interactive process which maximizes responding to significant stimuli and suppresses responding to irrelevant or redundant stimuli. This article is part of a Special Issue entitled SI: Brain and Memory. PMID:25289586

  19. The Mechanization of Mining.

    ERIC Educational Resources Information Center

    Marovelli, Robert L.; Karhnak, John M.

    1982-01-01

    Mechanization of mining is explained in terms of its effect on the mining of coal, focusing on, among others, types of mining, productivity, machinery, benefits to retired miners, fatality rate in underground coal mines, and output of U.S. mining industry. (Author/JN)

  20. Mechanical Drawing and Design.

    ERIC Educational Resources Information Center

    Mikulsky, Marilyn; McEnaney, Walter K.

    A syllabus is provided for a comprehensive foundation course in mechanical drawing and design for grades 9, 10, 11, or 12 that is prerequisite to advanced elective courses. Introductory materials include course objectives, an overview of basic concepts, and guidelines for implementation. Brief discussions of and suggestions for the areas of design…

  1. Haemostatic mechanism in uraemia

    PubMed Central

    Hutton, R. A.; O'Shea, M. J.

    1968-01-01

    The haemostatic mechanism was investigated in 20 patients with renal failure, of whom nine had evidence of a bleeding tendency. A defect of platelet function was the most common finding. The effect of dialysis on the bleeding state is briefly discussed, and a scheme for the routine investigation of haemostasis in renal failure is put forward. PMID:5699082

  2. Neuter docking mechanism study

    NASA Technical Reports Server (NTRS)

    Jones, J. C.

    1972-01-01

    Neuter (or androgynous) docking systems that allow space vehicles with similar or identical docking hardware to dock are discussed. Basic requirements applicable to docking mechanism design, four neuter concepts that were studied, and the concept selected by the NASA Manned Spacecraft Center for detailed investigation are presented.

  3. Department of Mechanical Engineering

    E-print Network

    Li, Teng

    Smart Materials and Structures Research Center inStRuctional diviSionS Design and Reliability of SystemsDepartment of Mechanical Engineering 2014 Fast Facts Faculty Based on 2013 statistics from · Design · Information Sciences · Risk and Reliability · Manufacturing Electronic Products and Systems

  4. Structured Mechanical Collage.

    PubMed

    Huang, Zhe; Wang, Jiang; Fu, Hongbo; Lau, Rynson W H

    2014-07-01

    We present a method to build 3D structured mechanical collages consisting of numerous elements from the database given artist-designed proxy models. The construction is guided by some graphic design principles, namely unity, variety and contrast. Our results are visually more pleasing than previous works as confirmed by a user study. PMID:26357362

  5. Checking Tripod Release Mechanism

    USGS Multimedia Gallery

    As part of an investigation of the mechanisms of coastal change in the Carolinas, instrumented tripods were deployed on Diamond Shoals near Cape Hatteras, NC. These tripods recorded data quantifying the currents, waves, turbidity, temperature and salinity at several levels near the seafloor between ...

  6. QUICK QUANTUM MECHANICS ---Introduction ---

    E-print Network

    Jackson, Andrew D.

    of Classical Mechanics After Newton found his equations of motion, physicists knew they would have to wait are completely equivalent to Newton's laws. 2 A generalized coordinate can be, e.g., a Cartesian coordinate the behaviour of all of the generalized coordinates, q(t), subject to initial boundary conditions. Since Newton

  7. Mechanical & Aerospace Engineering Department

    E-print Network

    Kim, John

    and organelles. With optical tweezers -- a scientific instrument that uses a focused laser beam to provide that understanding the forces and mechanisms that are responsible for maintaining the geometries of the organelles will help them uncover the crucial factors that lead to changes or malfunctions in organelles. "When cells

  8. Respiratory Mechanisms of Support

    E-print Network

    Kay, Mark A.

    the respiratory system is working to compensate for a metabolic issue so as to normalize the blood pH. HCO3 - 22Respiratory Mechanisms of Support Nasal Cannula Hi Flow Nasal Cannula CPAP Continuous positive for toxicity Usually 5-20 +ppm ABG Interpretations Respiratory Acidosis:pCO2 pH *impaired ventilation (example

  9. Imaging the Antikythera Mechanism

    SciTech Connect

    Malzbender, Tom

    2011-01-12

    In 1900, a party of sponge divers chanced on the wreck of a Roman merchant vessel between Crete and mainland Greece. It was found to contain numerous ancient Greek treasures, among them a mysterious lump of clay that split open to reveal 'mathematical gears' as it dried out. This object is now known as the Antikythera Mechanism, one of the most enlightening artifacts in terms of revealing the advanced nature of ancient Greek science and technology. In 2005 we travelled to the National Archeological Museum in Athens to apply our Reflectance Imaging methods to the mechanism in the hopes of revealing ancient writing on the device. We were successful, and along with the results of Microfocus CT imaging, we are able to decipher 3000 characters compared with the original 800 known. This lead to an understanding that the device was a mechanical, astronomical computer from 150 B.C.E. capable of predicting solar and lunar eclipses along with other celestial events. This talk will overview both the imaging methods as well as what they reveal about the Antikythera Mechanism.

  10. Residential Mechanical Precooling

    SciTech Connect

    German, A.; Hoeschele, M.

    2014-12-01

    This research conducted by the Alliance for Residential Building Innovation team evaluated mechanical air conditioner pre-cooling strategies in homes throughout the United States. EnergyPlus modeling evaluated two homes with different performance characteristics in seven climates. Results are applicable to new construction homes and most existing homes built in the last 10 years, as well as fairly efficient retrofitted homes.

  11. Diesel Mechanics: Electrical Systems.

    ERIC Educational Resources Information Center

    Foutes, William; And Others

    This publication is the second in a series of three texts for a diesel mechanics curriculum. Its purpose is to teach the concepts related to electricity and circuitry in a diesel trade. The text contains nine units. Each instructional unit includes some or all of these basic components: unit and specific (performance) objectives, suggested…

  12. Mechanical & Aerospace Engineering Department

    E-print Network

    Kim, John

    robot enjoy ice cream together. BACK COVER: UCLA Racing | Baja SAE Team takes honors in El Paso in the science and art of mechanical and aerospace engineering.Further,we seek to expand the frontiers of engineering science and to encourage technological innovation while fostering academic excellence

  13. Manpower Implications of Mechanization.

    ERIC Educational Resources Information Center

    Cargill, B. F.

    The fruit and vegetable industry is on the road to total mechanization. The scientific and social communities need to collaborate as technological innovations influence manpower development and utilization. An awareness of the implications of technological advancement and manpower problems is required so that the U. S. fruit and vegetable grower…

  14. Rugged Iris Mechanism

    NASA Technical Reports Server (NTRS)

    Ferragut, Nelson J.

    2005-01-01

    A rugged iris mechanism has been designed to satisfy several special requirements, including a wide aperture in the "open" position, full obscuration in the "closed" position, ability to function in a cryogenic or other harsh environment, and minimization of friction through minimization of the number of components. An important element of the low-friction aspect of the design is maximization of the flatness of, and provision of small gaps between, adjacent iris blades. The tolerances of the design can be very loose, accommodating thermal expansions and contractions associated with large temperature excursions. The design is generic in that it is adaptable to a wide range of aperture sizes and can be implemented in a variety of materials to suit the thermal, optical, and mechanical requirements of various applications. The mechanism (see figure) includes an inner flat ring, an outer flat ring, and an even number of iris blades. The iris blades shown in front in the figure are denoted as "upper," and the iris blades shown partly hidden behind the front ones are denoted as "lower." Each iris blade is attached to the inner ring by a pivot assembly and to the outer ring by a roller/slider assembly. The upper and lower rings are co-centered and are kept in sliding contact. The iris is opened or closed by turning the outer ring around the center while holding the inner ring stationary. The mechanism is enclosed in a housing (not shown in the figure) that comprises an upper and a lower housing shell. The housing provides part of the sliding support for the outer ring and keeps the two rings aligned as described above. The aforementioned pivot assemblies at the inner ring also serve as spacers for the housing. The lower housing shell contains part of the lower sliding surface and features for mounting the overall mechanism and housing assembly. The upper housing shell contains part of the upper sliding surface.

  15. How Minds Work Schema Mechanism

    E-print Network

    Memphis, University of

    1 How Minds Work Schema Mechanism Stan Franklin Computer Science Division & Institute for Intelligent Systems The University of Memphis #12;HMW: Schema Mechanism 2 Schema Mechanism · Implements early stages of Piaget's theory of child development · A mechanism of mind · Controls a body

  16. Advances in ice mechanics - 1987

    SciTech Connect

    Chung, J.S.; Hallam, S.D.; Maatanen, M.; Sinha, N.K.; Sodhi, D.S.

    1987-01-01

    This book presents the papers given at a symposium on the interaction of icebergs with offshore platforms. Topics considered at the symposium included advances in ice mechanics in the United Kingdom, ice mechanics in Finland, recent advances in ice mechanics in Canada, advances in sea ice mechanics in the USA, foundations, monitoring, hazards, risk assessment, and deformation.

  17. 35th Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    Boesiger, Edward A. (Compiler); Doty, Laura W. (Technical Monitor)

    2001-01-01

    The proceedings of the 35th Aerospace Mechanisms Symposium are reported. Ames Research Center hosted the conference, which was held at the Four Points Sheraton, Sunnyvale, California, on May 9-11, 2001. The symposium was sponsored by the Mechanisms Education Association. Technology areas covered included bearings and tribology; pointing, solar array, and deployment mechanisms; and other mechanisms for spacecraft and large space structures.

  18. From Quantum Mechanics to Thermodynamics?

    E-print Network

    Steinhoff, Heinz-Jürgen

    From Quantum Mechanics to Thermodynamics? Dresden, 22.11.2004 Jochen Gemmer Universit¨at Osnabr Description? Quantum Mechanics i¯h t = (- ¯h2 2m + V ) Classical Mechanics: m d2 dt2 x = - V Thermodynamics: dU = TdS - pdV dS dt > 0 #12;Fundamental Law or Emergent Description? Quantum Mechanics i

  19. Bohmian Mechanics Detlef Durr1

    E-print Network

    Goldstein, Sheldon

    Bohmian Mechanics Detlef D¨urr1 , Sheldon Goldstein2 , Roderich Tumulka3 , and Nino Zangh`i4, Via Dodecaneso 33, 16146 Genova, Italy. E-mail: zanghi@ge.infn.it #12;Bohmian mechanics is a theory mechanics, observers see the same statistics for experimental results as predicted by quantum mechanics

  20. QUANTUM MECHANICS II Physics 342

    E-print Network

    Rosner, Jonathan L.

    QUANTUM MECHANICS II Physics 342 KPTC 103 9:00 ­ 10:20 a.m. 1 Tues., Thurs. ­ Winter Quarter 2011 quantum mechanics at the graduate level. The text for Quantum Mechanics II will be J. J. Sakurai and Jim Napolitano, Modern Quantum Mechanics, Second Edition (Addison-Wesley, San Francisco, 2011). For supplemental

  1. Chaos and Quantum Mechanics

    E-print Network

    Habib, S; Greenbaum, B; Jacobs, K; Shizume, K; Sundaram, B; Habib, Salman; Bhattacharya, Tanmoy; Greenbaum, Benjamin; Jacobs, Kurt; Shizume, Kosuke; Sundaram, Bala

    2005-01-01

    The relationship between chaos and quantum mechanics has been somewhat uneasy -- even stormy, in the minds of some people. However, much of the confusion may stem from inappropriate comparisons using formal analyses. In contrast, our starting point here is that a complete dynamical description requires a full understanding of the evolution of measured systems, necessary to explain actual experimental results. This is of course true, both classically and quantum mechanically. Because the evolution of the physical state is now conditioned on measurement results, the dynamics of such systems is intrinsically nonlinear even at the level of distribution functions. Due to this feature, the physically more complete treatment reveals the existence of dynamical regimes -- such as chaos -- that have no direct counterpart in the linear (unobserved) case. Moreover, this treatment allows for understanding how an effective classical behavior can result from the dynamics of an observed quantum system, both at the level of t...

  2. Hierarchical Auxetic Mechanical Metamaterials

    PubMed Central

    Gatt, Ruben; Mizzi, Luke; Azzopardi, Joseph I.; Azzopardi, Keith M.; Attard, Daphne; Casha, Aaron; Briffa, Joseph; Grima, Joseph N.

    2015-01-01

    Auxetic mechanical metamaterials are engineered systems that exhibit the unusual macroscopic property of a negative Poisson's ratio due to sub-unit structure rather than chemical composition. Although their unique behaviour makes them superior to conventional materials in many practical applications, they are limited in availability. Here, we propose a new class of hierarchical auxetics based on the rotating rigid units mechanism. These systems retain the enhanced properties from having a negative Poisson's ratio with the added benefits of being a hierarchical system. Using simulations on typical hierarchical multi-level rotating squares, we show that, through design, one can control the extent of auxeticity, degree of aperture and size of the different pores in the system. This makes the system more versatile than similar non-hierarchical ones, making them promising candidates for industrial and biomedical applications, such as stents and skin grafts. PMID:25670400

  3. Advanced mechanisms for robotics

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1992-01-01

    An overview of applied research and development at NASA-Goddard (GSFC) on mechanisms and the collision avoidance skin for robots is presented. First the work on robot end effectors is outlined, followed by a brief discussion on robot-friendly payload latching mechanisms and compliant joints. This, in turn, is followed by the collision avoidance/management skin and the GSFC research on magnetostrictive direct drive motors. Finally, a new project, the artificial muscle, is introduced. Each of the devices is described in sufficient detail to permit a basic understanding of its purpose, fundamental principles of operation, and capabilities. In addition, the development status of each is reported along with descriptions of breadboards and prototypes and their test results. In each case, the implications of the research for commercialization is discussed. The chronology of the presentation will give a clear idea of both the evolution of the R&D in recent years and its likely direction in the future.

  4. Mechanisms of embodiment

    PubMed Central

    Dijkstra, Katinka; Post, Lysanne

    2015-01-01

    This paper is a critical review of recent studies demonstrating the mechanism of sensorimotor simulation in different cognitive domains. Empirical studies that specify conditions under which embodiment occurs in different domains will be discussed and evaluated. Examples of relevant domains are language comprehension (Tucker and Ellis, 1998), autobiographical memory (Dijkstra et al., 2007), gestures (Alibali et al., 2014), facial mimicry (Stel and Vonk, 2010), and problem solving (Wiemers et al., 2014). The focus of the review is on supporting claims regarding sensorimotor simulation as well as on factors that modulate dynamic relationships between sensorimotor components in action and cognitive domains, such as expertise (Boschker et al., 2002). This discussion takes place within the context of currently debated issues, specifically the need to specify the underlying mechanisms of embodied representations (Zwaan, 2014; Körner et al., 2015). PMID:26528203

  5. High pressure mechanical seal

    NASA Technical Reports Server (NTRS)

    Babel, Henry W. (Inventor); Anderson, Raymond H. (Inventor)

    1996-01-01

    A relatively impervious mechanical seal is formed between the outer surface of a tube and the inside surface of a mechanical fitting of a high pressure fluid or hydraulic system by applying a very thin soft metal layer onto the outer surface of the hard metal tube and/or inner surface of the hard metal fitting. The thickness of such thin metal layer is independent of the size of the tube and/or fittings. Many metals and alloys of those metals exhibit the requisite softness, including silver, gold, tin, platinum, indium, rhodium and cadmium. Suitably, the coating is about 0.0025 millimeters (0.10 mils) in thickness. After compression, the tube and fitting combination exhibits very low leak rates on the order or 10.sup.-8 cubic centimeters per second or less as measured using the Helium leak test.

  6. High pressure mechanical seal

    NASA Technical Reports Server (NTRS)

    Babel, Henry W. (Inventor); Fuson, Phillip L. (Inventor); Chickles, Colin D. (Inventor); Jones, Cherie A. (Inventor); Anderson, Raymond H. (Inventor)

    1995-01-01

    A relatively impervious mechanical seal is formed between the outer surface of a tube and the inside surface of a mechanical fitting of a high pressure fluid or hydraulic system by applying a very thin soft metal layer onto the outer surface of the hard metal tube and/or inner surface of the hard metal fitting, prior to swaging the fitting onto the tube. The thickness of such thin metal layer is independent of the size of the tube and/or fittings. Many metals and alloys of those metals exhibit the requisite softness, including silver, gold, nickel, tin, platinum, indium, rhodium and cadmium. Suitably, the coating is about 0.0025 millimeters (0.10 mils) in thickness. After swaging, the tube and fitting combination exhibits very low leak rates on the order or 10.sup.-8 cubic centimeters per second or less as meaured using the Helium leak test.

  7. Mechanism of Cancer Pain

    PubMed Central

    Schmidt, Brian L.; Hamamoto, Darryl T.; Simone, Donald A.; Wilcox, George L.

    2010-01-01

    Ongoing and breakthrough pain is a primary concern for the cancer patient. Although the etiology of cancer pain remains unclear, animal models of cancer pain have allowed investigators to unravel some of the cancer-induced neuropathologic processes that occur in the region of tumor growth and in the dorsal horn of the spinal cord. Within the cancer microenvironment, cancer and immune cells produce and secrete mediators that activate and sensitize primary afferent nociceptors. Pursuant to these peripheral changes, nociceptive secondary neurons in spinal cord exhibit increased spontaneous activity and enhanced responsiveness to three modes of noxious stimulation: heat, cold, and mechanical stimuli. As our understanding of the peripheral and central mechanisms that underlie cancer pain improves, targeted analgesics for the cancer patient will likely follow. PMID:20539035

  8. Discrete Quantum Mechanics

    E-print Network

    Odake, Satoru

    2011-01-01

    A comprehensive review of the discrete quantum mechanics with the pure imaginary shifts and the real shifts is presented in parallel with the corresponding results in the ordinary quantum mechanics. The main subjects to be covered are the factorised Hamiltonians, the general structure of the solution spaces of the Schroedinger equation (Crum's theorem and its modification), the shape invariance, the exact solvability in the Schroedinger picture as well as in the Heisenberg picture, the creation/annihilation operators and the dynamical symmetry algebras, the unified theory of exact and quasi-exact solvability based on the sinusoidal coordinates, the infinite families of new orthogonal (the exceptional) polynomials. Two new infinite families of orthogonal polynomials, the X_\\ell Meixner-Pollaczek and the X_\\ell Meixner polynomials are reported.

  9. Discrete Quantum Mechanics

    E-print Network

    Satoru Odake; Ryu Sasaki

    2011-08-11

    A comprehensive review of the discrete quantum mechanics with the pure imaginary shifts and the real shifts is presented in parallel with the corresponding results in the ordinary quantum mechanics. The main subjects to be covered are the factorised Hamiltonians, the general structure of the solution spaces of the Schroedinger equation (Crum's theorem and its modification), the shape invariance, the exact solvability in the Schroedinger picture as well as in the Heisenberg picture, the creation/annihilation operators and the dynamical symmetry algebras, the unified theory of exact and quasi-exact solvability based on the sinusoidal coordinates, the infinite families of new orthogonal (the exceptional) polynomials. Two new infinite families of orthogonal polynomials, the X_\\ell Meixner-Pollaczek and the X_\\ell Meixner polynomials are reported.

  10. Discrete quantum mechanics

    NASA Astrophysics Data System (ADS)

    Odake, Satoru; Sasaki, Ryu

    2011-09-01

    A comprehensive review of the discrete quantum mechanics with the pure imaginary shifts and the real shifts is presented in parallel with the corresponding results in the ordinary quantum mechanics. The main subjects to be covered are the factorized Hamiltonians, the general structure of the solution spaces of the Schrödinger equation (Crum's theorem and its modification), the shape invariance, the exact solvability in the Schrödinger picture as well as in the Heisenberg picture, the creation/annihilation operators and the dynamical symmetry algebras, the unified theory of exact and quasi-exact solvability based on the sinusoidal coordinates, and the infinite families of new orthogonal (the exceptional) polynomials. Two new infinite families of orthogonal polynomials, the X? Meixner-Pollaczek and the X? Meixner polynomials, are reported.

  11. Modelling Cochlear Mechanics

    PubMed Central

    Elliott, Stephen J.; Teal, Paul D.

    2014-01-01

    The cochlea plays a crucial role in mammal hearing. The basic function of the cochlea is to map sounds of different frequencies onto corresponding characteristic positions on the basilar membrane (BM). Sounds enter the fluid-filled cochlea and cause deflection of the BM due to pressure differences between the cochlear fluid chambers. These deflections travel along the cochlea, increasing in amplitude, until a frequency-dependent characteristic position and then decay away rapidly. The hair cells can detect these deflections and encode them as neural signals. Modelling the mechanics of the cochlea is of help in interpreting experimental observations and also can provide predictions of the results of experiments that cannot currently be performed due to technical limitations. This paper focuses on reviewing the numerical modelling of the mechanical and electrical processes in the cochlea, which include fluid coupling, micromechanics, the cochlear amplifier, nonlinearity, and electrical coupling. PMID:25136555

  12. Institute for Mechanical Engineering

    NASA Astrophysics Data System (ADS)

    The Institute of Mechanical Engineering has the objectives of supporting in Canada the following activities: improvement of vehicles, propulsion systems, and transportation-related facilities and services; improvements in the design and operation of maritime engineering works; protection of the environment; enhancement of energy flexibility; advancement of firms engaged in manufacturing and resource extraction; and related programs of other government departments and agencies. In 1990-91 the Institute, which had changed its name that year from the Division of Mechanical Engineering, consolidated its research activities from nine laboratories to six programs. Activities in these six programs are described: Advanced Manufacturing Technology, Coastal Zone Engineering, Cold Regions Engineering, Combustion and Fluids Engineering, Ground Transportation Technology, and Machinery and Engine Technology.

  13. Universal quantum mechanics

    SciTech Connect

    Giddings, Steven B.

    2008-10-15

    If gravity respects quantum mechanics, it is important to identify the essential postulates of a quantum framework capable of incorporating gravitational phenomena. Such a construct likely requires elimination or modification of some of the 'standard' postulates of quantum mechanics, in particular, those involving time and measurement. This paper proposes a framework that appears sufficiently general to incorporate some expected features of quantum gravity. These include the statement that space and time may only emerge approximately and relationally. One perspective on such a framework is as a sort of generalization of the S-matrix approach to dynamics. Within this framework, more dynamical structure is required to fully specify a theory; this structure is expected to lack some of the elements of local quantum field theory. Some aspects of this structure are discussed, both in the context of scattering of perturbations about a flat background, and in the context of cosmology.

  14. Antimicrobial mechanism of lantibiotics.

    PubMed

    Islam, Mohammad R; Nagao, Jun-Ichi; Zendo, Takeshi; Sonomoto, Kenji

    2012-12-01

    Lantibiotics are ribosomally synthesized antimicrobial peptides that commonly target the cell wall precursor lipid II during their antimicrobial mechanism and exert their inhibitory activity by (i) inhibition of cell wall biosynthesis, and (ii) stable pore formation in the target membrane. Type-A(I) (i.e. nisin) and two-component (i.e. lacticin 3147) lantibiotics initially interact with lipid II to stabilize the complex, which then proceeds to inhibit cell wall biosynthesis and pore formation. Type-A(II) (i.e. nukacin ISK-1) and type-B (i.e. mersacidin) lantibiotics also use lipid II as a docking molecule, but can only inhibit cell wall biosynthesis without forming pores. In the present paper, we review the antimicrobial mechanism of different types of lantibiotics, their current progress and future prospect. PMID:23176511

  15. Relational Quantum Mechanics

    E-print Network

    Nicolaidis, Argyris

    2012-01-01

    We suggest that the inner syntax of Quantum Mechanics is relational logic, a form of logic developed by C. S. Peirce during the years 1870 - 1880. The Peircean logic has the structure of category theory, with relation serving as an arrow (or morphism). At the core of the relational logical system is the law of composition of relations. This law leads to the fundamental quantum rule of probability as the square of an amplitude. Our study of a simple discrete model, extended to the continuum, indicates that a finite number of degrees of freedom can live in phase space. This "granularity" of phase space is determined by Planck's constant h. We indicate also the broader philosophical ramifications of a relational quantum mechanics.

  16. Relational Quantum Mechanics

    E-print Network

    Argyris Nicolaidis

    2012-11-09

    We suggest that the inner syntax of Quantum Mechanics is relational logic, a form of logic developed by C. S. Peirce during the years 1870 - 1880. The Peircean logic has the structure of category theory, with relation serving as an arrow (or morphism). At the core of the relational logical system is the law of composition of relations. This law leads to the fundamental quantum rule of probability as the square of an amplitude. Our study of a simple discrete model, extended to the continuum, indicates that a finite number of degrees of freedom can live in phase space. This "granularity" of phase space is determined by Planck's constant h. We indicate also the broader philosophical ramifications of a relational quantum mechanics.

  17. Shielded, Automated Umbilical Mechanism

    NASA Technical Reports Server (NTRS)

    Barron, Daniel R.; Morrill, Brion F.; Jasulaitis, Vytas

    1995-01-01

    Umbilical mechanism automatically connects and disconnects various fluid couplings and/or electrical contacts while shielding mating parts from debris. Reacts mating and demating loads internally, without additional supporting structures. All functions - extension of plug, mating, and movement of debris shields - actuated by single motor. If mechanism jams or fails at any point in sequence, override feature in drive train allows manual operation. Designed for service in outer space, where its shields protect against micrometeoroids, debris, ultraviolet radiation, and atomic oxygen. Used on Earth to connect or disconnect fluid or electrical utilities in harsh environments like those of nuclear powerplants or undersea construction sites, or in presence of radioactive, chemical, or biological hazards, for example.

  18. Mechanics of Suture Joints

    NASA Astrophysics Data System (ADS)

    Li, Yaning; Song, Juha; Ortiz, Christine; Boyce, Mary; Ortiz Group/DMSE/MIT Team; Boyce Group/ME/MIT Team

    2011-03-01

    Biological sutures are joints which connect two stiff skeletal or skeletal-like components. These joints possess a wavy geometry with a thin organic layer providing adhesion. Examples of biological sutures include mammalian skulls, the pelvic assembly of the armored fish Gasterosteus aculeatus (the three-spined stickleback), and the suture joints in the shell of the red-eared slider turtle. Biological sutures allow for movement and compliance, control stress concentrations, transmit loads, reduce fatigue stress and absorb energy. In this investigation, the mechanics of the role of suture geometry in providing a naturally optimized joint is explored. In particular, analytical and numerical micromechanical models of the suture joint are constructed. The anisotropic mechanical stiffness and strength are studied as a function of suture wavelength, amplitude and the material properties of the skeletal and organic components, revealing key insights into the optimized nature of these ubiquitous natural joints.

  19. Responding to Mechanical Antigravity

    NASA Technical Reports Server (NTRS)

    Millis, Marc G.; Thomas, Nicholas E.

    2006-01-01

    Based on the experiences of the NASA Breakthrough Propulsion Physics Project, suggestions are offered for constructively responding to proposals that purport breakthrough propulsion using mechanical devices. Because of the relatively large number of unsolicited submissions received (about 1 per workday) and because many of these involve similar concepts, this report is offered to help the would-be submitters make genuine progress as well as to help reviewers respond to such submissions. Devices that use oscillating masses or gyroscope falsely appear to create net thrust through differential friction or by misinterpreting torques as linear forces. To cover both the possibility of an errant claim and a genuine discovery, reviews should require that submitters meet minimal thresholds of proof before engaging in further correspondence; such as achieving sustained deflection of a level-platform pendulum in the case of mechanical thrusters.

  20. Mechanisms of Nitrite Bioactivation

    PubMed Central

    Kim-Shapiro, Daniel B.; Gladwin, Mark T.

    2014-01-01

    It is now accepted that the anion nitrite, once considered an inert oxidation product of nitric oxide (NO), contributes to hypoxic vasodilation, physiological blood pressure control, and redox signaling. As such, its application in therapeutics is being actively testing in pre-clinical models and in human phase I–II clinical trials. Major pathways for nitrite bioactivation involve its reduction to NO by members of the hemoglobin or molybdopterin family of proteins, or catalyzed dysproportionation. These conversions occur preferentially under hypoxic and acidic conditions. A number of enzymatic systems reduce nitrite to NO and their activity and importance are defined by oxygen tension, specific organ system and allosteric and redox effectors. In this work, we review different proposed mechanisms of nitrite bioactivation, focusing on analysis of kinetics and experimental evidence for the relevance of each mechanism under different conditions. PMID:24315961

  1. Schwinger mechanism and graphene

    SciTech Connect

    Allor, Danielle; Cohen, Thomas D.; McGady, David A.

    2008-11-01

    The Schwinger mechanism, the production of charged particle-antiparticle pairs in a macroscopic external electric field, is derived for 2+1-dimensional theories. The rate of pair production per unit area for four species of massless fermions, with charge q, in a constant electric field E is given by {pi}{sup -2}({Dirac_h}/2{pi}){sup -3/2}c-tilde{sup -1/2}(qE){sup 3/2} where c-tilde is the speed of light for the two-dimensional system. To the extent undoped graphene behaves like the quantum field-theoretic vacuum for massless fermions in 2+1 dimensions, the Schwinger mechanism should be testable experimentally. A possible experimental configuration for this is proposed. Effects due to deviations from this idealized picture of graphene are briefly considered. It is argued that with present day samples of graphene, tests of the Schwinger formula may be possible.

  2. Epigenetic mechanisms in schizophrenia

    PubMed Central

    Akbarian, Schahram

    2014-01-01

    Schizophrenia is a major psychiatric disorder that lacks a unifying neuropathology, while currently available pharmacological treatments provide only limited benefits to many patients. This review will discuss how the field of neuroepigenetics could contribute to advancements of the existing knowledge on the neurobiology and treatment of psychosis. Genome-scale mapping of DMA methylation, histone modifications and variants, and chromosomal loopings for promoter-enhancer interactions and other epigenetic determinants of genome organization and function are likely to provide important clues about mechanisms contributing to dysregulated expression of synaptic and metabolic genes in schizophrenia brain, including the potential links to the underlying genetic risk architecture and environmental exposures. In addition, studies in animal models are providing a rapidly increasing list of chromatin-regulatory mechanisms with significant effects on cognition and complex behaviors, thereby pointing to the therapeutic potential of epigenetic drug targets in the nervous system. PMID:25364289

  3. Origami based Mechanical Metamaterials

    PubMed Central

    Lv, Cheng; Krishnaraju, Deepakshyam; Konjevod, Goran; Yu, Hongyu; Jiang, Hanqing

    2014-01-01

    We describe mechanical metamaterials created by folding flat sheets in the tradition of origami, the art of paper folding, and study them in terms of their basic geometric and stiffness properties, as well as load bearing capability. A periodic Miura-ori pattern and a non-periodic Ron Resch pattern were studied. Unexceptional coexistence of positive and negative Poisson's ratio was reported for Miura-ori pattern, which are consistent with the interesting shear behavior and infinity bulk modulus of the same pattern. Unusually strong load bearing capability of the Ron Resch pattern was found and attributed to the unique way of folding. This work paves the way to the study of intriguing properties of origami structures as mechanical metamaterials. PMID:25099402

  4. On Foundations of Newtonian Mechanics

    E-print Network

    Al Cheremensky

    2011-03-27

    Being based on V. Konoplev's axiomatic approach to continuum mechanics, the paper broadens its frontiers in order to bring together continuum mechanics with classical mechanics in a new theory of mechanical systems. There are derived motion equations of `abstract' mechanical systems specified for mass-points, multibody systems and continua: Newton-Euler equations, Lagrange equations of II kind and Navier-Stokes ones. Quasi-linear constitutive equations are introduced in conformity with V. Konoplev's definition of stress and strain (rate) matrices.

  5. Mechanics of collective unfolding

    E-print Network

    M Caruel; J. -M Allain; L Truskinovsky

    2015-01-07

    Mechanically induced unfolding of passive crosslinkers is a fundamental biological phenomenon encountered across the scales from individual macro-molecules to cytoskeletal actin networks. In this paper we study a conceptual model of athermal load-induced unfolding and use a minimalistic setting allowing one to emphasize the role of long-range interactions while maintaining full analytical transparency. Our model can be viewed as a description of a parallel bundle of N bistable units confined between two shared rigid backbones that are loaded through a series spring. We show that the ground states in this model correspond to synchronized, single phase configurations where all individual units are either folded or unfolded. We then study the fine structure of the wiggly energy landscape along the reaction coordinate linking the two coherent states and describing the optimal mechanism of cooperative unfolding. Quite remarkably, our study shows the fundamental difference in the size and structure of the folding-unfolding energy barriers in the hard (fixed displacements) and soft (fixed forces) loading devices which persists in the continuum limit. We argue that both, the synchronization and the non-equivalence of the mechanical responses in hard and soft devices, have their origin in the dominance of long-range interactions. We then apply our minimal model to skeletal muscles where the power-stroke in acto-myosin crossbridges can be interpreted as passive folding. A quantitative analysis of the muscle model shows that the relative rigidity of myosin backbone provides the long-range interaction mechanism allowing the system to effectively synchronize the power-stroke in individual crossbridges even in the presence of thermal fluctuations. In view of the prototypical nature of the proposed model, our general conclusions pertain to a variety of other biological systems where elastic interactions are mediated by effective backbones.

  6. DARPA's Big Mechanism program

    NASA Astrophysics Data System (ADS)

    Cohen, Paul R.

    2015-07-01

    Reductionist science produces causal models of small fragments of complicated systems. Causal models of entire systems can be hard to construct because what is known of them is distributed across a vast amount of literature. The Big Mechanism program aims to have machines read the literature and assemble the causal fragments found in individual papers into huge causal models, automatically. The current domain of the program is cell signalling associated with Ras-driven cancers.

  7. Acoustic Mechanical Feedthroughs

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Walkemeyer, Phillip; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea

    2013-01-01

    Electromagnetic motors can have problems when operating in extreme environments. In addition, if one needs to do mechanical work outside a structure, electrical feedthroughs are required to transport the electric power to drive the motor. In this paper, we present designs for driving rotary and linear motors by pumping stress waves across a structure or barrier. We accomplish this by designing a piezoelectric actuator on one side of the structure and a resonance structure that is matched to the piezoelectric resonance of the actuator on the other side. Typically, piezoelectric motors can be designed with high torques and lower speeds without the need for gears. One can also use other actuation materials such as electrostrictive, or magnetostrictive materials in a benign environment and transmit the power in acoustic form as a stress wave and actuate mechanisms that are external to the benign environment. This technology removes the need to perforate a structure and allows work to be done directly on the other side of a structure without the use of electrical feedthroughs, which can weaken the structure, pipe, or vessel. Acoustic energy is pumped as a stress wave at a set frequency or range of frequencies to produce rotary or linear motion in a structure. This method of transferring useful mechanical work across solid barriers by pumping acoustic energy through a resonant structure features the ability to transfer work (rotary or linear motion) across pressure or thermal barriers, or in a sterile environment, without generating contaminants. Reflectors in the wall of barriers can be designed to enhance the efficiency of the energy/power transmission. The method features the ability to produce a bi-directional driving mechanism using higher-mode resonances. There are a variety of applications where the presence of a motor is complicated by thermal or chemical environments that would be hostile to the motor components and reduce life and, in some instances, not be feasible. A variety of designs that have been designed, fabricated and tested will be presented

  8. Quantum conformal mechanics

    E-print Network

    K. Andrzejewski

    2015-06-18

    The quantum mechanics of one degree of freedom exhibiting the exact conformal SL(2,R) symmetry is presented. The starting point is the classification of the unitary irreducible representations of the SL(2,R) group (or, to some extent, its universal covering). The coordinate representation is defined as the basis diagonalizing the special conformal generator K. It is indicated how the resulting theory emerges from the canonical/geometric quantization of the Hamiltonian dynamics on the relevant coadjoint orbits.

  9. Quantum conformal mechanics

    E-print Network

    Andrzejewski, K

    2015-01-01

    The quantum mechanics of one degree of freedom exhibiting the exact conformal SL(2,R) symmetry is presented. The starting point is the classification of the unitary irreducible representations of the SL(2,R) group (or, to some extent, its universal covering). The coordinate representation is defined as the basis diagonalizing the special conformal generator K. It is indicated how the resulting theory emerges from the canonical/geometric quantization of the Hamiltonian dynamics on the relevant coadjoint orbits.

  10. Perspectives in Fluid Mechanics

    NASA Astrophysics Data System (ADS)

    Coles, Donald

    Distinguished authors discuss topics in physical oceanography, transonic aerodynamics, dynamics of vorticity, numerical simulation of turbulent flows, astrophysical jets, strange attractors, human-powered flight, and the fluid mechanics of the Old Faithful geyser and of the Mount St. Helens eruption of 1980. The authors deal with specific problems, but the emphasis is usually on the way that research is carried out at the edge of understanding, and often on the role of new techniques, instruments, and research strategies.

  11. 1999 Flight Mechanics Symposium

    NASA Technical Reports Server (NTRS)

    Lynch, John P. (Editor)

    1999-01-01

    This conference publication includes papers and abstracts presented at the Flight Mechanics Symposium held on May 18-20, 1999. Sponsored by the Guidance, Navigation and Control Center of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers.

  12. Bohm and Bohmian Mechanics

    NASA Astrophysics Data System (ADS)

    Introzzi, Gianluca; Rossetti, Marco

    2006-06-01

    The standard, or Copenhagen, formulation of quantum mechanics postulates that the complete specification of a quantum state is given by the corresponding state vector (completeness). A different approach is possible, assuming instead the incompleteness of the theory. Additional parameters, called "hidden variables" since they are not empirically known, would be needed to completely characterize the quantum state. The knowledge of these hidden variables would allow the precise determination of the values for the observables of the quantum system. In 1952 David Bohm, starting from such an assumption, has proposed a hidden variables formulation of quantum mechanics that is empirically equivalent to standard quantum mechanics, but offers a more rational and coherent picture of reality. Bohm's model integrates the ordinary quantum theory by introducing particle coordinates as hidden variables. Therefore, particles are distinguishable and describe trajectories in space or in configuration space that are causally determinate. In this context it is possible to explain double slit experiments and interference phenomena in terms of particle trajectories. Quantum probabilities become epistemic: the probabilistic nature of physical predictions is not an intrinsic characteristic of nature, but depends on our ignorance of the exact value of the hidden variables. Since Bohm's interpretation is, both epistemologically and ontologically, a natural extension of classical mechanics to the quantum domain, the visualization of physical processes is still possible, and the corresponding picture of reality is more intuitive. Bohm's interpretation clearly also presents limits and weaknesses: a Lorentz invariant formulation of the model is still lacking, and all the observables result to be dependent on the global context (contextuality), with the only exception of position observables.

  13. Principles of Rock Mechanics

    NASA Astrophysics Data System (ADS)

    Beeler, N. M.

    Imagine for a moment that you are a field structural geologist, and you have just realized that your star graduate student does not know how to estimate the failure strength of intact rock at 10 km depth in a normal faulting environment. Or perhaps you are a geophysicist with graduate students modeling mantle convection who, as you come to find out, do not know what a dislocation is. You might decide that your students need to take a course in basic rock mechanics, but, and this may be easiest to imagine, you are the only staff member in your department available to teach such a course.If you are developing an introductory course in rock mechanics or you have been teaching such a course without a suitable text, this new book by Ruud Wiejermars was written specifically for you and your students. Principles of Rock Mechanics is a textbook to a one-semester course for graduate students and advanced undergraduates. There are 13 chapters, a math review section, and the obligatory introduction and final overview chapters. Each chapter is designed to be covered in two 50-minute lectures and one laboratory session. Following a formal introduction to the topic, the subsequent seven chapters serve as an introduction to the physical concepts and processes; physical quantities in rock mechanics, force and pressure, stress, elasticity, brittle failure, and ductile creep, taking the students to midterm. An unusual and welcome feature appears at the midsemester point—a math review of notation and associated concepts: differentiation of vectors and scalars, differential equations, tensors, matrices and determinants, and complex variables. This review provides an indication of the rigor to follow.

  14. Acoustic mechanical feedthroughs

    NASA Astrophysics Data System (ADS)

    Sherrit, Stewart; Walkemeyer, Phillip; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea

    2013-04-01

    Electromagnetic motors can have problems when operating in extreme environments. In addition, if one needs to do mechanical work outside a structure, electrical feedthroughs are required to transport the electric power to drive the motor. In this paper, we present designs for driving rotary and linear motors by pumping stress waves across a structure or barrier. We accomplish this by designing a piezoelectric actuator on one side of the structure and a resonance structure that is matched to the piezoelectric resonance of the actuator on the other side. Typically, piezoelectric motors can be designed with high torques and lower speeds without the need for gears. One can also use other actuation materials such as electrostrictive, or magnetostrictive materials in a benign environment and transmit the power in acoustic form as a stress wave and actuate mechanisms that are external to the benign environment. This technology removes the need to perforate a structure and allows work to be done directly on the other side of a structure without the use of electrical feedthroughs, which can weaken the structure, pipe, or vessel. Acoustic energy is pumped as a stress wave at a set frequency or range of frequencies to produce rotary or linear motion in a structure. This method of transferring useful mechanical work across solid barriers by pumping acoustic energy through a resonant structure features the ability to transfer work (rotary or linear motion) across pressure or thermal barriers, or in a sterile environment, without generating contaminants. Reflectors in the wall of barriers can be designed to enhance the efficiency of the energy/power transmission. The method features the ability to produce a bi-directional driving mechanism using higher-mode resonances. There are a variety of applications where the presence of a motor is complicated by thermal or chemical environments that would be hostile to the motor components and reduce life and, in some instances, not be feasible. A variety of designs that have been designed, fabricated and tested will be presented.

  15. Jet fuel instability mechanisms

    NASA Technical Reports Server (NTRS)

    Daniel, S. R.

    1985-01-01

    The mechanisms of the formation of fuel-insoluble deposits were studied in several real fuels and in a model fuel consisting of tetralin in dodecane solution. The influence of addition to the fuels of small concentrations of various compounds on the quantities of deposits formed and on the formation and disappearance of oxygenated species in solution was assessed. The effect of temperature on deposit formation was also investigated over the range of 308-453 K.

  16. Noumen Mechanics: a Program

    NASA Astrophysics Data System (ADS)

    Rocher, Edouard

    2006-03-01

    Noumen Mechanics (NM): geometric synthesis between Relativistic Mechanics (RM) and Quantum Mechanics (QM) based on a more fundamental approach to RM. Events (1905) are geometric points in Minkowski space-time M^4, noumens (1972) in C^4, M^4 complex extension. A noumen is a chiral entity containing more information than an event, thus suggesting doing physics in C^4 instead of M^4. Three main principles: Representation duality: M^4= C^4*xC^4 since Sl(2;C) acts on C^4 and is the fundamental representation of the Lorentz group. Homogeneous hypercomplex space: C^4 and M^4 are quotient spaces of homogeneous spaces CC^4 and MM^4. A geometric point is represented by a homogeneous class; the coefficients of homogeneity ? is its electroweak charge in CC^4, and ?=|?|^2 its mass in MM^4. Analytic function of physical points: Physical points are bounded sets of geometric points, noumens in C^4, events in M^4, with the resulting electroweak charge and mass. Phase 1: gain a deeper understanding of the mathematical sources of QM and RM. Two main NM results: bound electrons do not radiate; C^4/M^4 is the solution to physics hierarchy problem. Phase 2: apply new concepts to nuclear physics, following Pauli's interpretation (1936) of Fermi's weak-interaction constant (1934).

  17. Copenhagen Quantum Mechanics

    E-print Network

    Timothy J. Hollowood

    2015-11-03

    In our quantum mechanics courses, measurement is usually taught in passing, as an ad-hoc procedure involving the ugly collapse of the wave function. No wonder we search for more satisfying alternatives to the Copenhagen interpretation. But this overlooks the fact that the approach fits very well with modern measurement theory with its notions of the conditioned state and quantum trajectory. In addition, what we know of as the Copenhagen interpretation is a later 1950's development and some of the earlier pioneers like Bohr did not talk of wave function collapse. In fact, if one takes these earlier ideas and mixes them with later insights of decoherence, a much more satisfying version of Copenhagen quantum mechanics emerges, one for which the collapse of the wave function is seen to be a harmless book keeping device. Along the way, we explain why chaotic systems lead to wave functions that spread out quickly on macroscopic scales implying that Schrodinger cat states are the norm rather than curiosities generated in physicists' laboratories. We then describe how the conditioned state of a quantum system depends crucially on how the system is monitored illustrating this with the example of a decaying atom monitored with a time of arrival photon detector, leading to Bohr's quantum jumps. On the other hand, other kinds of detection lead to much smoother behaviour, providing yet another example of complementarity. Finally we explain how classical behaviour emerges, including classical mechanics but also thermodynamics.

  18. Gaia Spacecraft Mechanical Development

    NASA Astrophysics Data System (ADS)

    Lebranchu, C.; Blender, F.; Touzeau, S.; Escolar, D.

    2012-07-01

    Gaia is the European Space Agency's cornerstone mission for global space astrometry. Its goal is to make the largest, most precise three-dimensional map of our Galaxy by surveying an unprecedented number of stars. This paper gives an overview of the mechanical system engineering and verification of the spacecraft. This development includes several technical challenges. First of all, the very high stability performance as required for the mission is a key driver for the design; which incurs a high degree of stability. This is achieved through decoupling between payload and service module, and the use of high-performance engineering tools and of Silicon Carbide (Boostec® SiC) for the Payload. Compliance of spacecraft mass and volume with launcher capability is another key challenge, as well as the development of the 10.3 meter diameter deployable sunshield. The spacecraft mechanical verification follows an innovative approach, with direct testing on the flight model, without dedicated structural model. Gaia mechanical development is the fruit of a successful international cooperation.

  19. Electromagnetic attachment mechanism

    NASA Technical Reports Server (NTRS)

    Monford, Leo G., Jr. (inventor)

    1992-01-01

    An electromagnetic attachment mechanism is disclosed for use as an end effector of a remote manipulator system. A pair of electromagnets, each with a U-shaped magnetic core with a pull-in coil and two holding coils, are mounted by a spring suspension system on a base plate of the mechanism housing with end pole pieces adapted to move through openings in the base plate when the attractive force of the electromagnets is exerted on a strike plate of a grapple fixture affixed to a target object. The pole pieces are spaced by an air gap from the strike plate when the mechanism first contacts the grapple fixture. An individual control circuit and power source is provided for the pull-in coil and one holding coil of each electromagnet. A back-up control circuit connected to the two power sources and a third power source is provided for the remaining holding coils. When energized, the pull-in coils overcome the suspension system and air gap and are automatically de-energized when the pole pieces move to grapple and impose a preload force across the grapple interface. A battery backup is a redundant power source for each electromagnet in each individual control circuit and is automatically connected upon failure of the primary source. A centerline mounted camera and video monitor are used in cooperation with a target pattern on the reflective surface of the strike plate to effect targeting and alignment.

  20. TRANSIENT QUANTUM MECHANICAL PROCESSES

    SciTech Connect

    L. COLLINS; J. KRESS; R. WALKER

    1999-07-01

    Our principal objective has centered on the development of sophisticated computational techniques to solve the time-dependent Schroedinger equation that governs the evolution of quantum mechanical systems. We have perfected two complementary methods, discrete variable representation and real space product formula, that show great promise in solving these complicated temporal problems. We have applied these methods to the interaction of laser light with molecules with the intent of not only investigating the basic mechanisms but also devising schemes for actually controlling the outcome of microscopic processes. Lasers now exist that produce pulses of such short duration as to probe a molecular process many times within its characteristic period--allowing the actual observation of an evolving quantum mechanical system. We have studied the potassium dimer as an example and found agreement with experimental changes in the intermediate state populations as a function of laser frequency--a simple control prescription. We have also employed elaborate quantum chemistry programs to improve the accuracy of basic input such as bound-bound and bound-free coupling moments. These techniques have far-ranging applicability; for example, to trapped quantum systems at very low temperatures such as Bose-Einstein condensates.

  1. Mechanisms of Memory Enhancement

    PubMed Central

    Stern, Sarah A.

    2012-01-01

    The ongoing quest for memory enhancement is one that grows necessary as the global population increasingly ages. The extraordinary progress that has been made in the past few decades elucidating the underlying mechanisms of how long-term memories are formed has provided insight into how memories might also be enhanced. Capitalizing on this knowledge, it has been postulated that targeting many of the same mechanisms, including CREB activation, AMPA/NMDA receptor trafficking, neuromodulation (e.g. via dopamine, adrenaline, cortisol or acetylcholine) and metabolic processes (e.g. via glucose and insulin) may all lead to the enhancement of memory. These and other mechanisms and/or approaches have been tested via genetic or pharmacological methods in animal models, and several have been investigated in humans as well. In addition, a number of behavioral methods, including exercise and reconsolidation, may also serve to strengthen and enhance memories. By capitalizing on this knowledge and continuing to investigate these promising avenues, memory enhancement may indeed be achieved in the future. PMID:23151999

  2. Pipeline welding goes mechanized

    SciTech Connect

    Beeson, R.

    1999-11-01

    Spread four has bugs in the cornfield--but not to worry. The bug referred to here is a mechanized welding bug, specifically a single welding head, computer-aided gas metal arc (GMAW) system from CRC-Evans Automatic Welding powered by a Miller Electric XMT{reg{underscore}sign} 304 inverter-based welding machine. The bug operator and owner of 32 inverters is Welded Construction, L.P., of Perrysburgh, Ohio. Spread four is a 147-mile stretch of the Alliance Pipeline system (Alliance) cutting through the cornfields of northeast Iowa. While used successfully in Canada and Europe for onshore and offshore pipeline construction for 30 years, this is the first large-scale use of mechanized welding in the US on a cross-country pipeline. On longer, larger-diameter and thicker-wall pipe projects--the Alliance mainline has 1,844 miles of pipe, most of it 36-in. diameter with a 0.622-in. wall thickness--mechanized GMAW offers better productivity than manual shielded metal arc welding (SMAW). In addition, high-strength steels, such as the API 5L Grade X70 pipe used on the Alliance, benefit from the low-hydrogen content of certain solid and tubular wire electrodes.

  3. Relativistic viscoelastic fluid mechanics

    E-print Network

    Masafumi Fukuma; Yuho Sakatani

    2011-09-01

    A detailed study is carried out for the relativistic theory of viscoelasticity which was recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. After rederiving the theory using a local argument with the entropy current, we show that this theory universally reduces to the standard relativistic Navier-Stokes fluid mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes fluids are significantly remedied. We in particular show that the wave equations for the propagation of disturbance around a hydrostatic equilibrium in Minkowski spacetime become symmetric hyperbolic for some range of parameters, so that the model is free of acausality problems. This observation suggests that the relativistic viscoelastic model with such parameters can be regarded as a causal completion of relativistic Navier-Stokes fluid mechanics. By adjusting parameters to various values, this theory can treat a wide variety of materials including elastic materials, Maxwell materials, Kelvin-Voigt materials, and (a nonlinearly generalized version of) simplified Israel-Stewart fluids, and thus we expect the theory to be the most universal description of single-component relativistic continuum materials. We also show that the presence of strains and the corresponding change in temperature are naturally unified through the Tolman law in a generally covariant description of continuum mechanics.

  4. Relativistic viscoelastic fluid mechanics

    SciTech Connect

    Fukuma, Masafumi; Sakatani, Yuho

    2011-08-15

    A detailed study is carried out for the relativistic theory of viscoelasticity which was recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. After rederiving the theory using a local argument with the entropy current, we show that this theory universally reduces to the standard relativistic Navier-Stokes fluid mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes fluids are significantly remedied. We in particular show that the wave equations for the propagation of disturbance around a hydrostatic equilibrium in Minkowski space-time become symmetric hyperbolic for some range of parameters, so that the model is free of acausality problems. This observation suggests that the relativistic viscoelastic model with such parameters can be regarded as a causal completion of relativistic Navier-Stokes fluid mechanics. By adjusting parameters to various values, this theory can treat a wide variety of materials including elastic materials, Maxwell materials, Kelvin-Voigt materials, and (a nonlinearly generalized version of) simplified Israel-Stewart fluids, and thus we expect the theory to be the most universal description of single-component relativistic continuum materials. We also show that the presence of strains and the corresponding change in temperature are naturally unified through the Tolman law in a generally covariant description of continuum mechanics.

  5. Beyond Mechanism Design

    NASA Technical Reports Server (NTRS)

    Wolpert, David H.; Turner, Kagan

    2004-01-01

    The field of mechanism design is concerned with setting (incentives superimposed on) the utility functions of a group of players so as to induce desirable joint behavior of those players. It arose in the context of traditional equilibrium game theory applied to games involving human players. This has led it to have many implicit restrictions, which strongly limits its scope. In particular, it ignores many issues that are crucial for systems that are large (and therefore far off-equilibrium in general) and/or composed of non-human players (e.g., computer-based agents). This also means it has concentrated on issues that are often irrelevant in those broader domains (e.g., incentive compatibility). This paper illustrates these shortcomings by reviewing some of the recent theoretical work on the design of collectives, a body of work that constitutes a substantial broadening of mechanism design. It then presents computer experiments based on a recently suggested nanotechnology testbed that demonstrates the power of that extended version of mechanism design.

  6. Principles of Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Landé, Alfred

    2013-10-01

    Preface; Introduction: 1. Observation and interpretation; 2. Difficulties of the classical theories; 3. The purpose of quantum theory; Part I. Elementary Theory of Observation (Principle of Complementarity): 4. Refraction in inhomogeneous media (force fields); 5. Scattering of charged rays; 6. Refraction and reflection at a plane; 7. Absolute values of momentum and wave length; 8. Double ray of matter diffracting light waves; 9. Double ray of matter diffracting photons; 10. Microscopic observation of ? (x) and ? (p); 11. Complementarity; 12. Mathematical relation between ? (x) and ? (p) for free particles; 13. General relation between ? (q) and ? (p); 14. Crystals; 15. Transition density and transition probability; 16. Resultant values of physical functions; matrix elements; 17. Pulsating density; 18. General relation between ? (t) and ? (?); 19. Transition density; matrix elements; Part II. The Principle of Uncertainty: 20. Optical observation of density in matter packets; 21. Distribution of momenta in matter packets; 22. Mathematical relation between ? and ?; 23. Causality; 24. Uncertainty; 25. Uncertainty due to optical observation; 26. Dissipation of matter packets; rays in Wilson Chamber; 27. Density maximum in time; 28. Uncertainty of energy and time; 29. Compton effect; 30. Bothe-Geiger and Compton-Simon experiments; 31. Doppler effect; Raman effect; 32. Elementary bundles of rays; 33. Jeans' number of degrees of freedom; 34. Uncertainty of electromagnetic field components; Part III. The Principle of Interference and Schrödinger's equation: 35. Physical functions; 36. Interference of probabilities for p and q; 37. General interference of probabilities; 38. Differential equations for ?p (q) and Xq (p); 39. Differential equation for ?? (q); 40. The general probability amplitude ??' (Q); 41. Point transformations; 42. General theorem of interference; 43. Conjugate variables; 44. Schrödinger's equation for conservative systems; 45. Schrödinger's equation for non-conservative systems; 46. Pertubation theory; 47. Orthogonality, normalization and Hermitian conjugacy; 48. General matrix elements; Part IV. The Principle of Correspondence: 49. Contact transformations in classical mechanics; 50. Point transformations; 51. Contact transformations in quantum mechanics; 52. Constants of motion and angular co-ordinates; 53. Periodic orbits; 54. De Broglie and Schrödinger function; correspondence to classical mechanics; 55. Packets of probability; 56. Correspondence to hydrodynamics; 57. Motion and scattering of wave packets; 58. Formal correspondence between classical and quantum mechanics; Part V. Mathematical Appendix: Principle of Invariance: 59. The general theorem of transformation; 60. Operator calculus; 61. Exchange relations; three criteria for conjugacy; 62. First method of canonical transformation; 63. Second method of canonical transformation; 64. Proof of the transformation theorem; 65. Invariance of the matrix elements against unitary transformations; 66. Matrix mechanics; Index of literature; Index of names and subjects.

  7. Upregulation of Nicotinic Acetylcholine Receptor alph4+beta2 through a Ligand-Independent PI3Kbeta Mechanism That Is Enhanced by TNFalpha and the Jak2/p38Mapk Pathways

    PubMed Central

    Rogers, Scott W.; Gahring, Lorise C.

    2015-01-01

    High affinity nicotine-binding sites in the mammalian brain are neuronal nicotinic acetylcholine receptors (nAChR) assembled from at least alpha4 and beta2 subunits into pentameric ion channels. When exposed to ligands such as nicotine, these receptors respond by undergoing upregulation, a correlate of nicotine addiction. Upregulation can be measured using HEK293 (293) cells that stably express alpha4 and beta2 subunits using quantification of [3H]epibatidine ([3H]Eb) binding to measure mature receptors. Treatment of these cells with choline also produces upregulation through a hemicholinium3 (HC3)-sensitive (choline kinase) and an HC3-insensitive pathway which are both independent of the mechanism used by nicotine for upregulation. In both cases, upregulation is significantly enhanced by the pro-inflammatory cytokine tumor necrosis factor alpha (TNF?) which signals through its receptor Tnfr1 to activate p38Mapk. Here we report that the inhibition of class1 phosphoinositide 3-kinases isoform PI3Kbeta using the selective antagonist PI828 is alone sufficient to produce upregulation and enhance both nicotine and choline HC3-sensitive mediated upregulation. Further, these processes are impacted upon by an AG-490 sensitive Jak2-associated pathway. Both PI3Kbeta (negative) and Jak2 (positive) modulation of upregulation converge through p38Mapk and both overlap with TNFalpha enhancement of this process. Upregulation through the PI3Kbeta pathway did not require Akt. Collectively these findings support upregulation of endogenous alpha4beta2 as a balance among cellular signaling networks that are highly responsive to multiple environmental, inflammatory and metabolic agents. The findings also suggest how illness and metabolic stress could alter the expression of this important nicotinic receptor and novel avenues to intercede in modifying its expression. PMID:26619345

  8. Upregulation of Nicotinic Acetylcholine Receptor alph4+beta2 through a Ligand-Independent PI3Kbeta Mechanism That Is Enhanced by TNFalpha and the Jak2/p38Mapk Pathways.

    PubMed

    Rogers, Scott W; Gahring, Lorise C

    2015-01-01

    High affinity nicotine-binding sites in the mammalian brain are neuronal nicotinic acetylcholine receptors (nAChR) assembled from at least alpha4 and beta2 subunits into pentameric ion channels. When exposed to ligands such as nicotine, these receptors respond by undergoing upregulation, a correlate of nicotine addiction. Upregulation can be measured using HEK293 (293) cells that stably express alpha4 and beta2 subunits using quantification of [3H]epibatidine ([3H]Eb) binding to measure mature receptors. Treatment of these cells with choline also produces upregulation through a hemicholinium3 (HC3)-sensitive (choline kinase) and an HC3-insensitive pathway which are both independent of the mechanism used by nicotine for upregulation. In both cases, upregulation is significantly enhanced by the pro-inflammatory cytokine tumor necrosis factor alpha (TNF?) which signals through its receptor Tnfr1 to activate p38Mapk. Here we report that the inhibition of class1 phosphoinositide 3-kinases isoform PI3Kbeta using the selective antagonist PI828 is alone sufficient to produce upregulation and enhance both nicotine and choline HC3-sensitive mediated upregulation. Further, these processes are impacted upon by an AG-490 sensitive Jak2-associated pathway. Both PI3Kbeta (negative) and Jak2 (positive) modulation of upregulation converge through p38Mapk and both overlap with TNFalpha enhancement of this process. Upregulation through the PI3Kbeta pathway did not require Akt. Collectively these findings support upregulation of endogenous alpha4beta2 as a balance among cellular signaling networks that are highly responsive to multiple environmental, inflammatory and metabolic agents. The findings also suggest how illness and metabolic stress could alter the expression of this important nicotinic receptor and novel avenues to intercede in modifying its expression. PMID:26619345

  9. Generalized Froggatt-Nielsen Mechanism

    E-print Network

    Fei Wang

    2011-03-31

    In this paper, we propose a Generalized Froggatt-Nielsen mechanism in which non-renormalizable operators involving a GUT group and $U(1)_H$ non-singlet Higgs field are introduced. Thus the GUT gauge symmetry breaking and the generation of hierarchical flavor hierarchy have a common origin in this mechanism. In this Generalized Froggatt-Nielsen mechanism, we propose universality conditions for coefficients corresponding to different contractions in the group productions. We find that the predictions in Generalized Froggatt-Nielsen mechanism for SU(5) GUT is different to that of ordinary Froggatt-Nielsen mechanism. Such Generalized Froggatt-Nielsen mechanism can be used in GUT models when ordinary Froggatt-Nielsen mechanism is no longer available. We study the application of Generalized Froggatt-Nielsen mechanism in SO(10) model. We find that realistic standard model mass hierarchy and mixings can be obtained both in SU(5) and SO(10) GUT models with such Generalized Froggatt-Nielsen mechanism.

  10. 37th Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    Boesiger, Edward A. (Compiler)

    2004-01-01

    The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is reporting problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, NASA and Lockheed Martin Space Systems Company (LMSSC) share the responsibility for hosting the AMS. Now in its 37th symposium, the AMS continues to be well attended, attracting participants from both the U.S. and abroad. The 37th AMS, hosted by the Johnson Space Center (JSC) in Galveston, Texas, was held May 19, 20 and 21, 2004. During these three days, 34 papers were presented. Topics included deployment mechanisms, tribology, actuators, pointing and optical mechanisms, Space Station and Mars Rover mechanisms, release mechanisms, and test equipment. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components.

  11. 41. After steering hydraulic mechanism from starboard side. Mechanism built ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    41. After steering hydraulic mechanism from starboard side. Mechanism built by the Superior Iron Works Co., Elizabeth, New Jersey, Lidgerwood Mfg Co. - U.S. Coast Guard Cutter BRAMBLE, Waterfront at Lincoln Avenue, Port Huron, St. Clair County, MI

  12. Thin film mechanics

    NASA Astrophysics Data System (ADS)

    Cooper, Ryan C.

    This doctoral thesis details the methods of determining mechanical properties of two classes of novel thin films suspended two-dimensional crystals and electron beam irradiated microfilms of polydimethylsiloxane (PDMS). Thin films are used in a variety of surface coatings to alter the opto-electronic properties or increase the wear or corrosion resistance and are ideal for micro- and nanoelectromechanical system fabrication. One of the challenges in fabricating thin films is the introduction of strains which can arise due to application techniques, geometrical conformation, or other spurious conditions. Chapters 2-4 focus on two dimensional materials. This is the intrinsic limit of thin films-being constrained to one atomic or molecular unit of thickness. These materials have mechanical, electrical, and optical properties ideal for micro- and nanoelectromechanical systems with truly novel device functionality. As such, the breadth of applications that can benefit from a treatise on two dimensional film mechanics is reason enough for exploration. This study explores the anomylously high strength of two dimensional materials. Furthermore, this work also aims to bridge four main gaps in the understanding of material science: bridging the gap between ab initio calculations and finite element analysis, bridging the gap between ab initio calculations and experimental results, nanoscale to microscale, and microscale to mesoscale. A nonlinear elasticity model is used to determine the necessary elastic constants to define the strain-energy density function for finite strain. Then, ab initio calculations-density functional theory-is used to calculate the nonlinear elastic response. Chapter 2 focuses on validating this methodology with atomic force microscope nanoindentation on molybdenum disulfide. Chapter 3 explores the convergence criteria of three density functional theory solvers to further verify the numerical calculations. Chapter 4 then uses this model to investigate the role of grain boundaries on the strength of chemical vapor deposited graphene. The results from these studies suggest that two dimensional films have remarkably high strength-reaching the intrinsic limit of molecular bonds. Chapter 5 explores the viscoelastic properties of heterogeneous polydimethylsiloxane (PDMS) microfilms through dynamic nanoindentation. PDMS microfilms are irradiated with an electron beam creating a 3 m-thick film with an increased cross-link density. The change in mechanical properties of PDMS due to thermal history and accelerator have been explored by a variety of tests, but the effect of electron beam irradiation is still unknown. The resulting structure is a stiff microfilm embedded in a soft rubber with some transformational strain induced by the cross-linking volume changes. Chapter 5 employs a combination of dynamic nanoindentation and finite element analysis to determine the change in stiffness as a function of electron beam irradiation. The experimental results are compared to the literature. The results of these experimental and numerical techniques provide exciting opportu- nities in future research. Two dimensional materials and flexible thin films are exciting materials for novel applications with new form factors, such as flexible electronics and microfluidic devices. The results herein indicate that you can accurately model the strength of two dimsensional materials and that these materials are robust against nanoscale defects. The results also reveal local variation of mechanical properties in PDMS microfilms. This allows one to design substrates that flex with varying amounts of strain on the surface. Combining the mechanics of two dimensional materials with that of a locally irradiated PDMS film could achieve a new class of flexible microelectromechanical systems. Large-scale growth of two dimensional materials will be structurally robust-even in the presence of nanostructural defects-and PDMS microfilms can be irradiated to vary strain of the electromechanical systems. These systems could be designed to investigate e

  13. Immunomodulatory mechanisms of lactobacilli

    PubMed Central

    2011-01-01

    Abstract Over the past decade it has become clear that lactobacilli and other probiotic and commensal organisms can interact with mucosal immune cells or epithelial cells lining the mucosa to modulate specific functions of the mucosal immune system. The most well understood signalling mechanisms involve the innate pattern recognition receptors such as Toll-like receptors, nucleotide oligomerization domain-like receptors and C-type lectin receptors. Binding of microbe-associated molecular patterns with these receptors can activate antigen presenting cells and modulate their function through the expression of surface receptors, secreted cytokines and chemokines. In vitro the cytokine response of human peripheral blood mononuclear cells and dendritic cells to lactobacilli can be strikingly different depending on both the bacterial species and the strain. Several factors have been identified in lactobacilli that influence the immune response in vitro and in vivo including cell surface carbohydrates, enzymes modifying the structure of lipoteichoic acids and metabolites. In mice mechanistic studies point to a role for the homeostatic control of inducible T regulatory cells in the mucosal tissues as one possible immunomodulatory mechanism. Increasing evidence also suggests that induction of epithelial signalling by intestinal lactobacilli can modulate barrier functions, defensin production and regulate inflammatory signalling. Other probiotic mechanisms include modulation of the T cell effector subsets, enhancement of humoral immunity and interactions with the epithelial-associated dendritic cells and macrophages. A major challenge for the future will be to gain more knowledge about the interactions occurring between lactobacilli and the host in vivo and to understand the molecular basis of innate signalling in response to whole bacteria which trigger multiple signalling pathways. PMID:21995674

  14. Magnetic attachment mechanism

    NASA Technical Reports Server (NTRS)

    Harwell, William D. (Inventor); Wu, Mitchell B. (Inventor)

    1990-01-01

    A magnetic attachment mechanism adapted for interfacing with the manipulator arm (11) of a remote manipulator system and comprising a pair of permanent magnets (31,32) of rare earth material which are arranged in a stator-rotor relationship. The rotor magnet (32), is journalled for rotation about its longitudinal axis between pole plates (35,36) of the stator magnet (31), each of which includes an adhering surface (35a,36a). In a first rotary position corresponding to the ON condition, each of the poles of the rotor magnet (32) is closely adjacent a stator magnet pole plate of like polarity whereby the respective magnet fields are additive for producing a strong magnetic field emanating from the adhering surfaces (35a,36a) for attracting a ferrous magnetic plate 20, or the like, affixed to the payload (20 or 50). When the rotor magnet (32) is rotated to a second position corresponding to the OFF condition, each of the poles of the rotor magnet (31) is disposed closely adjacent a pole plate of unlike polarity whereby the magnetic fields of the magnets are in cancelling relationship at the adhering surfaces (35a,36a) which permits the release of a payload. An actuator (51 or 70) for selectively rotating the rotor magnet (32) between the ON and OFF positions is provided for interfacing and connecting the magnetic attachment mechanism with a manipulator arm. For effecting an optimal rigidized attachment the payload is provided with guides (91,92) cooperable with guides (96,16,17) on the housing of the mechanism for directing adhering surfaces (35a,36a) of the polar plates to the ferrous plate (20).

  15. Analysis driven mechanical redesign

    SciTech Connect

    Ames, A.L.; Robison, R.H.

    1997-08-01

    This paper documents an effort to use a constrained nonlinear optimization package (OptdesX) to drive a feature-based mechanical design system (Pro/Engineer) in an optimization loop. Optimizations performed in this manner can maximally respect the design intent built into the model, and eliminate the need to propagate optimization results back to design, a flaw of most current optimization systems. A prototype system was built to demonstrate the capability; use of the prototype uncovered a variety of issues that should be addressed to productionize this kind of capability.

  16. Gravitomagnetism in quantum mechanics

    SciTech Connect

    Adler, Ronald J.; Chen Pisin

    2010-07-15

    We give a systematic treatment of the quantum mechanics of a spin zero particle in a combined electromagnetic field and a weak gravitational field that is produced by a slow moving matter source. The analysis is based on the Klein-Gordon equation expressed in generally covariant form and coupled minimally to the electromagnetic field. The Klein-Gordon equation is recast into Schroedinger equation form, which we then analyze in the nonrelativistic limit. We include a discussion of some rather general observable physical effects implied by the Schroedinger equation form, concentrating on gravitomagnetism. Of particular interest is the interaction of the orbital angular momentum of the particle with the gravitomagnetic field.

  17. [Diverse mechanisms of itch].

    PubMed

    Kuraishi, Yasushi

    2005-08-01

    Itch is known to be a sensation that provokes a desire to scratch. It is a bio-warning sensation, which serves to detect and remove parasites and irritants in the superficial layers of the skin and the mucous membrane. The mechanisms of itch are not simple. It is mediated by mast cells and keratinocytes, which each produce and release a few itch mediators. Alterations in the distribution of primary afferent fibers in the epidermis are also involved in itch. Agents that have a wide spectrum of inhibitory action on mast cells, keratinocytes and primary afferents may be needed to effectively suppress itch. PMID:16190369

  18. Molecular mechanisms of etoposide

    PubMed Central

    Montecucco, Alessandra; Zanetta, Francesca; Biamonti, Giuseppe

    2015-01-01

    Etoposide derives from podophyllotoxin, a toxin found in the American Mayapple. It was first synthesized in 1966 and approved for cancer therapy in 1983 by the U.S. Food and Drug Administration (Hande, 1998[25]). Starting from 1980s several studies demonstrated that etoposide targets DNA topoisomerase II activities thus leading to the production of DNA breaks and eliciting a response that affects several aspects of cell metabolisms. In this review we will focus on molecular mechanisms that account for the biological effect of etoposide.

  19. Mechanisms of metastasis

    PubMed Central

    Hunter, Kent W; Crawford, Nigel PS; Alsarraj, Jude

    2008-01-01

    Metastasis is an enormously complex process that remains to be a major problem in the management of cancer. The fact that cancer patients might develop metastasis after years or even decades from diagnosis of the primary tumor makes the metastatic process even more complex. Over the years many hypotheses were developed to try to explain the inefficiency of the metastatic process, but none of these theories completely explains the current biological and clinical observations. In this review we summarize some of the proposed models that were developed in attempt to understand the mechanisms of tumor dissemination and colonization as well as metastatic progression. PMID:19091006

  20. [Mechanical resuscitation assist devices].

    PubMed

    Fischer, M; Breil, M; Ihli, M; Messelken, M; Rauch, S; Schewe, J-C

    2014-03-01

    In Germany 100,000-160,000 people suffer from out-of-hospital cardiac arrest (OHCA) annually. The incidence of cardiopulmonary resuscitation (CPR) after OHCA varies between emergency ambulance services but is in the range of 30-90 CPR attempts per 100,000 inhabitants per year. Basic life support (BLS) involving chest compressions and ventilation is the key measure of resuscitation. Rapid initiation and quality of BLS are the most critical factors for CPR success. Even healthcare professionals are not always able to ensure the quality of CPR measures. Consequently in recent years mechanical resuscitation devices have been developed to optimize chest compression and the resulting circulation. In this article the mechanical resuscitation devices currently available in Germany are discussed and evaluated scientifically in context with available literature. The ANIMAX CPR device should not be used outside controlled trials as no clinical results have so far been published. The same applies to the new device Corpuls CPR which will be available on the market in early 2014. Based on the current published data a general recommendation for the routine use of LUCAS™ and AutoPulse® CPR cannot be given. The preliminary data of the CIRC trial and the published data of the LINC trial revealed that mechanical CPR is apparently equivalent to good manual CPR. For the final assessment further publications of large randomized studies must be analyzed (e.g. the CIRC and PaRAMeDIC trials). However, case control studies, case series and small studies have already shown that in special situations and in some cases patients will benefit from the automatic mechanical resuscitation devices (LUCAS™, AutoPulse®). This applies especially to emergency services where standard CPR quality is far below average and for patients who require prolonged CPR under difficult circumstances. This might be true in cases of resuscitation due to hypothermia, intoxication and pulmonary embolism as well as for patients requiring transport or coronary intervention when cardiac arrest persists. Three prospective randomized studies and the resulting meta-analysis are available for active compression-decompression resuscitation (ACD-CPR) in combination with an impedance threshold device (ITD). These studies compared ACD-ITD-CPR to standard CPR and clearly demonstrated that ACD-ITD-CPR is superior to standard CPR concerning short and long-term survival with good neurological recovery after OHCA. PMID:24569931

  1. 2001 Flight Mechanics Symposium

    NASA Technical Reports Server (NTRS)

    Lynch, John P. (Editor)

    2001-01-01

    This conference publication includes papers and abstracts presented at the Flight Mechanics Symposium held on June 19-21, 2001. Sponsored by the Guidance, Navigation and Control Center of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to attitude/orbit determination, prediction and control; attitude simulation; attitude sensor calibration; theoretical foundation of attitude computation; dynamics model improvements; autonomous navigation; constellation design and formation flying; estimation theory and computational techniques; Earth environment mission analysis and design; and, spacecraft re-entry mission design and operations.

  2. Mechanics of extensional wedges

    NASA Astrophysics Data System (ADS)

    Xiao, Hong-Bin; Dahlen, F. A.; Suppe, John

    1991-06-01

    The extensional wedges that overlie low-angle basal detachment faults are characterized by a tapered cross section similar to that exhibited by a fold-and-thrust belt, but with an opposite sense of shear on the basal fault. Such wedges are common in zones of crustal extension, such as the Basin and Range province of the North American Cordillera, the North Sea, and the U.S. Gulf Coast. This paper examines the mechanics of these upper crustal extensional wedges, using a modification of the compressional Coulomb critical taper model developed for fold-and-thrust belts and accretionary wedges. If a compressional wedge is mechanically analogous to a wedge of soil being pushed up an incline by a moving bulldozer, then an extensional wedge is analogous to the same wedge with the bulldozer moving in reverse gear down the incline. A critically tapered extensional wedge is one that is on the verge of Coulomb failure everywhere. A wedge whose taper is narrower may be slid stably down the same incline without internal deformation; a wedge whose taper is greater will fail by normal faulting and reduce its taper until it is critical. After testing the quantitative predictions of this extensional critical taper theory in a series of laboratory experiments on dry sand wedges, we apply the theory to a pair of active extensional wedges in the Brazos area, offshore Texas. Both wedges are underlain by well-imaged basal detachment faults dipping at 17° down to depths of 10 km; one wedge exhibits relatively little internal deformation, whereas the other is pervasively faulted along a series of moderately dipping synthetic normal faults. Direct and indirect estimates of the pore fluid pressure distribution within the two wedges suggest that the undeformed wedge is stable whereas the pervasively faulted wedge is unstable but nearly critical. Regional values for the coefficients of basal and internal friction in excess of 0.3 together with vertical cohesion gradients in excess of 1 kPa/m are consistent with the observed pore pressures and the geometry of the wedges, as well as with in situ stress data acquired during drilling and the dips of active synthetic normal faults. Such values are comparable to values inferred from mechanical and thermal models of compressional wedges, and they are consistent with laboratory rock mechanics data.

  3. NASA Access Mechanism (NAM)

    NASA Technical Reports Server (NTRS)

    Hunter, Judy

    1993-01-01

    A 1991 user survey indicated that NASA users want (1) access to diverse sources of information; (2) an intuitive approach to system use; (3) avoidance of system query languages; (4) access to peers and other informal sources of information; and (5) simplified and enhanced presentation of search results. Based on these requirements and the use of an intelligent gateway processor, the NASA Access Mechanism (NAM) is being developed to provide the users with the semblance of a one stop shopping environment for information management.

  4. Teaching Continuum Mechanics in a Mechanical Engineering Program

    ERIC Educational Resources Information Center

    Liu, Yucheng

    2011-01-01

    This paper introduces a graduate course, continuum mechanics, which is designed for and taught to graduate students in a Mechanical Engineering (ME) program. The significance of continuum mechanics in engineering education is demonstrated and the course structure is described. Methods used in teaching this course such as topics, class…

  5. 646 ULTRASONIC PHYSICAL MECHANISMS AND CHEMICAL EFFECTS ULTRASONIC PHYSICAL MECHANISMS

    E-print Network

    Suslick, Kenneth S.

    646 ULTRASONIC PHYSICAL MECHANISMS AND CHEMICAL EFFECTS ULTRASONIC PHYSICAL MECHANISMS AND CHEMICAL. Copyright # 1999 John Wiley & Sons, Inc. #12;ULTRASONIC PHYSICAL MECHANISMS AND CHEMICAL EFFECTS 647 sion. In addition, high- velocity interparticle collisions will occur during ultrasonic ir- can be extremely violent

  6. Chaos and quantum mechanics.

    PubMed

    Habib, Salman; Bhattacharya, Tanmoy; Greenbaum, Benjamin; Jacobs, Kurt; Shizume, Kosuke; Sundaram, Bala

    2005-06-01

    The relationship between chaos and quantum mechanics has been somewhat uneasy--even stormy, in the minds of some people. However, much of the confusion may stem from inappropriate comparisons using formal analyses. In contrast, our starting point here is that a complete dynamical description requires a full understanding of the evolution of measured systems, necessary to explain actual experimental results. This is of course true, both classically and quantum mechanically. Because the evolution of the physical state is now conditioned on measurement results, the dynamics of such systems is intrinsically nonlinear even at the level of distribution functions. Due to this feature, the physically more complete treatment reveals the existence of dynamical regimes--such as chaos--that have no direct counterpart in the linear (unobserved) case. Moreover, this treatment allows for understanding how an effective classical behavior can result from the dynamics of an observed quantum system, both at the level of trajectories as well as distribution functions. Finally, we have the striking prediction that time-series from measured quantum systems can be chaotic far from the classical regime, with Lyapunov exponents differing from their classical values. These predictions can be tested in next-generation experiments. PMID:15980320

  7. Chaos and Quantum Mechanics

    E-print Network

    Salman Habib; Tanmoy Bhattacharya; Benjamin Greenbaum; Kurt Jacobs; Kosuke Shizume; Bala Sundaram

    2005-05-11

    The relationship between chaos and quantum mechanics has been somewhat uneasy -- even stormy, in the minds of some people. However, much of the confusion may stem from inappropriate comparisons using formal analyses. In contrast, our starting point here is that a complete dynamical description requires a full understanding of the evolution of measured systems, necessary to explain actual experimental results. This is of course true, both classically and quantum mechanically. Because the evolution of the physical state is now conditioned on measurement results, the dynamics of such systems is intrinsically nonlinear even at the level of distribution functions. Due to this feature, the physically more complete treatment reveals the existence of dynamical regimes -- such as chaos -- that have no direct counterpart in the linear (unobserved) case. Moreover, this treatment allows for understanding how an effective classical behavior can result from the dynamics of an observed quantum system, both at the level of trajectories as well as distribution functions. Finally, we have the striking prediction that time-series from measured quantum systems can be chaotic far from the classical regime, with Lyapunov exponents differing from their classical values. These predictions can be tested in next-generation experiments.

  8. Mechanisms of cadmium carcinogenesis

    SciTech Connect

    Joseph, Pius

    2009-08-01

    Cadmium (Cd), a heavy metal of considerable occupational and environmental concern, has been classified as a human carcinogen by the International Agency for Research on Cancer (IARC). The carcinogenic potential of Cd as well as the mechanisms underlying carcinogenesis following exposure to Cd has been studied using in vitro cell culture and in vivo animal models. Exposure of cells to Cd results in their transformation. Administration of Cd in animals results in tumors of multiple organs/tissues. Also, a causal relationship has been noticed between exposure to Cd and the incidence of lung cancer in human. It has been demonstrated that Cd induces cancer by multiple mechanisms and the most important among them are aberrant gene expression, inhibition of DNA damage repair, induction of oxidative stress, and inhibition of apoptosis. The available evidence indicates that, perhaps, oxidative stress plays a central role in Cd carcinogenesis because of its involvement in Cd-induced aberrant gene expression, inhibition of DNA damage repair, and apoptosis.

  9. Mechanical Properties of Cells

    NASA Technical Reports Server (NTRS)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  10. Transmission shift mechanism

    SciTech Connect

    Smith, R.R.

    1989-06-20

    This patent describes a mechanism for selecting the gear of an automatic transmission in a vehicle. The mechanism consists of: a pressure source; a gear selection valve having an inlet means for receiving fluid from the pressure source, first outlet ports, and second outlet ports; a manual override means for opening and blocking communication between the pressure source and the first ports and for simultaneously opening and blocking communication between the pressure source and the second outlet ports; a port selector means within the valve for controlling flow through the second ports, the port selector means being movable to a plurality of positions, each position permitting a selected second outlet port to open; a selector control mans for moving the port selector means from one position to another, the selector control means including a planetary gear set connected by an input shaft to the transmission and connected to a vehicle load by an output shaft, the planetary gear set having a ring gear whose angular position is a function of reaction torque imposed by the load on the output shaft, the selector control means further including an arm assembly connected between the ring gear and the port selector means so that the position of the port selector means is a function of the reaction torque on the output shaft.

  11. Mechanical passive logic module

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Tanay; Caulfield, H. John

    2015-02-01

    Nothing from nothing gives simple simile, but something from nothing is an interesting and challenging task. Adolf Lohmann once proposed 'do nothing machine' in optics, which only copies input to output. Passive logic module (PALM) is a special type of 'do nothing machine' which can converts inputs into one of 16 possible binary outputs. This logic module is not like the conventional irreversible one. It is a simple type of reversible Turing machine. In this manuscript we discussed and demonstrated PALM using mechanical movement of plane mirrors. Also we discussed the theoretical model of micro electro mechanical system (MEMS) based PALM in this manuscript. It may have several valuable properties such as passive operation (no need for nonlinear elements as other logic device require) and modular logic (one device implementing any Boolean logic function with simple internal changes). The result is obtained from the demonstration by only looking up the output. No calculation is required to get the result. Not only that, PALM is a simple type of the famous 'billiard ball machine', which also discussed in this manuscript.

  12. Time Asymmetric Quantum Mechanics

    E-print Network

    Arno R. Bohm; Manuel Gadella; Piotr Kielanowski

    2011-09-03

    The meaning of time asymmetry in quantum physics is discussed. On the basis of a mathematical theorem, the Stone--von Neumann theorem, the solutions of the dynamical equations, the Schr\\"odinger equation (1) for states or the Heisenberg equation (6a) for observables are given by a unitary group. Dirac kets require the concept of a RHS (rigged Hilbert space) of Schwartz functions; for this kind of RHS a mathematical theorem also leads to time symmetric group evolution. Scattering theory suggests to distinguish mathematically between states (defined by a preparation apparatus) and observables (defined by a registration apparatus (detector)). If one requires that scattering resonances of width $\\Gamma$ and exponentially decaying states of lifetime $\\tau=\\frac{\\hbar}{\\Gamma}$ should be the same physical entities (for which there is sufficient evidence) one is led to a pair of RHS's of Hardy functions and connected with it, to a semigroup time evolution $t_{0}\\leq tbig bang time for the universe, when it was a quantum system. The decay of quasi-stable particles is used to illustrate this quantum mechanical time asymmetry. From the analysis of these processes, we show that the properties of rigged Hilbert spaces of Hardy functions are suitable for a formulation of time asymmetry in quantum mechanics.

  13. 15. Amygdala pain mechanisms

    PubMed Central

    Neugebauer, Volker

    2015-01-01

    A limbic brain area the amygdala plays a key role in emotional responses and affective states and disorders such as learned fear, anxiety and depression. The amygdala has also emerged as an important brain center for the emotional-affective dimension of pain and for pain modulation. Hyperactivity in the laterocapsular division of the central nucleus of the amygdala (CeLC, also termed the “nociceptive amygdala”) accounts for pain-related emotional responses and anxiety-like behavior. Abnormally enhanced output from the CeLC is the consequence of an imbalance between excitatory and inhibitory mechanisms. Impaired inhibitory control mediated by a cluster of GABAergic interneurons in the intercalated cell masses (ITC) allows the development of glutamate- and neuropeptide-driven synaptic plasticity of excitatory inputs from the brainstem (parabrachial area) and from the lateral-basolateral amygdala network (LA-BLA, site of integration of polymodal sensory information). BLA hyperactivity also generates abnormally enhanced feedforward inhibition of principal cells in the medial prefrontal cortex (mPFC), a limbic cortical area that is strongly interconnected with the amygdala. Pain-related mPFC deactivation results in cognitive deficits and failure to engage cortically driven ITC-mediated inhibitory control of amygdala processing. Impaired cortical control allows the uncontrolled persistence of amygdala pain mechanisms. PMID:25846623

  14. Hatch securing mechanism

    NASA Astrophysics Data System (ADS)

    Culling, Robert K.

    1992-09-01

    The invention is a hatch securing mechanism having a base attached to a hatchway and a hasp attached to a hatch lid. The base has an apertured retainer and a pinway element, the hasp being held between the retainer and pinway element during closure of the lid. A latch pin translatable in the pinway element has an angled tip which slides against a bevelled surface of the hasp to force the hasp into tighter, locked engagement with the base. The latch pin has a helical groove segment about the pin's axis, and a stud fixed to the pinway element engages the groove segment. The interaction of the stud and groove segment effects translation of the latch pin when the pin is manually rotated. The action of the latch pin also compresses an elastically deformable seal between the door and door frame so that the seal is increasingly effective against explosive blast pressures. The invention includes a lock mechanism for keeping the latch pin in a hasp retaining position unless the pin is manually moved.

  15. Copenhagen Quantum Mechanics

    E-print Network

    Hollowood, Timothy J

    2015-01-01

    In our quantum mechanics courses, measurement is usually taught in passing, as an ad-hoc procedure involving the ugly collapse of the wave function. No wonder we search for more satisfying alternatives to the Copenhagen interpretation. But this overlooks the fact that the approach fits very well with modern measurement theory with its notions of the conditioned state and quantum trajectory. In addition, what we know of as the Copenhagen interpretation is a later 1950's development and some of the earlier pioneers like Bohr did not talk of wave function collapse. In fact, if one takes these earlier ideas and mixes them with later insights of decoherence, a much more satisfying version of Copenhagen quantum mechanics emerges, one for which the collapse of the wave function is seen to be a harmless book keeping device. Along the way, we explain why chaotic systems lead to wave functions that spread out quickly on macroscopic scales implying that Schrodinger cat states are the norm rather than curiosities generat...

  16. Essays on dynamic sales mechanisms

    E-print Network

    Chen, Chia-Hui, Ph. D. Massachusetts Institute of Technology

    2009-01-01

    This thesis is a collection of three essays on dynamic sales mechanisms. The first chapter analyzes the Name Your Own Price (NYOP) mechanism adopted by Priceline.com. Priceline.com, a website helping travelers obtain ...

  17. 39th Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    Boesiger, E. A. (Compiler)

    2008-01-01

    The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production, and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, NASA Marshall Space Flight Center (MSFC) and Lockheed Martin Space Systems Company (LMSSC) share the responsibility for hosting the AMS. Now in its 39th symposium, the AMS continues to be well attended, attracting participants from both the United States and abroad. The 39th AMS was held in Huntsville, Alabama, May 7-9, 2008. During these 3 days, 34 papers were presented. Topics included gimbals and positioning mechanisms, tribology, actuators, deployment mechanisms, release mechanisms, and sensors. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components.

  18. 34th Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    Boesiger, Edward A. (Compiler)

    2000-01-01

    The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. The National Aeronautics and Space Administration and Lockheed Martin Space Systems Company (LMSSC) share the responsibility for organizing the AMS. Now in its 34th year, the AMS continues to be well attended, attracting participants from both the U.S. and abroad. The 34th AMS, hosted by the Goddard Space Flight Center (GSFC) in Greenbelt, Maryland, was held May 10, 11 and 12, 2000. During these three days, 34 papers were presented. Topics included deployment mechanisms, bearings, actuators, pointing and optical mechanisms, Space Station mechanisms, release mechanisms, and test equipment. Hardware displays during the vendor fair gave attendees an opportunity to meet with developers of current and future mechanism components.

  19. Exclusion Statistics in Classical Mechanics

    E-print Network

    T. H. Hansson; S. B. Isakov; J. M. Leinaas; U. Lindstrom

    2000-04-28

    We present a general method to derive the classical mechanics of a system of identical particles in a way that retains information about quantum statistics. The resulting statistical mechanics can be interpreted as a classical version of Haldane's exclusion statistics.

  20. 38th Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    Boesiger, Edward A. (Compiler)

    2006-01-01

    The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, the National Aeronautics and Space Administration and Lockheed Martin Space Systems Company (LMSSC) share the responsibility for hosting the AMS. Now in its 38th symposium, the AMS continues to be well attended, attracting participants from both the U.S. and abroad. The 38th AMs, hosted by the NASA Langley Research Center in Williamsburg, Virginia, was held May 17-19, 2006. During these three days, 34 papers were presented. Topics included gimbals, tribology, actuators, aircraft mechanisms, deployment mechanisms, release mechanisms, and test equipment. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components.

  1. Integrating behavior, mechanics and physiology

    E-print Network

    Hawai'i at Manoa, University of

    · Animal behavior and orientation · Swimming mechanics · When combined with other sensors providesIntegrating behavior, mechanics and physiology: use of acceleration sensors to study shark behavior behind observed behaviors · Variety of sensors available, but not utilized · Some modification

  2. On Randomness in Quantum Mechanics

    E-print Network

    Alberto C. de la Torre

    2007-07-19

    The quantum mechanical probability densities are compared with the probability densities treated by the theory of random variables. The relevance of their difference for the interpretation of quantum mechanics is commented.

  3. 33rd Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    Boesiger, Edward A. (Compiler); Litty, Edward C. (Compiler); Sevilla, Donald R. (Compiler)

    1999-01-01

    The proceedings of the 33rd Aerospace Mechanisms Symposium are reported. JPL hosted the conference, which was held at the Pasadena Conference and Exhibition Center, Pasadena, California, on May 19-21, 1999. Lockheed Martin Missiles and Space cosponsored the symposium. Technology areas covered include bearings and tribology; pointing, solar array and deployment mechanisms; orbiter/space station; and other mechanisms for spacecraft.

  4. Three Pictures of Quantum Mechanics

    E-print Network

    Olszewski Jr., Edward A.

    Three Pictures of Quantum Mechanics Thomas R. Shafer April 17, 2009 #12;Outline of the Talk · Brief review of (or introduction to) quantum mechanics. · 3 different viewpoints on calculation. · Schrödinger the Stage: Quantum Mechanics in Five Minutes #12;The Wave Function · A particle or system is described

  5. Snapping Mechanical Metamaterials under Tension.

    PubMed

    Rafsanjani, Ahmad; Akbarzadeh, Abdolhamid; Pasini, Damiano

    2015-10-01

    A snapping mechanical metamaterial is designed, which exhibits a sequential snap-through behavior under tension. The tensile response of this mechanical metamaterial can be altered by tuning the architecture of the snapping segments to achieve a range of nonlinear mechanical responses, including monotonic, S-shaped, plateau, and non-monotonic snap-through behavior. PMID:26314680

  6. Department of Mechanical Engineering FELLOWSHIPS

    E-print Network

    Barthelat, Francois

    Department of Mechanical Engineering FELLOWSHIPS INFORMATION SESSION 2011-2012 NSERC, FQRNT Graduate Fellowships #12;Department of Mechanical Engineering 2:00 ­ 2:05 Introduction 2:05 ­ 2:25 NSERC 2-Doctoral Rankings. #12;Department of Mechanical Engineering Why Apply for a Graduate Fellowship? It provides

  7. A Primer on Geometric Mechanics

    E-print Network

    Christian Lessig

    2012-06-14

    Geometric mechanics is usually studied in applied mathematics and most introductory texts are hence aimed at a mathematically minded audience. The present note tries to provide the intuition of geometric mechanics and to show the relevance of the subject for an understanding of "mechanics".

  8. SOLID MECHANICS James R. Rice

    E-print Network

    1 SOLID MECHANICS James R. Rice School of Engineering and Applied Sciences, and Department of Earth: February 2010 Downloadable at: http://esag.harvard.edu/rice/e0_Solid_Mechanics_94_10.pdf TABLE OF CONTENTS provided on last three pages, pp. 87-89 INTRODUCTION The application of the principles of mechanics to bulk

  9. 41st Aerospace Mechanisms Symposium

    NASA Technical Reports Server (NTRS)

    Boesiger, Edward A. (Editor)

    2012-01-01

    The proceedings of the 41st Aerospace Mechanisms Symposium are reported. JPL hosted the conference, which was held in Pasadena Hilton, Pasadena, California on May 16-18, 2012. Lockheed Martin Space Systems cosponsored the symposium. Technology areas covered include gimbals and positioning mechanisms, components such as hinges and motors, CubeSats, tribology, and Mars Science Laboratory mechanisms.

  10. Lecture notes Introductory fluid mechanics

    E-print Network

    Malham, Simon J.A.

    Lecture notes Introductory fluid mechanics Simon J.A. Malham Simon J.A. Malham (15th September 2014 of fluid mechanics and along the way see lots of interesting applications. 2 Fluid flow, the Continuum are generally incompressible--a feature essential to all modern car braking mechanisms. Fluids can be further

  11. MAE Student Handbook MECHANICAL ENGINEERING

    E-print Network

    Fainman, Yeshaiahu

    of attitude determination and control, space structures, orbital mechanics, and rocket propulsion (AE14MAE Student Handbook 2015-2016 MECHANICAL ENGINEERING AEROSPACE ENGINEERING ENVIRONMENTAL ENGINEERING mae.ucsd.edu #12;2 | P a g e Welcome to the Mechanical and Aerospace Engineering Department

  12. Cellular mechanics and motility

    NASA Astrophysics Data System (ADS)

    Hénon, Sylvie; Sykes, Cécile

    2015-10-01

    The term motility defines the movement of a living organism. One widely known example is the motility of sperm cells, or the one of flagellar bacteria. The propulsive element of such organisms is a cilium(or flagellum) that beats. Although cells in our tissues do not have a flagellum in general, they are still able to move, as we will discover in this chapter. In fact, in both cases of movement, with or without a flagellum, cell motility is due to a dynamic re-arrangement of polymers inside the cell. Let us first have a closer look at the propulsion mechanism in the case of a flagellum or a cilium, which is the best known, but also the simplest, and which will help us to define the hydrodynamic general conditions of cell movement. A flagellum is sustained by cellular polymers arranged in semi-flexible bundles and flagellar beating generates cell displacement. These polymers or filaments are part of the cellular skeleton, or "cytoskeleton", which is, in this case, external to the cellular main body of the organism. In fact, bacteria move in a hydrodynamic regime in which viscosity dominates over inertia. The system is thus in a hydrodynamic regime of low Reynolds number (Box 5.1), which is nearly exclusively the case in all cell movements. Bacteria and their propulsion mode by flagella beating are our unicellular ancestors 3.5 billion years ago. Since then, we have evolved to form pluricellular organisms. However, to keep the ability of displacement, to heal our wounds for example, our cells lost their flagellum, since it was not optimal in a dense cell environment: cells are too close to each other to leave enough space for the flagella to accomplish propulsion. The cytoskeleton thus developed inside the cell body to ensure cell shape changes and movement, and also mechanical strength within a tissue. The cytoskeleton of our cells, like the polymers or filaments that sustain the flagellum, is also composed of semi-flexible filaments arranged in bundles, and also in cross-linked or branched networks. It is a highly dynamical system in which filaments are able to elongate or slide one on the other with the contribution of very active cellular proteins like molecular motors. The versatile properties of this cytoskeleton ensure the diversity of mechanical behaviors to explain cell rigidity as well as cell motility.

  13. Mechanics of forearc basins

    NASA Astrophysics Data System (ADS)

    Cassola, Teodoro; Willett, Sean D.; Kopp, Heidrun

    2010-05-01

    In this study, the mechanics of forearc basins will be the object of a numerical investigation to understand the relationships between wedge deformation and forearc basin formation. The aim of this work is to gain an insight into the dynamics of the formation of the forearc basin, in particular the mechanism of formation of accommodation space and the preservation of basin stratigraphy. Our tool is a two-dimensional numerical model that includes the rheological properties of the rock, including effective internal friction angle, effective basal friction angle and thermally-dependent viscosity. We also simulate different sedimentation rates in the basin, to study the influence of underfilled and overfilled basin conditions on wedge deformation. The stratigraphy of the basin will also be studied, because in underfilled conditions the sediments are more likely to undergo tectonic deformation due to inner wedge deformation. We compare the numerical model with basins along the Sunda-Java Trench. This margin shows a variety of structural-settings and basin types including underfilled and overfilled basins and different wedge geometries. We interpret and document these structural styles, using depth migrated seismic sections of the Sunda Trench, obtained in three surveys, GINCO (11/98 - 01/99), MERAMEX (16/09/04 - 7/10/04) and SINDBAD (9/10/06 - 9/11/06) and made available through the IFM-GEOMAR and the Bundesanstalt für Geowissenschaften and Rohstoffe (BGR). One important aspect of these margins that we observe is the presence of a dynamic backstop, characterized by older accreted material, that, although deformed during and after accretion, later becomes a stable part of the upper plate. We argue that, following critical wedge theory, it entered into the stable field of a wedge either by steepening or weakening of the underlying detachment. As a stable wedge, this older segment of the wedge acts as a mechanical backstop for the frontal deforming wedge. This dynamic backstop moves seaward in time, in response to isostatic loading by the growing wedge, or due to seaward retreat of the slab with a consequent steepening of the base of the wedge.

  14. Payload Launch Lock Mechanism

    NASA Technical Reports Server (NTRS)

    Young, Ken (Inventor); Hindle, Timothy (Inventor)

    2014-01-01

    A payload launch lock mechanism includes a base, a preload clamp, a fastener, and a shape memory alloy (SMA) actuator. The preload clamp is configured to releasibly restrain a payload. The fastener extends, along an axis, through the preload clamp and into the base, and supplies a force to the preload clamp sufficient to restrain the payload. The SMA actuator is disposed between the base and the clamp. The SMA actuator is adapted to receive electrical current and is configured, upon receipt of the electrical current, to supply a force that causes the fastener to elongate without fracturing. The preload clamp, in response to the fastener elongation, either rotates or pivots to thereby release the payload.

  15. Moyal quantum mechanics

    E-print Network

    Osborn, T A

    1997-01-01

    The Moyal--Weyl description of quantum mechanics provides a comprehensive phase space representation of dynamics. The Weyl symbol image of the Heisenberg picture evolution operator is regular in \\hbar. Its semiclassical expansion `coefficients,' acting on symbols that represent observables, are simple, globally defined differential operators constructed in terms of the classical flow. Two methods of constructing this expansion are discussed. The first introduces a cluster-graph expansion for the symbol of an exponentiated operator, which extends Groenewold's formula for the Weyl product of symbols. This Poisson bracket based cluster expansion determines the Jacobi equations for the semiclassical expansion of `quantum trajectories.' Their Green function solutions construct the regular \\hbar\\downarrow0 asymptotic series for the Heisenberg--Weyl evolution map. The second method directly substitutes such a series into the Moyal equation of motion and determines the \\hbar coefficients recursively. The Heisenberg--...

  16. Rhodium hydroformylation mechanisms

    SciTech Connect

    Oswald, A.A.; Hendriksen, D.E.; Kastrup, R.V.; Merola, J.S.

    1982-03-01

    While the first 25 years of hydroformylation, i.e. oxo-process, chemistry were dominated by cobalt based catalysts, there has been rapid development of rhodium complex hydroformylation catalysts during the last 10 years. Although rhodium is about 100 times more expensive than cobalt, the low pressure activity of some rhodium complex catalysts is highly attractive when compared with the high pressure activity of the main cobalt catalyst, i.e., cobalt tetracarbonyl hydride. As a consequence, new plants for the selective hydroformylation of propylene to n-butyraldehyde, a key intermediate in the production of diethylhexyl phthalate plasticizer, have been for the most part based on a triphenylphosphine (Ph/sub 3/P) rhodium complex catalyst system, jointly developed by Union Carbide Corporation and Davy McKee Ltd. The mechanism of this catalyst system, which is presently of paramount importance in rhodium hydroformylation, is the main topic of the present paper.

  17. Mechanical origin of aftershocks

    PubMed Central

    Lippiello, E.; Giacco, F.; Marzocchi, W.; Godano, C.; de Arcangelis, L.

    2015-01-01

    Aftershocks are the most striking evidence of earthquake interactions and the physical mechanisms at the origin of their occurrence are still intensively debated. Novel insights stem from recent results on the influence of the faulting style on the aftershock organisation in magnitude and time. Our study shows that the size of the aftershock zone depends on the fault geometry. We find that positive correlations among parameters controlling aftershock occurrence in time, energy and space are a stable feature of seismicity independently of magnitude range and geographic areas. We explain the ensemble of experimental findings by means of a description of the Earth Crust as an heterogeneous elastic medium coupled with a Maxwell viscoelastic asthenosphere. Our results show that heterogeneous stress distribution in an elastic layer combined with a coupling to a viscous flow are sufficient ingredients to describe the physics of aftershock triggering. PMID:26497720

  18. Mechanisms of Phosphine Toxicity

    PubMed Central

    Nath, Nisa S.; Bhattacharya, Ishita; Tuck, Andrew G.; Schlipalius, David I.; Ebert, Paul R.

    2011-01-01

    Fumigation with phosphine gas is by far the most widely used treatment for the protection of stored grain against insect pests. The development of high-level resistance in insects now threatens its continued use. As there is no suitable chemical to replace phosphine, it is essential to understand the mechanisms of phosphine toxicity to increase the effectiveness of resistance management. Because phosphine is such a simple molecule (PH3), the chemistry of phosphorus is central to its toxicity. The elements above and below phosphorus in the periodic table are nitrogen (N) and arsenic (As), which also produce toxic hydrides, namely, NH3 and AsH3. The three hydrides cause related symptoms and similar changes to cellular and organismal physiology, including disruption of the sympathetic nervous system, suppressed energy metabolism and toxic changes to the redox state of the cell. We propose that these three effects are interdependent contributors to phosphine toxicity. PMID:21776261

  19. General relativistic statistical mechanics

    E-print Network

    Carlo Rovelli

    2012-11-19

    Understanding thermodynamics and statistical mechanics in the full general relativistic context is an open problem. I give tentative definitions of equilibrium state, mean values, mean geometry, entropy and temperature, which reduce to the conventional ones in the non-relativistic limit, but remain valid for a general covariant theory. The formalism extends to quantum theory. The construction builds on the idea of thermal time, on a notion of locality for this time, and on the distinction between global and local temperature. The last is the temperature measured by a local thermometer, and is given by kT = hbar d tau/ds, with k the Boltzmann constant, hbar the Planck constant, ds proper time and d tau the equilibrium thermal time.

  20. Mechanical origin of aftershocks

    NASA Astrophysics Data System (ADS)

    Lippiello, E.; Giacco, F.; Marzocchi, W.; Godano, C.; de Arcangelis, L.

    2015-10-01

    Aftershocks are the most striking evidence of earthquake interactions and the physical mechanisms at the origin of their occurrence are still intensively debated. Novel insights stem from recent results on the influence of the faulting style on the aftershock organisation in magnitude and time. Our study shows that the size of the aftershock zone depends on the fault geometry. We find that positive correlations among parameters controlling aftershock occurrence in time, energy and space are a stable feature of seismicity independently of magnitude range and geographic areas. We explain the ensemble of experimental findings by means of a description of the Earth Crust as an heterogeneous elastic medium coupled with a Maxwell viscoelastic asthenosphere. Our results show that heterogeneous stress distribution in an elastic layer combined with a coupling to a viscous flow are sufficient ingredients to describe the physics of aftershock triggering.