Studies in Jurkat leukemia cells have suggested that protein-tyrosine phosphatase PTPL1/FAP-1 rescues Fas-induced cell death. However, we have previously shown that this enzyme triggers ...4-hydroxytamoxifen-induced growth inhibition in human breast cancer cells. The present study addresses the role of PTPL1/FAP-1 in antiestrogen-regulated apoptotic effect and insulin-like growth factor-I survival action in MCF7 cells and further identifies the impacted signaling pathway. By terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling and cytoplasmic nucleosome enzyme-linked immunosorbent assay, we demonstrated that 4-hydroxytamoxifen-induced apoptosis was totally lost in PTPL1/FAP-1 antisense transfectants in which enzyme expression was abrogated, revealing the crucial role of this phosphatase in the apoptotic process in human breast cancer cells. Time-dependent expression of PTPL1/FAP-1 in MCF7 cells completely abolished the survival action of insulin-like growth factor-I. This effect occurred through a highly significant reduction in phosphatidylinositol 3-kinase/Akt pathway activation (80% reduction in phosphatidylinositol 3-kinase activity, 55% inhibition of Akt activation) accompanied by a 65% decrease in insulin receptor substrate-1 growth factor-induced tyrosine phosphorylation. These results provide the first evidence that PTPL1/FAP-1 has a key role in the apoptotic process in human breast cancer cells independent of Fas but associated with an early inhibition of the insulin receptor substrate-1/phosphatidylinositol 3-kinase pathway. Our data therefore suggest new therapeutic routes and strengthen the importance of identifying endogenous regulators and substrates of this phosphatase in breast tumors.
Gram-negative bacteria have developed several different transport systems for solute uptake. One of these, the tripartite ATP independent periplasmic transport system (TRAP-T), makes use of an ...extracytoplasmic solute receptor (ESR) which captures specific solutes with high affinity and transfers them to their partner permease complex located in the bacterial inner membrane. We hereby report the structures of DctP6 and DctP7, two such ESRs from
Bordetella pertussis. These two proteins display a high degree of sequence and structural similarity and possess the “Venus flytrap” fold characteristic of ESRs, comprising two globular α/β domains hinged together to form a ligand binding cleft. DctP6 and DctP7 both show a closed conformation due to the presence of one pyroglutamic acid molecule bound by highly conserved residues in their respective ligand binding sites. BLAST analyses have revealed that the DctP6 and DctP7 residues involved in ligand binding are strictly present in a number of predicted TRAP-T ESRs from other bacteria. In most cases, the genes encoding these TRAP-T systems are located in the vicinity of a gene coding for a pyroglutamic acid metabolising enzyme. Both the high degree of conservation of these ligand binding residues and the genomic context of these TRAP-T-coding operons in a number of bacterial species, suggest that DctP6 and DctP7 constitute the prototypes of a novel TRAP-T DctP subfamily involved in pyroglutamic acid transport.
Price forecast is a key issue in competitive electricity markets. It provides useful information for the market players and the regulators, in both short and long ran. Different approaches have been ...proposed and implemented. A new dynamic approach for forecasting the market price of electricity in the short term is proposed. The price dates are first clustered according to different types of daily profiles and then, given a proper function representing the trend in price, the set of unknown parameters are identified based on the zeroing of a Lyapunov function. The forecast can be dynamically updated with the latest data available. Higher weight can be attributed to this data in determining the future prices. The proposed approach is validated with reference to real systems in the form of the Italian, New England and New York electricity markets. In addition, an extensive price forecast is provided for the Italian market, an example of a young market that is rather difficult to predict patterns for.
This paper provides an overview of research on core from Oman Drilling Project Hole BT1B and the surrounding area, plus new data and calculations, constraining processes in the Tethyan subduction ...zone beneath the Samail ophiolite. The area is underlain by gently dipping, broadly folded layers of allochthonous Hawasina pelagic sediments, the metamorphic sole of the Samail ophiolite, and Banded Unit peridotites at the base of the Samail mantle section. Despite reactivation of some faults during uplift of the Jebel Akdar and Saih Hatat domes, the area preserves the tectonic “stratigraphy” of the Cretaceous subduction zone. Gently dipping listvenite bands, parallel to peridotite banding and to contacts between the peridotite and the metamorphic sole, replace peridotite at and near the basal thrust. Listvenites formed at less than 200°C and (poorly constrained) depths of 25–40 km by reaction with CO2‐rich, aqueous fluids migrating from greater depths, derived from devolatilization of subducting sediments analogous to clastic sediments in the Hawasina Formation, at 400°–500°. Such processes could form important reservoirs for subducted CO2. Listvenite formation was accompanied by ductile deformation of serpentinites and listvenites—perhaps facilitated by fluid‐rock reaction—in a process that could lead to aseismic subduction in some regions. Addition of H2O and CO2 to the mantle wedge, forming serpentinites and listvenites, caused large increases in the solid mass and volume of the rocks. This may have been accommodated by fractures formed as a result of volume changes, mainly at a serpentinization front.
Plain Language Summary
This paper reports initial results from study of core from Oman Drilling Project Hole BT1B and the surrounding area. It provides insights into subduction zone processes, including large fluxes of recycled CO2 from subducting sediments into the leading edge of the mantle wedge, and surprisingly low temperature ductile deformation at less than 200°C. Recycling of CO2 via carbon mineralization in the hanging wall of subduction zones may produce an important, lithospheric reservoir in the global carbon cycle. Ductile deformation of serpentinite, and during or after transformation of peridotite to listvenites (mixtures of carbonates and opal or quartz) could explain aseismic subduction atop some subduction zones.
Key Points
The area at and around OmanDP Hole BT1B preserves nearly flat‐lying tectonic “stratigraphy” of the basal thrust of the Samail ophiolite
Recycling of CO2 from subducting sediment into the mantle wedge produced listvenites (carbonated peridotite) at <200°C
Subduction beneath the ophiolite was accommodated, in part, by ductile deformation of serpentinite and listvenite at <200°C
► New approach of thermal fatigue of 304L pipes, with microstructure gradients. ► Cyclic biaxial loading applied to a Representative Volume Element (EBSD mappings). ► Surface scratches and gradient ...of pre-hardening are introduced into the RVE. ► Local fields computed via a polycrystal model based on the dislocation theory. ► Different damage criteria are studied.
The 304L stainless steel is a major component of residual heat removal circuits of pressurized water reactors (PWRs). The main purpose of this study is to understand the risk of thermal fatigue damage resulting from the machining of the 304L steel pipes inner surface (pre-hardening gradient, residual stresses and scratches), at the scale of the microstructure. This work is based on previous results obtained for pipe specimens thanks to a macroscopic elasto-visco-plastic model. Applied to the pipe specimens, this modelling showed that a thermal loading with temperature gradient, induced a cyclic non-linear biaxial loading at the inner surface of the pipe. In this paper, a polycrystal plasticity model, implemented in a Finite Element (FE) code, is adapted to cyclic loading. An elementary volume (3D aggregate), representing the inner surface and sub-surface of the 304L steel tube, is built from successive polishings and orientation mappings thanks to an Electron Back Scattering Diffraction method. At the grain scale, the polycrystal model is used as a “numerical microscope” to compute the local mechanical fields. Different fatigue criteria are tested to determine their sensitivity to surface properties (roughness, residual stress and pre-hardening) and to the microstructure of the material (crystallographic orientation and grain size). Pre-hardening leads to a lower and more homogeneous distribution of local strain amplitudes in the aggregate, but slightly higher stresses when compared to initial material without hardening. By contrast, surface roughness leads to large localized strain and stress fields in grains located at the bottom of scratches. To determine the surface micro-structural “hot spots” features and to test the sensitivity of different surface conditions, three different fatigue criteria (Manson-Coffin, Fatemi–Socie and Dissipated Energy criteria) have been computed. We point out that the pre-hardening may have a complex effect on fatigue resistance, since it reduces local plastic strain amplitudes, but increases local stresses. Moreover, the pre-hardening has a positive effect on fatigue since it delays damage initiation. By contrast, the surface roughness leads to a negative effect. However, we have shown that the three different fatigue criteria do not deliver similar quantitative predictions. Relevant criteria for high cycle fatigue, such as stress based criteria, are not considered in this paper, since the thermal loading used for computation is large enough to reduce cyclic plastic strain straining within all grains of 304L pipe inner surface for midlife of experiments.
PTPL1 is the largest known cytoplasmic protein tyrosine phosphatase (PTP) containing a FERM (four point-1, ezrin, radixin and moesin) domain. Enzyme localization and PTP-substrate specificity are ...thought to play crucial roles in the regulation of PTP activity, which determines their functions. Here we report that PTPL1 is predominantly localized at the apical face of plasma membrane enriched in dorsal microvilli when expressed in HeLa cells. By comparing localization of the full-length enzyme with its FERM domain or FERM-deleted PTPL1 construct, we first concluded that PTPL1-FERM domain is necessary and sufficient to address the wild-type enzyme at the membrane. Two potential phosphatidylinositol 4,5-biphosphate PtdIns(4,5)P2-binding motifs were identified within the PTPL1-FERM sequence. We further showed that mutation of both sites altered PTPL1 localization similarly to FERM domain deletion, and impaired its subcellular distribution as confirmed biochemically by cell-fractionation experiments. Using protein-lipid overlays, we demonstrated an interaction of the FERM domain of PTPL1 with PtdIns(4,5)P2, which was lost after mutation of potential PtdIns(4,5)P2-binding motifs. Moreover, neomycin, which masks PtdIns(4,5)P2 polar heads, was shown to decrease by 50% the association of PTPL1 with the cytoskeletal fraction. These results identify the crucial role of the FERM domain in PTPL1 intracellular targeting and demonstrate that localization of PTPL1 is regulated by phosphoinositide metabolism.
Periplasmic binding proteins of a new family particularly well represented in
Bordetella pertussis have been called Bug receptors. One
B.
pertussis
Bug protein is part of a tripartite tricarboxylate ...transporter while the functions of the other 77 are unknown. We report the first structure of a Bug receptor, BugD. It adopts the characteristic Venus flytrap motif observed in other periplasmic binding proteins, with two globular domains bisected by a deep cleft. BugD displays a closed conformation resulting from the fortuitous capture of a ligand, identified from the electron density as an aspartate. The structure reveals a distinctive α carboxylate-binding motif, involving two water molecules that bridge the carboxylate oxygen atoms to the protein. Both water molecules are hydrogen bonded to a common carbonyl group from Ala14, and each forms a hydrogen bond with one carboxylate oxygen atom of the ligand. Additional hydrogen bonds are found between the ligand α carboxylate oxygen atoms and protein backbone amide groups and with a threonine hydroxyl group. This specific ligand-binding motif is highly conserved in Bug proteins, indicating that they may all be receptors of amino acids or other carboxylated solutes, with a similar binding mode. The present structure thus unveils the bases of ligand binding in this large family of periplasmic binding proteins, several hundred members of which have been identified in various bacterial species.
PDF
