Protein associated with SMAD1 (PAWS1/FAM83G) is a substrate for type I bone morphogenetic protein receptors and modulates bone morphogenetic protein signalling

Bone morphogenetic proteins (BMPs) control multiple cellular processes in embryos and adult tissues. BMPs signal through the activation of type I BMP receptor kinases, which then phosphorylate SMADs 1/5/8. In the canonical pathway, this triggers the association of these SMADs with SMAD4 and their translocation to the nucleus, where they regulate gene expression. BMPs can also signal independently of SMAD4, but this pathway is poorly understood. Here, we report the discovery and characterization of PAWS1/FAM83G as a novel SMAD1 interactor. PAWS1 forms a complex with SMAD1 in a SMAD4-independent manner, and BMP signalling induces the phosphorylation of PAWS1 through BMPR1A. The phosphorylation of PAWS1 in response to BMP is essential for activation of the SMAD4-independent BMP target genes NEDD9 and ASNS. Our findings identify PAWS1 as the first non-SMAD substrate for type I BMP receptor kinases and as a novel player in the BMP pathway. We also demonstrate that PAWS1 regulates the expression of several non-BMP target genes, suggesting roles for PAWS1 beyond the BMP pathway

Dynamical effects induced by long range activation in a nonequilibrium reaction-diffusion system

We both show experimentally and numerically that the time scales separation introduced by long range activation can induce oscillations and excitability in nonequilibrium reaction-diffusion systems that would otherwise only exhibit bistability. Namely, we show that the Chlorite-Tetrathionate reaction, where autocatalytic species diffuses faster than the substrates, the spatial bistability domain in the nonequilibrium phase diagram is extended with oscillatory and excitability domains. A simple model and a more realistic model qualitatively account for the observed behavior. The latter model provides quantitative agreement with the experiments.Comment: 19 pages + 9 figure

Cellulose production is coupled to sensing of the pyrimidine biosynthetic pathway via c-di-GMP production by the DgcQ protein of Escherichia coli

Production of cellulose, a stress response-mediated process in enterobacteria, is modulated in Escherichia coli by the activity of the two pyrimidine nucleotide biosynthetic pathways, namely, the de novo biosynthetic pathway and the salvage pathway, which relies on the environmental availability of pyrimidine nitrogenous bases. We had previously reported that prevalence of the salvage over the de novo pathway triggers cellulose production via synthesis of the second messenger c-di-GMP by the DgcQ (YedQ) diguanylate cyclase. In this work, we show that DgcQ enzymatic activity is enhanced by UTP, whilst being inhibited by N-carbamoyl-aspartate, an intermediate of the de novo pathway. Thus, direct allosteric control by these ligands allows full DgcQ activity exclusively in cells actively synthesizing pyrimidine nucleotides via the salvage pathway. Inhibition of DgcQ activity by N-carbamoyl-aspartate appears to be favoured by protein-protein interaction between DgcQ and PyrB, a subunit of aspartate transcarbamylase, which synthesizes N-carbamoyl-aspartate. Our results suggest that availability of pyrimidine bases might be sensed, somehow paradoxically, as an environmental stress by E. coli. We hypothesize that this link might have evolved since stress events, leading to extensive DNA/RNA degradation or lysis of neighbouring cells, can result in increased pyrimidine concentrations and activation of the salvage pathway

Experimental Demonstration of Signal-to-Noise-Ratio Improvement of Fourier-Domain Optical Coherence Tomography

A recent advance in optical coherence tomography (OCT), termed swept-source OCT, is generalized into a new technique, Fourier-domain OCT. It represents a realization of a full-field OCT system in place of the conventional serial image acquisition in transverse directions typically implemented in "flying-spot" mode. To realize the full-field image acquisition, a Fourier holography system illuminated with a swept-source is employed instead of a Michelson interferometer commonly used in OCT. Fourier-domain OCT offers a new leap in signal-to-noise ratio improvement, as compared to flying-spot OCT systems. This paper presents experimental evidence that the signal-to-noise ratio of this new technique is indeed improved.Comment: submitted to Optics Letters 7/14/200

Signal-to-signal-to-noise ratio of full-field Fourier domain optical coherence tomography: experiment

We report a new approach in optical coherence tomography (OCT) termed full-field Fourier-domain OCT (3F-OCT). A three-dimensional image of a sample is obtained by digital reconstruction of a three-dimensional data cube, acquired using a Fourier holography recording system illuminated with a swept-source. This paper presents theoretical and experimental study of the signal-to-noise ratio of the full-field approach versus serial image acquisition approach, represented by 3F-OCT and "flying-spot" OCT systems, respectively

Calculating quench propagation with ANSYS®

A commercial Finite-Element-Analysis program, ANSYS®, is widely used in structural and thermal analysis. With the program's ability to include nonlinear material properties and import complex CAD files, one can generate coil geometries and simulate quench propagation in superconducting magnets. A "proof-of-principle" finite element model was developed assuming a resistivity that increases linearly from zero to its normal value at a temperature consistent with the assumed B magnetic field. More sophisticated models could easily include finer-grained coil, cable, structural, and circuit details. A quench is provoked by raising the temperature of an arbitrary superconducting element above its T . The time response to this perturbation is calculated using small time-steps to allow convergence between steps. Snapshots of the temperature and voltage distributions allow examination of longitudinal and turn-to-turn quench propagation, quench-front annihilation, and cryo-stability. Modeling details are discussed, and a computed voltage history was compared with measurements from a recent magnet test.

The WNK-regulated SPAK/OSR1 kinases directly phosphorylate and inhibit the K+-Cl- co-transporters

This is the final version of the article. Available from Portland Press via the DOI in this record.There is another ORE record for this publication: http://hdl.handle.net/10871/32310Precise homoeostasis of the intracellular concentration of Cl- is achieved via the co-ordinated activities of the Cl- influx and efflux. We demonstrate that the WNK (WNK lysine-deficient protein kinase)-activated SPAK (SPS1-related proline/alanine-rich kinase)/OSR1 (oxidative stress-responsive kinase 1) known to directly phosphorylate and stimulate the N[K]CCs (Na+-K+ ion co-transporters), also promote inhibition of the KCCs (K+-Cl- co-transporters) by directly phosphorylating a recently described C-terminal threonine residue conserved in all KCC isoforms [Site-2 (Thr1048)]. First, we demonstrate that SPAK and OSR1, in the presence of the MO25 regulatory subunit, robustly phosphorylates all KCC isoforms at Site-2 in vitro. Secondly, STOCK1S-50699, a WNK pathway inhibitor, suppresses SPAK/OSR1 activation and KCC3A Site-2 phosphorylation with similar efficiency. Thirdly, in ES (embryonic stem) cells lacking SPAK/OSR1 activity, endogenous phosphorylation of KCC isoforms at Site-2 is abolished and these cells display elevated basal activity of 86Rb+ uptake that was not markedly stimulated further by hypotonic high K+ conditions, consistent with KCC3A activation. Fourthly, a tight correlation exists between SPAK/OSR1 activity and the magnitude of KCC3A Site-2 phosphorylation. Lastly, a Site-2 alanine KCC3A mutant preventing SPAK/OSR1 phosphorylation exhibits increased activity. We also observe that KCCs are directly phosphorylated by SPAK/OSR1, at a novel Site-3 (Thr5 in KCC1/KCC3 and Thr6 in KCC2/KCC4), and a previously recognized KCC3-specific residue, Site-4 (Ser96). These data demonstrate that the WNK-regulated SPAK/OSR1 kinases directly phosphorylate the N[K]CCs and KCCs, promoting their stimulation and inhibition respectively. Given these reciprocal actions with anticipated net effects of increasing Cl- influx, we propose that the targeting of WNK-SPAK/OSR1 with kinase inhibitors might be a novel potent strategy to enhance cellular Cl- extrusion, with potential implications for the therapeutic modulation of epithelial and neuronal ion transport in human disease states.This work was supported by the Medical Research Council and the Wellcome Trust [grant number 091415] as well as the pharmaceutical companies supporting the Division of Signal Transduction Therapy Unit (AstraZeneca, Boehringer-Ingelheim, GlaxoSmithKline, Merck KgaA, Janssen Pharmaceutica and Pfizer). K.T.K. is supported by the Manton Center for Orphan Diseases at Children's Hospital Boston at Harvard Medical School, and the Harvard/MIT Joint Research Grants Program in Basic Neuroscience

Learning from the early adopters: developing the digital practitioner

This paper explores how Sharpe and Beetham’s Digital Literacies Framework which was derived to model students’ digital literacies, can be applied to lecturers’ digital literacy practices. Data from a small-scale phenomenological study of higher education lecturers who used Web 2.0 in their teaching and learning practices are used to examine if this pyramid model represents their motivations for adopting technology-enhanced learning in their pedagogic practices. The paper argues that whilst Sharpe and Beetham’s model has utility in many regards, these lecturers were mainly motivated by the desire to achieve their pedagogic goals rather than by a desire to become a digital practitioner

Design and evaluation of a short period Nb3Sn superconducting undulator prototype

The design of a class of short period superconducting undulators is presented. We begin with a parameter-based analysis that provides insight into potential device performance as a function of the properties of superconducting materials. We present data on candidate low-temperature superconducting materials and the motivation to consider low-copper fraction, high Jc materials. Measured data on recent Nb Sn conductors is provided, together with wire and cable design issues that are tailored for undulator applications. Key design concerns are then addressed, in particular the quench protection system limitations and the system performance. Progress on the construction and testing of a prototype 30mm period device is described.

The Hydrogen Atom in Combined Electric and Magnetic Fields with Arbitrary Mutual Orientations

For the hydrogen atom in combined magnetic and electric fields we investigate the dependence of the quantum spectra, classical dynamics, and statistical distributions of energy levels on the mutual orientation of the two external fields. Resonance energies and oscillator strengths are obtained by exact diagonalization of the Hamiltonian in a complete basis set, even far above the ionization threshold. At high excitation energies around the Stark saddle point the eigenenergies exhibit strong level repulsions when the angle between the fields is varied. The large avoided crossings occur between states with the same approximately conserved principal quantum number, n, and this intramanifold mixing of states cannot be explained, not even qualitatively, by conventional perturbation theory. However, it is well reproduced by an extended perturbation theory which takes into account all couplings between the angular momentum and Runge-Lenz vector. The large avoided crossings are interpreted as a quantum manifestation of classical intramanifold chaos. This interpretation is supported by both classical Poincar\'e surfaces of section, which reveal a mixed regular-chaotic intramanifold dynamics, and the statistical analysis of nearest-neighbor-spacingComment: two-column version, 10 pages, REVTeX, 10 figures, uuencoded, submitted to Rhys. Rev.