A core function for p120-catenin in cadherin turnover

p120-catenin stabilizes epithelial cadherin (E-cadherin) in SW48 cells, but the mechanism has not been established. Here, we show that p120 acts at the cell surface to control cadherin turnover, thereby regulating cadherin levels. p120 knockdown by siRNA expression resulted in dose-dependent elimination of epithelial, placental, neuronal, and vascular endothelial cadherins, and complete loss of cell–cell adhesion. ARVCF and δ-catenin were functionally redundant, suggesting that proper cadherin-dependent adhesion requires the presence of at least one p120 family member. The data reveal a core function of p120 in cadherin complexes, and strongly predict a dose-dependent loss of E-cadherin in tumors that partially or completely down-regulate p120

Work in Progress: The WSU Model for Engineering Mathematics Education

This paper summarizes progress to date on the WSU model for engineering mathematics education, an NSF funded curriculum reform initiative at Wright State University. The WSU model seeks to increase student retention, motivation and success in engineering through application-driven, just-in-time engineering math instruction. The WSU approach involves the development of a novel freshman-level engineering mathematics course EGR 101, as well as a large-scale restructuring of the engineering curriculum. By removing traditional math prerequisites and moving core engineering courses earlier in the program, the WSU model shifts the traditional emphasis on math prerequisite requirements to an emphasis on engineering motivation for math, with a just-in-time structuring of the new math sequence. This paper summarizes the development to date of the WSU model for engineering mathematics education, including a preliminary assessment of student performance and perception during the initial implementation of EGR 101. In addition, an assessment of first-year retention results is anticipated in time for the conference

Intrinsic Absorption Lines in Seyfert 1 Galaxies. I. Ultraviolet Spectra from the Hubble Space Telescope

We present a study of the intrinsic absorption lines in the ultraviolet spectra of Seyfert 1 galaxies. We find that the fraction of Seyfert 1 galaxies that show absorption associated with their active nuclei is more than one-half (10/17), which is much higher than previous estimates (3 - 10%) . There is a one-to-one correspondence between Seyferts that show intrinsic UV absorption and X-ray ``warm absorbers''. The intrinsic UV absorption is generally characterized by high ionization: C IV and N V are seen in all 10 Seyferts with detected absorption (in addition to Ly-alpha), whereas Si IV is present in only four of these Seyferts, and Mg II absorption is only detected in NGC 4151. The absorption lines are blueshifted (or in a few cases at rest) with respect to the narrow emission lines, indicating that the absorbing gas is undergoing net radial outflow. At high resolution, the absorption often splits into distinct kinematic components that show a wide range in widths (20 - 400 km/s FWHM), indicating macroscopic motions (e.g., radial velocity subcomponents or turbulence) within a component. The strong absorption components have cores that are much deeper than the continuum flux levels, indicating that the regions responsible for these components lie completely outside of the broad emission-line regions. The covering factor of the absorbing gas in the line of sight, relative to the total underlying emission, is C > 0.86, on average. The global covering factor, which is the fraction of emission intercepted by the absorber averaged over all lines of sight, is C > 0.5.Comment: 56 pages, Latex, includes 4 figures (encapsulated postscript), Fig. 1 has 2 parts and Fig. 2 has 3 parts, to appear in the Astrophysical Journa

Single-chain Fv phage display propensity exhibits strong positive correlation with overall expression levels

<p>Abstract</p> <p>Background</p> <p>Single chain Fvs (scFvs) are widely applied in research, diagnostics and therapeutic settings. Display and selection from combinatorial libraries is the main route to their discovery and many factors influence the success of this process. They exhibit low thermodynamic stability, resulting in low levels of premature cytosolic folding or aggregation which facilitates <it>sec </it>YEG-mediated translocation and phage in <it>E. coli</it>. However, there is little data analysing how this is related to and influenced by scFv protein expression.</p> <p>Results</p> <p>We characterised the relationship between overall scFv expression and display propensity for a panel of 15 anti-tetanus toxin scFvs and found a strong positive correlation (Rho = 0.88, p < 0.005) between the two parameters. Display propensity, overall expression and soluble localisation to the periplasm and extracellular fractions were clone specific characteristics which varied despite high levels of sequence homology. There was no correlation between display of scFv or its expression in non-fused (free) form with soluble scFv localisation to the periplasm or culture supernatant. This suggests that divergence in the fate of scFv-pIII and non-fused scFv after translocation to the periplasm accounts for the observed disparity. Differential degrees of periplasmic aggregation of non-fused scFv between clones may affect the partitioning of scFv in the periplasm and culture supernatant abrogating any correlation. We suggest that these factors do not apply to the scFv-pIII fusion since it remains anchored to the bacterial inner membrane as part of the innate phage packaging and budding process.</p> <p>Conclusion</p> <p>We conclude that in the absence of premature cytosolic aggregation or folding, the propensity of a scFv to be displayed on phage is directly related to its overall expression level and is thus indirectly influenced by factors such as codon bias, mRNA abundance or putative DNA motifs affecting expression. This suggests that scFvs capable of high overall expression and display levels may not produce high yields of non phage-fused soluble protein in either the periplasmic or extracellular fractions of <it>E. coli</it>. This should be considered when screening clones selected from combinatorial libraries for further study.</p> <p>The nucleotide and amino acid sequences of the anti-tetanus toxin scFvs have been deposited in the EMBL data base: accession numbers-C1: <ext-link ext-link-type="embl" ext-link-id="AM749134">AM749134</ext-link>, C2: <ext-link ext-link-type="embl" ext-link-id="AM749135">AM749135</ext-link>, C3: <ext-link ext-link-type="embl" ext-link-id="AM749136">AM749136</ext-link>, C4: <ext-link ext-link-type="embl" ext-link-id="AM749137">AM749137</ext-link>, C5: <ext-link ext-link-type="embl" ext-link-id="AM749138">AM749138</ext-link>, N1: <ext-link ext-link-type="embl" ext-link-id="AM749139">AM749139</ext-link>, N2: <ext-link ext-link-type="embl" ext-link-id="AM749140">AM749140</ext-link>, N3: <ext-link ext-link-type="embl" ext-link-id="AM749141">AM749141</ext-link>, N4: <ext-link ext-link-type="embl" ext-link-id="AM749142">AM749142</ext-link>, N5: <ext-link ext-link-type="embl" ext-link-id="AM749143">AM749143</ext-link> J1; <ext-link ext-link-type="embl" ext-link-id="AM749144">AM749144</ext-link>, J2: <ext-link ext-link-type="embl" ext-link-id="AM749145">AM749145</ext-link>, J3: <ext-link ext-link-type="embl" ext-link-id="AM749146">AM749146</ext-link>, J4: <ext-link ext-link-type="embl" ext-link-id="AM749147">AM749147</ext-link>, J5: <ext-link ext-link-type="embl" ext-link-id="AM749148">AM749148</ext-link>.</p

Membrane-associated heparan sulfate is not required for rAAV-2 infection of human respiratory epithelia

BACKGROUND: Adeno-associated virus type 2 (AAV-2) attachment and internalization is thought to be mediated by host cell membrane-associated heparan sulfate proteoglycans (HSPG). Lack of HSPG on the apical membrane of respiratory epithelial cells has been identified as a reason for inefficient rAAV-2 infection in pulmonary applications in-vivo. The aim of this investigation was to determine the necessity of cell membrane HSPG for efficient infection by rAAV-2. RESULTS: Rates of transduction with rAAV2-CMV-EGFP3 in several different immortalized airway epithelial cell lines were determined at different multiplicities of infection (MOI) before and after removal of membrane HSPG by heparinase III. Removal of HSPG decreased the efficacy of infection with rAAV2 by only 30–35% at MOI ≤ 100 for all of respiratory cell lines tested, and had even less effect at an MOI of 1000. Studies in mutant Chinese Hamster Ovary cell lines known to be completely deficient in surface HSPG also demonstrated only moderate effect of absence of HSPG on rAAV-2 infection efficacy. However, mutant CHO cells lacking all membrane proteoglycans demonstrated dramatic reduction in susceptibility to rAAV-2 infection, suggesting a role of membrane glycosaminoglycans other than HSPG in mediating rAAV-2 infection. CONCLUSION: Lack of cell membrane HSPG in pulmonary epithelia and other cell lines results in only moderate decrease in susceptibility to rAAV-2 infection, and this decrease may be less important at high MOIs. Other cell membrane glycosaminoglycans can play a role in permitting attachment and subsequent rAAV-2 internalization. Targeting alternative membrane glycosaminoglycans may aid in improving the efficacy of rAAV-2 for pulmonary applications

p120-Catenin Mediates Inflammatory Responses in the Skin

SummaryAlthough p120-catenin regulates adherens junction (AJ) stability in cultured cells, genetic studies in lower eukaryotes have not revealed a role for this protein in vivo. Using conditional targeting in mice, we show that p120 null neonatal epidermis exhibits reduced intercellular AJ components but no overt disruption in barrier function or intercellular adhesion. As the mice age, however, they display epidermal hyperplasia and chronic inflammation, typified by hair degeneration and loss of body fat. Using skin engraftments and anti-inflammatory drugs, we show that these features are not attributable to reductions in junctional cadherins and catenins, but rather NFkB activation. Both in vivo and in vitro, p120 null epidermal cells activate nuclear NFkB, triggering a cascade of proinflammatory NFkB targets. Although the underlying mechanism is likely complex, we show that p120 affects NFkB activation and immune homeostasis in part through regulation of Rho GTPases. These findings provide important new insights into p120 function

Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. II. Physical Conditions Near the NGC 1068 ``Hot-Spot''

The physical conditions near the optical continuum peak (``hot spot'') in the inner narrow line region (NLR) of the Seyfert 2 galaxy, NGC 1068. Spectra were taken with HST/STIS through the 0.1X52 arcsec slit, covering the full STIS 1200 to 10000 Angstrom waveband, and are from a region that includes the hot spot, extending 0.2, or ~ 14 pc (for H= 75 km/sec/Mpc). Perhaps the most striking feature of these spectra is the presence of strong coronal emission lines, including [S XII] 7611 which has hitherto only been identified in spectra of the solar corona. There is an apparent correlation between ionization energy and velocity of the emission lines with respect to the systemic velocity of the host galaxy, with the coronal lines blueshifted, most other high excitation lines near systemic, and some of the low ionization lines redshifted. From the results of our modeling, we find that the emission-line gas consists of three principal components: 1) one in which most of the strong emission-lines, such as [O III] 5007, [Ne V] 3426, C IV 1550, arise, 2) a more tenuous, highly ionized component, which is the source of the coronal-line emission, and 3) a component, which is not co-planar with the other two, in which the low ionization and neutral lines, such as [N II] 6548 and [O I] 6300, are formed. The first two components are directly ionized by the EUV-Xray continuum emitted by the central source, while the low ionization gas is ionized by a combination of highly absorbed continuum radiation and a small fraction of unabsorbed continuum scattered by free electrons associated with the hot spot. The combination of covering factor and Thomson optical depth of the high ionization components is insufficient to scatter the observed fraction of continuum radiation into our line-of-sight.Comment: 42 pages, Latex, includes 5 figures (postscript), to appear in the Astrophysical Journa

M87: A Misaligned BL LAC?

The nuclear region of M87 was observed with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) at 6 epochs, spanning 18 months, after the HST image quality was improved with the deployment of the corrective optics (COSTAR) in December 1993. From the FOS target acquisition data, we have established that the flux from the optical nucleus of M87 varies by a factor ~2 on time scales of ~2.5 months and by as much as 25% over 3 weeks, and remains unchanged (<= 2.5%) on time scales of ~1 day. The changes occur in an unresolved central region <= 5 pc in diameter, with the physical size of the emitting region limited by the observed time scales to a few hundred gravitational radii. The featureless continuum spectrum becomes bluer as it brightens while emission lines remain unchanged. This variability combined with the observations of the continuum spectral shape, strong relativistic boosting and the detection of significant superluminal motions in the jet, strongly suggest that M87 belongs to the class of BL Lac objects but is viewed at an angle too large to reveal the classical BL Lac properties.Comment: 12 pages, 3 Postscript figure

Scalar conservation laws with nonconstant coefficients with application to particle size segregation in granular flow

Granular materials will segregate by particle size when subjected to shear, as occurs, for example, in avalanches. The evolution of a bidisperse mixture of particles can be modeled by a nonlinear first order partial differential equation, provided the shear (or velocity) is a known function of position. While avalanche-driven shear is approximately uniform in depth, boundary-driven shear typically creates a shear band with a nonlinear velocity profile. In this paper, we measure a velocity profile from experimental data and solve initial value problems that mimic the segregation observed in the experiment, thereby verifying the value of the continuum model. To simplify the analysis, we consider only one-dimensional configurations, in which a layer of small particles is placed above a layer of large particles within an annular shear cell and is sheared for arbitrarily long times. We fit the measured velocity profile to both an exponential function of depth and a piecewise linear function which separates the shear band from the rest of the material. Each solution of the initial value problem is non-standard, involving curved characteristics in the exponential case, and a material interface with a jump in characteristic speed in the piecewise linear case