196 research outputs found
Development and Ground-Test Validation of Fiber Optic Sensor Attachment Techniques for Hot Structures Applications
Fiber Optic Strain Measurements: a) Successfully attached silica fiber optic sensors to both metallics and composites; b) Accomplished valid EFPI strain measurements to 1850 F; c) Successfully attached EFPI sensors to large scale hot-structures; and d) Attached and thermally validated FBG bond and epsilon(sub app). Future Development a) Improve characterization of sensors on C-C and C-SiC substrates; b) Apply application to other composites such as SiC-SiC; c) Assist development of interferometer based Sapphire sensor currently being conducted under a Phase II SBIR; and d) Complete combined thermal/mechanical testing of FBG on composite substrates in controlled laboratory environment
Breast cancer cell migration is regulated through junctional adhesion molecule-A-mediated activation of Rap1 GTPase
ABSTRACT: INTRODUCTION: The adhesion protein junctional adhesion molecule-A (JAM-A) regulates epithelial cell morphology and migration, and its over-expression has recently been linked with increased risk of metastasis in breast cancer patients. As cell migration is an early requirement for tumor metastasis, we sought to identify the JAM-A signalling events regulating migration in breast cancer cells. METHODS: MCF7 breast cancer cells (which express high endogenous levels of JAM-A) and primary cultures from breast cancer patients were used for this study. JAM-A was knocked down in MCF7 cells using siRNA to determine the consequences for cell adhesion, cell migration and the protein expression of various integrin subunits. As we had previously demonstrated a link between the expression of JAM-A and β1-integrin, we examined activation of the β1-integrin regulator Rap1 GTPase in response to JAM-A knockdown or functional antagonism. To test whether JAM-A, Rap1 and β1-integrin lie in a linear pathway, we tested functional inhibitors of all three proteins separately or together in migration assays. Finally we performed immunoprecipitations in MCF7 cells and primary breast cells to determine the binding partners connecting JAM-A to Rap1 activation. RESULTS: JAM-A knockdown in MCF7 breast cancer cells reduced adhesion to, and migration through, the β1-integrin substrate fibronectin. This was accompanied by reduced protein expression of β1-integrin and its binding partners αV- and α5-integrin. Rap1 activity was reduced in response to JAM-A knockdown or inhibition, and pharmacological inhibition of Rap1 reduced MCF7 cell migration. No additive anti-migratory effect was observed in response to simultaneous inhibition of JAM-A, Rap1 and β1-integrin, suggesting that they lie in a linear migratory pathway. Finally, in an attempt to elucidate the binding partners putatively linking JAM-A to Rap1 activation, we have demonstrated the formation of a complex between JAM-A, AF-6 and the Rap1 activator PDZ-GEF2 in MCF7 cells and in primary cultures from breast cancer patients. CONCLUSIONS: Our findings provide compelling evidence of a novel role for JAM-A in driving breast cancer cell migration via activation of Rap1 GTPase and β1-integrin. We speculate that JAM-A over-expression in some breast cancer patients may represent a novel therapeutic target to reduce the likelihood of metastasis
Natural compound Tetrocarcin-A downregulates Junctional Adhesion Molecule-A in conjunction with HER2 and inhibitor of apoptosis proteins and inhibits tumor cell growth.
Overexpression of the tight junction protein Junctional Adhesion Molecule-A (JAM-A) has been linked to aggressive disease in breast and other cancers, but JAM-targeting drugs remain elusive. Screening of a natural compound library identified the antibiotic Tetrocarcin-A as a novel downregulator of JAM-A and human epidermal growth factor receptor-2 (HER2) protein expression in breast cancer cells. Lysosomal inhibition partially rescued the downregulation of JAM-A and HER2 caused by Tetrocarcin-A, and attenuated its cytotoxic activity. Tetrocarcin-A treatment or JAM-A silencing reduced AKT and ERK phosphorylation, inhibited c-FOS phosphorylation at Threonine-232 (its transcriptional regulation site), inhibited nuclear localization of c-FOS, and downregulated expression of the inhibitor of apoptosis proteins (IAP). This was accompanied by Tetrocarcin-A-induced caspase-dependent apoptosis. To begin evaluating the potential clinical relevance of our findings, we extended our studies to other models. Encouragingly, Tetrocarcin-A downregulated JAM-A expression and caused cytotoxicity in primary breast cells and lung cancer stem cells, and inhibited the growth of xenografts in a semi-in vivo model involving invasion across the chicken egg chorioallantoic membrane. Taken together, our data suggest that Tetrocarcin-A warrants future evaluation as a novel cancer therapeutic by virtue of its ability to downregulate JAM-A expression, reduce tumorigenic signaling and induce apoptosis
Selective inhibition of N-linked glycosylation impairs receptor tyrosine kinase processing
Global inhibition of N-linked glycosylation broadly reduces glycan occupancy on glycoproteins, but identifying how this inhibition functionally impacts specific glycoproteins is challenging. This limits our understanding of pathogenesis in the congenital disorders of glycosylation (CDG). We used selective exo-enzymatic labeling of cells deficient in the two catalytic subunits of oligosaccharyltransferase - STT3A and STT3B - to monitor the presence and glycosylation status of cell surface glycoproteins. We show reduced abundance of two canonical tyrosine receptor kinases - the insulin receptor and insulin-like growth factor 1 receptor (IGF-1R) - at the cell surface in STT3A-null cells, due to decreased N-linked glycan site occupancy and proteolytic processing in combination with increased endoplasmic reticulum localization. Providing cDNA for Golgi-resident proprotein convertase subtilisin/kexin type 5a (PCSK5a) and furin cDNA to wild-type and mutant cells produced under-glycosylated forms of PCSK5a, but not furin, in cells lacking STT3A. Reduced glycosylation of PCSK5a in STT3A-null cells or cells treated with the oligosaccharyltransferase inhibitor NGI-1 corresponded with failure to rescue receptor processing, implying that alterations in the glycosylation of this convertase have functional consequences. Collectively, our findings show that STT3A-dependent inhibition of N-linked glycosylation on receptor tyrosine kinases and their convertases combines to impair receptor processing and surface localization. These results provide new insight into CDG pathogenesis and highlight how the surface abundance of some glycoproteins can be dually impacted by abnormal glycosylation
CFHTLenS: Co-evolution of galaxies and their dark matter haloes
Galaxy-galaxy weak lensing is a direct probe of the mean matter distribution
around galaxies. The depth and sky coverage of the CFHT Legacy Survey yield
statistically significant galaxy halo mass measurements over a much wider range
of stellar masses ( to ) and redshifts () than previous weak lensing studies. At redshift , the
stellar-to-halo mass ratio (SHMR) reaches a maximum of percent as a
function of halo mass at . We find, for the first
time from weak lensing alone, evidence for significant evolution in the SHMR:
the peak ratio falls as a function of cosmic time from percent at
to percent at , and shifts to lower
stellar mass haloes. These evolutionary trends are dominated by red galaxies,
and are consistent with a model in which the stellar mass above which star
formation is quenched "downsizes" with cosmic time. In contrast, the SHMR of
blue, star-forming galaxies is well-fit by a power law that does not evolve
with time. This suggests that blue galaxies form stars at a rate that is
balanced with their dark matter accretion in such a way that they evolve along
the SHMR locus. The redshift dependence of the SHMR can be used to constrain
the evolution of the galaxy population over cosmic time.Comment: 18 pages, MNRAS, in pres
CFHTLenS: A Weak Lensing Shear Analysis of the 3D-Matched-Filter Galaxy Clusters
We present the cluster mass-richness scaling relation calibrated by a weak
lensing analysis of >18000 galaxy cluster candidates in the
Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). Detected using the
3D-Matched-Filter cluster-finder of Milkeraitis et al., these cluster
candidates span a wide range of masses, from the small group scale up to
, and redshifts 0.2 0.9. The total
significance of the stacked shear measurement amounts to 54. We compare
cluster masses determined using weak lensing shear and magnification, finding
the measurements in individual richness bins to yield 1 compatibility,
but with magnification estimates biased low. This first direct mass comparison
yields important insights for improving the systematics handling of future
lensing magnification work. In addition, we confirm analyses that suggest
cluster miscentring has an important effect on the observed 3D-MF halo
profiles, and we quantify this by fitting for projected cluster centroid
offsets, which are typically 0.4 arcmin. We bin the cluster candidates
as a function of redshift, finding similar cluster masses and richness across
the full range up to 0.9. We measure the 3D-MF mass-richness scaling
relation . We find a normalization , and a logarithmic slope of
, both of which are in 1 agreement with results
from the magnification analysis. We find no evidence for a redshift-dependence
of the normalization. The CFHTLenS 3D-MF cluster catalogue is now available at
cfhtlens.org.Comment: 3D-MF cluster catalog is NOW AVAILABLE at cfhtlens.org.
Magnification-shear mass comparison in Figure 10. 19 pages, 10 figures.
Accepted to MNRA
CFHTLenS: Weak lensing constraints on the ellipticity of galaxy-scale matter haloes and the galaxy-halo misalignment
We present weak lensing constraints on the ellipticity of galaxy-scale matter
haloes and the galaxy-halo misalignment. Using data from the
Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), we measure the
weighted-average ratio of the aligned projected ellipticity components of
galaxy matter haloes and their embedded galaxies, , split by
galaxy type. We then compare our observations to measurements taken from the
Millennium Simulation, assuming different models of galaxy-halo misalignment.
Using the Millennium Simulation we verify that the statistical estimator used
removes contamination from cosmic shear. We also detect an additional signal in
the simulation, which we interpret as the impact of intrinsic shape-shear
alignments between the lenses and their large-scale structure environment.
These alignments are likely to have caused some of the previous observational
constraints on to be biased high. From CFHTLenS we find
for early-type galaxies, which is consistent with
current models for the galaxy-halo misalignment predicting . For late-type galaxies we measure
from CFHTLenS. This can be compared to the simulated results which yield
for misaligned late-type models.Comment: 21 pages, 3 tables, 9 figures. This replacement matches the version
accepted for publication in MNRA
CFHTLenS tomographic weak lensing: Quantifying accurate redshift distributions
The Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) comprises deep
multi-colour (u*g'r'i'z') photometry spanning 154 square degrees, with accurate
photometric redshifts and shape measurements. We demonstrate that the redshift
probability distribution function summed over galaxies provides an accurate
representation of the galaxy redshift distribution accounting for random and
catastrophic errors for galaxies with best fitting photometric redshifts z_p <
1.3.
We present cosmological constraints using tomographic weak gravitational
lensing by large-scale structure. We use two broad redshift bins 0.5 < z_p <=
0.85 and 0.85 < z_p <= 1.3 free of intrinsic alignment contamination, and
measure the shear correlation function on angular scales in the range ~1-40
arcmin. We show that the problematic redshift scaling of the shear signal,
found in previous CFHTLS data analyses, does not afflict the CFHTLenS data. For
a flat Lambda-CDM model and a fixed matter density Omega_m=0.27, we find the
normalisation of the matter power spectrum sigma_8=0.771 \pm 0.041. When
combined with cosmic microwave background data (WMAP7), baryon acoustic
oscillation data (BOSS), and a prior on the Hubble constant from the HST
distance ladder, we find that CFHTLenS improves the precision of the fully
marginalised parameter estimates by an average factor of 1.5-2. Combining our
results with the above cosmological probes, we find Omega_m=0.2762 \pm 0.0074
and sigma_8=0.802 \pm 0.013.Comment: 17 pages, 12 figures, submitted to MNRA
An imbalance in progenitor cell populations reflects tumour progression in breast cancer primary culture models
Many factors influence breast cancer progression, including the ability of progenitor cells to sustain or increase net tumour cell numbers. Our aim was to define whether alterations in putative progenitor populations could predict clinicopathological factors of prognostic importance for cancer progression.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe
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