The NAE Pathway : autobahn to the nucleus for cell surface receptors

Various growth factors and full-length cell surface receptors such as EGFR are translocated from the cell surface to the nucleoplasm, baffling cell biologists to the mechanisms and functions of this process. Elevated levels of nuclear EGFR correlate with poor prognosis in various cancers. In recent years, nuclear EGFR has been implicated in regulating gene transcription, cell proliferation and DNA damage repair. Different models have been proposed to explain how the receptors are transported into the nucleus. However, a clear consensus has yet to be reached. Recently, we described the nuclear envelope associated endosomes (NAE) pathway, which delivers EGFR from the cell surface to the nucleus. This pathway involves transport, docking and fusion of NAEs with the outer membrane of the nuclear envelope. EGFR is then presumed to be transported through the nuclear pore complex, extracted from membranes and solubilised. The SUN1/2 nuclear envelope proteins, Importin-beta, nuclear pore complex proteins and the Sec61 translocon have been implicated in the process. While this framework can explain the cell surface to nucleus traffic of EGFR and other cell surface receptors, it raises several questions that we consider in this review, together with implications for health and disease

The Role of Ponds in Pesticide Dissipation at the Agricultural Catchment Scale: A Critical Review

Ponds in agricultural areas are ubiquitous water retention systems acting as reactive biogeochemical hotspots controlling pesticide dissipation and transfer at the catchment scale. Several issues need to be addressed in order to understand, follow-up and predict the role of ponds in limiting pesticide transfer at the catchment scale. In this review, we present a critical overview of functional processes underpinning pesticide dissipation in ponds. We highlight the need to distinguish degradative and non-degradative processes and to understand the role of the sediment-water interface in pesticide dissipation. Yet it is not well-established how pesticide dissipation in ponds governs the pesticide transfer at the catchment scale under varying hydro-climatic conditions and agricultural operation practices. To illustrate the multi-scale and dynamic aspects of this issue, we sketch a modelling framework integrating the role of ponds at the catchment scale. Such an integrated framework can improve the spatial prediction of pesticide transfer and risk assessment across the catchment-ponds-river continuum to facilitate management rules and operations

L-Ilf3 and L-NF90 Traffic to the Nucleolus Granular Component: Alternatively-Spliced Exon 3 Encodes a Nucleolar Localization Motif

Ilf3 and NF90, two proteins containing double-stranded RNA-binding domains, are generated by alternative splicing and involved in several functions. Their heterogeneity results from posttranscriptional and posttranslational modifications. Alternative splicing of exon 3, coding for a 13 aa N-terminal motif, generates for each protein a long and short isoforms. Subcellular fractionation and localization of recombinant proteins showed that this motif acts as a nucleolar localization signal. Deletion and substitution mutants identified four arginines, essential for nucleolar targeting, and three histidines to stabilize the proteins within the nucleolus. The short isoforms are never found in the nucleoli, whereas the long isoforms are present in the nucleoplasm and the nucleoli. For Ilf3, only the posttranslationally-unmodified long isoform is nucleolar, suggesting that this nucleolar targeting is abrogated by posttranslational modifications. Confocal microscopy and FRAP experiments have shown that the long Ilf3 isoform localizes to the granular component of the nucleolus, and that L-Ilf3 and L-NF90 exchange rapidly between nucleoli. The presence of this 13 aminoacid motif, combined with posttranslational modifications, is responsible for the differences in Ilf3 and NF90 isoforms subcellular localizations. The protein polymorphism of Ilf3/NF90 and the various subcellular localizations of their isoforms may partially explain the various functions previously reported for these proteins

" Pouvoir, santé et société " : Ires journées d'histoire du droit de la santé "

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The Effect of the Bending Beam Width Variations on the Discrepancy of the Resulting Quadrature Errors in MEMS Gyroscopes

In this paper, we develop a new approach in order to understand the origin of the quadrature error in MEMS gyroscopes. As the width of the flexure springs is a critical parameter in the MEMS design, it is necessary to investigate the impact of the width variations on the stiffness coupling, which can generate a quadrature signal. To do so, we developed a method to determine the evolution of the stiffness matrix of the gyroscope springs with respect to the variation of the bending beams width of the springs through finite element analysis (FEA). Then, a statistical analysis permits the computation of the first two statistical moments of the quadrature error for a given beam width defect. It turns out that even small silicon etching defects can generate high quadrature level with up to a root mean square (RMS) value of 1220°/s for a bending beam width defect of 0.9%. Moreover, the quadrature error obtained through simulations has the same order of magnitude as the ones measured on the gyroscopes. This result constitutes a great help for designing MEMS gyroscopes, as the consideration of the bending beams width defects is needed in order to avoid high quadrature error

Genome-Wide RNAi Screens Identify Genes Required for Ricin and PE Intoxications

SummaryProtein toxins such as Ricin and Pseudomonas exotoxin (PE) pose major public health challenges. Both toxins depend on host cell machinery for internalization, retrograde trafficking from endosomes to the ER, and translocation to cytosol. Although both toxins follow a similar intracellular route, it is unknown how much they rely on the same genes. Here we conducted two genome-wide RNAi screens identifying genes required for intoxication and demonstrating that requirements are strikingly different between PE and Ricin, with only 13% overlap. Yet factors required by both toxins are present from the endosomes to the ER, and, at the morphological level, the toxins colocalize in multiple structures. Interestingly, Ricin, but not PE, depends on Golgi complex integrity and colocalizes significantly with a medial Golgi marker. Our data are consistent with two intertwined pathways converging and diverging at multiple points and reveal the complexity of retrograde membrane trafficking in mammalian cells

Fluorescence recovery in HeLa cell nucleoli after photobleaching (FRAP) of GFP-tagged L-Ilf3, L-NF90 or B23.

<p>Plasmids pEGFP-N1-L-Ilf3, pEGFP-N1-L-NF90 or pEGFP-N1-B23 were transfected into HeLa cells. After 24 hours, living cells were subjected to photobleaching. A. In HeLa cells expressing L-NF90-GFP, one nucleolus was targeted for laser bleaching (left panel, green circle in the upper cell) whereas another nucleolus from the same cell (blue circle in the upper cell) and a nucleolus from a distinct cell (yellow circle in the lower cell) were marked to serve as controls. Images were acquired every two seconds during 40 seconds before, immediately after or during 240 seconds after bleaching (prebleach, bleach, post-bleach 6 and 240 seconds, respectively). B. Fluorescence recordings emitted from the 3 delimited regions in A (green: bleached nucleolus; purple: control nucleolus from the same cell; yellow: control nucleolus from another unbleached cell). C. Kinetics of mean fluorescence recovery after photobleaching of GFP-tagged L-Ilf3 (n = 14), L-NF90 (n = 15) or B23 (n = 11) after a normalization of fluorescence intensity. The t¹/₂ of mean fluorescence recovery are indicated in the figure.</p

Occurrence frequencies (%) of possible NoLS sequences (K/R-K/R-X-K/R) and of the twenty aminoacids at the X position in several NoLS-containing nucleolar proteins.

a<p>Among the eight possible sequence combinations (upper line), observed frequency (OF) of each aminoacid at the X position in NoLS present in 61 well-characterized nucleolar proteins and using for the analysis.</p>b<p>Mean frequency (MF) of each aminoacid observed in vertebrate proteins.</p

Ilf3 and NF90 polymorphism in nuclear fractions purified from P19 cells.

<p>Ilf3 and NF90 from P19 cell nuclear fractions were submitted to 2-D PAGE and immunodetected with polyclonal antibody 78. Arrows positioned in the same coordinates in Ilf3 or NF90 panels indicate the positions of Ilf3 and NF90 long and short isoforms. The faint signal in the middle right panel was detected with a ten fold longer time exposure than that of the other panels.</p

Subcellular distribution of Ilf3 and NF90 in P19 cells.

<p>After subcellular fractionation, proteins from identical percentages of each fraction were submitted to SDS-PAGE, blotted onto nitrocellulose and immunodetected with the serum Ab78 raised against Ilf3 and NF90 (S.E.: short exposure time; L.E.: long exposure time), anti-UBF serum (UBF) or anti-α-tubulin antibody (α-tub.). Molecular weight markers (kDa) are indicated at the right.</p