INGEDICO, Instruments de Gestion et Dispositifs Collectifs de conservation et valorisation de ressources naturelles renouvelables

International audienc

INGEDICO - Instruments de Gestion et Dispositifs Collectifs de conservation et valorisation de ressources naturelles renouvelables

International audiencePour chaque situation d'étude une méthodologie de recherche spécifique a été mise en place : recherche-intervention, observation participante, observation directe, entretiens. Ces six situations d'étude sont mises en perspective autour de deux thématiques : les démarches de diagnostic multi-usage (DMU) et les indicateurs de gestion.

Involvement of p21 in the PKC-induced regulation of the G2/M cell cycle transition

International audienceActivation of protein kinase C (PKC) inhibits cell cycle progression at the G1/S and G2/M transitions. We found that phorbol 12-myristate 13-acetate (PMA) induced upregulation of p21, not only in MCF-7 cells arrested in the G1 phase as previously shown, but also in cells delayed in the G2 phase. This increase in p21 in cells accumulated in the G1 and G2/M phases of the cell cycle after PMA treatment was inhibited by the PKC inhibitor GF109203X. This indicates that PKC activity is required for PMA-induced p21 upregulation and cell cycle arrest in the G1 and G2/M phases of the cell cycle. To further assess the role of p21 in the PKC-induced G2/M cell cycle arrest independently of its G1 arrest, we used aphidicolin-synchronised MCF-7 cells. Our results show that, in parallel with the inhibition of cdc2 activity, PMA addition enhanced the associations between p21 and either cyclin B or cdc2. Furthermore, we found that after PMA treatment p21 was able to associate with the active Tyr-15 dephosphorylated form of cdc2, but this complex was devoid of kinase activity indicating that p21 may play a role in inhibition of cdc2 induced by PMA. Taken together, these observations provide evidence that p21 is involved in integrating the PKC signaling pathway to the cell cycle machinery at the G2/M cell cycle checkpoint

High-throughput screening of dipeptide utilization mediated by the ABC transporter DppBCDF and its substrate-binding proteins DppA1-A5 in Pseudomonas aeruginosa.

In this study, we show that the dppBCDF operon of Pseudomonas aeruginosa PA14 encodes an ABC transporter responsible for the utilization of di/tripeptides. The substrate specificity of ABC transporters is determined by its associated substrate-binding proteins (SBPs). Whereas in E. coli only one protein, DppA, determines the specificity of the transporter, five orthologous SBPs, DppA1-A5 are present in P. aeruginosa. Multiple SBPs might broaden the substrate specificity by increasing the transporter capacity. We utilized the Biolog phenotype MicroArray technology to investigate utilization of di/tripeptides in mutants lacking either the transport machinery or all of the five SBPs. This high-throughput method enabled us to screen hundreds of dipeptides with various side-chains, and subsequently, to determine the substrate profile of the dipeptide permease. The substrate spectrum of the SBPs was elucidated by complementation of a penta mutant, deficient of all five SBPs, with plasmids carrying individual SBPs. It became apparent that some dipeptides were utilized with different affinity for each SBP. We found that DppA2 shows the highest flexibility on substrate recognition and that DppA2 and DppA4 have a higher tendency to utilize tripeptides. DppA5 was not able to complement the penta mutant under our screening conditions. Phaseolotoxin, a toxic tripeptide inhibiting the enzyme ornithine carbamoyltransferase, is also transported into P. aeruginosa via the DppBCDF permease. The SBP DppA1, and with much greater extend DppA3, are responsible for delivering the toxin to the permease. Our results provide a first overview of the substrate pattern of the ABC dipeptide transport machinery in P. aeruginosa

Prenatal exposure to low doses of fungicides corrupts neurogenesis in neonates

International audienceNeurogenesis plays a crucial role during neurodevelopment and its dysfunction can lead to neurodevelopmental disorders. A recent hypothesis stipulates that exogenous factors could corrupt this process and predispose to neurodegenerative disorders later in life. The presence of pesticide residues in the diet represents a threat of which we have recently become aware of. Indeed, they could corrupt neurogenesis, especially during gestation, potentially leading to impaired neuronal and synaptic functions. Since the effects of this low-noise contamination have not yet been evaluated on the neurodevelopment, we investigated the impact of fungicide residues on WT mice exposed throughout gestation. Thus, mice were exposed to fungicides, cyprodinil, mepanipyrim and pyrimethanil, alone at 0.1 μg/L during gestation until P3. Besides, another group was exposed to a cocktail of these three fungicides (0.1 μg/L each) for the same time. Exposure was performed through drinking water at the regulatory limit dose of the European countries (0.1 μg/L). No general toxicity was observed in neonates on body and brain weight upon fungicide exposure. However, results showed that gestational exposure to fungicide residues substantially promoted an increase of neural precursor cells at P3. This corrupted neurogenesis was linked to increased levels of β-catenin, likely through the crosstalk of the PI3K/Akt and Wnt/β-catenin pathways, both involved in cell proliferation. Fungicide exposure also altered protein expression of PSD95 and NMDA receptors in P3 neonates, two targets of the β-catenin signaling pathway. Adult neural stem cell extractions from mice treated with the fungicide cocktail, showed an increase proliferation and differentiation combined with a reduction of their migration properties. In addition, in vitro studies on hippocampal primary cell cultures treated with various concentrations of fungicides showed neurotoxic effects. To conclude, corruption of neurogenesis by this chemical assault could be a fertile ground for the development of neurological diseases later in life

Phylogenetic relationships between (A) dipeptide transporter permeases and (B) dipeptide substrate-binding proteins.

<p>Phylogenetic relationships between (A) dipeptide transporter permeases and (B) dipeptide substrate-binding proteins.</p

Bacterial strains used in this study.

<p>Bacterial strains used in this study.</p

Schematic presentation of the genomic region of the <i>P. aeruginosa</i> PA14 dipeptide transport machinery.

<p>(A) Region surrounding the dipeptide transporter operon <i>dppBCDF</i> and its substrate-binding proteins <i>dppA1–A4</i>. The 3,952-bp deletion of the ABC transporter <i>dppBCDF</i> operon is indicated. (B) Genomic region surrounding <i>dppA5</i>. The subcellular location of the proteins is indicated by colors. Black arrows indicate operon structures <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111311#pone.0111311-Winsor1" target="_blank">[77]</a>.</p

Global utilization pattern of dipeptides by PA14, the dipeptide transporter DppBCDF and the SBPs DppA1–A5.

<p>The rings show the total number of dipeptides utilized by the wild-type strain PA14 (outer purple ring), transported by the dipeptide transporter system DppBCDF (middle blue ring), and recognized by the substrate-binding proteins (inner dark green ring). The oval rings (green) present different pools of dipeptides (nonpolar, acidic, uncharged) containing a specific amino acid side-chain either at the N- or C-terminal end of the dipeptide (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111311#pone-0111311-t002" target="_blank">Table 2</a>). Dipeptides containing positively charged amino acid residues were excluded from the analysis (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111311#s4" target="_blank">Materials and Methods</a>).</p

Utilization of dipeptides by strains of the SBP penta mutant complemented with individual SBPs.

<p>The numbers in parentheses indicate the total number of dipeptides analyzed. There are no significant differences among the complemented SBPs DppA1 to DppA4 as determined by single factor ANOVA. DppA1 to DppA4 show significant difference to DppA5 (<i>p</i><0.05) as determined by a two-sided t test with equal variances.</p