The p38/MK2/Hsp25 Pathway Is Required for BMP-2-Induced Cell Migration

Background: Bone morphogenetic proteins (BMPs) have been shown to participate in the patterning and specification of several tissues and organs during development and to regulate cell growth, differentiation and migration in different cell types. BMP-mediated cell migration requires activation of the small GTPase Cdc42 and LIMK1 activities. In our earlier report we showed that activation of LIMK1 also requires the activation of PAKs through Cdc42 and PI3K. However, the requirement of additional signaling is not clearly known. Methodology/Principal Findings: Activation of p38 MAPK has been shown to be relevant for a number of BMP-2¿s physiological effects. We report here that BMP-2 regulation of cell migration and actin cytoskeleton remodelling are dependent on p38 activity. BMP-2 treatment of mesenchymal cells results in activation of the p38/MK2/Hsp25 signaling pathway downstream from the BMP receptors. Moreover, chemical inhibition of p38 signaling or genetic ablation of either p38¿ or MK2 blocks the ability to activate the downstream effectors of the pathway and abolishes BMP-2-induction of cell migration. These signaling effects on p38/MK2/Hsp25 do not require the activity of either Cdc42 or PAK, whereas p38/MK2 activities do not significantly modify the BMP-2-dependent activation of LIMK1, measured by either kinase activity or with an antibody raised against phospho-threonine 508 at its activation loop. Finally, phosphorylated Hsp25 colocalizes with the BMP receptor complexes in lamellipodia and overexpression of a phosphorylation mutant form of Hsp25 is able to abolish the migration of cells in response to BMP-2. Conclusions: These results indicate that Cdc42/PAK/LIMK1 and p38/MK2/Hsp25 pathways, acting in parallel and modulating specific actin regulatory proteins, play a critical role in integrating responses during BMP-induced actin reorganization and cell migration

Is wetland degradation impacting eel population? Identification of landuses in the Adour Barthes and its potential effects on European eel (Anguilla anguilla) habitat

Cet article résume les impacts des activités anthropiques sur les populations d'anguilles dans les zones humides du bassin de l'Adour, à partir d'une approche géographique et sociologique.info:eu-repo/semantics/publishe

Bis(phosphinimino)methanide borohydride complexes of the rare earth elements as initiators for the ring-opening polymerization of -caprolactone: combined experimental and computational investigations

International audienceRare-earth-metal borohydrides are known to be efficient catalysts for the polymerization of apolar and polar monomers. The bis-borohydrides [{CH(PPh2NSiMe3)2}La(BH4)2-(THF)] and [{CH(PPh2NSiMe3)2}Ln-(BH4)2] (Ln=Y, Lu) have been synthesized by two different synthetic routes. The lanthanum and the lutetium complexes were prepared from [Ln(BH4)3-(THF)3] and K{CH(PPh2NSiMe3)2}, whereas the yttrium analogue was obtained from in situ prepared [{CH(PPh2NSiMe3)2}YCl2]2 and NaBH4. All new compounds were characterized by standard analytical/spectroscopic techniques, and the solid-state structures were established by single-crystal X-ray diffraction. The ring-opening polymerization (ROP) of ε-caprolactone initiated by [{CH(PPh2NSiMe3)2}La(BH4)2(THF)] and [{CH(PPh2NSiMe3)2}Ln(BH4)2] (Ln=Y, Lu) was studied. At 0°C the molar mass distributions determined were the narrowest values (Mw/Mn = 1.06-1.11) ever obtained for the ROP of ε-caprolactone initiated by rare-earth-metal borohydride species. DFT investigations of the reaction mechanism indicate that this type of complex reacts in an unprecedented manner with the first B-H activation being achieved within two steps. This particularity has been attributed to the metallic fragment based on the natural bond order analysis

Chelation-assisted cross-coupling of anilines through in situ activation as diazonium salts with boronic acids under ligand-, base-, and salt-free conditions

cited By 11International audienceWe describe the coupling of anilines with aryl boronic acids, under ligand-, base-, and salt-free conditions at room temperature. This new reaction proceeds through the formation of an aryl palladium alkoxo complex, which allows the transmetalation step with aryl boronic acids without any external base. Importantly, this sustainable procedure generates only environmentally friendly byproducts such as tBuOH, H2O, N2, and B(OH)3. The reaction mechanism has been deeply investigated through experimental and theoretical studies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Ring-Opening Polymerization of rac-Lactide by Bis(phenolate)amine-Supported Samarium Borohydride Complexes: An Experimental and DFT Study

The synthesis and ring-opening polymerization (ROP) capability of bis(phenolate)amine-supported samarium borohydride and amide complexes are reported, together with a DFT study. Reaction of Na2O 2NL (L = OMe, NMe2, py, or Pr) with Sm(BH 4)3(THF)3 gave the borohydride complexes Sm(O2NL)(BH4)(THF) (L = OMe (2), NMe 2 (3), or py (4)) or Sm(O2NPr)(BH 4)(THF)2 (5). Compounds 4 and 5 lost THF in vacuo, forming phenolate O-bridged dimers 1 and 6, respectively. Reaction of H 2O2NL with Sm{N(SiHMe2) 2}3(THF)2 formed monomeric Sm(O 2NL){N(SiHMe2)2}(THF) (L = OMe (7), NMe2 (8), or py (9)) with tetradentate O2NL ligands, but dimeric Sm2(μ-O2NPr) 2(O2NPr)(THF) (10) with tridentate O 2NPr. Reaction of Sm{N(SiMe3)2} 3 with H2O2NL (L = OMe or NMe 2) led to zwitterionic products Sm(O2NL) (HO2NL). The bulkier amide compounds Sm(O 2NL){N(SiMe3)2}(OEt 2)n (n = 1, L = OMe (12) or py (13); n = 0, L = NMe 2 (14)) were prepared by reaction of Sm(O2N L)(BH4)(THF) with KN(SiMe3)2. The X-ray structures of 2, 5, 6, 7, 10, 13, and 14 were determined. The borohydrides 2-5 were very efficient initiators for the ROP of ε-CL, giving linear dihydroxytelechelic poly(ε-CL). Selected amide initiators were also assessed but gave poorer control, as judged by broad PDI (Mw/M n) values and significant amounts of cyclic poly(ε-CL)s. Of the borohydrides, only 2-4 were active for the ROP of rac-LA, and activity increased in the order O2NL = O2NOMe ≈ O2Npy < O2NNMe2. The latter ligand also gave the best control of the ROP, as judged by the PDIs and M n values. All gave heterotactically enriched poly(rac-LA) with P r values in the range 0.82-0.84. The ROP of rac-LA with the amides 7, 9, and 12 was faster but much less well controlled. Overall, the borohydride initiators were superior for the ROP of both ε-CL and rac-LA when compared to otherwise identical amide initiators. MALDI-ToF MS analysis of the poly(rac-LA) formed with 3 showed both-CH(Me)CHO and-CH(Me)CH2OH end groups originating from the insertion of the first LA monomer into the Sm-BH4 moiety of 3. In contrast, 2 and 4 formed only α,ω-dihydroxy-terminated polyesters with-CH(Me)CH2OH and-CH(Me)OH end groups. DFT calculations on Eu(O2′N NMe2)(BH4) found two mechanisms for the initial ring-opening step of LA by the borohydride group, giving pathways leading to either aldehyde-or alcohol-terminated poly(lactide)s. Of these two pathways, the one giving α,ω-dihydroxy-terminated polymers was the most favored, in agreement with experiment. (Ligand abbreviations: O2NL = RCH2N(CH2-2-O-3,5-C6H2tBu2)2 where R = CH2OMe, CH 2NMe2, py, or Et for L = OMe, NMe2, py, or Pr, respectively; O2′NNMe2 = Me2NCH 2CH2N(CH2-2-O-C6H4) 2.) © 2010 American Chemical Society

Dynamics of particulate organic matter in a coastal system characterized by the occurrence of marine mucilage – A stable isotope study

International audienceIn coastal systems, particulate organic matter (POM) originates from various autochthonous and allochthonous organic matter sources. Also, some coastal systems are characterized by the occurrence of large amounts of mucilaginous material of biologic origin (i.e. phytoplankton, bacteria), which aggregates and potentially traps other organisms and particles present in the water column. This study focuses on POM origin and spatio-temporal dynamics in the South-East coast of the Bay of Biscay, an area subject to mucilage occurrence. In order to investigate POM quantitative and qualitative (C and N elemental and isotopic ratios) characteristics, sampling was performed over an annual cycle at two sites experiencing different mucilage occurrence and river influence. Contribution of phytoplankton, terrestrial POM and anthropogenic POM to coastal-POM composition was calculated using a three-sources mixing model. Overall, phytoplankton dominated the coastal-POM composition at all seasons, sites and most of the depths (71.6 ± 24.2%). Terrestrial-POM contribution was moderate (22.7 ± 21.8%) and anthropogenic-POM contribution was usually negligible (5.7 ± 7.4%). Both sites mainly exhibited similar vertical and temporal variations in terms of POM origin and dynamics: terrestrial-POM contribution increased with depth and was higher in winter at all depths and in autumn in bottom waters, compared to other seasons. The main differences between both sites were related to the vertical dynamics of the terrestrial contribution to the coastal POM. Horizontal, vertical and temporal variation of POM composition was linked to processes driving the sedimentary hydrodynamics: the river flow, the direction of the river plume and events of sediment resuspension/deposition. During the study period, the mucilage occurred only as flocs (small aggregates). The mucilage was of autochthonous origin and did not trap detectable amount of allochthonous material. © 2016 Elsevier B.V