The P34G mutation reduces the transforming activity of K-Ras and N-Ras in NIH 3T3 cells but not of H-Ras

Retraction in The P34G mutation reduces the transforming activity of K-Ras and N-Ras in NIH 3T3 cells but not of H-Ras. [J Biol Chem. 2018]Ras proteins (H-, N-, and K-Ras) operate as molecular switches in signal transduction cascades controlling cell proliferation, differentiation, or apoptosis. The interaction of Ras with its effectors is mediated by the effector-binding loop, but different data about Ras location to plasma membrane subdomains and new roles for some docking/scaffold proteins point to signaling specificities of the different Ras proteins. To investigate the molecular mechanisms for these specificities, we compared an effector loop mutation (P34G) of three Ras isoforms (H-, N-, and K-Ras4B) for their biological and biochemical properties. Although this mutation diminished the capacity of Ras proteins to activate the Raf/ERK and the phosphatidylinositol 3-kinase/AKT pathways, the H-Ras V12G34 mutant retained the ability to cause morphological transformation of NIH 3T3 fibroblasts, whereas both the N-Ras V12G34 and the K-Ras4B V12G34 mutants were defective in this biological activity. On the other hand, although both the N-Ras V12G34 and the K-Ras4B V12G34 mutants failed to promote activation of the Ral-GDS/Ral A/PLD and the Ras/Rac pathways, the H-Ras V12G34 mutant retained the ability to activate these signaling pathways. Interestingly, the P34G mutation reduced specifically the N-Ras and K-Ras4B in vitro binding affinity to Ral-GDS, but not in the case of H-Ras. Thus, independently of Ras location to membrane subdomains, there are marked differences among Ras proteins in the sensitivity to an identical mutation (P34G) affecting the highly conserved effector-binding loop.This work was supported in part by Programa General del Conocimiento (BMC2001-0057), Intramural Instituto de Salud Carlos III (ISCIII) (01/16), and SAF2003-02604 (Ministerio de Ciencia y Tecnología) grants (to J. M. R.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.S

A retention-release mechanism based on RAB11FIP2 for AMPA receptor synaptic delivery during long-term potentiation

It is well­-established that Rab11-dependent recycling endosomes drive the activity-dependent delivery of AMPA receptors (AMPARs) into synapses during long-term potentiation (LTP). Nevertheless, the molecular basis for this specialized function of recycling endosomes is still unknown. Here, we have investigated RAB11FIP2 (FIP2 hereafter) as a potential effector of Rab11-dependent trafficking during LTP in rat hippocampal slices. Surprisingly, we found that FIP2 operates independently from Rab11 proteins, and acts as a negative regulator of AMPAR synaptic trafficking. Under basal conditions, FIP2 associates with AMPARs at immobile compartments, separately from recycling endosomes. Using shRNA-mediated knockdown, we found that FIP2 prevents GluA1 (encoded by the Gria1 gene) AMPARs from reaching the surface of dendritic spines in the absence of neuronal stimulation. Upon induction of LTP, FIP2 is rapidly mobilized, dissociates from AMPARs and undergoes dephosphorylation. Interestingly, this dissociation of the FIP2¿AMPAR complex, together with FIP2 dephosphorylation, is required for LTP, but the interaction between FIP2 and Rab11 proteins is not. Based on these results, we propose a retention¿release mechanism, where FIP2 acts as a gate that restricts the trafficking of AMPARs, until LTP induction triggers their release and allows synaptic delivery.Ministerio de Ciencia, Innovación y Universidades (Spanish Ministry of Science, Innovation and Universities) (SAF2015-72988-EXP, SAF2017-86983-R) and the European Union Joint Programming Initiative A healthy diet for a healthy life (PCIN-2016-095). M.R. and Y.G. were recipients of pre-doctoral contracts from the Instituto de Salud Carlos III and from the Ministerio de Educación, Cultura y Deporte (Spanish Ministry of Education, Culture and Sport

KIF13A drives AMPA receptor synaptic delivery for long-term potentiation via endosomal remodeling

The regulated trafficking of AMPA-type glutamate receptors (AMPARs) from dendritic compartments to the synaptic membrane in response to neuronal activity is a core mechanism for long-term potentiation (LTP). However, the contribution of the microtubule cytoskeleton to this synaptic transport is still unknown. In this work, using electrophysiological, biochemical, and imaging techniques, we have found that one member of the kinesin-3 family of motor proteins, KIF13A, is specifically required for the delivery of AMPARs to the spine surface during LTP induction. Accordingly, KIF13A depletion from hippocampal slices abolishes LTP expression. We also identify the vesicular protein centaurin-α1 as part of a motor transport machinery that is engaged with KIF13A and AMPARs upon LTP induction. Finally, we determine that KIF13A is responsible for the remodeling of Rab11-FIP2 endosomal structures in the dendritic shaft during LTP. Overall, these results identify specific kinesin molecular motors and endosomal transport machinery that catalyzes the dendrite-to-synapse translocation of AMPA receptors during synaptic plasticity.Spanish Ministry of Science and Innovation (grants SAF2014-57233-R and SAF2017-86983-R) and the European Union (PCIN-2016-095) to J.A. Esteban, and by the Institut National de la Santé et de la Recherche Médicale, Institut Curie, and the Centre National de la Recherche Scientifique (LabEx Cell(n)Scale, ANR-11-LABX-0038) to C. Delevoye. Y. Gutiérrez and S. López-García are recipients of predoctoral contracts from the Spanish Ministry of Educatio

Unveiling the age and origin of biogenic aggregates produced by earthworm species with their NIRS fingerprint in a subalpine meadow of Central Pyrenees.

In this study the near-infrared reflectance (NIR) spectra signals (750-2,500 nm) of soil samples was compared with the NIR signals of the biogenic aggregates produced in the lab by three earthworm species, i.e., Aporrectodea rosea (Savigny 1826), Lumbricus friendi Cognetti, 1904 and Prosellodrilus pyrenaicus (Cognetti, 1904) from subalpine meadows in the Central Pyrenees. NIR spectral signatures of biogenic aggregates, root-aggregates, and non-aggregated soil were obtained together with soil carbon (C), nitrogen (N), [Formula: see text] and [Formula: see text] determinations. The concentrations of C, N and C:N ratio in the three types of soil aggregates identified were not statistically significant (ANOVA, p>0.05) although non-macroaggregated soil had slightly higher C concentrations (66.3 g kg-1 dry soil) than biogenic aggregates (earthworm- and root-aggregates, 64.9 and 63.5 g kg-1 dry soil, respectively), while concentrations of [Formula: see text] and [Formula: see text] were highest in the root-attached aggregates (3.3 and 0.31 mg kg dry soil-1). Total earthworm density and biomass in the sampled area was 137.6 ind. m-2, and 55.2 g fresh weight m-2, respectively. The biomass of aggregates attached to roots and non-macroaggregated soil was 122.3 and 134.8 g m-2, respectively, while biomass of free (particulate) organic matter and invertebrate biogenic aggregates was 62.9 and 41.7 g m-2, respectively. Multivariate analysis of NIR spectra signals of field aggregates separated root aggregates with high concentrations of [Formula: see text] and [Formula: see text] (41.5% of explained variance, axis I) from those biogenic aggregates, including root aggregates, with large concentrations of C and high C:N ratio (21.6% of total variability, axis II). Partial Least Square (PLS) regressions were used to compare NIR spectral signals of samples (casts and soil) and develop calibration equations relating these spectral data to those data obtained for chemical variables in the lab. After a derivatization process, the NIR spectra of field aggregates were projected onto the PLS factorial plane of the NIR spectra from the lab incubation. The projection of the NIR spectral signals onto the PLSR models for C, N, [Formula: see text] and [Formula: see text] from casts produced and incubated in the lab allowed us to identify the species and the age of the field biogenic aggregates. Our hypothesis was to test whether field aggregates would match or be in the vicinity of the NIR signals that corresponded to a certain species and the age of the depositions produced in the lab. A NIRS biogenic background noise (BBN) is present in the soil as a result of earthworm activity. This study provides insights on how to analyse the role of these organisms in important ecological processes of soil macro-aggregation and associated organic matter dynamics by means of analyzing the BBN in the soil matrix