Mario Ruiz

High-resolution imaging of the Pyrenees and Massif Central from the data of the PYROPE and IBERARRAY portable array deployments

The lithospheric structures beneath the Pyrenees, which holds the key to settle long-standing controversies regarding the opening of the Bay of Biscay and the formation of the Pyrenees, are still poorly known. The temporary PYROPE and IBERARRAY experiments have recently filled a strong deficit of seismological stations in this part of western Europe, offering a new and unique opportunity to image crustal and mantle structures with unprecedented resolution. Here we report the results of the first tomographic study of the Pyrenees relying on this rich data set. The important aspects of our tomographic study are the precision of both absolute and relative traveltime measurements obtained by a nonlinear simulated annealing waveform fit and the detailed crustal model that has been constructed to compute accurate crustal corrections. Beneath the Massif Central, the most prominent feature is a widespread slow anomaly that reflects a strong thermal anomaly resulting from the thinning of the lithosphere and upwelling of the asthenosphere. Our tomographic images clearly exclude scenarios involving subduction of oceanic lithosphere beneath the Pyrenees. In contrast, they reveal the segmentation of lithospheric structures, mainly by two major lithospheric faults, the Toulouse fault in the central Pyrenees and the Pamplona fault in the western Pyrenees. These inherited Hercynian faults were reactivated during the Cretaceous rifting of the Aquitaine and Iberian margins and during the Cenozoic Alpine convergence. Therefore, the Pyrenees can be seen as resulting from the tectonic inversion of a segmented continental rift that was buried by subduction beneath the European plate.

Siderocalin/Lcn2/NGAL/24p3 does not drive apoptosis through gentisic acid mediated iron withdrawal in hematopoietic cell lines.

Siderocalin (also lipocalin 2, NGAL or 24p3) binds iron as complexes with specific siderophores, which are low molecular weight, ferric ion-specific chelators. In innate immunity, siderocalin slows the growth of infecting bacteria by sequestering bacterial ferric siderophores. Siderocalin also binds simple catechols, which can serve as siderophores in the damaged urinary tract. Siderocalin has also been proposed to alter cellular iron trafficking, for instance, driving apoptosis through iron efflux via BOCT. An endogenous siderophore composed of gentisic acid (2,5-dihydroxybenzoic acid) substituents was proposed to mediate cellular efflux. However, binding studies reported herein contradict the proposal that gentisic acid forms high-affinity ternary complexes with siderocalin and iron, or that gentisic acid can serve as an endogenous siderophore at neutral pH. We also demonstrate that siderocalin does not induce cellular iron efflux or stimulate apoptosis, questioning the role siderocalin plays in modulating iron metabolism.

The deep roots of the western Pyrenees revealed by full waveform inversion of teleseismic P waves

Imaging the architecture of mountain roots is required to understand the support of topography and for kinematic reconstructions at convergent plate boundaries, but is still challenging with conventional seismic imaging approaches. Here we present a three-dimensional model of both compressional and shear velocities in the lithosphere beneath the western Pyrenees (southwest Europe), obtained by full waveform inversion of teleseismic P waves. This tomographic model reveals the subduction of the Iberian crust beneath the European plate, and the European serpentinized subcontinental mantle emplaced at shallow crustal levels beneath the Mauleon basin. The rift-inherited mantle wedge acted as an indenter during the Pyrenean convergence. These new results provide compelling evidence for the role of rift-inherited structures during mountain building in Alpine-type orogens.

Lipid‐binding properties of human ApoD and Lazarillo‐related lipocalins: functional implications for cell differentiation

Lipocalins are a family of proteins characterized by a conserved eight‐stranded β‐barrel structure with a ligand‐binding pocket. They perform a wide range of biological functions and this functional multiplicity must relate to the lipid partner involved. Apolipoprotein D (ApoD) and its insect homologues, Lazarillo (Laz) and neural Lazarillo (NLaz), share common ancestral functions like longevity, stress resistance and lipid metabolism regulation, coexisting with very specialized functions, like courtship behavior. Using tryptophan fluorescence titration, we screened the binding of 15 potential lipid partners for NLaz, ApoD and Laz and uncovered several novel ligands with apparent dissociation constants in the low micromolar range. Retinoic acid (RA), retinol, fatty acids and sphingomyelin are shared ligands. Sterols, however, showed a species‐specific binding pattern: cholesterol did not show strong binding to human ApoD, whereas NLaz and Laz did bind ergosterol. Among the lipocalin‐specific ligands, we found that ApoD selectively binds the endocannabinoid anandamide but not 2‐acylglycerol, and that NLaz binds the pheromone 7‐tricosene, but not 7,11‐heptacosadiene or 11‐cis‐vaccenyl acetate. To test the functional relevance of lipocalin ligand binding at the cellular level, we analyzed the effect of ApoD, Laz and NLaz preloaded with RA on neuronal differentiation. Our results show that ApoD is necessary and sufficient to allow for RA differentiating activity. Both human ApoD and Drosophila NLaz successfully deliver RA to immature neurons, driving neurite outgrowth. We conclude that ApoD, NLaz and Laz bind selectively to a different but overlapping set of lipid ligands. This multispecificity can explain their varied physiological functions.

Seismic monitoring of an Alpine mountain river

The Canfranc underground laboratory (LSC), excavated under the Central Pyrenees, is mainly devoted to the study of phenomena which needs “cosmic silence.” It also hosts a geodynamical facility, named Geodyn, which holds an accelerometer, a broadband seismometer, and two high-resolution laser strainmeters. During the routine processing of the seismic data, we detected an unusual spectral signature in the 2–10u2009Hz frequency band, which does not correspond to the typical sources of seismic noise and which can also be recognized in the strain records. After checking against meteorological and hydrological data, we can relate those signals to variations in the discharge by the Aragon River, an Alpine-style river in the southern Pyrenees, located about 400u2009m from the LSC Geodyn facility. Four main episodes have been identified since early 2011, each lasting 1–2 to 6–8u2009days. Additionally, a limited number of shorter episodes have also been detected. Three types of river-generated seismic events have been identified, related respectively to moderate rainfall, snowmelt, and flooding events associated to severe storms. Each of those types has distinctive characteristics which allow monitoring the hydrological events from the analysis of seismic and deformation data. A few previous studies have already described the seismic noise close to rivers with larger discharge or in small-scale experimental settings, and we are showing here that the so-called “fluvial seismology” can be useful to study the hydrological evolution of Alpine style streams and may have a potential interest for the civil authorities in charge of the management of hydrological basins.

Galline Ex-FABP Is an Antibacterial Siderocalin and a Lysophosphatidic Acid Sensor Functioning through Dual Ligand Specificities

Galline Ex-FABP was identified as another candidate antibacterial, catecholate siderophore binding lipocalin (siderocalin) based on structural parallels with the family archetype, mammalian Siderocalin. Binding assays show that Ex-FABP retains iron in a siderophore-dependent manner in both hypertrophic and dedifferentiated chondrocytes, where Ex-FABP expression is induced after treatment with proinflammatory agents, and specifically binds ferric complexes of enterobactin, parabactin, bacillibactin and, unexpectedly, monoglucosylated enterobactin, which does not bind to Siderocalin. Growth arrest assays functionally confirm the bacteriostatic effect of Ex-FABP inxa0vitro under iron-limiting conditions. The 1.8xa0Å crystal structure of Ex-FABP explains the expanded specificity, but also surprisingly reveals an extended, multi-chambered cavity extending through the protein and encompassing two separate ligand specificities, one for bacterial siderophores (as in Siderocalin) at one end and one specifically binding copurified lysophosphatidic acid, a potent cell signaling molecule, at the other end, suggesting Ex-FABP employs dual functionalities to explain its diverse endogenous activities.

Teleseismic imaging of alpine crustal underthrusting beneath Niberia

[1]xa0The deep crustal structure of the northern part of Iberia, extensively explored by active seismic methods, has been investigated here by the teleseismic receiver function (RF) technique. Two N-S transects were implemented across the Cantabrian Mountains (CMT) and the western Pyrenees (WPT). The resulting RFs were migrated to obtain depth sections of the lithosphere. These images are fairly consistent with previous seismic sections and velocity-depth modeling. The WPT shows a clear northward-dipping interface, interpreted as the Iberian lower crust underthrusting an European Moho identified at the northern end of the transect. In the CMT a similar pattern can be inferred, although the deep crustal geometry is not well resolved. In this transect, intra-crustal convertors are associated to high-velocity materials of European lower crust imbricated at shallower levels. The new results provide farther evidence on the lateral extent of the Alpine underthrusting of Iberia beneath Europe.

Grasshopper Lazarillo, a GPI-anchored Lipocalin, increases Drosophila longevity and stress resistance, and functionally replaces its secreted homolog NLaz

Lazarillo (Laz) is a glycosyl-phosphatidylinositol (GPI)-linked glycoprotein first characterized in the developing nervous system of the grasshopper Schistocerca americana. It belongs to the Lipocalins, a functionally diverse family of mostly secreted proteins. In this work we test whether the protective capacity known for Laz homologs in flies and vertebrates (NLaz, GLaz and ApoD) is evolutionarily conserved in grasshopper Laz, and can be exerted from the plasma membrane in a cell-autonomous manner. First we demonstrate that extracellular forms of Laz have autocrine and paracrine protecting effects for oxidative stress-challenged Drosophila S2 cells. Then we assay the effects of overexpressing GPI-linked Laz in adult Drosophila and whether it rescues both known and novel phenotypes of NLaz null mutants. Local effects of GPI-linked Laz inside and outside the nervous system promote survival upon different stress forms, and extend lifespan and healthspan of the flies in a cell-type dependent manner. Outside the nervous system, expression in fat body cells but not in hemocytes results in protection. Within the nervous system, glial cell expression is more effective than neuronal expression. Laz actions are sexually dimorphic in some expression domains. Fat storage promotion and not modifications in hydrocarbon profiles or quantities explain the starvation-desiccation resistance caused by Laz overexpression. This effect is exerted when Laz is expressed ubiquitously or in dopaminergic cells, but not in hemocytes. Grasshopper Laz functionally restores the loss of NLaz, rescuing stress-sensitivity as well as premature accumulation of aging-related damage, monitored by advanced glycation end products (AGEs). However Laz does not rescue NLaz courtship behavioral defects. Finally, the presence of two new Lipocalins with predicted GPI-anchors in mosquitoes shows that the functional advantages of GPI-linkage have been commonly exploited by Lipocalins in the arthropodan lineage.

Anisotropic features of the Alpine lithosphere in Northern Spain

[1]xa0As part of an extensive seismic research carried out in the last years at the Northern part of Iberia affected by the Alpine compressional tectonics, the mantle anisotropic features have been investigated with the shear-wave splitting technique. Two N-S transects across the western Pyrenees and the eastern part of the Cantabrian Mountains were instrumented. In both cases the average fast velocity direction (FVD) and the delay times are remarkably consistent. The δt values are less than 1 s and the average FVD is close to E/W, subparallel to the trend of the Pyrenean belt. However, in each station the results show a significant variation of the splitting parameters with respect to the backazimuthal direction. This azimuthal dependence is compatible with synthetic models including two distinct anisotropic layers and suggests a complex distribution at depth of the anisotropic features, to be related with imprints of different geodynamic processes in the area.

Ligand binding-dependent functions of the lipocalin NLaz: an in vivo study in Drosophila

Lipocalins are small extracellular proteins mostly described as lipid carriers. The Drosophila lipocalin NLaz (neural Lazarillo) modulates the IIS pathway and regulates longevity, stress resistance, and behavior. Here, we test whether a native hydrophobic pocket structure is required for NLaz to perform its functions. We use a point mutation altering the binding pocket (NLazL130R) and control mutations outside NLaz binding pocket. Tryptophan fluorescence titration reveals that NLazL130R loses its ability to bind ergosterol and the pheromone 7(z)‐tricosene but retains retinoic acid binding. Using site‐directed transgenesis in Drosophila, we test the functionality of the ligand binding‐altered lipocalin at the organism level. NLaz‐dependent life span reduction, oxidative stress and starvation sensitivity, aging markers accumulation, and deficient courtship are rescued by overexpression of NLazWT, but not of NLazL130R. Transcriptional responses to aging and oxidative stress show a large set of age‐responsive genes dependent on the integrity of NLaz binding pocket. Inhibition of IIS activity and modulation of oxidative stress and infection‐responsive genes are binding pocket‐dependent processes. Control of energy metabolites on starvation appears to be, however, insensitive to the modification of the NLaz binding pocket.—Ruiz, M., Ganfornina, M. D., Correnti, C., Strong, R. K., and Sanchez, D. Ligand binding‐dependent functions of the lipocalin NLaz: an in vivo study in Drosophila. FASEB J. 28, 1555–1567 (2014). www.fasebj.org