40 research outputs found
Les caractéristiques cinétiques du transport ionique par les différents variants du cotransporteur NKCC2
Le cotransporteur Na⁺-K⁺-Cl⁻ de type 2 (NKCC2) appartient à la famille des cotransporteurs cation-Cl⁻ (CCC). Il existe en tant que trois variants d'épissage, appelés A, B et F, qui ne diffèrent entre eux que de 32 acides aminés et qui sont tous localisés sur la membrane apicale de l'anse ascendante de Henle (AAH) à l'état homodimérique. Ils sont cependant exprimés de façon différentielle : NKCC2F se retrouve à la partie initiale de l'AAH où il assure une réabsorption importante du NaCl pour le maintien du volume extracellulaire alors que NKCC2A et NKCC2B se retrouvent à la partie distale de l'AAH et dans la macula densa où ils assurent une réabsorption plus modeste du NaCl pour aider au maintien du volume extracellulaire et soutenir la rétroaction tubuloglomérulaire. Comme « A » et « B » se retrouvent dans des types cellulaires communs, nous nous sommes demandé : 1) s'ils pouvaient former des hétérodimères AB dont les caractéristiques de transport ionique différaient de AA et BB et 2) si les quantités relatives de AA, AB et BB pouvaient être régulés pour permettre à l'AAH distale et à la macula densa d'opérer adéquatement à l'intérieur d'un éventail de concentrations ioniques plus large. L'objectif de recherche a donc été de générer des constructions d'ADNc où deux variants sont connectés entre eux par un « linker » inerte pour forcer la formation de dimères AA, AB ou BB, d'exprimer le produit de ces constructions dans des ovocytes de Xenopus laevis et d'en caractériser la cinétique de transport. Nous avons trouvé que des hétérodimères déployaient des caractéristiques fonctionnelles uniques (différentes par rapport à AA ou BB). Les vitesses maximales de transport atteintes par l'hétérodimère AB étaient beaucoup plus élevées que les homodimères AA et BB. Nos données suggèrent ainsi que les sous-unités assemblées coopèrent entre elles durant le processus de transport. Nos données ouvrent aussi la voie sur la possibilité que la quantité d'hétérodimères formés puisse être régulée de manière à permettre un spectre de réponses en fonction des besoins à combler.The Na⁺-K⁺-Cl⁻ cotransporter type 2 (NKCC2) belongs to the cation-Cl⁻ cotransporter (CCC) family. It exists as three splice variants called A, B and F that differ among each other by 32 residues and that are all localized on the apical membrane of the thick ascending loop of Henle (TALH) as homodimers. However, they are differentially distributed along this nephron segment: NKCC2F is localized in the initial part of the TALH where it ensures substantial NaCl reabsorption to maintain the extracellular fluid volume and NKCC2A and NKCC2B are localized in the distal part of the TALH where it ensure more modest NaCl reabsorption to help in the maintenance of the extracellular fluid volume and support the tubuloglomerular feedback. As "A" and "B" are localized in the same cellular types, we asked ourselves: 1) whether they could form AB heterodimers with transport characteristics that differ from AA and BB and 2) whether the relative quantities of AA, AB and BB formed could be regulated to allow the distal TALH and macula densa to operate adequately within a wider range of ionic concentrations. My research objective was thus to generate cDNA constructs in which the A and/or B variants are connected to each other by an inert "linker" to force the formation of AA, AB or BB by proximity, to express the product of these cDNA constructs in Xenopus laevis oocytes and to characterize the transport kinetics of the NKCC2 produced. We found that AB heterodimers exhibited unique functional characteristics (relative to AA or BB). In particular, maximal transport rates were much higher for the AB heterodimers than for the AA and BB homodimers. Our data therefore suggest that the assembled subunits cooperate with each other during the transport cycle. Our data also pave the way towards the possibility that the quantity of AB heterodimers formed is regulated such that an array of responses are allowed as a function of the needs to be met
Involvement of Pinus taeda MYB1 and MYB8 in phenylpropanoid metabolism and secondary cell wall biogenesis: a comparative in planta analysis
The involvement of two R2R3-MYB genes from Pinus taeda L., PtMYB1 and PtMYB8, in phenylpropanoid metabolism and secondary cell wall biogenesis was investigated in planta. These pine MYBs were constitutively overexpressed (OE) in Picea glauca (Moench) Voss, used as a heterologous conifer expression system. Morphological, histological, chemical (lignin and soluble phenols), and transcriptional analyses, i.e. microarray and reverse transcription quantitative PCR (RT-qPCR) were used for extensive phenotyping of MYB-overexpressing spruce plantlets. Upon germination of somatic embryos, root growth was reduced in both transgenics. Enhanced lignin deposition was also a common feature but ectopic secondary cell wall deposition was more strongly associated with PtMYB8-OE. Microarray and RT-qPCR data showed that overexpression of each MYB led to an overlapping up-regulation of many genes encoding phenylpropanoid enzymes involved in lignin monomer synthesis, while misregulation of several cell wall-related genes and other MYB transcription factors was specifically associated with PtMYB8-OE. Together, the results suggest that MYB1 and MYB8 may be part of a conserved transcriptional network involved in secondary cell wall deposition in conifers
New genetic loci link adipose and insulin biology to body fat distribution.
Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms
A Galaxy-Scale Fountain of Cold Molecular Gas Pumped by a Black Hole
We present ALMA and MUSE observations of the Brightest Cluster Galaxy in
Abell 2597, a nearby (z=0.0821) cool core cluster of galaxies. The data map the
kinematics of a three billion solar mass filamentary nebula that spans the
innermost 30 kpc of the galaxy's core. Its warm ionized and cold molecular
components are both cospatial and comoving, consistent with the hypothesis that
the optical nebula traces the warm envelopes of many cold molecular clouds that
drift in the velocity field of the hot X-ray atmosphere. The clouds are not in
dynamical equilibrium, and instead show evidence for inflow toward the central
supermassive black hole, outflow along the jets it launches, and uplift by the
buoyant hot bubbles those jets inflate. The entire scenario is therefore
consistent with a galaxy-spanning "fountain", wherein cold gas clouds drain
into the black hole accretion reservoir, powering jets and bubbles that uplift
a cooling plume of low-entropy multiphase gas, which may stimulate additional
cooling and accretion as part of a self-regulating feedback loop. All
velocities are below the escape speed from the galaxy, and so these clouds
should rain back toward the galaxy center from which they came, keeping the
fountain long-lived. The data are consistent with major predictions of chaotic
cold accretion, precipitation, and stimulated feedback models, and may trace
processes fundamental to galaxy evolution at effectively all mass scales.Comment: 31 pages, 19 figures. Accepted for publication in the Astrophysical
Journa
Surveillance programs for detection and characterization of emergent pathogens and antimicrobial resistance: results from the Division of Infectious Diseases, UNIFESP
Innovative organotypic in vitro models for safety assessment: aligning with regulatory requirements and understanding models of the heart, skin, and liver as paradigms
Genetic associations at 53 loci highlight cell types and biological pathways relevant for kidney function.
Reduced glomerular filtration rate defines chronic kidney disease and is associated with cardiovascular and all-cause mortality. We conducted a meta-analysis of genome-wide association studies for estimated glomerular filtration rate (eGFR), combining data across 133,413 individuals with replication in up to 42,166 individuals. We identify 24 new and confirm 29 previously identified loci. Of these 53 loci, 19 associate with eGFR among individuals with diabetes. Using bioinformatics, we show that identified genes at eGFR loci are enriched for expression in kidney tissues and in pathways relevant for kidney development and transmembrane transporter activity, kidney structure, and regulation of glucose metabolism. Chromatin state mapping and DNase I hypersensitivity analyses across adult tissues demonstrate preferential mapping of associated variants to regulatory regions in kidney but not extra-renal tissues. These findings suggest that genetic determinants of eGFR are mediated largely through direct effects within the kidney and highlight important cell types and biological pathways
Tracking Transitions in Spider Wrapping Silk Conformation and Dynamics by <sup>19</sup>F Nuclear Magnetic Resonance Spectroscopy
Aciniform
silk protein (AcSp1) is the primary component of wrapping
silk, the toughest of the spider silks because of a combination of
high tensile strength and extensibility. <i>Argiope trifasciata</i> AcSp1 contains a core repetitive domain with at least 14 homogeneous
200-amino acid units (“W” units). Upon fibrillogenesis,
AcSp1 converts from an α-helix-rich soluble state to a mixed
α-helical/β-sheet conformation. Solution-state nuclear
magnetic resonance (NMR) spectroscopy allowed demonstration of variable
local stability within the W unit, but comprehensive characterization
was confounded by spectral overlap, which was exacerbated by decreased
chemical shift dispersion upon denaturation. Here, <sup>19</sup>F
NMR spectroscopy, in the context of a single W unit (W<sub>1</sub>), is applied to track changes in structure and dynamics. Four strategic
positions in the W unit were mutated to tryptophan and biosynthetically
labeled with 5-fluorotryptophan (5F-Trp). Simulated annealing-based
structure calculations implied that these substitutions should be
tolerated, while circular dichroism (CD) spectroscopy and <sup>1</sup>H–<sup>15</sup>N chemical shift displacements indicated minimal
structural perturbation in W<sub>1</sub> mutants. Fiber formation
by W<sub>2</sub> concatemers containing 5F-Trp substitutions in both
W units demonstrated retention of functionality, a somewhat surprising
finding in light of sequence conservation between species. Each 5F-Trp-labeled
W<sub>1</sub> exhibited a unique <sup>19</sup>F chemical shift, line
width, longitudinal relaxation time constant (<i>T</i><sub>1</sub>), and solvent isotope shift. Perturbation to <sup>19</sup>F chemical shift and nuclear spin relaxation parameters reflected
changes in the conformation and dynamics at each 5F-Trp site upon
addition of urea and dodecylphosphocholine (DPC). <sup>19</sup>F NMR
spectroscopy allowed unambiguous localized tracking throughout titration
with each perturbant, demonstrating distinct behavior for each perturbant
not previously revealed by heteronuclear NMR experiments