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931.
Annika Eiteneuer Jonas Seiler Matthias Weith Monique Beullens Bart Lesage Veronica Krenn Andrea Musacchio Mathieu Bollen Hemmo Meyer 《The EMBO journal》2014,33(22):2704-2720
Faithful chromosome segregation during mitosis is tightly regulated by opposing activities of Aurora B kinase and protein phosphatase-1 (PP1). PP1 function at kinetochores has been linked to SDS22, but the exact localization of SDS22 and how it affects PP1 are controversial. Here, we confirm that SDS22 is required for PP1 activity, but show that SDS22 does not normally localize to kinetochores. Instead, SDS22 is kept in solution by formation of a ternary complex with PP1 and inhibitor-3 (I3). Depletion of I3 does not affect the amount of PP1 at kinetochores but causes quantitative association of SDS22 with PP1 on KNL1 at the kinetochore. Such accumulation of SDS22 at kinetochores interferes with PP1 activity and inhibits Aurora B threonine-232 dephosphorylation, which leads to increased Aurora B activity in metaphase and persistence in anaphase accompanied with segregation defects. We propose a model in which I3 regulates an SDS22-mediated PP1 activation step in solution that precedes SDS22 dissociation and transfer of PP1 to kinetochores, and which is required for PP1 to efficiently antagonize Aurora B. 相似文献
932.
Edouard Boex-Fontvieille Mathieu Jossier Marlène Davanture Michel Zivy Michael Hodges Guillaume Tcherkez 《Plant Molecular Biology Reporter》2014,32(5):987-1001
Phototropin-dependent chloroplast movement is essential to the photosynthetic acclimation of mesophyll cells to incident light. Chloroplast movement involves many cellular actors, such as chloroplast-associated actin filaments and proteins that mediate signalling between phototropins and chloroplast motion. In the past few years, genetic approaches have identified several key proteins but the intrinsic mechanisms of the signalling cascade, such as phosphorylation events, remain undefined. Here, we took advantage of phosphoproteomics to examine the involvement of protein phosphorylation in chloroplast movement in darkness or under high light, at different CO2 mole fractions (100, 380 or 1,000 ppm) to vary photosynthetic activity. Amongst the 100 relevant identified phosphopeptides, 19 (corresponding to 8 proteins) were differentially phosphorylated in darkness vs. high light. There was no significant CO2 effect on the observed phosphorylation patterns. We further characterized the phosphorylation sites in THRUMIN1, which is believed to be crucial for the attachment of chloroplast-associated actin filaments to the plasma membrane and thus for chloroplast movements. The mutant thrumin1 was complemented with a mutated protein in which phospho-sites were substituted to a phosphomimetic (Asp) or a non-phosphorylatable (Ala) residue. While the phosphomimetic substitution altered the chloroplast response in the light only, both light and dark responses were altered with the non-phosphorylatable substitution. Our data suggest a key role of protein phosphorylation, including that of THRUMIN1, in the light/dark control of chloroplast movements. 相似文献
933.
Mathieu Lachance André Longtin Catherine E. Morris Na Yu Béla Joós 《Journal of computational neuroscience》2014,37(3):523-531
Neural tissue injuries render voltage-gated Na+ channels (Nav) leaky, thereby altering excitability, disrupting propagation and causing neuropathic pain related ectopic activity. In both recombinant systems and native excitable membranes, membrane damage causes the kinetically-coupled activation and inactivation processes of Nav channels to undergo hyperpolarizing shifts. This damage-intensity dependent change, called coupled left-shift (CLS), yields a persistent or “subthreshold” Nav window conductance. Nodes of Ranvier simulations involving various degrees of mild CLS showed that, as the system’s channel/pump fluxes attempt to re-establish ion homeostasis, the CLS elicits hyperexcitability, subthreshold oscillations and neuropathic type action potential (AP) bursts. CLS-induced intermittent propagation failure was studied in simulations of stimulated axons, but pump contributions were ignored, leaving open an important question: does mild-injury (small CLS values, pumps functioning well) render propagation-competent but still quiescent axons vulnerable to further impairments as the system attempts to cope with its normal excitatory inputs? We probe this incipient diffuse axonal injury scenario using a 10-node myelinated axon model. Fully restabilized nodes with mild damage can, we show, become ectopic signal generators (“ectopic nodes”) because incoming APs stress Na+/K+ gradients, thereby altering spike thresholds. Comparable changes could contribute to acquired sodium channelopathies as diverse as epileptic phenomena and to the neuropathic amplification of normally benign sensory inputs. Input spike patterns, we found, propagate with good fidelity through an ectopically firing site only when their frequencies exceed the ectopic frequency. This “propagation window” is a robust phenomenon, occurring despite Gaussian noise, large jitter and the presence of several consecutive ectopic nodes. 相似文献
934.
PERK, the PKR-like endoplasmic reticulum (ER) kinase, is an ER transmembrane serine/threonine protein kinase activated during ER stress. In this study, we provide evidence that the Src-homology domain–containing adaptor Nck1 negatively regulates PERK. We show that Nck directly binds to phosphorylated Y561 in the PERK juxtamembrane domain through its SH2 domain. We demonstrate that mutation of Y561 to a nonphosphorylatable residue (Y561F) promotes PERK activity, suggesting that PERK phosphorylation at Y561 (pY561PERK) negatively regulates PERK. In agreement, we show that pY561PERK delays PERK activation and signaling during ER stress. Compatible with a role for PERK in pancreatic β-cells, we provide strong evidence that Nck1 contributes to PERK regulation of pancreatic β-cell proteostasis. In fact, we demonstrated that down-regulation of Nck1 in mouse insulinoma MIN6 cells results in faster dephosphorylation of pY561PERK, which correlates with enhanced PERK activation, increased insulin biosynthesis, and PERK-dependent increase in proinsulin content. Furthermore, we report that pancreatic islets in whole-body Nck1-knockout mice contain more insulin than control littermates. Together our data strongly suggest that Nck1 negatively regulates PERK by interacting with PERK and protecting PERK from being dephosphorylated at its inhibitory site pY561 and in this way affects pancreatic β-cell proinsulin biogenesis. 相似文献
935.
Jean-Philippe Brosseau Jean-Fran?ois Lucier Hanad Nwilati Philippe Thibault Daniel Garneau Daniel Gendron Mathieu Durand Sonia Couture Elvy Lapointe Panagiotis Prinos Roscoe Klinck Jean-Pierre Perreault Benoit Chabot Sherif Abou-Elela 《RNA (New York, N.Y.)》2014,20(2):189-201
Pre-mRNA alternative splicing is modified in cancer, but the origin and specificity of these changes remain unclear. Here, we probed ovarian tumors to identify cancer-associated splicing isoforms and define the mechanism by which splicing is modified in cancer cells. Using high-throughput quantitative PCR, we monitored the expression of splice variants in laser-dissected tissues from ovarian tumors. Surprisingly, changes in alternative splicing were not limited to the tumor tissues but were also found in the tumor microenvironment. Changes in the tumor-associated splicing events were found to be regulated by splicing factors that are differentially expressed in cancer tissues. Overall, ∼20% of the alternative splicing events affected by the down-regulation of the splicing factors QKI and RBFOX2 were altered in the microenvironment of ovarian tumors. Together, our results indicate that the tumor microenvironment undergoes specific changes in alternative splicing orchestrated by a limited number of splicing factors. 相似文献
936.
Milena Niño Kurt P. McLaren Henrik Meilby Mathieu Lévesque Byron Wilson Morag McDonald 《Plant Ecology》2014,215(10):1081-1097
We used data from experimental plots (control, partially cut and clear-cut) established in 1998, in a tropical dry forest (TDF) in Jamaica, to assess changes in above ground biomass (AGB) 10 years after disturbance. The treatments reduced AGB significantly in 1999 (partially cut: 37.6 %, clear-cut: 94.4 %) and after 10 years, AGB did not recover overall, nor did it recover in the clear-cut plots. Partially cut plots, however, recovered the lost AGB in 10 years via growth of uncut trees, which contributed significantly to biomass recovery, with only minor contributions from recruited trees and coppice shoots. For clear-cut plots, coppice shoots contributed significantly to the recovered AGB when compared with recruited biomass. Together, they recovered 26 % of AGB lost, despite recovering 78 % of the density and height of the control plots. The probability of survivorship decreased for trees with higher pre-treatment AGB values, but was higher for trees with multiple stems in 1998, regardless of treatment. The magnitude of biomass reduction varied among the species assessed and this had a differential effect on their ability to recover AGB. We estimate that it will take approximately 45.4 years for the clear-cut plots to recover pre-treatment AGB; this is significantly longer than AGB recovery time for some successional rainforests on abandoned pastures/farmland. Consequently, this TDF may not be as resilient as tropical rainforests. 相似文献
937.
Recent research has highlighted interdependencies between dispersal and other life‐history traits, i.e. dispersal syndromes, thereby revealing constraints on the evolution of dispersal and opportunities for improved ability to predict dispersal by considering suites of dispersal‐related traits. This review adds to the growing list of life‐history traits linked to spatial dispersal by emphasising the interdependence between dispersal through space and time, i.e. life‐history diversity that distributes individuals into separate reproductive events. We reviewed the literature that has simultaneously investigated spatial and temporal dispersal to examine the prediction that traits of these two dispersal strategies are negatively correlated. Our results suggest that negative covariation is widely anticipated from theory. Empirical studies often reported evidence of weak negative covariation, although more complicated patterns were also evident, including across levels of biological organisation. Existing literature has largely focused on plants with dormancy capability, one or two phases of the dispersal process (emigration and/or transfer) and a single level of biological organisation (theory: individual; empirical: species). We highlight patterns of covariation across levels of organisation and conclude with a discussion of the consequences of dispersal through space and time and future research areas that should improve our understanding of dispersal‐related life‐history syndromes. 相似文献
938.
Omics technologies provide new insights into the molecular physiopathology of equine osteochondrosis
Clémence Desjardin Julie Riviere Anne Vaiman Caroline Morgenthaler Mathieu Diribarne Michel Zivy Céline Robert Laurence Le Moyec Laurence Wimel Olivier Lepage Claire Jacques Edmond Cribiu Laurent Schibler 《BMC genomics》2014,15(1)
Background
Osteochondrosis (OC(D)) is a juvenile osteo-articular disorder affecting several mammalian species. In horses, OC(D) is considered as a multifactorial disease and has been described as a focal disruption of endochondral ossification leading to the development of osteoarticular lesions. Nevertheless, OC(D) physiopathology is poorly understood. Affected horses may present joint swelling, stiffness and lameness. Thus, OC(D) is a major concern for the equine industry. Our study was designed as an integrative approach using omics technologies for the identification of constitutive defects in epiphyseal cartilage and/or subchondral bone associated with the development of primary lesions to further understand OC(D) pathology. This study compared samples from non-affected joints (hence lesion-free) from OC(D)-affected foals (n = 5, considered predisposed samples) with samples from OC-free foals (n = 5) considered as control samples. Consequently, results are not confounded by changes associated with the evolution of the lesion, but focus on altered constitutive molecular mechanisms. Comparative proteomics and micro computed tomography analyses were performed on predisposed and OC-free bone and cartilage samples. Metabolomics was also performed on synovial fluid from OC-free, OC(D)-affected and predisposed joints.Results
Two lesion subtypes were identified: OCD (lesion with fragment) and OC (osteochondral defects). Modulated proteins were identified using omics technologies (2-DE proteomics) in cartilage and bone from affected foals compare to OC-free foals. These were associated with cellular processes including cell cycle, energy production, cell signaling and adhesion as well as tissue-specific processes such as chondrocyte maturation, extracellular matrix and mineral metabolism. Of these, five had already been identified in synovial fluid of OC-affected foals: ACTG1 (actin, gamma 1), albumin, haptoglobin, FBG (fibrinogen beta chain) and C4BPA (complement component 4 binding protein, alpha).Conclusion
This study suggests that OCD lesions may result from a cartilage defect whereas OC lesions may be triggered by both bone and cartilage defects, suggesting that different molecular mechanisms responsible for the equine osteochondrosis lesion subtypes and predisposition could be due to a defect in both bone and cartilage. This study will contribute to refining the definition of OC(D) lesions and may improve diagnosis and development of therapies for horses and other species, including humans.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-947) contains supplementary material, which is available to authorized users. 相似文献939.
Mariko Dacher Miguel A. Morales Pascale Pescher Olivier Leclercq Najma Rachidi Eric Prina Mathieu Cayla Albert Descoteaux Gerald F. Späth 《Molecular microbiology》2014,93(1):146-166
Leishmania parasites cause important human morbidity and mortality. Essential Leishmania genes escape genetic assessment by loss‐of‐function analyses due to lethal null mutant phenotypes, even though these genes and their products are biologically most significant and represent validated drug targets. Here we overcome this limitation using a facilitated null mutant approach applied for the functional genetic analysis of the MAP kinase LmaMPK4. This system relies on the episomal expression of the target gene from vector pXNG that expresses the Herpes simplex virus thymidine kinase gene thus rendering transgenic parasites susceptible for negative selection using the antiviral drug ganciclovir. Using this system we establish the genetic proof of LmaMPK4 as essential kinase in promastigotes. LmaMPK4 structure/function analysis by plasmid shuffle allowed us to identify regulatory kinase sequence elements relevant for chemotherapeutic intervention. A partial null mutant, expressing an MPK4 derivative with altered ATP‐binding properties, showed defects in metacyclogenesis, establishing a first link of MPK4 function to parasite differentiation. The approaches presented here are broadly applicable to any essential gene in Leishmania thus overcoming major bottlenecks for their functional genetic analysis and their exploitation for structure‐informed drug development. 相似文献
940.