59 research outputs found
Molecular mechanisms of disruption of E-cadherin adhesion induced by Arf6 and Rac small GTPases
Epithelial cells are characterised by a tight intercellular adhesion. Disassembly of E-cadherin-mediated cell-cell adhesion can induce a transition from a benign epithelial phenotype to an invasive mesenchymal phenotype. Therefore, understanding the underlying mechanisms leading to adherens junction disruption will provide insights into potential therapeutic agents to prevent tumour metastasis. The small GTPases Arf6 and Rac can each disassemble E-cadherin-based junctions, upon which epithelial cells scatter. Preliminary results in our lab showed that Rae requires PAK function during junction disassembly and that Arf6 disrupts keratinocyte junctions in a process dependent on Rac signalling. Crosstalk between Arf6 and Rac has been described previously, but.the exact molecular mechanisms involved during Arf6-induced junction disassembly are not known. A good candidate molecule to provide the link between Arf6 and Rac is GIT1. GIT1 interacts with active Arf6 by an Arf6GAP domain and induces Rac activation via binding to the RacGEF 0PIX. Rac regulates many cellular. processes in which no effector proteins have been yet identified, inclUding perturbation of cell-cell contacts. Using a keratinocyte eDNA library screen with active Rac as bait, a new Rac binding protein named Armus has been isolated previously.. This protein is interesting as in addition to binding specifically to active Rac, it contains a TBC/RabGAP domain at its C-terminus, which is predicted to inactivate Rab small GTPases. Armus function is currently unknown. The aim of my PhD project was to test the involvement of GIT1, PAK and Armus in the disassembly of E-cadherin junctions induced by active Arf6 and Rac. I found that GIT1 and D-PIX might provide the link towards Rac signalling during Arf6induced junction disassembly. Furthermore, expression of the TBC/RabGAP domain of Armus can block Arf6-induced junction disruption by inactivating Rab7. In contrast, the Rac effector PAK1 does not playa role in Arf6-dependent junction disassembly. Moreover, I found that Armus and GIT1 are distributed on similar vesicular structures, suggesting that these proteins are spatially and functionally linked.Imperial Users onl
Incidence of Interval Colorectal Cancer After Negative Results From First-Round Fecal Immunochemical Screening Tests, by Cutoff Value and Participant Sex and Age
Background & Aims: We evaluated the incidence of interval cancers between the first and second rounds of colorectal cancer (CRC) screening with the FOB-Gold fecal immunochemical test (FIT), and the effects of different cutoff values and patient sex and age. Methods: We collected data from participants in a population-based
Thousands of Rab GTPases for the Cell Biologist
Rab proteins are small GTPases that act as essential regulators of vesicular trafficking. 44 subfamilies are known in humans, performing specific sets of functions at distinct subcellular localisations and tissues. Rab function is conserved even amongst distant orthologs. Hence, the annotation of Rabs yields functional predictions about the cell biology of trafficking. So far, annotating Rabs has been a laborious manual task not feasible for current and future genomic output of deep sequencing technologies. We developed, validated and benchmarked the Rabifier, an automated bioinformatic pipeline for the identification and classification of Rabs, which achieves up to 90% classification accuracy. We cataloged roughly 8.000 Rabs from 247 genomes covering the entire eukaryotic tree. The full Rab database and a web tool implementing the pipeline are publicly available at www.RabDB.org. For the first time, we describe and analyse the evolution of Rabs in a dataset covering the whole eukaryotic phylogeny. We found a highly dynamic family undergoing frequent taxon-specific expansions and losses. We dated the origin of human subfamilies using phylogenetic profiling, which enlarged the Rab repertoire of the Last Eukaryotic Common Ancestor with Rab14, 32 and RabL4. Furthermore, a detailed analysis of the Choanoflagellate Monosiga brevicollis Rab family pinpointed the changes that accompanied the emergence of Metazoan multicellularity, mainly an important expansion and specialisation of the secretory pathway. Lastly, we experimentally establish tissue specificity in expression of mouse Rabs and show that neo-functionalisation best explains the emergence of new human Rab subfamilies. With the Rabifier and RabDB, we provide tools that easily allows non-bioinformaticians to integrate thousands of Rabs in their analyses. RabDB is designed to enable the cell biology community to keep pace with the increasing number of fully-sequenced genomes and change the scale at which we perform comparative analysis in cell biology
Vps34 PI 3-kinase inactivation enhances insulin sensitivity through reprogramming of mitochondrial metabolism
Postdoctoral fellowships were from EU Marie Curie (PIEF-GA-2009–252916) and
EMBO (ALTF 753–2010) for SA and EU Marie Curie (PIIF-GA-2009–252846) for C.C. J.
M.H. was a recipient of a doctoral fellowship from Eisai UK Ltd. Work in our laboratories
was supported as follows: BV: MRC [G0700755], BBSRC (BB/I007806/1 and BB/
M013278/1), CRUK (C23338/A15965), the Ludwig Institute for Cancer Research and the
National Institute for Health Research (NIHR) UCL Hospitals Biomedical Research
Centre; J.M.B.: NIH AG039632, GM112524. and the Albert Einstein Diabetes Research
and Training Center Animal Physiology Core DK020541; E.G.: Barry Reed Cancer
Research fund; G.S.: BBSRC (BB/L020874/1) and B.H.F.; S.S.: Anatomical Society of
Great Britain (GT) and a Wellcome Trust Career Development Fellowship 074246/Z04/Z
(S.S.); R.K.S.: Wellcome Trust (WT098498) and M.R.C. (MRC_MC_UU_12012/5); S.A.
T. and L.C.: the Francis Crick Institute, which receives its core funding from CRUK
(FC001187), MRC (FC001187), and the Wellcome Trust (FC001187); Y.-L.C.: the CRUK
Cancer Imaging Centre in association with the MRC and DoH (England) grant C1060/
A10334, C1060/A16464, NHS funding to the NIHR BRC; B.P.: Inserm and the Fondation
pour la recherche médicale
Clinical characteristics of women captured by extending the definition of severe postpartum haemorrhage with 'refractoriness to treatment': a cohort study
Background: The absence of a uniform and clinically relevant definition of severe postpartum haemorrhage
hampers comparative studies and optimization of clinical management. The concept of persistent postpartum
haemorrhage, based on refractoriness to initial first-line treatment, was proposed as an alternative to common
definitions that are either based on estimations of blood loss or transfused units of packed red blood cells
(RBC). We compared characteristics and outcomes of women with severe postpartum haemorrhage captured
by these three types of definitions.
Methods: In this large retrospective cohort study in 61 hospitals in the Netherlands we included 1391 consecutive
women with postpartum haemorrhage who received either ≥4 units of RBC or a multicomponent transfusion. Clinical
characteristics and outcomes of women with severe postpartum haemorrhage defined as persistent postpartum
haemorrhage were compared to definitions based on estimated blood loss or transfused units of RBC within 24 h
following birth. Adverse maternal outcome was a composite of maternal mortality, hysterectomy, arterial embolisation
and intensive care unit admission.
Results: One thousand two hundred sixty out of 1391 women (90.6%) with postpartum haemorrhage fulfilled the
definition of persistent postpartum haemorrhage. The majority, 820/1260 (65.1%), fulfilled this definition within 1 h
following birth, compared to 819/1391 (58.7%) applying the definition of ≥1 L blood loss and 37/845 (4.4%) applying
the definition of ≥4 units of RBC. The definition persistent postpartum haemorrhage captured 430/471 adverse maternal
outcomes (91.3%), compared to 471/471 (100%) for ≥1 L blood loss and 383/471 (81.3%) for ≥4 units of RBC. Persistent
postpartum haemorrhage did not capture all adverse outcomes because of missing data on timing of initial, first-line
treatment.
Conclusion: The definition persistent postpartum haemo
Molecular mechanisms of disruption of E-cadherin adhesion induced by Arf6 and Rac small GTPases
Epithelial cells are characterised by a tight intercellular adhesion. Disassembly of E-cadherin-mediated cell-cell adhesion can induce a transition from a benign epithelial phenotype to an invasive mesenchymal phenotype. Therefore, understanding the underlying mechanisms leading to adherens junction disruption will provide insights into potential therapeutic agents to prevent tumour metastasis. The small GTPases Arf6 and Rac can each disassemble E-cadherin-based junctions, upon which epithelial cells scatter. Preliminary results in our lab showed that Rae requires PAK function during junction disassembly and that Arf6 disrupts keratinocyte junctions in a process dependent on Rac signalling. Crosstalk between Arf6 and Rac has been described previously, but.the exact molecular mechanisms involved during Arf6-induced junction disassembly are not known. A good candidate molecule to provide the link between Arf6 and Rac is GIT1. GIT1 interacts with active Arf6 by an Arf6GAP domain and induces Rac activation via binding to the RacGEF 0PIX. Rac regulates many cellular. processes in which no effector proteins have been yet identified, inclUding perturbation of cell-cell contacts. Using a keratinocyte eDNA library screen with active Rac as bait, a new Rac binding protein named Armus has been isolated previously. This protein is interesting as in addition to binding specifically to active Rac, it contains a TBC/RabGAP domain at its C-terminus, which is predicted to inactivate Rab small GTPases. Armus function is currently unknown. The aim of my PhD project was to test the involvement of GIT1, PAK and Armus in the disassembly of E-cadherin junctions induced by active Arf6 and Rac. I found that GIT1 and D-PIX might provide the link towards Rac signalling during Arf6induced junction disassembly. Furthermore, expression of the TBC/RabGAP domain of Armus can block Arf6-induced junction disruption by inactivating Rab7. In contrast, the Rac effector PAK1 does not playa role in Arf6-dependent junction disassembly. Moreover, I found that Armus and GIT1 are distributed on similar vesicular structures, suggesting that these proteins are spatially and functionally linked.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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