The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Sue R Downie - One of the best experts on this subject based on the ideXlab platform.
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the role of the small airways in the clinical expression of asthma in adults
The Journal of Allergy and Clinical Immunology, 2012Co-Authors: Gregory G King, C S Farah, Nathan J Brown, Sue R DownieAbstract:Background The clinical relevance of increased ventilation heterogeneity, a marker of small-airways disease, in asthmatic patients is unclear. Ventilation heterogeneity is an independent determinant of airway hyperresponsiveness (AHR), improves with bronchodilators and inhaled corticosteroids (ICSs), and worsens during exacerbations, but its relationship to asthma control is unknown. Objective We sought to determine the association between ventilation heterogeneity and current asthma control before and after ICS treatment. Methods Adult subjects with asthma had lung function and asthma control (5-item Asthma Control Questionnaire [ACQ-5 score] ≥1.5 = poorly controlled, ACQ-5 score ≤0.75 = well controlled) measured at baseline. A subgroup with AHR had repeat measurements after 3 months of high-dose ICS treatment. The indices of ventilation heterogeneity in the regions of the lung where gas transport occurs predominantly through convection (ventilation heterogeneity in convection-dependent airways [Scond]) and through diffusion (ventilation heterogeneity in diffusion-dependent airways [Sacin]) were derived by using the multiple-breath nitrogen washout technique. Results At baseline (n = 105), subjects with poorly controlled asthma had worse FEV 1 , fraction of exhaled nitric oxide measured at 200 mL/s (Feno), Scond, and Sacin values. In the treatment group (n = 50) spirometric, Feno, residual volume (RV)/total lung capacity (TLC), AHR, and Scond values significantly improved. Asthma control also improved (mean ACQ-5 score, 1.3-0.7; P r s = 0.31, P = .03), Sacin ( r s = 0.32, P = .02), and Scond ( r s = 0.41, P = .003) values. The independent predictors of a change in asthma control were changes in Scond and Sacin values (model r 2 = 0.20, P = .005). Conclusions Current asthma control is associated with markers of small-airways disease. Improvements in ventilation heterogeneity with anti-inflammatory therapy are associated with improvements in symptoms. Sensitive measures of small-airway function might be useful in monitoring the response to therapy in asthmatic subjects.
David A Parfitt - One of the best experts on this subject based on the ideXlab platform.
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mitochondrial dysfunction and purkinje cell loss in autosomal recessive spastic ataxia of charlevoix saguenay arsacs
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Martine Girard, David A Parfitt, Esmeralda G M Vermeulen, Roxanne Larivière, Rébecca Gaudet, Emily C Deane, Nadya Nossova, Francois Blondeau, George A Prenosil, Michael R DuchenAbstract:Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a childhood-onset neurological disease resulting from mutations in the SACS gene encoding Sacsin, a 4,579-aa protein of unknown function. Originally identified as a founder disease in Quebec, ARSACS is now recognized worldwide. Prominent features include pyramidal spasticity and cerebellar ataxia, but the underlying pathology and pathophysiological mechanisms are unknown. We have generated an animal model for ARSACS, Sacsin knockout mice, that display age-dependent neurodegeneration of cerebellar Purkinje cells. To explore the pathophysiological basis for this observation, we examined the cell biological properties of Sacsin. We show that Sacsin localizes to mitochondria in non-neuronal cells and primary neurons and that it interacts with dynamin-related protein 1, which participates in mitochondrial fission. Fibroblasts from ARSACS patients show a hyperfused mitochondrial network, consistent with defects in mitochondrial fission. Sacsin knockdown leads to an overly interconnected and functionally impaired mitochondrial network, and mitochondria accumulate in the soma and proximal dendrites of Sacsin knockdown neurons. Disruption of mitochondrial transport into dendrites has been shown to lead to abnormal dendritic morphology, and we observe striking alterations in the organization of dendritic fields in the cerebellum of knockout mice that precedes Purkinje cell death. Our data identifies mitochondrial dysfunction/mislocalization as the likely cellular basis for ARSACS and indicates a role for Sacsin in regulation of mitochondrial dynamics.
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the ataxia protein Sacsin is a functional co chaperone that protects against polyglutamine expanded ataxin 1
Human Molecular Genetics, 2009Co-Authors: David A Parfitt, Gregory J Michael, Esmeralda G M Vermeulen, Natalia V Prodromou, Tom R Webb, Jeanmarc Gallo, Michael E Cheetham, William S Nicoll, Gregory L Blatch, Paul J ChappleAbstract:An extensive protein–protein interaction network has been identified between proteins implicated in inherited ataxias. The protein Sacsin, which is mutated in the early-onset neurodegenerative disease autosomal recessive spastic ataxia of Charlevoix-Saguenay, is a node in this interactome. Here, we have established the neuronal expression of Sacsin and functionally characterized domains of the 4579 amino acid protein. Sacsin is most highly expressed in large neurons, particularly within brain motor systems, including cerebellar Purkinje cells. Its subcellular localization in SH-SY5Y neuroblastoma cells was predominantly cytoplasmic with a mitochondrial component. We identified a putative ubiquitin-like (UbL) domain at the N-terminus of Sacsin and demonstrated an interaction with the proteasome. Furthermore, Sacsin contains a predicted J-domain, the defining feature of DnaJ/Hsp40 proteins. Using a bacterial complementation assay, the Sacsin J-domain was demonstrated to be functional. The presence of both UbL and J-domains in Sacsin suggests that it may integrate the ubiquitin–proteasome system and Hsp70 function to a specific cellular role. The Hsp70 chaperone machinery is an important component of the cellular response towards aggregation prone mutant proteins that are associated with neurodegenerative diseases. We therefore investigated the effects of siRNA-mediated Sacsin knockdown on polyglutamine-expanded ataxin-1. Importantly, SACS siRNA did not affect cell viability with GFP-ataxin-1[30Q], but enhanced the toxicity of GFP-ataxin-1[82Q], suggesting that Sacsin is protective against mutant ataxin-1. Thus, Sacsin is an ataxia protein and a regulator of the Hsp70 chaperone machinery that is implicated in the processing of other ataxia-linked proteins.
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© 2009 The Author(s)
2009Co-Authors: David A Parfitt, Gregory J Michael, Esmeralda G M Vermeulen, Tom R Webb, Jeanmarc Gallo, Michael E Cheetham, William S, Gregory L BlatchAbstract:The ataxia protein Sacsin is a functional cochaperone that protects against polyglutamine expanded ataxin-1
Cheryl M Salome - One of the best experts on this subject based on the ideXlab platform.
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effects of methacholine on small airway function measured by forced oscillation technique and multiple breath nitrogen washout in normal subjects
Respiratory Physiology & Neurobiology, 2005Co-Authors: Gregory G King, Norbert Berend, William C Thorpe, Cheryl M Salome, Stephen R Downie, Sylvia VerbanckAbstract:The multiple breath nitrogen washout (MBNW) can be analysed to produce the parameters Scond and Sacin as measures of ventilation heterogeneity in conductive and acinar airways, respectively. The derivation of these parameters is based on a model of pulmonary ventilation and results of similar modelling suggest that respiratory system conductance (Grs) measured by forced oscillation technique (FOT) is also sensitive to heterogeneity and to airway closure. Therefore, Scond, the volume of gas trapping at FRC (VtrappedFRC) and Grs may be inter-related parameters. These relationships were examined in 12 normals under baseline and bronchoconstricted states. Specific Grs was measured at 5 Hz (sGrs 5 =Grs 5 /FRC) and Scond, Sacin and VtrappedFRC by MBNW, before and after methacholine challenge. Scond was independently predicted by VtrappedFRC and FRC in a multivariate model (R 2 = 0.68, p = 0.002). Post methacholine challenge, Scond related only to VtrappedFRC (R 2 = 0.79, p<0.0001). The absolute change in Scond induced by methacholine challenge were predicted by the changes in VtrappedFRC and sGrs 5 in a multivariate model (R 2 = 0.82, p=0.0002). Sacin was unrelated to VtrappedFRC and sGrs 5 before and after methacholine challenge. In conclusion, Scond and sGrs 5 are measurements that are sensitive to changes occurring to the function of peripheral conducting airways, in particular heterogeneity and airway closure, while Sacin and presumably heterogeneity in termina] airways, are independent of these. Scond is also related to lung size. We review the current state of knowledge of FOT and MBNW in obstructive lung diseases and discuss future research directions.
Markus Plomann - One of the best experts on this subject based on the ideXlab platform.
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polycystin 1 regulates actin cytoskeleton organization and directional cell migration through a novel pc1 pacsin 2 n wasp complex
Human Molecular Genetics, 2014Co-Authors: Gang Yao, Markus Plomann, Vy Nguyen, Kristina A Roberts, Ayumi Takakura, Jing ZhouAbstract:How epithelial cells form a tubule with defined length and lumen diameter remains a fundamental question in cell and developmental biology. Loss of control of tubule lumen size in multiple organs including the kidney, liver and pancreas features polycystic kidney disease (PKD). To gain insights into autosomal dominant polycystic kidney disease, we performed yeast two-hybrid screens using the C-terminus of polycystin-1 (PC1) as bait. Here, we report that PC1 interacts with Pacsin 2, a cytoplasmic phosphoprotein that has been implicated in cytoskeletal organization, vesicle trafficking and more recently in cell intercalation during gastrulation. PC1 binds to a 107-residue fragment containing the α3 helix of the F-BAR domain of Pacsin 2 via a coiled-coil domain in its C-tail. PC1 and Pacsin 2 co-localize on the lamellipodia of migrating kidney epithelial cells. PC1 and Pacsin 2-deficient kidney epithelial cells migrate at a slower speed with reduced directional persistency. We further demonstrate that PC1, Pacsin 2 and N-Wasp are in the same protein complex, and both PC1 and Pacsin 2 are required for N-Wasp/Arp2/3-dependent actin remodeling. We propose that PC1 modulates actin cytoskeleton rearrangements and directional cell migration through the Pacsin 2/N-Wasp/Arp2/3 complex, which consequently contributes to the establishment and maintenance of the sophisticated tubular architecture. Disruption of this complex contributes to cyst formation in PKD.
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casein kinase 2 phosphorylation of protein kinase c and casein kinase 2 substrate in neurons pacsin 1 protein regulates neuronal spine formation
Journal of Biological Chemistry, 2013Co-Authors: Sylvia Schael, Jan Kormann, Julian Nuchel, Stefan Muller, Philipp Petermann, Isabel Perezotano, Sonia Marco Martinez, Mats Paulsson, Markus PlomannAbstract:Abstract The PACSIN (protein kinase C and casein kinase 2 substrate in neurons) adapter proteins couple components of the clathrin-mediated endocytosis machinery with regulators of actin polymerization and thereby regulate the surface expression of specific receptors. The brain-specific PACSIN 1 is enriched at synapses and has been proposed to affect neuromorphogenesis and the formation and maturation of dendritic spines. In studies of how phosphorylation of PACSIN 1 contributes to neuronal function, we identified serine 358 as a specific site used by casein kinase 2 (CK2) in vitro and in vivo. Phosphorylated PACSIN 1 was found in neuronal cytosol and membrane fractions. This localization could be modulated by trophic factors such as brain-derived neurotrophic factor (BDNF). We further show that expression of a phospho-negative PACSIN 1 mutant, S358A, or inhibition of CK2 drastically reduces spine formation in neurons. We identified a novel protein complex containing the spine regulator Rac1, its GTPase-activating protein neuron-associated developmentally regulated protein (NADRIN), and PACSIN 1. CK2 phosphorylation of PACSIN 1 leads to a dissociation of the complex upon BDNF treatment and induces Rac1-dependent spine formation in dendrites of hippocampal neurons. These findings suggest that upon BDNF signaling PACSIN 1 is phosphorylated by CK2 which is essential for spine formation.
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pacsin 1 forms tetramers via its n terminal f bar domain
FEBS Journal, 2007Co-Authors: Arndt Halbach, Mats Paulsson, Matthias Morgelin, Maria Baumgarten, Mark Milbrandt, Markus PlomannAbstract:The ability of protein kinase C and casein kinase 2 substrate in neurons (PACSIN)/syndapin proteins to self-polymerize is crucial for the simultaneous interactions with more than one Src homology 3 domain-binding partner or with lipid membranes. The assembly of this network has profound effects on the neural Wiskott-Aldrich syndrome protein-mediated attachment of the actin polymerization machinery to vesicle membranes as well as on the movement of the corresponding vesicles. Also, the sensing of vesicle membranes and/or the induction of membrane curvature are more easily facilitated in the presence of larger PACSIN complexes. The N-terminal Fes-CIP homology and Bin-Amphiphysin-Rvs (F-BAR) domains of several PACSIN-related proteins have been shown to mediate self-interactions, whereas studies using deletion mutants derived from closely related proteins led to the view that oligomerization depends on the formation of a trimeric complex via a coiled-coil region present in these molecules. To address whether the model of trimeric complex formation is applicable to PACSIN 1, the protein was recombinantly expressed and tested in four different assays for homologous interactions. The results showed that PACSIN 1 forms tetramers of about 240 kDa, with the self-interaction having a K-D of 6.4 x 10(-8) M. Ultrastructural analysis of these oligomers after negative staining showed that laterally arranged PACSIN molecules bind to each other via a large globular domain and form a barrel-like structure. Together, these results demonstrate that the N-terminal F-BAR domain of PACSIN 1 forms the contact site for a tetrameric structure, which is able to simultanously interact with multiple Src homology 3 binding partners. (Less)
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pacsins bind to the trpv4 cation channel pacsin 3 modulates the subcellular localization of trpv4
Journal of Biological Chemistry, 2006Co-Authors: Math P Cuajungco, Markus Plomann, Dieter Dhoedt, Christian Grimm, Bernd Nilius, Kazuo Oshima, Arjen R Mensenkamp, Rene J M Bindels, Stefan HellerAbstract:TRPV4 is a cation channel that responds to a variety of stimuli including mechanical forces, temperature, and ligand binding. We set out to identify TRPV4-interacting proteins by performing yeast two-hybrid screens, and we isolated with the avian TRPV4 amino terminus the chicken orthologues of mammalian PACSINs 1 and 3. The PACSINs are a protein family consisting of three members that have been implicated in synaptic vesicular membrane trafficking and regulation of dynamin-mediated endocytotic processes. In biochemical interaction assays we found that all three murine PACSIN isoforms can bind to the amino terminus of rodent TRPV4. No member of the PACSIN protein family was able to biochemically interact with TRPV1 and TRPV2. Co-expression of PACSIN 3, but not PACSINs 1 and 2, shifted the ratio of plasma membrane-associated versus cytosolic TRPV4 toward an apparent increase of plasma membrane-associated TRPV4 protein. A similar shift was also observable when we blocked dynamin-mediated endocytotic processes, suggesting that PACSIN 3 specifically affects the endocytosis of TRPV4, thereby modulating the subcellular localization of the ion channel. Mutational analysis shows that the interaction of the two proteins requires both a TRPV4-specific proline-rich domain upstream of the ankyrin repeats of the channel and the carboxyl-terminal Src homology 3 domain of PACSIN 3. Such a functional interaction could be important in cell types that show distribution of both proteins to the same subcellular regions such as renal tubule cells where the proteins are associated with the luminal plasma membrane.
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the ras rac guanine nucleotide exchange factor mammalian son of sevenless interacts with pacsin 1 syndapin i a regulator of endocytosis and the actin cytoskeleton
Journal of Biological Chemistry, 2001Co-Authors: Sylwia Wasiak, Christopher C Quinn, Brigitte Ritter, Elaine De Heuvel, Danny Baranes, Markus Plomann, Peter S McphersonAbstract:Abstract Mammalian Son-of-sevenless (mSos) functions as a guanine nucleotide exchange factor for Ras and Rac, thus regulating signaling to mitogen-activated protein kinases and actin dynamics. In the current study, we have identified a new mSos-binding protein of 50 kDa (p50) that interacts with the mSos1 proline-rich domain. Mass spectrometry analysis and immunodepletion studies reveal p50 as PACSIN 1/syndapin I, a Src homology 3 domain-containing protein functioning in endocytosis and regulation of actin dynamics. In addition to PACSIN 1, which is neuron-specific, mSos also interacts with PACSIN 2, which is expressed in neuronal and nonneuronal tissues. PACSIN 2 shows enhanced binding to the mSos proline-rich domain in pull-down assays from brain extracts as compared with lung extracts, suggesting a tissue-specific regulation of the interaction. Proline to leucine mutations within the Src homology 3 domains of PACSIN 1 and 2 abolish their binding to mSos, demonstrating the specificity of the interactions. In situ, PACSIN 1 and mSos1 are co-expressed in growth cones and actin-rich filopodia in hippocampal and dorsal root ganglion neurons, and the two proteins co-immunoprecipitate from brain extracts. Moreover, epidermal growth factor treatment of COS-7 cells causes co-localization of PACSIN 1 and mSos1 in actin-rich membrane ruffles, and their interaction is regulated through epidermal growth factor-stimulated mSos1 phosphorylation. These data suggest that PACSINs may function with mSos1 in regulation of actin dynamics.
Esmeralda G M Vermeulen - One of the best experts on this subject based on the ideXlab platform.
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mitochondrial dysfunction and purkinje cell loss in autosomal recessive spastic ataxia of charlevoix saguenay arsacs
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Martine Girard, David A Parfitt, Esmeralda G M Vermeulen, Roxanne Larivière, Rébecca Gaudet, Emily C Deane, Nadya Nossova, Francois Blondeau, George A Prenosil, Michael R DuchenAbstract:Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a childhood-onset neurological disease resulting from mutations in the SACS gene encoding Sacsin, a 4,579-aa protein of unknown function. Originally identified as a founder disease in Quebec, ARSACS is now recognized worldwide. Prominent features include pyramidal spasticity and cerebellar ataxia, but the underlying pathology and pathophysiological mechanisms are unknown. We have generated an animal model for ARSACS, Sacsin knockout mice, that display age-dependent neurodegeneration of cerebellar Purkinje cells. To explore the pathophysiological basis for this observation, we examined the cell biological properties of Sacsin. We show that Sacsin localizes to mitochondria in non-neuronal cells and primary neurons and that it interacts with dynamin-related protein 1, which participates in mitochondrial fission. Fibroblasts from ARSACS patients show a hyperfused mitochondrial network, consistent with defects in mitochondrial fission. Sacsin knockdown leads to an overly interconnected and functionally impaired mitochondrial network, and mitochondria accumulate in the soma and proximal dendrites of Sacsin knockdown neurons. Disruption of mitochondrial transport into dendrites has been shown to lead to abnormal dendritic morphology, and we observe striking alterations in the organization of dendritic fields in the cerebellum of knockout mice that precedes Purkinje cell death. Our data identifies mitochondrial dysfunction/mislocalization as the likely cellular basis for ARSACS and indicates a role for Sacsin in regulation of mitochondrial dynamics.
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the ataxia protein Sacsin is a functional co chaperone that protects against polyglutamine expanded ataxin 1
Human Molecular Genetics, 2009Co-Authors: David A Parfitt, Gregory J Michael, Esmeralda G M Vermeulen, Natalia V Prodromou, Tom R Webb, Jeanmarc Gallo, Michael E Cheetham, William S Nicoll, Gregory L Blatch, Paul J ChappleAbstract:An extensive protein–protein interaction network has been identified between proteins implicated in inherited ataxias. The protein Sacsin, which is mutated in the early-onset neurodegenerative disease autosomal recessive spastic ataxia of Charlevoix-Saguenay, is a node in this interactome. Here, we have established the neuronal expression of Sacsin and functionally characterized domains of the 4579 amino acid protein. Sacsin is most highly expressed in large neurons, particularly within brain motor systems, including cerebellar Purkinje cells. Its subcellular localization in SH-SY5Y neuroblastoma cells was predominantly cytoplasmic with a mitochondrial component. We identified a putative ubiquitin-like (UbL) domain at the N-terminus of Sacsin and demonstrated an interaction with the proteasome. Furthermore, Sacsin contains a predicted J-domain, the defining feature of DnaJ/Hsp40 proteins. Using a bacterial complementation assay, the Sacsin J-domain was demonstrated to be functional. The presence of both UbL and J-domains in Sacsin suggests that it may integrate the ubiquitin–proteasome system and Hsp70 function to a specific cellular role. The Hsp70 chaperone machinery is an important component of the cellular response towards aggregation prone mutant proteins that are associated with neurodegenerative diseases. We therefore investigated the effects of siRNA-mediated Sacsin knockdown on polyglutamine-expanded ataxin-1. Importantly, SACS siRNA did not affect cell viability with GFP-ataxin-1[30Q], but enhanced the toxicity of GFP-ataxin-1[82Q], suggesting that Sacsin is protective against mutant ataxin-1. Thus, Sacsin is an ataxia protein and a regulator of the Hsp70 chaperone machinery that is implicated in the processing of other ataxia-linked proteins.
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© 2009 The Author(s)
2009Co-Authors: David A Parfitt, Gregory J Michael, Esmeralda G M Vermeulen, Tom R Webb, Jeanmarc Gallo, Michael E Cheetham, William S, Gregory L BlatchAbstract:The ataxia protein Sacsin is a functional cochaperone that protects against polyglutamine expanded ataxin-1
