Rho

Distribution by Scientific Domains
Distribution within Medical Sciences

Kinds of Rho

  • gtpase rho
  • spearman rho

  • Terms modified by Rho

  • rho GTPase
  • rho activation
  • rho family
  • rho kinase
  • rho kinase inhibitor
  • rho pathway
  • rho protein

  • Selected Abstracts


    p.Gln200Glu, a putative constitutively active mutant of rod ,-transducin (GNAT1) in autosomal dominant congenital stationary night blindness,,

    HUMAN MUTATION, Issue 7 2007
    Viktoria Szabo
    Abstract Congenital stationary night blindness (CSNB) is a non-progressive Mendelian condition resulting from a functional defect in rod photoreceptors. A small number of unique missense mutations in the genes encoding various members of the rod phototransduction cascade, e.g. rhodopsin (RHO), cGMP phosphodiesterase ,-subunit (PDE6B), and transducin ,-subunit (GNAT1) have been reported to cause autosomal dominant (ad) CSNB. While the RHO and PDE6B mutations result in constitutively active proteins, the only known adCSNB-associa-ted GNAT1 change (p.Gly38Asp) produces an ,-transducin that is unable to activate its downstream effector molecule in vitro. In a multigeneration Danish family with adCSNB, we identified a novel heterozygous C to G transversion (c.598C>G) in exon 6 of GNAT1 that should result in a p.Gln200Glu substitution in the evolutionarily highly conserved Switch 2 region of ,-transducin, a domain that has an important role in binding and hydrolyzing GTP. Computer modeling based on the known crystal structure of transducin suggests that the p.Gln200Glu mutant exhibits impaired GTPase activity, and thereby leads to constitutive activation of phototransduction. This assumption is in line with our results of trypsin protection assays as well as previously published biochemical data on mutants of this glutamine in the GTPase active site of ,-transducin following in vitro expression, and observations that inappropriately activating mutants of various members of the rod phototransduction cascade represent one of the major molecular causes of adCSNB. © 2007 Wiley-Liss, Inc. [source]


    Development of photoreceptor-specific promoters and their utility to investigate EIAV lentiviral vector mediated gene transfer to photoreceptors

    THE JOURNAL OF GENE MEDICINE, Issue 12 2007
    Marjorie Nicoud
    Abstract Background We wanted to investigate the ability of recombinant equine infectious anemia virus (EIAV) vectors to transduce photoreceptor cells by developing a series of photoreceptor-specific promoters that drive strong gene expression in photoreceptor cells. Methods Promoter fragments derived from the rhodopsin (RHO), the beta phosphodiesterase (PDE) and the retinitis pigmentosa (RP1) genes were cloned in combination with an enhancer element, derived from the interphotoreceptor retinoid-binding protein gene (IRBP), into luciferase reporter plasmids. An in vitro transient reporter assay was carried out in the human Y-79 retinoblastoma cell line. The optimal promoters from this screen were then cloned into the recombinant EIAV vector for evaluation in vivo following subretinal delivery into mice. Results All promoters maintained a photoreceptor-specific expression profile in vitro and the gene expression was further enhanced in combination with the IRBP enhancer. The use of IRBP-combined RHO or PDE promoters showed modest but exclusive expression in photoreceptors following subretinal delivery to mice. By contrast an EIAV vector containing the cytomegalovirus (CMV) promoter drove reporter gene expression in both photoreceptors and retinal pigment epithelium. Conclusions It may be possible to use recombinant EIAV vectors containing photoreceptor-specific promoters to drive therapeutic gene expression to treat a range of retinal degenerative diseases where the photoreceptor cell is the primary disease target. Copyright © 2007 John Wiley & Sons, Ltd. [source]


    Spin State, Structure, and Reactivity of Terminal Oxo and Dioxygen Complexes of the (PNP)Rh Moiety

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2008
    Alexander
    Abstract [RhIIIH{(tBu2PCH2SiMe2NSiMe2CH2PtBu{CMe2CH2})}], ([RhH(PNP*)]), reacts with O2 in the time taken to mix the reagents to form a 1:1 ,2 -O2 adduct, for which OO bond length is discussed with reference to the reducing power of [RhH(PNP*)]; DFT calculations faithfully replicate the observed O,O distance, and are used to understand the oxidation state of this coordinated O2. The reactivity of [Rh(O2)(PNP)] towards H2, CO, N2, and O2 is tested and compared to the associated DFT reaction energies. Three different reagents effect single oxygen atom transfer to [RhH(PNP*)]. The resulting [RhO(PNP)], characterized at and above ,60,°C and by DFT calculations, is a ground-state triplet, is nonplanar, and reacts, above about +15,°C, with its own tBu CH bond, to cleanly form a diamagnetic complex, [Rh(OH){N(SiMe2CH2PtBu2)(SiMe2CH2PtBu{CMe2CH2})}]. [source]


    Shareholder Activism: Corporate Governance Reform in Korea , By Han-Kyun Rho

    CORPORATE GOVERNANCE, Issue 6 2007
    Woochan Kim
    No abstract is available for this article. [source]


    Rho plays a central role in regulating local cell-matrix mechanical interactions in 3D culture

    CYTOSKELETON, Issue 6 2007
    N. Lakshman
    Abstract The purpose of this study was to assess quantitatively the role of the small GTPase Rho on cell morphology, f-actin organization, and cell-induced matrix remodeling in 3D culture. Human corneal fibroblasts (HTK) were infected with adenoviruses that express green fluorescent protein (GFP) or GFP-N19Rho (dominant negative Rho). One day later cells were plated inside collagen matrices and allowed to spread for 24 h. Cells were fixed and stained for f-actin. Fluorescent (for f-actin) and reflected light (for collagen fibrils) images were acquired using confocal microscopy. Fourier transform analysis was used to assess local collagen fibril alignment, and changes in cell morphology and collagen density were measured using MetaMorph. The decrease in matrix height was used as an indicator of global matrix contraction. HTK and HTK-GFP cells induced significant global matrix contraction; this was inhibited by N19Rho. HTK and HTK-GFP fibroblasts generally had a bipolar morphology and occasional intracellular stress fibers. Collagen fibrils were compacted and aligned parallel to stress fibers and pseudopodia. In contrast, HTK-GFPN19 cells were elongated, and had a more cortical f-actin distribution. Numerous small extensions were also observed along the cell body. In addition, both local collagen fibril density and alignment were significantly reduced. Rho plays a key role in regulating both the morphology and mechanical behavior of corneal fibroblasts in 3D culture. Overall, the data suggest that Rho-kinase dependent cell contractility contributes to global and local matrix remodeling, whereas Rho dependent activation of mDia and/or other downstream effectors regulates the structure and number of cell processes. Cell Motil. Cytoskeleton 2007. © 2007 Wiley-Liss, Inc. [source]


    Myosin-mediated cytoskeleton contraction and Rho GTPases regulate laminin-5 matrix assembly

    CYTOSKELETON, Issue 2 2004
    Gregory W. deHart
    Abstract Laminin-5 is a major structural element of epithelial tissue basement membranes. In the matrix of cultured epithelial cells, laminin-5 is arranged into intricate patterns. Here we tested a hypothesis that myosin II-mediated actin contraction is necessary for the proper assembly of a laminin-5 matrix by cultured SCC12 epithelial cells. To do so, the cells were treated with ML-7, a myosin II light chain kinase inhibitor, or Y-27632, an inhibitor of Rho-kinase (ROCK), both of which block actomyosin contraction. Under these conditions, laminin-5 shows an aberrant localization in dense patches at the cell periphery. Since ROCK activity is regulated by the small GTPase Rho, this suggests that members of the Rho family of GTPases may also be important for laminin-5 matrix assembly by SCC12 cells. We confirmed this hypothesis since SCC12 cells expressing mutant proteins that inhibit RhoA, Rac, and Cdc42 assemble the same aberrant laminin-5 protein arrays as drug-treated cells. We have also evaluated the organization of the laminin-5 receptors ,3,1 and ,6,4 integrin and hemidesmosome proteins in ML-7- and Y-27632-treated cells or in cells in which RhoA, Rac, and Cdc42 activity were inhibited. In all instances, ,3,1 and ,6,4 integrin heterodimers, as well as hemidesmosome proteins, localize precisely with laminin-5 in the matrix of the cells. In summary, our results provide evidence that myosin II-mediated actin contraction and the activity of Rho GTPases are necessary for the proper organization of a laminin-5 matrix and localization of hemidesmosome protein arrays in epithelial cells. Cell Motil. Cytoskeleton 57:107,117, 2004. © 2004 Wiley-Liss, Inc. [source]


    Neuroprotective signal transduction in model motor neurons exposed to thrombin: G-protein modulation effects on neurite outgrowth, Ca2+ mobilization, and apoptosis ,

    DEVELOPMENTAL NEUROBIOLOGY, Issue 2 2001
    Irina V. Smirnova
    Abstract Thrombin, the ultimate protease in the blood coagulation cascade, mediates its known cellular effects by unique proteolytic activation of G-protein-coupled protease-activated receptors (PARs), such as PAR1, PAR3, and PAR4, and a "tethered ligand" mechanism. PAR1 is variably expressed in subpopulations of neurons and largely determines thrombin's effects on morphology, calcium mobilization, and caspase-mediated apoptosis. In spinal cord motoneurons, PAR1 expression correlates with transient thrombin-mediated [Ca2+]i flux, receptor cleavage, and elevation of rest [Ca2+]i activating intracellular proteases. At nanomolar concentrations, thrombin retracts neurites via PAR1 activation of the monomeric, 21 kDa Ras G-protein RhoA, which is also involved in neuroprotection at lower thrombin concentrations. Such results suggest potential downstream targets for thrombin's injurious effects. Consequently, we employed several G-protein-specific modulators prior to thrombin exposure in an attempt to uncouple both heterotrimeric and monomeric G-proteins from motoneuronal PAR1. Cholera toxin, stimulating Gs, and lovastatin, which blocks isoprenylation of Rho, reduced thrombin-induced calcium mobilization. In contrast, pertussis toxin and mastoparan, inhibiting or stimulating Go/Gi, were found to exacerbate thrombin action. Effects on neuronal rounding and apoptosis were also detected, suggesting therapeutic utility may result from interference with downstream components of thrombin signaling pathways in human motor neuron disorders, and possibly other neurodegenerative diseases. Published 2001 John Wiley & Sons, Inc. J Neurobiol 48: 87,100, 2001 [source]


    Mechanical stretch induces TGF-, synthesis in hepatic stellate cells

    EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2 2004
    R. Sakata
    Abstract Background, It is known that mechanical stress induces extracellular matrix via transforming growth factor-, (TGF-,) synthesis in vascular smooth muscle cells. Activated hepatic stellate cells (HSCs) are an important source of TGF-, in the liver. However, it remains unclear whether mechanical stress induces TGF-, in HSCs. The Rho small GTP-binding protein (Rho) has recently emerged as an important regulator of actin and cytoskeleton. We examined whether TGF-, is expressed in stretched HSCs and whether Rho is involved in stretch-induced TGF-, synthesis. Materials and methods, A cultured human HSC cell line, LI90, was used for this study. Hepatic stellate cells were cyclically stretched using the Flexercell® strain unit. Concentration of TGF-, in the conditioned medium was estimated by a bioassay using mink lung epithelial cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct. Transforming growth factor-, mRNA expression of HSCs was estimated by a reverse-transcription polymerase chain reaction. Replication-defective adenoviral vectors expressing a dominant negative type of Rho was utilized to suppress its effect on HSCs. Results, Transforming growth factor-, concentration of the conditioned media of stretched HSCs showed time-dependent increases as compared to nonstretched HSCs from 2 h to 24 h. Transforming growth factor-, mRNA expression in stretched HSCs was increased compared with that in nonstretched HSCs. Transfection of dominant negative Rho inhibited the stretch-induced TGF-, synthesis. Conclusions, Mechanical stretch enhanced TGF-, expression on mRNA and protein level in HSCs. Rho was closely related to stretch-induced TGF-, synthesis in HSCs. [source]


    Zoledronate has an antitumor effect and induces actin rearrangement in dexamethasone-resistant myeloma cells

    EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 5 2007
    Masayuki Koizumi
    Abstract New strategies are needed to overcome the resistance of multiple myeloma (MM) to dexamethasone (Dex). Several recent in vitro studies demonstrated the antitumor effect of nitrogen-containing amino-bisphosphonates (N-BPs) in various tumor cell lines. Inhibition of the prenylation of small G proteins is assumed to be one of the principal mechanisms by which N-BPs exert their effects. There have been few reports on N-BP treatment of MM cells that are resistant to Dex. Additionally, it is not known how small G proteins are altered in N-BP-treated MM cells. In this study, we evaluated the effect of the most potent N-BP, zoledronate (ZOL), on a Dex-resistant human MM cell subline (Dex-R) that we established from the well-documented RPMI8226 cell line. ZOL reduced the viability and induced apoptosis of Dex-R cells. Some of the ZOL-treated RPMI8226 cells and ZOL-treated Dex-R cells were elongated; however, elongated cells were not seen among the Dex-treated RPMI8226 cells. Furthermore, we found that portions of the small G proteins, Rho and Rap1A, were unprenylated in the ZOL-treated MM cells. Geranylgeraniol reduced the above-mentioned ZOL-induced effects. These findings suggest that ZOL may be beneficial for the treatment of Dex-resistant MM by suppressing the processing of RhoA and Rap1A. [source]


    Role of the monomeric GTPase Rho in hematopoietic progenitor cell migration and transplantation

    EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2006
    Stephan Göttig
    Abstract To investigate the role of the monomeric guanosine triphosphatase (GTPase) Rho on migration of hematopoietic progenitor cells (HPC), we employed different clostridial toxins which inhibit the Rho family of GTPases. Pretreatment with C2I-C3, a cell-accessible C3 transferase fusion protein that targets Rho, increased chemokinetic migration of the factor-dependent multipotent cell line Factor Dependent Cell Paterson with mixed lineage differentiation potential (FDCP-mix) and of primary lineage marker-depleted HPC in vitro. In contrast, treatment with lethal toxin (LT) from Clostridium sordellii, which predominantly inactivates Rac, and with toxin,B from C.,difficile, which inactivates Rho, Rac and Cdc42, decreased in vitro migration. When HPC pretreated with LT or toxin,B were transplanted into mice, homing to the bone marrow was impaired, whereas C2I-C3 treatment did not alter HPC homing. However, in a competitive hematopoietic repopulation experiment in C57BL/6 mice, pretreatment of bone marrow cells with any of the inhibitors, including the Rho inhibitor C2I-C3, resulted in suppressed donor-type hematopoiesis. Our data indicate that whereas Rac supports HPC cell cycling, migration, short-term homing and hematopoietic regeneration, Rho coordinates down-regulation of HPC migration and is required for hematopoietic regeneration. [source]


    Axon behaviour at Schwann cell , astrocyte boundaries: manipulation of axon signalling pathways and the neural adhesion molecule L1 can enable axons to cross

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2004
    Kathryn H. Adcock
    Abstract Axon regeneration in vivo is blocked at boundaries between Schwann cells and astrocytes, such as occur at the dorsal root entry zone and around peripheral nerve or Schwann cell grafts. We have created a tissue culture model of these boundaries in Schwann cell , astrocyte monolayer co-cultures. Axon behaviour resembles that in vivo, with axons showing a strong preference for Schwann cells over astrocytes. At boundaries between the two cell types, axons growing on astrocytes cross readily onto Schwann cells, but only 15% of axons growing on Schwann cells are able to cross onto astrocytes. Treatment with chondroitinase or chlorate to reduce inhibition by proteoglycans did not change this behaviour. The neural adhesion molecule L1 is present on Schwann cells and not astrocytes, and manipulation of L1 by application of an antibody, L1-Fc in solution, or adenoviral transduction of L1 into astrocytes increased the proportion of axons able to cross onto astrocytes to 40,50%. Elevating cAMP levels increased crossing from Schwann cells onto astrocytes in live and fixed cultures, and had a co-operative effect with NT-3 but not with NGF. Inactivation of Rho with a cell-permeant form of C3 exoenzyme also increased crossing from Schwann cells to astrocytes. Our experiments indicate that the preference of axons for Schwann cells is largely mediated by the presence of L1 on Schwann cells but not astrocytes, and that manipulation of growth cone signalling pathways can allow axons to disregard boundaries between the two cell types. [source]


    Characterization of the expression of PDZ-RhoGEF, LARG and G,12/G,13 proteins in the murine nervous system

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2002
    R. Kuner
    Small GTPases of the Rho-family, like Rho, Rac and Cdc42, are involved in neuronal morphogenesis by regulating growth cone morphology or dendritic spine formation. G-proteins of the G12 -family, G12 and G13, couple G-protein-coupled receptors (GPCRs) to the activation of RhoA. Recently, two novel Rho-specific guanine nucleotide exchange factors (RhoGEFs), PDZ-RhoGEF and LARG, have been identified to interact with the activated ,-subunits of G12/G13 and are thus believed to mediate GPCR-induced Rho activation. Although studies in neuronal cell lines have shown that G12/G13 and PDZ-RhoGEF mediate GPCR-induced neurite retraction, the role, as well as the expression of this signalling pathway, in intact brain has not been adequately studied. In the present study, we have characterized systematically the expression of G,12, G,13, PDZ-RhoGEF and LARG in various murine tissues as well as their subcellular localization in the central and peripheral nervous systems. By performing immunohistochemistry, using polyclonal antibodies raised against the above proteins, we observed that G,12, G,13 and their RhoGEF-effectors are distributed widely in the mammalian nervous system. Moreover, these proteins localize to distinct morphological compartments within neurons. While LARG and G,12 were mainly found in somata of the neurons, PDZ-RhoGEF and G,13 were predominantly localized in the neuropil of central neurons. Interestingly, PDZ-RhoGEF is a neural-specific protein, whereas LARG is nearly ubiqoutous. Our data provide evidence that the G12/13,RhoGEF-mediated pathway is present throughout the adult brain and may be involved in regulation of neuronal morphogenesis and function via GPCRs. [source]


    Quantitative solid-state 13C NMR spectroscopy of organic matter fractions in lowland rice soils

    EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2004
    R. J. Smernik
    Summary Spin counting on solid-state 13C cross-polarization (CP) nuclear magnetic resonance (NMR) spectra of two humic fractions isolated from tropical lowland soils showed that only 32,81% of potential 13C NMR signal was detected. The observability of 13C NMR signal (Cobs) was higher in the mobile humic acid (MHA) than in the calcium humate (CaHA) fraction, and increased with increasing intensity of irrigated rice cropping. NMR observability appeared to be related to the nature of the organic carbon, with phenol- and methoxyl-rich samples having the higher values of Cobs. The Bloch decay (BD) technique provided more quantitatively reliable 13C NMR spectra, as evidenced by values of Cobs in the range 91,100% for seven of the eight humic fractions studied. The BD spectra contained considerably more aryl and carbonyl signal, and less O,alkyl and alkyl signal, with the greatest differences between CP and BD spectra observed for the samples with low Cobs(CP). The causes of low CP observability were investigated using the spectral editing technique RESTORE ( REstoration of Spectra via TCH and T One Rho (T1,H) Editing). Rapid T1,H relaxation was found to be primarily responsible for the under-representation of carbonyl carbon, whereas inefficient cross-polarization was primarily responsible for the under-representation of aryl carbon in CP spectra. Proton NMR relaxation rates T1H and T1,H were found to correlate with other NMR properties and also with cropping management. Non-uniform rates of T1H relaxation in two of the CaHA fractions enabled the generation of proton spin relaxation editing subspectra. [source]


    Rho1-GEFs Rgf1 and Rgf2 are involved in formation of cell wall and septum, while Rgf3 is involved in cytokinesis in fission yeast

    GENES TO CELLS, Issue 12 2005
    Tadashi Mutoh
    The Rho GTPase acts as a binary molecular switch by converting between a GDP-bound inactive and a GTP-bound active conformational state. The guanine nucleotide exchange factors (GEFs) are critical activators of Rho. Rho1 has been shown to regulate actin cytoskeleton and cell wall synthesis in the fission yeast Schizosaccharomyces pombe. Here we studied function of fission yeast RhoGEFs, Rgf1, Rgf2, and Rgf3. It was shown that these proteins have similar molecular structures, and function as GEFs for Rho1. Disruption of either rgf1 or rgf2 did not show a serious effect on the cell. On the other hand, disruption of rgf3 caused severe defects in contractile ring formation, F-actin patch localization, and septation during cytokinesis. Rgf1 and Rgf2 were localized to the cell ends during interphase and the septum. Rgf3 formed a ring at the division site, which was located outside the contractile ring and inside the septum where Rho1 was accumulated. In summary, Rgf1 and Rgf2 show functional redundancy, and roles of these RhoGEFs are likely to be different from that of Rgf3. Rho1 is likely to be activated by Rgf3 at the division site, and involved in contractile ring formation and/or maintenance and septation. [source]


    Involvement of Cdc42 and Rac small G proteins in invadopodia formation of RPMI7951 cells

    GENES TO CELLS, Issue 12 2003
    Hirokazu Nakahara
    Background:, Invadopodia are membrane protrusions into the extracellular matrix by aggressive tumour cells. These structures are associated with sites of matrix degradation and invasiveness of malignant tumour cells in an in vitro fibronectin degradation/invasion assay. The Rho family small G proteins, consisting of the Rho, Rac and Cdc42 subfamilies, are implicated in various cell functions, such as cell shape change, adhesion, and motility, through reorganization of the actin cytoskeleton. We studied the roles of the Rho family small G proteins in invadopodia formation. Results:, We first demonstrated that invadopodia of RPMI7951 human melanoma cells extended into the matrix substratum on a vertical view using a laser scanning confocal microscope system. We confirmed that invadopodia were rich in actin filaments (F-actin) and visualized clearly with F-actin staining on a vertical view as well as on a horizontal view. We then studied the roles of Rho, Rac, and Cdc42 in invasiveness of the same cell line. In the in vitro fibronectin degradation/invasion assay, a dominant active mutant of Cdc42 enhanced dot-like degradation, whereas a dominant active mutant of Rac enhanced diffuse-type degradation. Furthermore, frabin, a GDP/GTP exchange protein for Cdc42 with F-actin-binding activity, enhanced both dot-like and diffuse-type degradation. However, a dominant active mutant of Rho did not affect the fibronectin degradation. Moreover, inhibition of phosphatidylinositol-3 kinase (PI3K) disrupted the Rac and Cdc42-dependent actin structures and blocked the fibronectin degradation. Conclusion:, These results suggest that Cdc42 and Rac play important roles in fibronectin degradation and invasiveness in a coordinate manner through the frabin-Cdc42/Rac-PI3K signalling pathway. [source]


    Phosphorylation and reorganization of vimentin by p21-activated kinase (PAK)

    GENES TO CELLS, Issue 2 2002
    Hidemasa Goto
    Background: Intermediate filament (IF) is one of the three major cytoskeletal filaments. Vimentin is the most widely expressed IF protein component. The Rho family of small GTPases, such as Cdc42, Rac and Rho, are thought to control the organization of actin filaments as well as other cytoskeletal filaments. Results: We determined if the vimentin filaments can be regulated by p21-activated kinase (PAK), one of targets downstream of Cdc42 or Rac. In vitro analyses revealed that vimentin served as an excellent substrate for PAK. This phosphorylated vimentin lost the potential to form 10 nm filaments. We identified Ser25, Ser38, Ser50, Ser65 and Ser72 in the amino-terminal head domain as the major phosphorylation sites on vimentin for PAK. The ectopic expression of constitutively active PAK in COS-7 cells induced vimentin phosphorylation. Fibre bundles or granulates of vimentin were frequent in these transfected cells. However, the kinase-inactive mutant induced neither vimentin phosphorylation nor filament reorganization. Conclusion: Our observations suggest that PAK may regulate the reorganization of vimentin filaments through direct vimentin phosphorylation. [source]


    Impaired efflux of cholesterol from aged cells and its molecular mechanism: A basis for age-related enhancement of atherosclerosis

    GERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 3 2007
    Shizuya Yamashita
    Aging is one of the risk factors for atherosclerotic cardiovascular diseases, however, its molecular mechanism is currently unknown. Many types of cells in the atherosclerotic lesions are considered to have various biological abnormalities such as impaired lipid homeostasis and slow cell proliferation, which may be related to senescence at cellular levels. One of the common characteristics of senescent cells in vitro is the alteration of actin cytoskeletons, which were reported to be involved in the intracellular transport of lipids. Cholesterol efflux from the cells is the initial step of reverse cholesterol transport, a major protective system against atherosclerosis. Recently, we demonstrated that Cdc42, a member of the Rho -GTPase family, might be crucial for cellular lipid transport and cholesterol efflux based upon studies of Tangier cells that are deficient in ABCA1 gene. In the current review, we also indicate that the expression of Cdc42 is decreased in the cells from aged subjects in close association with the retarded intracellular lipid transport. Furthermore, the Cdc42 expression is reduced by culturing fibroblasts in vitro for a long duration. Werner syndrome (WS) is characterized by the early onset of senescent phenotypes including premature atherosclerotic cardiovascular diseases, although the underlying molecular mechanism for the enhanced atherosclerosis has not been fully understood yet. We examined the intracellular lipid transport and cholesterol efflux and the expression levels of cholesterol efflux-related molecules in skin fibroblasts obtained from patients with WS. Cholesterol efflux was markedly reduced in the WS fibroblasts in association with an increased cellular cholesterol content. Fluorescent recovery after photobleaching technique revealed that intracellular lipid transport around Golgi apparatus was markedly reduced when using a C6-NBD-ceramide as a tracer. Cdc42 protein and its guanosine 5,-triphosphate-bound active form were markedly reduced in the WS fibroblasts. The adenovirus-mediated complementation of wild-type Cdc42 corrected the impaired cholesterol efflux, intracellular lipid transport and cellular cholesterol levels in the WS fibroblasts. These data indicate that the reduced expression of Cdc42 might be responsible for the abnormal lipid transport, which in turn might be related to the accelerated cardiovascular manifestations in WS patients. The current review focuses on the impaired efflux of cholesterol from aged cells and its molecular mechanism as a basis for age-related enhancement of atherosclerosis. [source]


    Involvement of IQGAP3, a regulator of Ras/ERK-related cascade, in hepatocyte proliferation in mouse liver regeneration and development,

    JOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2009
    Koshi Kunimoto
    The spatio-temporal regulation of hepatocyte proliferation is a critical issue in liver regeneration. Here, in normal and regenerating liver as well as in developing liver, we examined its expression/localization of IQGAP3, which was most recently reported as a Ras/Rac/Cdc42-binding proliferation factor associated with cell,cell contacts in epithelial-type cells. In parallel, the expression/localization of Rac/Cdc42-binding IQGAP1/2 was examined. IQGAP3 showed a specific expression in proliferating hepatocytes positive for the proliferating marker Ki-67, the levels of expressions of mRNAs and proteins were significantly increased in hepatocytes in liver regeneration and development. In immunofluorescence, IQGAP3 was highly enriched at cell,cell contacts of hepatocytes. IQGAP1 and IQGAP2 were exclusively expressed in Kupffer and sinusoidal endothelial cells, respectively, in normal, regenerating, and developing liver. The expression of IQGAP1, but not of IQGAP2, was increased in CCl4 -induced (but not in partial hepatectomy-induced) liver regeneration. Exclusive expression/localization of IQGAP3 to hepatocytes in the liver likely reflects the specific involvement of the IQGAP3/Ras/ERK signaling cascade in hepatocyte proliferation in addition to the previously identified signaling pathways, possibly by integrating cell,cell contact-related proliferating signaling events. On the other hand, the Rac/Cdc42-binding properties of IQGAP1/2/3 may be related to the distinct modes of remodeling due to the different strategies which induced proliferation of liver cells; partial hepatectomy, CCl4 injury, or embryonic development. Thus, the functional orchestration of Ras and the Ras homologous (Rho) family proteins Rac/Cdc42 likely plays a critical role in liver regeneration and development. J. Cell. Physiol. 220: 621,631, 2009. © 2009 Wiley-Liss, Inc. [source]


    McGill Pain Questionnaire: A multi-dimensional verbal scale assessing postoperative changes in pain symptoms associated with severe endometriosis

    JOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 4 2009
    Elena Fabbri
    Abstract Background:, Objective evaluation of pelvic pain symptoms using a standard pain questionnaire is essential to assessing the treatment of endometriosis and related pain. Aim:, To evaluate the McGill Pain Questionnaire (MPQ) as a multi-dimensional verbal scale in providing information about chronic pelvic pain associated with endometriosis, before and after laparoscopic surgery. Methods:, Fifty-five women undergoing laparoscopy for severe endometriosis were asked to complete the MPQ before surgery and at the 6-month follow up. All patients presented with preoperative pain symptoms of variable severity. We obtained the pain indexes and studied their relation with: patients' characteristics (age, body mass index, parity, qualification, occupation); operative findings (number, site and size of endometriotic lesions and presence of pelvic adhesions); and postoperative evolution of variable MPQ pain indexes at the 6-month follow up. Results:, Median present pain index (PPI) (index of pain intensity), before surgical treatment was 3 (2,4): preoperative PPI was <2 in 25% of patients while 25% of patients had PPI > 4. Overall median PPI after surgical treatment was 1 (0,2): postoperative index of pain intensity was <1 in 50% of patients, >2 in 25% of patients while 25% of patients did not experience postoperative pain. Overall pain intensity significantly decreased after laparoscopic treatment of endometriosis (Wilcoxon test P < 0.0005). None of the patients' characteristics were found to be significantly correlated with the severity or improvement of preoperative pain at postoperative follow up (P > 0.05), and the intensity of preoperative pain was not correlated to any of the operative variables. There was a significant reduction in all individual MPQ pain indexes; however 18.2% of women did not show improvement of pain symptoms after laparoscopic surgery. An increasing endometrioma diameter was associated with a significant decrease in the difference in evaluative rank score of pain rating index between pain indexes at the 6-month follow up and preoperatively (P = 0.04, Spearman's rank correlation Rho = ,0.277). Conclusions:, MPQ appears to be useful as a multi-dimensional scale in describing patients' pain semiology and evaluating pain evolution after surgical treatment. However, due to the extreme variability of pain experience, MPQ results don't clarify the relationship between pain intensity and the severity of endometriosis. [source]


    Potential roles of melatonin and chronotherapy among the new trends in hypertension treatment

    JOURNAL OF PINEAL RESEARCH, Issue 2 2009
    Fedor Simko
    Abstract:, The number of well-controlled hypertensives is unacceptably low worldwide. Respecting the circadian variation of blood pressure, nontraditional antihypertensives, and treatment in early stages of hypertension are potential ways to improve hypertension therapy. First, prominent variations in circadian rhythm are characteristic for blood pressure. The revolutionary MAPEC (Ambulatory Blood Pressure Monitoring and Cardiovascular Events) study, in 3000 adult hypertensives investigates, whether chronotherapy influences the cardiovascular prognosis beyond blood pressure reduction per se. Second, melatonin, statins and aliskiren are hopeful drugs for hypertension treatment. Melatonin, through its scavenging and antioxidant effects, preservation of NO availability, sympatholytic effect or specific melatonin receptor activation exerts antihypertensive and anti-remodeling effects and may be useful especially in patients with nondipping nighttime blood pressure pattern or with nocturnal hypertension and in hypertensives with left ventricular hypertrophy (LVH). Owing to its multifunctional physiological actions, this indolamine may offer cardiovascular protection far beyond its hemodynamic benefit. Statins exert several pleiotropic effects through inhibition of small guanosine triphosphate-binding proteins such as Ras and Rho. Remarkably, statins reduce blood pressure in hypertensive patients and more importantly they attenuate LVH. Addition of statins should be considered for high-risk hypertensives, for hypertensives with LVH, and possibly for high-risk prehypertensive patients. The direct renin inhibitor, aliskiren, inhibits catalytic activity of renin molecules in circulation and in the kidney, thus lowering angiotensin II levels. Furthermore, aliskiren by modifying the prorenin conformation may prevent prorenin activation. At present, aliskiren should be considered in hypertensive patients not sufficiently controlled or intolerant to other inhibitors of renin,angiotensin system. Third, TROPHY (Trial of Preventing Hypertension) is the first pharmacological intervention for prehypertensive patients revealing that treatment with angiotensin II type 1 receptor blocker attenuates hypertension development and thus decreases the risk of cardiovascular events. [source]


    A query language for discovering semantic associations, Part II: sample queries and query evaluation

    JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 11 2007
    Timo Niemi
    In our query language introduced in Part I (Niemi & Jämsen, in press) the user can formulate queries to find out (possibly complex) semantic relationships among entities. In this article we demonstrate the usage of our query language and discuss the new applications that it supports. We categorize several query types and give sample queries. The query types are categorized based on whether the entities specified in a query are known or unknown to the user in advance, and whether text information in documents is utilized. Natural language is used to represent the results of queries in order to facilitate correct interpretation by the user. We discuss briefly the issues related to the prototype implementation of the query language and show that an independent operation like Rho (Sheth et al., 2005; Anyanwu & Sheth, 2002, 2003), which presupposes entities of interest to be known in advance, is exceedingly inefficient in emulating the behavior of our query language. The discussion also covers potential problems, and challenges for future work. [source]


    A differential role of the platelet ADP receptors P2Y1 and P2Y12 in Rac activation

    JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2005
    C. SOULET
    Summary., The dynamics of the actin cytoskeleton, largely controlled by the Rho family of small GTPases (Rho, Rac and Cdc42), is critical for the regulation of platelet responses such as shape change, adhesion, spreading and aggregation. Here, we investigated the role of adenosine diphosphate (ADP), a major co-activator of platelets, on the activation of Rac. ADP rapidly activated Rac in a dose-dependent manner and independently of GPIIb/IIIa and phosphoinositide 3-kinase. ADP alone, used as a primary agonist, activated Rac and its effector PAK via its P2Y1 receptor, through a Gq -dependent pathway and independently of P2Y12. The P2Y12 receptor appeared unable to activate the GTPase per se as also observed for the adenosine triphosphate receptor P2X1. Conversely, secreted ADP strongly potentiated Rac activation induced by Fc,RIIa clustering or TRAP via its P2Y12 receptor, the target of antithrombotic thienopyridines. Stimulation of the ,2A -adrenergic receptor/Gz pathway by epinephrine was able to replace the P2Y12/Gi -mediated pathway to amplify Rac activation by Fc,RIIa or by the thrombin receptor PAR-1. This co-activation appeared necessary to reach a full stimulation of Rac as well as PAK activation and actin polymerization and was blocked by a G-protein ,, subunits scavenger peptide. [source]


    Rho A participates in the regulation of phosphatidylserine-dependent procoagulant activity at the surface of megakaryocytic cells

    JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 4 2004
    C. Kunzelmann
    Summary. Once exposed at the external surface of activated platelets or apoptotic cells, phosphatidylserine, an anionic phospholipid mostly sequestered in the inner leaflet of the plasma membrane, plays essential roles in hemostasis and phagocytosis. The mechanism governing the migration of the phosphatidylserine to the exoplasmic leaflet is not yet fully understood. We have proposed that store-operated calcium entry (SOCE) constitutes a key step of this process. ERK pathway is among the elements modulating SOCE and phosphatidylserine externalization in megakaryocytic HEL cells. Here, we investigated the role of small GTPase Rho A, which may interact with the ERK pathway. Specific inhibitors of Rho A (exoenzyme C3 and toxin B) reduced both SOCE and phosphatidylserine-dependent procoagulant activity. Simultaneous inhibition of Rho A and extracellular signal-regulated kinase (ERK) pathways did not elicit further reduction with respect to each individual one. Rho A can regulate SOCE and phosphatidylserine exposure through the reorganization of actin cytoskeleton, but not through ROCK pathway. Hence, Rho A is another regulatory element for the completion of SOCE-induced phosphatidylserine transmembrane redistribution in HEL cells. [source]


    Complementary (secondary) metabolites in a soft coral: sex-specific variability, inter-clonal variability, and competition

    MARINE ECOLOGY, Issue 3 2006
    Beatriz Fleury
    Abstract Sex-specific interactions involving competition for space between the dioecious alcyonacean soft coral Sarcophyton glaucum and the scleractinian coral Acropora robusta were assessed experimentally on Bald Rock, central region of the Great Barrier Reef. To examine this, plus inter-clonal responses, one male colony of S. glaucum, known to produce sarcophytoxide as its predominant complementary (secondary) metabolite, was sectioned, producing 10 clones. The same was done for a female colony. These two sets of clones were then relocated to grids and placed in contact with Acropora clones. Relocated and non-relocated controls were also monitored. High levels of tissue necrosis were observed in the hard coral under contact conditions with both the male and female clones after 20 days. The development of a protective polysaccharide layer in the alcyonacean was also observed. Differences observed in the concentrations of complementary metabolites within the two different S. glaucum colonies were related to sex. Both under competition and non-competition conditions, females exhibited significantly higher concentrations of sarcophytoxide than males, and this increased with time. Fatty ester concentration was also higher in females than males, varying significantly through time, and falling dramatically just after spawning. Fatty ester concentrations decreased linearly through time in the male clones. When involved in competition for space, females possessed higher concentrations of fatty esters than males, both at the site of contact and in non-contact sites, again, decreasing after spawning. No significant changes in sarcophytoxide levels were noted in the parental colonies, but such changes were observed in fatty esters, with the female producing higher concentrations until after spawning. The use of these two variates in the form of a ratio (sarcophytoxide concentration:fatty ester concentration) yielded a variable Rho (,) which was a more sensitive indicator of biochemical change than either of its components alone. These two sets of compounds appeared to have a negative association through time and varied highly significantly between sexes. The diterpene sarcophytoxide may be considered an allelopathic or stress metabolite, while the lipids act as energy storage metabolites. [source]


    Associations between sleep quality with cardiorespiratory fitness and BMI among adolescent girls

    AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2010
    Jorge Mota
    The main goal of this study was to examine the association between sleeping quality with cardiorespiratory fitness (CRF) and obesity status (BMI) This was a cross-sectional study of 1,726 adolescent girls, aged 10 to 18 years. CRF was predicted by maximal multistage 20 m shuttle-run test according to procedures described from FITNESSGRAM. Children's BMI was classified according to International Obesity Task Force and sleeping quality was assessed by questionnaire. The prevalence of overweight and obesity was 21.2% and 5.7%, respectively. Sleeping quality was significantly associated with CRF (Rho = 0.17; P < 0.05), but not with BMI. Girls who were classified as fit were more likely (OR: 2.25; P < 0.05) to report better sleep quality compared to their unfit peers. Poor sleep quality was associated with lower CRF although no associations have been shown with BMI. Am. J. Hum. Biol. 2010. © 2009 Wiley-Liss, Inc. [source]


    Rac and Rho: The Story Behind Melanocyte Dendrite Formation

    PIGMENT CELL & MELANOMA RESEARCH, Issue 5 2002
    Glynis Scott
    Melanocyte dendrites are hormonally responsive actin and microtubule containing structures whose primary purpose is to transport melanosomes to the dendrite tip. Melanocyte dendrites have been an area of intense interest for melanocyte biologists, but it was not until recently that we began to understand the mechanisms underlying their formation. In contrast with melanogenesis, for which numerous mutations in pigment producing genes and mouse models have been identified, a genetic defect resulting in impaired dendrite formation has not been found. Therefore, much of the insight into melanocyte dendrites has come from electron microscopy or in vitro culture systems of normal human and murine melanocytes as well as melanoma cell lines. The growth factors that regulate the formation of melanocyte dendrites have been thoroughly studied and it is clear that multiple signalling systems are able to stimulate, and in some cases inhibit, dendrite formation. Recent data points to the Rho family of small guanosine triphosphate (GTP)-binding proteins as master regulators of dendrite formation, particularly Rac and Rho. In this review I will summarize the progress scientists have made in understanding the structure, hormonal regulation and molecular mediators of melanocyte dendrite formation. [source]


    Thermodynamic characterization of two homologous protein complexes: Associations of the semaphorin receptor plexin-B1 RhoGTPase binding domain with Rnd1 and active Rac1

    PROTEIN SCIENCE, Issue 5 2009
    Prasanta K. Hota
    Abstract Plexin receptors function in response to semaphorin guidance cues in a variety of developmental processes involving cell motility. Interactions with Rho, as well as Ras family small GTPases are critical events in the cell signaling mechanism. We have recently determined the structure of a cytoplasmic domain (RBD) of plexin-B1 and mapped its binding interface with several Rho-GTPases, Rac1, Rnd1, and RhoD. All three GTPases associate with a similar region of this plexin domain, but show different functional behavior in cells. To understand whether thermodynamic properties of the GTPase,RBD interaction contribute to such different behavior, we have examined the interaction at different temperatures, buffer, and pH conditions. Although the binding affinity of both Rnd1 and Rac1 with the plexin-B1 RBD is similar, the detailed thermodynamic properties of the interactions are considerably different. These data suggest that on Rac1 binding to the plexin-B1 RBD, the proteins become more rigid in the complex. By contrast, Rnd1 binding is consistent with unchanged or slightly increased flexibility in one or both proteins. Both GTPases show an appreciable reduction in affinity for the dimeric plexin-B1 RBD indicating that GTPase binding is not cooperative with dimer formation, but that a partial steric hindrance destabilizes the dimer. However, a reduced affinity binding mode to a disulphide stabilized model for the dimeric RBD is also possible. Consistent with cellular studies, the interaction thermodynamics imply that further levels of regulation involving additional binding partners and/or regions outside of the RhoGTPase binding domain are required for receptor activation. [source]


    An improved tripod amphiphile for membrane protein solubilization

    PROTEIN SCIENCE, Issue 12 2000
    Seungju M. Yu
    Abstract Intrinsic membrane proteins represent a large fraction of the proteins produced by living organisms and perform many crucial functions. Structural and functional characterization of membrane proteins generally requires that they be extracted from the native lipid bilayer and solubilized with a small synthetic amphiphile, for example, a detergent. We describe the development of a small molecule with a distinctive amphiphilic architecture, a "tripod amphiphile," that solubilizes both bacteriorhodopsin (BR) and bovine rhodopsin (Rho). The polar portion of this amphiphile contains an amide and an amine-oxide; small variations in this polar segment are found to have profound effects on protein solubilization properties. The optimal tripod amphiphile extracts both BR and Rho from the native membrane environments and maintains each protein in a monomeric native-like form for several weeks after delipidation. Tripod amphiphiles are designed to display greater conformational rigidity than conventional detergents, with the long-range goal of promoting membrane protein crystallization. The results reported here represent an important step toward that ultimate goal. [source]


    Ca2+ -independent hypoxic vasorelaxation in porcine coronary artery

    THE JOURNAL OF PHYSIOLOGY, Issue 3 2005
    Min Gu
    To demonstrate a Ca2+ -independent component of hypoxic vasorelaxation and to investigate its mechanism, we utilized permeabilized porcine coronary arteries, in which [Ca2+] could be clamped. Arteries permeabilized with ,-escin developed maximum force in response to free Ca2+ (6.6 ,m), concomitant with a parallel increase in myosin regulatory light chain phosphorylation (MRLC-Pi), from 0.183 ± 0.023 to 0.353 ± 0.019 MRLC-Pi (total light chain),1. Hypoxia resulted in a significant decrease in both force (,31.9 ± 4.1% prior developed force) and MRLC-Pi (from 0.353 to 0.280 ± 0.023), despite constant [Ca2+] buffered by EGTA (4 mm). Forces developed in response to Ca2+ (6.6 ,m), Ca2+ (0.2 ,m) + GTP,S (1 mm), or in the absence of Ca2+ after treatment with ATP,S (1 mm), were of similar magnitude. Hypoxia also relaxed GTP,S contractures but importantly, arteries could not be relaxed after treatment with ATP,S. Permeabilization with Triton X-100 for 60 min also abolished hypoxic relaxation. The blocking of hypoxic relaxation after ATP,S suggests that this Ca2+ -independent mechanism(s) may operate through alteration of MRLC-Pi or of phosphorylation of the myosin binding subunit of myosin light chain phosphatase. Treatment with the Rho kinase inhibitor Y27632 (1 ,m) relaxed GTP,S and Ca2+ contractures; but the latter required a higher concentration (10 ,m) for consistent relaxation. Relaxations to N2 and/or Y27632 averaged 35% and were not additive or dependent on order. Our data suggest that the GTP-mediated, Rho kinase-coupled pathway merits further investigation as a potential site of this novel, Ca2+ -independent O2 -sensing mechanism. Importantly, these results unambiguously show that hypoxia-induced vasorelaxation can occur in permeabilized arteries where the Ca2+ is clamped at a constant value. [source]


    The effect of the sampling scale on zooplankton community assessment and its implications for the conservation of temporary ponds in south-west Spain

    AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2007
    Khalid Fahd
    Abstract 1.The zooplankton (rotifer and microcrustacean) assemblages of temporary ponds in the Doñana National Park (south-west Spain) have been compared in two surveys of contrasting scales that resulted in the same number of samples: an extensive survey of 36 ponds sampled in May 1998 (or widespread survey) and a survey of nine ponds sampled four times over 2 years (or cumulative survey). 2.The total number of microcrustacean and rotifer taxa was larger in the cumulative survey (43 and 41 taxa, respectively) than in the widespread survey (39 and 34, respectively). Crustacean assemblages became less alike throughout the cumulative survey. 3.The presence of invertebrates (Coleoptera, Odonata, Heteroptera and crayfish) and aquatic vertebrates (fish and salamanders) was recorded as an estimate of potential predator impact on zooplankton. Several pond features (water depth, conductivity, pH, chlorophyll a concentration, distance to the nearest permanent pond and to the marsh) were also measured in both surveys. 4.A combination of these environmental factors was more strongly related to the similarity matrices derived from the zooplankton assemblages of the cumulative survey (Rho=0.7) than to those of the widespread survey (Rho<0.4). The distance of ponds to the marsh was an important factor in explaining this correlation as well as the strongest factor in the ordination of crustacean assemblages following a CCA. 5.Predation by exotic fish in long-hydroperiod ponds where overflow drains to the nearby marsh (fish source) is the mechanism likely to explain the changes in crustacean composition recorded in the cumulative survey. 6.The cumulative survey was more suitable for the study of zooplankton diversity as it rendered a higher number of taxa and gave more insight into the mechanisms that explain taxon richness. Thus, conservation strategies in temporary habitats require a scale of observation that includes long temporal changes. Copyright © 2006 John Wiley & Sons, Ltd. [source]