PubMed Central (PMC3 - NLM DTD)
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Archive of life sciences journal literature at the U.S. National Institutes of Health (NIH), developed and managed by NIH's National Center for Biotechnology Information (NCBI) in the National Library of Medicine (NLM).
Mostrando recursos 161 - 180 de 9,978
161.
PAK1 and aPKC? Regulate Myosin II-B Phosphorylation: A Novel Signaling Pathway Regulating Filament Assembly - Even-Faitelson, Liron; Ravid, Shoshana
Many signaling pathways regulate the function of the cellular cytoskeleton. Yet we know very little about the proteins involved in the cross-talk between the signaling and the cytoskeletal systems. Here we show that myosin II-B, an important cytoskeletal protein, resides in a complex with p21-activated kinase 1 (PAK1) and atypical protein kinase C (PKC) zeta (aPKC?) and that the interaction between these proteins is EGF-dependent. We further show that PAK1 is involved in aPKC? phosphorylation and that aPKC? phosphorylates myosin II-B directly on a specific serine residue in an EGF-dependent manner. This latter phosphorylation is specific to isoform B of...
162.
Cortactin Has an Essential and Specific Role in Osteoclast Actin Assembly - Tehrani, Shandiz; Faccio, Roberta; Chandrasekar, Indra; Ross, F. Patrick; Cooper, John A.
Osteoclasts are essential for bone dynamics and calcium homeostasis. The cells form a tight seal on the bone surface, onto which they secrete acid and proteases to resorb bone. The seal is associated with a ring of actin filaments. Cortactin, a c-Src substrate known to promote Arp2/3-mediated actin assembly in vitro, is expressed in osteoclasts and localizes to the sealing ring. To address the role of cortactin and actin assembly in osteoclasts, we depleted cortactin by RNA interference. Cortactin-depleted osteoclasts displayed a complete loss of bone resorption with no formation of sealing zones. On nonosteoid surfaces, osteoclasts flatten with a...
163.
Stat-mediated Signaling Induced by Type I and Type II Interferons (IFNs) Is Differentially Controlled through Lipid Microdomain Association and Clathrin-dependent Endocytosis of IFN Receptors - Marchetti, Marta; Monier, Marie-Noelle; Fradagrada, Alexandre; Mitchell, Keith; Baychelier, Florence; Eid, Pierre; Johannes, Ludger; Lamaze, Christophe
Type I (?/?) and type II (?) interferons (IFNs) bind to distinct receptors, although they activate the same signal transducer and activator of transcription, Stat1, raising the question of how signal specificity is maintained. Here, we have characterized the sorting of IFN receptors (IFN-Rs) at the plasma membrane and the role it plays in IFN-dependent signaling and biological activities. We show that both IFN-? and IFN-? receptors are internalized by a classical clathrin- and dynamin-dependent endocytic pathway. Although inhibition of clathrin-dependent endocytosis blocked the uptake of IFN-? and IFN-? receptors, this inhibition only affected IFN-?induced Stat1 and Stat2 signaling. Furthermore,...
164.
A Conserved Organization of Transcription during Embryonic Stem Cell Differentiation and in Cells with High C Value - Faro-Trindade, Inês; Cook, Peter R.
Although we have detailed information on the alterations occurring in steady-state levels of all cellular mRNAs during differentiation, we still know little about more global changes. Therefore, we investigated the numbers of molecules of RNA polymerase II that are activeand the way those molecules are organizedas two mouse cells (aneuploid F9 teratocarcinoma, and euploid and totipotent embryonic stem cells) differentiate into parietal endoderm. Quantitative immunoblotting shows the number of active molecules roughly halves. Transcription sites (detected by light and electron microscopy after allowing engaged polymerases to extend nascent transcripts in bromouridine-triphosphate) are uniformly distributed throughout the nucleoplasm. The numbers of...
165.
Aneugenic Activity of Op18/Stathmin Is Potentiated by the Somatic Q18?E Mutation in Leukemic Cells - Holmfeldt, Per; Brännström, Kristoffer; Stenmark, Sonja; Gullberg, Martin
Op18/stathmin (Op18) is a phosphorylation-regulated microtubule destabilizer that is frequently overexpressed in tumors. The importance of Op18 in malignancy was recently suggested by identification of a somatic Q18?E mutation of Op18 in an adenocarcinoma. We addressed the functional consequences of aberrant Op18 expression in leukemias by analyzing the cell cycle of K562 cells either depleted of Op18 by expression of interfering hairpin RNA or induced to express wild-type or Q18E substituted Op18. We show here that although Op18 depletion increases microtubule density during interphase, the density of mitotic spindles is essentially unaltered and cells divide normally. This is consistent with...
166.
Muc4ErbB2 Complex Formation and Signaling in Polarized CACO-2 Epithelial Cells Indicate That Muc4 Acts as an Unorthodox Ligand for ErbB2 - Ramsauer, Victoria P.; Pino, Vanessa; Farooq, Amjad; Carothers Carraway, Coralie A.; Salas, Pedro J.I.; Carraway, Kermit L.
Muc4 serves as an intramembrane ligand for the receptor tyrosine kinase ErbB2. The time to complex formation and the stoichiometry of the complex were determined to be <15 min and 1:1 by analyses of Muc4 and ErbB2 coexpressed in insect cells and A375 tumor cells. In polarized CACO-2 cells, Muc4 expression causes relocalization of ErbB2, but not its heterodimerization partner ErbB3, to the apical cell surface, effectively segregating the two receptors. The apically located ErbB2 is phosphorylated on tyrosines 1139 and 1248. The phosphorylated ErbB2 in CACO-2 cells recruits the cytoplasmic adaptor protein Grb2, consistent with previous studies showing phosphotyrosine...
167.
A Distant Coilin Homologue Is Required for the Formation of Cajal Bodies in Arabidopsis - Collier, Sarah; Pendle, Alison; Boudonck, Kurt; van Rij, Tjeerd; Dolan, Liam; Shaw, Peter
Cajal bodies (CBs) are subnuclear bodies that are widespread in eukaryotes, being found in mammals, many other vertebrates and in all plant species so far examined. They are mobile structures, moving, fusing, and budding within the nucleus. Here we describe a screen for Arabidopsis mutants with altered CBs and describe mutants that have smaller Cajal bodies (ncb-2, ncb-3), lack them altogether (ncb-1), have increased numbers of CBs (pcb) or have flattened CBs (ccb). We have identified the gene affected in the ncb mutants as a distant homolog of the vertebrate gene that encodes coilin (At1g13030) and have termed the resulting...
168.
Yeast Gcn4p Stabilization Is Initiated by the Dissociation of the Nuclear Pho85p/Pcl5p Complex - Bömeke, Katrin; Pries, Ralph; Korte, Virginia; Scholz, Eva; Herzog, Britta; Schulze, Florian; Braus, Gerhard H.
Protein stability of the c-jun-like yeast bZIP transcriptional activator Gcn4p is exclusively controlled in the yeast nucleus. Phosphorylation by the nuclear Pho85p cyclin-dependent protein kinase, a functional homolog of mammalian Cdk5, initiates the Gcn4p degradation pathway in complex with the cyclin Pcl5p. We show that the initial step in Gcn4p stabilization is the dissociation of the Pho85p/Pcl5p complex. Pcl7p, another nuclear and constantly present cyclin, is required for Gcn4p stabilization and is able to associate to Pho85p independently of the activity of the Gcn4p degradation pathway. In addition, the nuclear cyclin-dependent Pho85p kinase inhibitor Pho81p is required for Gcn4p stabilization....
169.
Phosphoinositide-3 KinaseRac1c-Jun NH2-terminal Kinase Signaling Mediates Collagen Iinduced Cell Scattering and Up-Regulation of N-Cadherin Expression in Mouse Mammary Epithelial Cells - Shintani, Yasushi; Wheelock, Margaret J.; Johnson, Keith R.
During epithelial-to-mesenchymal transitions (EMTs), cells must change their interactions with one another and with their extracellular matrix in a synchronized manner. To characterize signaling pathways cells use to coordinate these changes, we used NMuMG mammary epithelial cells. We showed that these cells become fibroblastic and scattered, with increased N-cadherin expression when cultured on collagen I. Rac1 and c-Jun NH2-terminal kinase (JNK) were activated when cells were plated on collagen I, and dominant inhibitory Rac1 (RacN17) or inhibition of JNK signaling prevented collagen Iinduced morphological changes and N-cadherin up-regulation. Furthermore, inhibiting phosphoinositide-3 kinase (PI3K) activity prevented Rac1 and JNK activation as...
170.
Postreplication Repair and PCNA Modification in Schizosaccharomyces pombe - Frampton, Jonathan; Irmisch, Anja; Green, Catherine M.; Neiss, Andrea; Trickey, Michelle; Ulrich, Helle D.; Furuya, Kanji; Watts, Felicity Z.; Carr, Antony M.; Lehmann, Alan R.
Ubiquitination of proliferating cell nuclear antigen (PCNA) plays a crucial role in regulating replication past DNA damage in eukaryotes, but the detailed mechanisms appear to vary in different organisms. We have examined the modification of PCNA in Schizosaccharomyces pombe. We find that, in response to UV irradiation, PCNA is mono- and poly-ubiquitinated in a manner similar to that in Saccharomyces cerevisiae. However in undamaged Schizosaccharomyces pombe cells, PCNA is ubiquitinated in S phase, whereas in S. cerevisiae it is sumoylated. Furthermore we find that, unlike in S. cerevisiae, mutants defective in ubiquitination of PCNA are also sensitive to ionizing radiation,...
171.
Forced Dimerization of gp130 Leads to Constitutive STAT3 Activation, Cytokine-independent Growth, and Blockade of Differentiation of Embryonic Stem Cells - Stuhlmann-Laeisz, Christiane; Lang, Sigrid; Chalaris, Athena; Krzysztof, Paliga; Enge, Sudarman; Eichler, Jutta; Klingmüller, Ursula; Samuel, Michael; Ernst, Matthias; Rose-John, Stefan; Scheller, Jürgen
The mode of activation of glycoprotein 130 kDa (gp130) and the transmission of the activation status through the plasma membrane are incompletely understood. In particular, the molecular function of the three juxtamembrane fibronectin III-like domains of gp130 in signal transmission remains unclear. To ask whether forced dimerization of gp130 is sufficient for receptor activation, we replaced the entire extracellular portion of gp130 with the c-jun leucine zipper region in the chimeric receptor protein L-gp130. On expression in cells, L-gp130 stimulates ligand-independent signal transducer and activator of transcription (STAT) 3 and extracellular signal-regulated kinase 1/2 phosphorylation. gp130 activation could be abrogated...
172.
On and Off Membrane Dynamics of the Endoplasmic ReticulumGolgi Tethering Factor p115 In Vivo - Brandon, Elizabeth; Szul, Tomasz; Alvarez, Cecilia; Grabski, Robert; Benjamin, Ronald; Kawai, Ryoichi; Sztul, Elizabeth
The mechanisms regulating membrane recruitment of the p115 tethering factor in vivo are unknown. Here, we describe cycling of p115 between membranes and cytosol and document the effects of Golgi matrix proteins, Rab1, and soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors (SNAREs) on this process. Rapid membrane/cytosol exchange is shown by swift (t1/2 ?20 s) loss of Golgi-localized p115-green fluorescent protein (GFP) after repeated photobleaching of cell periphery and rapid (t1/2 ?13 s) fluorescence recovery after photobleaching Golgi-localized p115-GFP. p115 mutant missing the GM130/giantin binding site exhibits analogous fluorescence recovery after photobleaching (FRAP) (t1/2 ?13 s), suggesting that GM130...
173.
Rtn1p Is Involved in Structuring the Cortical Endoplasmic Reticulum - De Craene, Johan-Owen; Coleman, Jeff; Estrada de Martin, Paula; Pypaert, Marc; Anderson, Scott; Yates, John R.; Ferro-Novick, Susan; Novick, Peter
The endoplasmic reticulum (ER) contains both cisternal and reticular elements in one contiguous structure. We identified rtn1? in a systematic screen for yeast mutants with altered ER morphology. The ER in rtn1? cells is predominantly cisternal rather than reticular, yet the net surface area of ER is not significantly changed. Rtn1-green fluorescent protein (GFP) associates with the reticular ER at the cell cortex and with the tubules that connect the cortical ER to the nuclear envelope, but not with the nuclear envelope itself. Rtn1p overexpression also results in an altered ER structure. Rtn proteins are found on the ER in...
174.
The Caenorhabditis elegans snf-11 Gene Encodes a Sodium-dependent GABA Transporter Required for Clearance of Synaptic GABA - Mullen, Gregory P.; Mathews, Eleanor A.; Saxena, Paurush; Fields, Stephen D.; McManus, John R.; Moulder, Gary; Barstead, Robert J.; Quick, Michael W.; Rand, James B.
Sodium-dependent neurotransmitter transporters participate in the clearance and/or recycling of neurotransmitters from synaptic clefts. The snf-11 gene in Caenorhabditis elegans encodes a protein of high similarity to mammalian GABA transporters (GATs). We show here that snf-11 encodes a functional GABA transporter; SNF-11mediated GABA transport is Na+ and Cl? dependent, has an EC50 value of 168 ?M, and is blocked by the GAT1 inhibitor SKF89976A. The SNF-11 protein is expressed in seven GABAergic neurons, several additional neurons in the head and retrovesicular ganglion, and three groups of muscle cells. Therefore, all GABAergic synapses are associated with either presynaptic or postsynaptic (or...
175.
Amino Acids Regulate Retrieval of the Yeast General Amino Acid Permease from the Vacuolar Targeting Pathway - Rubio-Texeira, Marta; Kaiser, Chris A.
Intracellular sorting of the general amino acid permease (Gap1p) in Saccharomyces cerevisiae depends on availability of amino acids such that at low amino acid concentrations Gap1p is sorted to the plasma membrane, whereas at high concentrations Gap1p is sorted to the vacuole. In a genome-wide screen for mutations that affect Gap1p sorting we identified deletions in a subset of components of the ESCRT (endosomal sorting complex required for transport) complex, which is required for formation of the multivesicular endosome (MVE). Gap1p-GFP is delivered to the vacuolar interior by the MVE pathway in wild-type cells, but when formation of the MVE...
176.
The Phosphoinositide Kinase PIKfyve/Fab1p Regulates Terminal Lysosome Maturation in Caenorhabditis elegans - Nicot, Anne-Sophie; Fares, Hanna; Payrastre, Bernard; Chisholm, Andrew D.; Labouesse, Michel; Laporte, Jocelyn
Membrane dynamics is necessary for cell homeostasis and signal transduction and is in part regulated by phosphoinositides. Pikfyve/Fab1p is a phosphoinositide kinase that phosphorylates phosphatidylinositol 3-monophosphate into phosphatidylinositol-3,5-bisphosphate [PtdIns(3,5)P2] and is implicated in membrane homeostasis in yeast and in mammalian cells. These two phosphoinositides are substrates of myotubularin phosphatases found mutated in neuromuscular diseases. We studied the roles of phosphatidylinositol phosphate kinase 3 (PPK-3), the orthologue of PIKfyve/Fab1p, in a multicellular organism, Caenorhabditis elegans. Complete loss of ppk-3 function induces developmental defects characterized by embryonic lethality, whereas partial loss of function leads to growth retardation. At the cellular level, ppk-3...
177.
Cell Aggregation-induced FGF8 Elevation Is Essential for P19 Cell Neural Differentiation - Wang, Chen; Xia, Caihong; Bian, Wei; Liu, Li; Lin, Wei; Chen, Ye-Guang; Ang, Siew-Lan; Jing, Naihe
FGF8, a member of the fibroblast growth factor (FGF) family, has been shown to play important roles in different developing systems. Mouse embryonic carcinoma P19 cells could be induced by retinoic acid (RA) to differentiate into neuroectodermal cell lineages, and this process is cell aggregation dependent. In this report, we show that FGF8 expression is transiently up-regulated upon P19 cell aggregation, and the aggregation-dependent FGF8 elevation is pluripotent stem cell related. Overexpressing FGF8 promotes RA-induced monolayer P19 cell neural differentiation. Inhibition of FGF8 expression by RNA interference or blocking FGF signaling by the FGF receptor inhibitor, SU5402, attenuates neural differentiation...
178.
Dynamic Regulation of Caveolin-1 Trafficking in the Germ Line and Embryo of Caenorhabditis elegans - Sato, Ken; Sato, Miyuki; Audhya, Anjon; Oegema, Karen; Schweinsberg, Peter; Grant, Barth D.
Caveolin is the major protein component required for the formation of caveolae on the plasma membrane. Here we show that trafficking of Caenorhabditis elegans caveolin-1 (CAV-1) is dynamically regulated during development of the germ line and embryo. In oocytes a CAV-1-green fluorescent protein (GFP) fusion protein is found on the plasma membrane and in large vesicles (CAV-1 bodies). After ovulation and fertilization the CAV-1 bodies fuse with the plasma membrane in a manner reminiscent of cortical granule exocytosis as described in other species. Fusion of CAV-1 bodies with the plasma membrane appears to be regulated by the advancing cell cycle,...
179.
Intrinsic Capacities of Molecular Sensors of the Unfolded Protein Response to Sense Alternate Forms of Endoplasmic Reticulum Stress - DuRose, Jenny B.; Tam, Arvin B.; Niwa, Maho
The unfolded protein response (UPR) regulates the protein-folding capacity of the endoplasmic reticulum (ER) according to cellular demand. In mammalian cells, three ER transmembrane components, IRE1, PERK, and ATF6, initiate distinct UPR signaling branches. We show that these UPR components display distinct sensitivities toward different forms of ER stress. ER stress induced by ER Ca2+ release in particular revealed fundamental differences in the properties of UPR signaling branches. Compared with the rapid response of both IRE1 and PERK to ER stress induced by thapsigargin, an ER Ca2+ ATPase inhibitor, the response of ATF6 was markedly delayed. These studies are the...
180.
Multiple Sequence Elements Facilitate Chp Rho GTPase Subcellular Location, Membrane Association, and Transforming Activity - Chenette, Emily J.; Mitin, Natalia Y.; Der, Channing J.
Cdc42 homologous protein (Chp) is a member of the Rho family of small GTPases and shares significant sequence and functional similarity with Cdc42. However, unlike classical Rho GTPases, we recently found that Chp depends on palmitoylation, rather than prenylation, for association with cellular membranes. Because palmitoylation alone is typically not sufficient to promote membrane association, we evaluated the possibility that other carboxy-terminal residues facilitate Chp subcellular association with membranes. We found that Chp membrane association and transforming activity was dependent on the integrity of a stretch of basic amino acids in the carboxy terminus of Chp and that the basic...
161.
