PubMed Central (PMC3 - NLM DTD)
(2,081,148 recursos)
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 141 - 160 de 9,978
141.
Engrailed-1 Negatively Regulates ?-Catenin Transcriptional Activity by Destabilizing ?-Catenin via a Glycogen Synthase Kinase-3?independent Pathway - Bachar-Dahan, Liora; Goltzmann, Janna; Yaniv, Abraham; Gazit, Arnona
The Wnt signaling pathway plays a major role in development, and upon deregulation it is implicated in neoplasia. The hallmark of the canonical Wnt signal is the protection of ?-catenin from ubiquitination and proteasomal degradation induced by glycogen synthase kinase (GSK)-3? inhibition. The stabilized ?-catenin translocates to the nucleus where it binds to T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription factors, activating the expression of Wnt target genes. In the absence of Wnt signal, TCF/LEF bind to Groucho (Gro)/TLE corepressors and repress Wnt target genes. Gro/TLE bind also to Engrailed (En) transcription factors mediating En-repressive activity on En target genes. Here,...
142.
Oxysterol-binding Protein and Vesicle-associated Membrane Proteinassociated Protein Are Required for Sterol-dependent Activation of the Ceramide Transport Protein - Perry, Ryan J.; Ridgway, Neale D.
Sphingomyelin (SM) and cholesterol are coregulated metabolically and associate physically in membrane microdomains involved in cargo sorting and signaling. One mechanism for regulation of this metabolic interface involves oxysterol binding protein (OSBP) via high-affinity binding to oxysterol regulators of cholesterol homeostasis and activation of SM synthesis at the Golgi apparatus. Here, we show that OSBP regulation of SM synthesis involves the endoplasmic reticulum (ER)-to-Golgi ceramide transport protein (CERT). RNA interference (RNAi) experiments in Chinese hamster ovary (CHO)-K1 cells revealed that OSBP and vesicle-associated membrane proteinassociated protein (VAP) were required for stimulation of CERT-dependent ceramide transport and SM synthesis by 25-hydroxycholesterol...
143.
Regulation of Synaptic Transmission by RAB-3 and RAB-27 in Caenorhabditis elegans - Mahoney, Timothy R.; Liu, Qiang; Itoh, Takashi; Luo, Shuo; Hadwiger, Gayla; Vincent, Rose; Wang, Zhao-Wen; Fukuda, Mitsunori; Nonet, Michael L.
Rab small GTPases are involved in the transport of vesicles between different membranous organelles. RAB-3 is an exocytic Rab that plays a modulatory role in synaptic transmission. Unexpectedly, mutations in the Caenorhabditis elegans RAB-3 exchange factor homologue, aex-3, cause a more severe synaptic transmission defect as well as a defecation defect not seen in rab-3 mutants. We hypothesized that AEX-3 may regulate a second Rab that regulates these processes with RAB-3. We found that AEX-3 regulates another exocytic Rab, RAB-27. Here, we show that C. elegans RAB-27 is localized to synapse-rich regions pan-neuronally and is also expressed in intestinal cells....
144.
Disruption of the A-Kinase Anchoring Domain in Flagellar Radial Spoke Protein 3 Results in Unregulated Axonemal cAMP-dependent Protein Kinase Activity and Abnormal Flagellar Motility - Gaillard, Anne R.; Fox, Laura A.; Rhea, Jeanne M.; Craige, Branch; Sale, Winfield S.
Biochemical studies of Chlamydomonas flagellar axonemes revealed that radial spoke protein (RSP) 3 is an A-kinase anchoring protein (AKAP). To determine the physiological role of PKA anchoring in the axoneme, an RSP3 mutant, pf14, was transformed with an RSP3 gene containing a mutation in the PKA-binding domain. Analysis of several independent transformants revealed that the transformed cells exhibit an unusual phenotype: a fraction of the cells swim normally; the remainder of the cells twitch feebly or are paralyzed. The abnormal/paralyzed motility is not due to an obvious deficiency of radial spoke assembly, and the phenotype cosegregates with the mutant RSP3....
145.
GUP1 of Saccharomyces cerevisiae Encodes an O-Acyltransferase Involved in Remodeling of the GPI Anchor - Bosson, Régine; Jaquenoud, Malika; Conzelmann, Andreas
The anchors of mature glycosylphosphatidylinositol (GPI)-anchored proteins of Saccharomyces cerevisiae contain either ceramide or diacylglycerol with a C26:0 fatty acid in the sn2 position. The primary GPI lipid added to newly synthesized proteins in the ER consists of diacylglycerol with conventional C16 and C18 fatty acids. Here we show that GUP1 is essential for the synthesis of the C26:0-containing diacylglycerol anchors. Gup1p is an ER membrane protein with multiple membrane-spanning domains harboring a motif that is characteristic of membrane-bound O-acyl-transferases (MBOAT). Gup1? cells make normal amounts of GPI proteins but most mature GPI anchors contain lyso-phosphatidylinositol, and others possess phosphatidylinositol...
146.
NuSAP, a Mitotic RanGTP Target That Stabilizes and Cross-links Microtubules - Ribbeck, Katharina; Groen, Aaron C.; Santarella, Rachel; Bohnsack, Markus T.; Raemaekers, Tim; Köcher, Thomas; Gentzel, Marc; Görlich, Dirk; Wilm, Matthias; Carmeliet, Geert; Mitchison, Timothy J.; Ellenberg, Jan; Hoenger, Andreas; Mattaj, Iain W.
Nucleolar and spindle-associated protein (NuSAP) was recently identified as a microtubule- and chromatin-binding protein in vertebrates that is nuclear during interphase. Small interfering RNA-mediated depletion of NuSAP resulted in aberrant spindle formation, missegregation of chromosomes, and ultimately blocked cell proliferation. We show here that NuSAP is enriched on chromatin-proximal microtubules at meiotic spindles in Xenopus oocytes. When added at higher than physiological levels to Xenopus egg extract, NuSAP induces extensive bundling of spindle microtubules and causes bundled microtubules within spindle-like structures to become longer. In vitro reconstitution experiments reveal two direct effects of NuSAP on microtubules: first, it can efficiently...
147.
The NHE3 Juxtamembrane Cytoplasmic Domain Directly Binds Ezrin: Dual Role in NHE3 Trafficking and Mobility in the Brush Border - Cha, Boyoung; Tse, Ming; Yun, Chris; Kovbasnjuk, Olga; Mohan, Sachin; Hubbard, Ann; Arpin, Monique; Donowitz, Mark
Based on physiological studies, the epithelial brush-border (BB) Na+/H+ antiporter3 (NHE3) seems to associate with the actin cytoskeleton both by binding to and independently of the PDZ domain containing proteins NHERF1 and NHERF2. We now show that NHE3 directly binds ezrin at a site in its C terminus between aa 475-589, which is separate from the PSD95/dlg/zonular occludens-1 (PDZ) interacting domain. This is an area predicted to be ?-helical, with a positive aa cluster on one side (K516, R520, and R527). Point mutations of these positively charged aa reduced (NHE3 double mutant [R520F, R527F]) or abolished (NHE3 triple mutant [K516Q,...
148.
Cytoplasmic Lipid Droplets Are Sites of Convergence of Proteasomal and Autophagic Degradation of Apolipoprotein B - Ohsaki, Yuki; Cheng, Jinglei; Fujita, Akikazu; Tokumoto, Toshinobu; Fujimoto, Toyoshi
Lipid esters stored in cytoplasmic lipid droplets (CLDs) of hepatocytes are used to synthesize very low-density lipoproteins (VLDLs), into which apolipoprotein B (ApoB) is integrated cotranslationally. In the present study, by using Huh7 cells, derived from human hepatoma and competent for VLDL secretion, we found that ApoB is highly concentrated around CLDs to make ApoB-crescents. ApoB-crescents were seen in <10% of Huh7 cells under normal conditions, but the ratio increased to nearly 50% after 12 h of proteasomal inhibition by N-acetyl-l-leucinyl-l-leucinyl-l-norleucinal. Electron microscopy showed ApoB to be localized to a cluster of electron-lucent particles 50100 nm in diameter adhering to...
149.
Fibronectin Rigidity Response through Fyn and p130Cas Recruitment to the Leading Edge - Kostic, Ana; Sheetz, Michael P.
Cell motility on extracellular matrices critically depends on matrix rigidity, which affects cell adhesion and formation of focal contacts. Receptor-like protein tyrosine phosphatase alpha (RPTP?) and the ?v?3 integrin form a rigidity-responsive complex at the leading edge. Here we show that the rigidity response through increased spreading and growth correlates with leading edge recruitment of Fyn, but not endogenous c-Src. Recruitment of Fyn requires the palmitoylation site near the N-terminus and addition of that site to c-Src enables it to support a rigidity response. In all cases, the rigidity response correlates with the recruitment of the Src family kinase to...
150.
MAP Kinase Pathwaydependent Phosphorylation of the L1-CAM Ankyrin Binding Site Regulates Neuronal Growth - Whittard, John D.; Sakurai, Takeshi; Cassella, Melanie R.; Gazdoiu, Mihaela; Felsenfeld, Dan P.
The growth of neuronal processes depends critically on the function of adhesion proteins that link extracellular ligands to the cytoskeleton. The neuronal adhesion protein L1-CAM serves as a receptor for nerve growthpromoting proteins, a process that is inhibited by the interaction between L1-CAM and the cytoskeleton adaptor ankyrin. Using a novel reporter based on intramolecular bioluminescence resonance energy transfer, we have determined that the MAP kinase pathway regulates the phosphorylation of the FIGQY motif in the adhesion protein L1-CAM and its interaction with ankyrin B. MAP kinase pathway inhibitors block L1-CAMmediated neuronal growth. However, this blockade is partially rescued by...
151.
A Critical Role for Tetraspanin CD151 in ?3?1 and ?6?4 Integrindependent Tumor Cell Functions on Laminin-5 - Winterwood, Nicole E.; Varzavand, Afshin; Meland, Marit N.; Ashman, Leonie K.; Stipp, Christopher S.
The basement membrane protein laminin-5 supports tumor cell adhesion and motility and is implicated at multiple steps of the metastatic cascade. Tetraspanin CD151 engages in lateral, cell surface complexes with both of the major laminin-5 receptors, integrins ?3?1 and ?6?4. To determine the role of CD151 in tumor cell responses to laminin-5, we used retroviral RNA interference to efficiently silence CD151 expression in epidermal carcinoma cells. Near total loss of CD151 had no effect on steady state cell surface expression of ?3?1, ?6?4, or other integrins with which CD151 associates. However, CD151-silenced carcinoma cells displayed markedly impaired motility on laminin-5,...
152.
Caenorhabditis elegans Kettin, a Large Immunoglobulin-like Repeat Protein, Binds to Filamentous Actin and Provides Mechanical Stability to the Contractile Apparatuses in Body Wall Muscle - Ono, Kanako; Yu, Robinson; Mohri, Kurato; Ono, Shoichiro
Kettin is a large actin-binding protein with immunoglobulin-like (Ig) repeats, which is associated with the thin filaments in arthropod muscles. Here, we report identification and functional characterization of kettin in the nematode Caenorhabditis elegans. We found that one of the monoclonal antibodies that were raised against C. elegans muscle proteins specifically reacts with kettin (Ce-kettin). We determined the entire cDNA sequence of Ce-kettin that encodes a protein of 472 kDa with 31 Ig repeats. Arthropod kettins are splice variants of much larger connectin/titin-related proteins. However, the gene for Ce-kettin is independent of other connectin/titin-related genes. Ce-kettin localizes to the thin...
153.
Involvement of Akt in ER-to-Golgi Transport of SCAP/SREBP: A Link between a Key Cell Proliferative Pathway and Membrane Synthesis - Du, Ximing; Kristiana, Ika; Wong, Jenny; Brown, Andrew J.
Akt is a critical regulator of cell growth, proliferation, and survival that is activated by phosphatidylinositol 3-kinase (PI3K). We investigated the effect of PI3K inhibition on activation of sterol regulatory element binding protein-2 (SREBP-2), a master regulator of cholesterol homeostasis. SREBP-2 processing increased in response to various cholesterol depletion approaches (including statin treatment) and this increase was blunted by treatment with a potent and specific inhibitor of PI3K, LY294002, or when a plasmid encoding a dominant-negative form of Akt (DN-Akt) was expressed. LY294002 also suppressed SREBP-2 processing induced by insulin-like growth factor-1. Furthermore, LY294002 treatment down-regulated SREBP-2 or -1c gene...
154.
Compartmentation of the Nucleolar Processing Proteins in the Granular Component Is a CK2-driven Process - Louvet, Emilie; Junéra, Henriette Roberte; Berthuy, Isabelle; Hernandez-Verdun, Danièle
To analyze the compartmentation of nucleolar protein complexes, the mechanisms controlling targeting of nucleolar processing proteins onto rRNA transcription sites has been investigated. We studied the reversible disconnection of transcripts and processing proteins using digitonin-permeabilized cells in assays capable of promoting nucleolar reorganization. The assays show that the dynamics of nucleolar reformation is ATP/GTP-dependent, sensitive to temperature, and CK2-driven. We further demonstrate the role of CK2 on the rRNA-processing protein B23. Mutation of the major CK2 site on B23 induces reorganization of nucleolar components that separate from each other. This was confirmed in assays using extracts containing B23 mutated in...
155.
CNF1-induced Ubiquitylation and Proteasome Destruction of Activated RhoA Is Impaired in Smurf1?/? Cells - Boyer, Laurent; Turchi, Laurent; Desnues, Benoit; Doye, Anne; Ponzio, Gilles; Mege, Jean-Louis; Yamashita, Motozo; Zhang, Ying E.; Bertoglio, Jacques; Flatau, Gilles; Boquet, Patrice; Lemichez, Emmanuel
Ubiquitylation of RhoA has emerged as an important aspect of both the virulence of Escherichia coli producing cytotoxic necrotizing factor (CNF) 1 toxin and the establishment of the polarity of eukaryotic cells. Owing to the molecular activity of CNF1, we have investigated the relationship between permanent activation of RhoA catalyzed by CNF1 and subsequent ubiquitylation of RhoA by Smurf1. Using Smurf1-deficient cells and by RNA interference (RNAi)-mediated Smurf1 knockdown, we demonstrate that Smurf1 is a rate-limiting and specific factor of the ubiquitin-mediated proteasomal degradation of activated RhoA. We further show that the cancer cell lines HEp-2, human embryonic kidney 293...
156.
Myosin VI Stabilizes an Actin Network during Drosophila Spermatid Individualization - Noguchi, Tatsuhiko; Lenartowska, Marta; Miller, Kathryn G.
Here, we demonstrate a new function of myosin VI using observations of Drosophila spermatid individualization in vivo. We find that myosin VI stabilizes a branched actin network in actin structures (cones) that mediate the separation of the syncytial spermatids. In a myosin VI mutant, the cones do not accumulate F-actin during cone movement, whereas overexpression of myosin VI leads to bigger cones with more F-actin. Myosin subfragment 1-fragment decoration demonstrated that the actin cone is made up of two regions: a dense meshwork at the front and parallel bundles at the rear. The majority of the actin filaments were oriented...
157.
Filopodia Formation in the Absence of Functional WAVE- and Arp2/3-Complexes - Steffen, Anika; Faix, Jan; Resch, Guenter P.; Linkner, Joern; Wehland, Juergen; Small, J. Victor; Rottner, Klemens; Stradal, Theresia E.B.
Cell migration is initiated by plasma membrane protrusions, in the form of lamellipodia and filopodia. The latter rod-like projections may exert sensory functions and are found in organisms as distant in evolution as mammals and amoeba such as Dictyostelium discoideum. In mammals, lamellipodia protrusion downstream of the small GTPase Rac1 requires a multimeric protein assembly, the WAVE-complex, which activates Arp2/3-mediated actin filament nucleation and actin network assembly. A current model of filopodia formation postulates that these structures arise from a dendritic network of lamellipodial actin filaments by selective elongation and bundling. Here, we have analyzed filopodia formation in mammalian cells...
158.
Cdc42p GDP/GTP Cycling Is Necessary for Efficient Cell Fusion during Yeast Mating - Barale, Sophie; McCusker, Derek; Arkowitz, Robert A.
The highly conserved small Rho G-protein, Cdc42p plays a critical role in cell polarity and cytoskeleton organization in all eukaryotes. In the yeast Saccharomyces cerevisiae, Cdc42p is important for cell polarity establishment, septin ring assembly, and pheromone-dependent MAP-kinase signaling during the yeast mating process. In this study, we further investigated the role of Cdc42p in the mating process by screening for specific mating defective cdc42 alleles. We have identified and characterized novel mating defective cdc42 alleles that are unaffected in vegetative cell polarity. Replacement of the Cdc42p Val36 residue with Met resulted in a specific cell fusion defect. This cdc42[V36M]...
159.
SMAP2, a Novel ARF GTPase-activating Protein, Interacts with Clathrin and Clathrin Assembly Protein and Functions on the AP-1positive Early Endosome/Trans-Golgi Network - Natsume, Waka; Tanabe, Kenji; Kon, Shunsuke; Yoshida, Naomi; Watanabe, Toshio; Torii, Tetsuo; Satake, Masanobu
We recently reported that SMAP1, a GTPase-activating protein (GAP) for Arf6, directly interacts with clathrin and regulates the clathrin-dependent endocytosis of transferrin receptors from the plasma membrane. Here, we identified a SMAP1 homologue that we named SMAP2. Like SMAP1, SMAP2 exhibits GAP activity and interacts with clathrin heavy chain (CHC). Furthermore, we show that SMAP2 interacts with the clathrin assembly protein CALM. Unlike SMAP1, however, SMAP2 appears to be a regulator of Arf1 in vivo, because cells transfected with a GAP-negative SMAP2 mutant were resistant to brefeldin A. SMAP2 colocalized with the adaptor proteins for clathrin AP-1 and EpsinR on...
160.
Aip1 and Cofilin Promote Rapid Turnover of Yeast Actin Patches and Cables: A Coordinated Mechanism for Severing and Capping Filaments - Okada, Kyoko; Ravi, Harini; Smith, Ellen M.; Goode, Bruce L.
Rapid turnover of actin structures is required for dynamic remodeling of the cytoskeleton and cell morphogenesis, but the mechanisms driving actin disassembly are poorly defined. Cofilin plays a central role in promoting actin turnover by severing/depolymerizing filaments. Here, we analyze the in vivo function of a ubiquitous actin-interacting protein, Aip1, suggested to work with cofilin. We provide the first demonstration that Aip1 promotes actin turnover in living cells. Further, we reveal an unanticipated role for Aip1 and cofilin in promoting rapid turnover of yeast actin cables, dynamic structures that are decorated and stabilized by tropomyosin. Through systematic mutagenesis of Aip1...
141.
