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 181 - 200 de 9,978
181.
A Unique Fungal Two-Component System Regulates Stress Responses, Drug Sensitivity, Sexual Development, and Virulence of Cryptococcus neoformans - Bahn, Yong-Sun; Kojima, Kaihei; Cox, Gary M.; Heitman, Joseph
The stress-activated mitogen-activated protein kinase (MAPK) pathway is widely used by eukaryotic organisms as a central conduit via which cellular responses to the environment effect growth and differentiation. The basidiomycetous human fungal pathogen Cryptococcus neoformans uniquely uses the stress-activated Pbs2-Hog1 MAPK system to govern a plethora of cellular events, including stress responses, drug sensitivity, sexual reproduction, and virulence. Here, we characterized a fungal two-component system that controls these fundamental cellular functions via the Pbs2-Hog1 MAPK cascade. A typical response regulator, Ssk1, modulated all Hog1-dependent phenotypes by controlling Hog1 phosphorylation, indicating that Ssk1 is the major upstream signaling component of the...
182.
The Stress-activated Mitogen-activated Protein Kinase Signaling Cascade Promotes Exit from Mitosis - Reiser, Vladimír; DAquino, Katharine E.; Ee, Ly-Sha; Amon, Angelika
In budding yeast, a signaling network known as the mitotic exit network (MEN) triggers exit from mitosis. We find that hypertonic stress allows MEN mutants to exit from mitosis in a manner dependent on the high osmolarity glycerol (HOG) mitogen-activated protein (MAP) kinase cascade. The HOG pathway drives exit from mitosis in MEN mutants by promoting the activation of the MEN effector, the protein phosphatase Cdc14. Activation of Cdc14 depends on the Cdc14 early anaphase release network, a group of proteins that functions in parallel to the MEN to promote Cdc14 function. Notably, exit from mitosis is promoted by the...
183.
The Caenorhabditis elegans Homologue of Deleted in Azoospermia Is Involved in the Sperm/Oocyte Switch - Otori, Muneyoshi; Karashima, Takeshi; Yamamoto, Masayuki
The Deleted in Azoospermia (DAZ) gene family encodes putative translational activators that are required for meiosis and other aspects of gametogenesis in animals. The single Caenorhabditis elegans homologue of DAZ, daz-1, is an essential factor for female meiosis. Here, we show that daz-1 is important for the switch from spermatogenesis to oogenesis (the sperm/oocyte switch), which is an essential step for the hermaphrodite germline to produce oocytes. RNA interference of the daz-1 orthologue in a related nematode, Caenorhabditis briggsae, resulted in a complete loss of the sperm/oocyte switch. The C. elegans hermaphrodite deficient in daz-1 also revealed a failure in...
184.
Rab10 Regulates Membrane Transport through Early Endosomes of Polarized Madin-Darby Canine Kidney Cells - Babbey, Clifford M.; Ahktar, Nahid; Wang, Exing; Chen, Carlos Chih-Hsiung; Grant, Barth D.; Dunn, Kenneth W.
Rab10, a protein originally isolated from Madin-Darby Canine Kidney (MDCK) epithelial cells, belongs to a family of Rab proteins that includes Rab8 and Rab13. Although both Rab8 and Rab13 have been found to mediate polarized membrane transport, the function of Rab10 in mammalian cells has not yet been established. We have used quantitative confocal microscopy of polarized MDCK cells expressing GFP chimeras of wild-type and mutant forms of Rab10 to analyze the function of Rab10 in polarized cells. These studies demonstrate that Rab10 is specifically associated with the common endosomes of MDCK cells, accessible to endocytic probes internalized from either...
185.
CytLEK1 Is a Regulator of Plasma Membrane Recycling through Its Interaction with SNAP-25 - Pooley, Ryan D.; Reddy, Samyukta; Soukoulis, Victor; Roland, Joseph T.; Goldenring, James R.; Bader, David M.
SNAP-25 is a component of the SNARE complex that is involved in membrane docking and fusion. Using a yeast two-hybrid screen, we identify a novel interaction between SNAP-25 and cytoplasmic Lek1 (cytLEK1), a protein previously demonstrated to associate with the microtubule network. The binding domains within each protein were defined by yeast two-hybrid, coimmunoprecipitation, and colocalization studies. Confocal analyses reveal a high degree of colocalization between the proteins. In addition, the endogenous proteins can be isolated as a complex by immunoprecipitation. Further analyses demonstrate that cytLEK1 and SNAP-25 colocalize and coprecipitate with Rab11a, myosin Vb, VAMP2, and syntaxin 4, components...
186.
The Docking Protein Cas Links Tyrosine Phosphorylation Signaling to Elongation of Cerebellar Granule Cell Axons - Huang, Jinhong; Sakai, Ryuichi; Furuichi, Teiichi
Crk-associated substrate (Cas) is a tyrosine-phosphorylated docking protein that is indispensable for the regulation of the actin cytoskeletal organization and cell migration in fibroblasts. The function of Cas in neurons, however, is poorly understood. Here we report that Cas is dominantly enriched in the brain, especially the cerebellum, of postnatal mice. During cerebellar development, Cas is highly tyrosine phosphorylated and is concentrated in the neurites and growth cones of granule cells. Cas coimmunoprecipitates with Src family protein tyrosine kinases, Crk, and cell adhesion molecules and colocalizes with these proteins in granule cells. The axon extension of granule cells is inhibited...
187.
Ongoing U snRNP Biogenesis Is Required for the Integrity of Cajal Bodies - Lemm, Ira; Girard, Cyrille; Kuhn, Andreas N.; Watkins, Nicholas J.; Schneider, Marc; Bordonné, Rémy; Lührmann, Reinhard
Cajal bodies (CBs) have been implicated in the nuclear phase of the biogenesis of spliceosomal U small nuclear ribonucleoproteins (U snRNPs). Here, we have investigated the distribution of the CB marker protein coilin, U snRNPs, and proteins present in C/D box small nucleolar (sno)RNPs in cells depleted of hTGS1, SMN, or PHAX. Knockdown of any of these three proteins by RNAi interferes with U snRNP maturation before the reentry of U snRNA Sm cores into the nucleus. Strikingly, CBs are lost in the absence of hTGS1, SMN, or PHAX and coilin is dispersed in the nucleoplasm into numerous small foci....
188.
Aurora-B/AIM-1 Regulates the Dynamic Behavior of HP1? at the G2M Transition - Terada, Yasuhiko
Heterochromatin protein 1 (HP1) plays an important role in heterochromatin formation and undergoes large-scale, progressive dissociation from heterochromatin in prophase cells. However, the mechanisms regulating the dynamic behavior of HP1 are poorly understood. In this study, the role of Aurora-B was investigated with respect to the dynamic behavior of HP1?. Mammalian Aurora-B, AIM-1, colocalizes with HP1? to the heterochromatin in G2. Depletion of Aurora-B/AIM-1 inhibited dissociation of HP1? from the chromosome arms at the G2M transition. In addition, depletion of INCENP led to aberrant cellular localization of Aurora-B/AIM-1, but it did not affect heterochromatin targeting of HP1?. It was proposed...
189.
Dynein-dependent Motility of Microtubules and Nucleation Sites Supports Polarization of the Tubulin Array in the Fungus Ustilago maydis - Fink, Gero; Steinberg, Gero
Microtubules (MTs) are often organized by a nucleus-associated MT organizing center (MTOC). In addition, in neurons and epithelial cells, motor-based transport of assembled MTs determines the polarity of the MT array. Here, we show that MT motility participates in MT organization in the fungus Ustilago maydis. In budding cells, most MTs are nucleated by three to six small and motile ?-tubulincontaining MTOCs at the boundary of mother and daughter cell, which results in a polarized MT array. In addition, free MTs and MTOCs move rapidly throughout the cytoplasm. Disruption of MTs with benomyl and subsequent washout led to an equal...
190.
Cell Cycle-dependent Roles for the FCH-Domain Protein Cdc15p in Formation of the Actomyosin Ring in Schizosaccharomyces pombe - Wachtler, Volker; Huang, Yinyi; Karagiannis, Jim; Balasubramanian, Mohan K.
Cell division in the fission yeast Schizosaccharomyces pombe requires the formation and constriction of an actomyosin ring at the division site. The actomyosin ring is assembled in metaphase and anaphase A, is maintained throughout mitosis, and constricts after completion of anaphase. Maintenance of the actomyosin ring during late stages of mitosis depends on the septation initiation network (SIN), a signaling cascade that also regulates the deposition of the division septum. However, SIN is not active in metaphase and is not required for the initial assembly of the actomyosin ring early in mitosis. The FER/CIP4-homology (FCH) domain protein Cdc15p is a...
191.
Role of Cell Cycle-regulated Expression in the Localized Incorporation of Cell Wall Proteins in Yeast - Smits, Gertien J.; Schenkman, Laura R.; Brul, Stanley; Pringle, John R.; Klis, Frans M.
The yeast cell wall is an essential organelle that protects the cell from mechanical damage and antimicrobial peptides, participates in cell recognition and adhesion, and is important for the generation and maintenance of normal cell shape. We studied the localization of three covalently bound cell wall proteins in Saccharomyces cerevisiae. Tip1p was found only in mother cells, whereas Cwp2p was incorporated in small-to-mediumsized buds. When the promoter regions of TIP1 and CWP2 (responsible for transcription in early G1 and S/G2 phases, respectively) were exchanged, the localization patterns of Tip1p and Cwp2p were reversed, indicating that the localization of cell wall...
192.
Dissection of Swa2p/Auxilin Domain Requirements for Cochaperoning Hsp70 Clathrin-uncoating Activity In Vivo - Xiao, Jing; Kim, Leslie S.; Graham, Todd R.
The auxilin family of J-domain proteins load Hsp70 onto clathrin-coated vesicles (CCVs) to drive uncoating. In vitro, auxilin function requires its ability to bind clathrin and stimulate Hsp70 ATPase activity via its J-domain. To test these requirements in vivo, we performed a mutational analysis of Swa2p, the yeast auxilin ortholog. Swa2p is a modular protein with three N-terminal clathrin-binding (CB) motifs, a ubiquitin association (UBA) domain, a tetratricopeptide repeat (TPR) domain, and a C-terminal J-domain. In vitro, clathrin binding is mediated by multiple weak interactions, but a Swa2p truncation lacking two CB motifs and the UBA domain retains nearly full...
193.
Laa1p, a Conserved AP-1 Accessory Protein Important for AP-1 Localization in Yeast - Fernández, G. Esteban; Payne, Gregory S.
AP-1 and Gga adaptors participate in clathrin-mediated protein transport between the trans-Golgi network and endosomes. Both adaptors contain homologous domains that act to recruit accessory proteins involved in clathrin-coated vesicle formation, but the spectrum of known adaptor-binding partners is limited. This study describes an evolutionarily conserved protein of Saccharomyces cerevisiae, Laa1p (Yjl207cp), that interacts and functions specifically with AP-1. Deletion of LAA1, when combined with a conditional mutation in clathrin heavy chain or deletion of GGA genes, accentuated growth defects and increased disruption of clathrin-dependent ?-factor maturation and transport of carboxypeptidase Y to the vacuole. In contrast, such genetic interactions...
194.
Annexin A4 Self-Association Modulates General Membrane Protein Mobility in Living Cells - Pilji?, Alen; Schultz, Carsten
Annexins are Ca2+-regulated phospholipid-binding proteins whose function is only partially understood. Annexin A4 is a member of this family that is believed to be involved in exocytosis and regulation of epithelial Cl? secretion. In this work, fluorescent protein fusions of annexin A4 were used to investigate Ca2+-induced annexin A4 translocation and self-association on membrane surfaces in living cells. We designed a novel, genetically encoded, FRET sensor (CYNEX4) that allowed for easy quantification of translocation and self-association. Mobility of annexin A4 on membrane surfaces was investigated by FRAP. The experiments revealed the immobile nature of annexin A4 aggregates on membrane surfaces,...
195.
Adenovirus E4orf4 Hijacks Rho GTPase-dependent Actin Dynamics to Kill Cells: A Role for Endosome-associated Actin Assembly - Robert, Amélie; Smadja-Lamère, Nicolas; Landry, Marie-Claude; Champagne, Claudia; Petrie, Ryan; Lamarche-Vane, Nathalie; Hosoya, Hiroshi; Lavoie, Josée N.
The adenovirus early region 4 ORF4 protein (E4orf4) triggers a novel death program that bypasses classical apoptotic pathways in human cancer cells. Deregulation of the cell cytoskeleton is a hallmark of E4orf4 killing that relies on Src family kinases and E4orf4 phosphorylation. However, the cytoskeletal targets of E4orf4 and their role in the death process are unknown. Here, we show that E4orf4 translocates to cytoplasmic sites and triggers the assembly of a peculiar juxtanuclear actinmyosin network that drives polarized blebbing and nuclear shrinkage. We found that E4orf4 activates the myosin II motor and triggers de novo actin polymerization in the...
196.
Cellular Analyses of the Mitotic Region in the Caenorhabditis elegans Adult Germ Line - Crittenden, Sarah L.; Leonhard, Kimberly A.; Byrd, Dana T.; Kimble, Judith
The Caenorhabditis elegans germ line provides a model for understanding how signaling from a stem cell niche promotes continued mitotic divisions at the expense of differentiation. Here we report cellular analyses designed to identify germline stem cells within the germline mitotic region of adult hermaphrodites. Our results support several conclusions. First, all germ cells within the mitotic region are actively cycling, as visualized by bromodeoxyuridine (BrdU) labeling. No quiescent cells were found. Second, germ cells in the mitotic region lose BrdU label uniformly, either by movement of labeled cells into the meiotic region or by dilution, probably due to replication....
197.
Distinct Mechanisms of Clathrin-independent Endocytosis Have Unique Sphingolipid Requirements - Cheng, Zhi-Jie; Singh, Raman Deep; Sharma, Deepak K.; Holicky, Eileen L.; Hanada, Kentaro; Marks, David L.; Pagano, Richard E.
Sphingolipids (SLs) play important roles in membrane structure and cell function. Here, we examine the SL requirements of various endocytic mechanisms using a mutant cell line and pharmacological inhibitors to disrupt SL biosynthesis. First, we demonstrated that in Chinese hamster ovary cells we could distinguish three distinct mechanisms of clathrin-independent endocytosis (caveolar, RhoA, and Cdc42 dependent) which differed in cargo, sensitivity to pharmacological agents, and dominant negative proteins. General depletion of SLs inhibited endocytosis by each clathrin-independent mechanism, whereas clathrin-dependent uptake was unaffected. Depletion of glycosphingolipids (GSLs; a subgroup of SLs) selectively blocked caveolar endocytosis and decreased caveolin-1 and caveolae...
198.
Substrate-dependent Contribution of Double-stranded RNA-binding Motifs to ADAR2 Function - Xu, Ming; Wells, K. Sam; Emeson, Ronald B.
ADAR2 is a double-stranded RNA-specific adenosine deaminase involved in the editing of mammalian RNAs by the site-specific conversion of adenosine to inosine (A-to-I). ADAR2 contains two tandem double-stranded RNA-binding motifs (dsRBMs) that are not only important for efficient editing of RNA substrates but also necessary for localizing ADAR2 to nucleoli. The sequence and structural similarity of these motifs have raised questions regarding the role(s) that each dsRBM plays in ADAR2 function. Here, we demonstrate that the dsRBMs of ADAR2 differ in both their ability to modulate subnuclear localization as well as to promote site-selective A-to-I conversion. Surprisingly, dsRBM1 contributes to...
199.
Rho Kinase, Myosin-II, and p42/44 MAPK Control Extracellular Matrix-mediated Apical Bile Canalicular Lumen Morphogenesis in HepG2 Cells - Herrema, Hilde; Czajkowska, Dominika; Théard, Delphine; van der Wouden, Johanna M.; Kalicharan, Dharamdajal; Zolghadr, Behnam; Hoekstra, Dick; van IJzendoorn, Sven C.D.
The molecular mechanisms that regulate multicellular architecture and the development of extended apical bile canalicular lumens in hepatocytes are poorly understood. Here, we show that hepatic HepG2 cells cultured on glass coverslips first develop intercellular apical lumens typically formed by a pair of cells. Prolonged cell culture results in extensive organizational changes, including cell clustering, multilayering, and apical lumen morphogenesis. The latter includes the development of large acinar structures and subsequent elongated canalicular lumens that span multiple cells. These morphological changes closely resemble the early organizational pattern during development, regeneration, and neoplasia of the liver and are rapidly induced when...
200.
Regulated Synthesis and Functions of Laminin 5 in Polarized Madin-Darby Canine Kidney Epithelial Cells - Mak, Grace Z.; Kavanaugh, Gina M.; Buschmann, Mary M.; Stickley, Shaun M.; Koch, Manuel; Goss, Kathleen Heppner; Waechter, Holly; Zuk, Anna; Matlin, Karl S.
Renal tubular epithelial cells synthesize laminin (LN)5 during regeneration of the epithelium after ischemic injury. LN5 is a truncated laminin isoform of particular importance in the epidermis, but it is also constitutively expressed in a number of other epithelia. To investigate the role of LN5 in morphogenesis of a simple renal epithelium, we examined the synthesis and function of LN5 in the spreading, proliferation, wound-edge migration, and apicalbasal polarization of Madin-Darby canine kidney (MDCK) cells. MDCK cells synthesize LN5 only when subconfluent, and they degrade the existing LN5 matrix when confluent. Through the use of small-interfering RNA to knockdown the...
181.
