Página 26 dos resultados de 6914 itens digitais encontrados em 0.020 segundos

‣ Chaperonin filaments: The archaeal cytoskeleton?

Trent, Jonathan D.; Kagawa, Hiromi K.; Yaoi, Takuro; Olle, Eric; Zaluzec, Nestor J.
Fonte: The National Academy of Sciences of the USA Publicador: The National Academy of Sciences of the USA
Tipo: Artigo de Revista Científica
Publicado em 13/05/1997 Português
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Chaperonins are high molecular mass double-ring structures composed of 60-kDa protein subunits. In the hyperthermophilic archaeon Sulfolobus shibatae the two chaperonin proteins represent ≈4% of its total protein and have a combined intracellular concentration of >30 mg/ml. At concentrations ≥ 0.5 mg/ml purified chaperonins form filaments in the presence of Mg2+ and nucleotides. Filament formation requires nucleotide binding (not hydrolysis), and occurs at physiological temperatures in biologically relevant buffers, including a buffer made from cell extracts. These observations suggest that chaperonin filaments may exist in vivo and the estimated 4600 chaperonins per cell suggest that such filaments could form an extensive cytostructure. We observed filamentous structures in unfixed, uranyl-acetate-stained S. shibatae cells, which resemble the chaperonin filaments in size and appearance. ImmunoGold (Janssen) labeling using chaperonin antibodies indicated that many chaperonins are associated with insoluble cellular structures and these structures appear to be filamentous in some areas, although they could not be uranyl-acetate-stained. The existence of chaperonin filaments in vivo suggests a mechanism whereby their protein-folding activities can be regulated. More generally...

‣ Attachment of Escherichia coli O157:H7 to the Surfaces and Internal Structures of Apples as Detected by Confocal Scanning Laser Microscopy

Burnett, Scott L.; Chen, Jinru; Beuchat, Larry R.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2000 Português
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Confocal scanning laser microscopy (CSLM) was used to demonstrate the attachment of Escherichia coli O157:H7 transformed with a plasmid encoding for green fluorescent protein (GFP) to the surface and within the internal structures of nonwaxed Red Delicious cv. apples. Apples at 2 or 25°C were inoculated with an E. coli O157:H7 cell suspension at 2 or 25°C. The effect of a negative temperature differential (cold inoculum, warm apple), a positive differential (warm inoculum, cold apple), and no differential (warm inoculum, warm apple), in combination with a pressure differential (atmospheric versus 10,130 Pa), on the attachment and infiltration of cells was determined. CSLM stereo images of external surfaces of apples subjected to all combinations of test parameters showed preferential cellular attachment to discontinuities in the waxy cuticle on the surface and to damaged tissue surrounding puncture wounds, where the pathogen was observed at depths up to 70 μm below the skin surface. Attachment to lenticels was sporadic but was occasionally observed at depths of up to 40 μm. Infiltration through the floral tube and attachment to seeds, cartilaginous pericarp, and internal trichomes were observed in all apples examined, regardless of temperature differential during inoculation. The pressure differential had no effect on infiltration or attachment of E. coli O157:H7. Image analysis to count cells at various depths within tissues was used to quantitatively compare the extent of infiltration into various apple structures as well as the effects of the temperature differential. Puncture wounds harbored greater numbers of the pathogen at greater depths than did other sites examined. Attachment or infiltration of cells was greater on the intact skin and in lenticels...

‣ Coiling Phagocytosis of Borrelia burgdorferi by Primary Human Macrophages Is Controlled by CDC42Hs and Rac1 and Involves Recruitment of Wiskott-Aldrich Syndrome Protein and Arp2/3 Complex

Linder, Stefan; Heimerl, Christiane; Fingerle, Volker; Aepfelbacher, Martin; Wilske, Bettina
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /03/2001 Português
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Lyme borreliosis is a multisystemic disorder primarily affecting the skin, nervous system, and joints. It is caused by the spirochete Borrelia burgdorferi sensu lato and is transmitted via ticks of the Ixodidae family. Persistence of borreliae within macrophages has been implicated in the often chronic history of borreliosis. The uptake of B. burgdorferi by professional phagocytes occurs predominantly by coiling phagocytosis, a host cell-driven process in which single pseudopods wrap around and engulf the spirochetes. In the present study, we investigated the molecular machinery and the signal transduction pathways controlling the formation of these unique uptake structures. We found that the phagocytosis of borreliae by primary human macrophages is accompanied by the formation of f-actin-rich structures, which in their morphological organization correspond well to the earlier described coiling pseudopods. Further experiments revealed that Wiskott-Aldrich Syndrome protein and Arp2/3 complex, major regulators of actin polymerization, are also recruited to these sites of actin accumulation. In addition, inhibition of an upstream regulator of Wiskott-Aldrich Syndrome protein, the Rho-family GTPase CDC42Hs, greatly inhibited the occurrence of borrelia-induced phagocytic uptake structures. Inhibition of Rac1...

‣ Evaluation of colocalization interactions between the IE110, IE175, and IE63 transactivator proteins of herpes simplex virus within subcellular punctate structures.

Mullen, M A; Gerstberger, S; Ciufo, D M; Mosca, J D; Hayward, G S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1995 Português
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A number of previous studies have implied that three herpes simplex virus-encoded nuclear transactivator proteins, IE175 (ICP4), IE110 (ICP0), and IE63 (ICP27), may cooperate in transcriptional and posttranscriptional stimulation of viral gene expression. Using double-label immunofluorescence assays (IFA) in transient expression assays, we have examined the intracellular localization of these three proteins in DNA-transfected cells. The IE110 protein on its own forms spherical punctate domains within the nucleus, whereas the IE175 and IE63 proteins alone give uniform and speckled diffuse patterns, respectively. In infected cells, the IE110 punctate granules have been shown to correspond to novel preexisting subnuclear structures referred to as ND10 domains or PODs that contain a variety of cellular proteins, including SP100 and the PML proto-oncogene product. Cotransfection experiments with wild-type nuclear forms of both IE175 and IE110 provided direct evidence for partial redistribution of IE175 into the same punctate granules that contained IE110. Surprisingly, nuclear forms of IE110 were found to move a cytoplasmic form of IE175 into nuclear punctate structures, and a cytoplasmic form of IE110 was able to retain nuclear forms of IE175 in cytoplasmic punctate structures. Therefore...

‣ Structures of the Oligosaccharides of the Glycoprotein Coded by Early Region E3 of Adenovirus 2

Kornfeld, Rosalind; Wold, William S. M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1981 Português
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Early region E3 of adenovirus 2 encodes a glycoprotein, E3-gp25K, that is a good model with which to study structure-function relationships in transmembrane glycoproteins. We have determined the structures of the oligosaccharides linked to E3-gp25K. The oligosaccharides were labeled with [2-3H]mannose in adenovirus 2-early infected KB cells for 5.5h (pulse) or for 5.5 h followed by a 3-h chase (pulse-chase). E3-gp25K was extracted and purified by chromatography on DEAE-Sephacel in 7 M urea, followed by gel filtration on a column of Bio-Gel A-1.5m in 6 M guanidine hydrochloride. An analysis of the purified protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that it was >95% pure. The oligosaccharides were isolated by pronase digestion followed by gel filtration on a column of Bio-Gel P-6, then by digestion with endo-β-N-acetylglucosaminidase H, followed by gel filtration on Bio-Gel P-6, and finally by paper chromatography. The pulse sample contained equal amounts of Man9GlcNAc and Man8GlcNAc and small amounts of Man7GlcNAc and Man6GlcNAc. The pulse-chase sample had predominantly Man8GlcNAc and much less Man9GlcNAc, indicating that processing of the Man9GlcNAc to Man8GlcNAc had occurred during the chase period. Thus...

‣ Capping Structures at the 5′-Terminus of Polyadenylated Ribonucleic Acid in Avena Coleoptiles

Haugland, Richard A.; Cline, Morris G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1978 Português
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Evidence is presented for the occurrence of 5′-terminal capping structures in the polyadenylated RNA of oat (Avena sativa) coleoptiles. These structures are composed of an inverted terminal nucleoside containing the modified base 7-methylguanine which is joined 5′ to 5′ with a second (penultimate) nucleoside by means of three phosphate groups in two pyrophosphate linkages. The penultimate nucleoside is joined to the remainder of the RNA molecule by a conventional 3′,5′ phosphodiester bond. A significant difference between the cap structures of oat coleoptile RNA and those of previously described higher eucaryotic cellular mRNAs is the lack of ribose methylations in the penultimate nucleosides of the plant RNA.

‣ The Yeast Actin Cytoskeleton: from Cellular Function to Biochemical Mechanism

Moseley, James B.; Goode, Bruce L.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2006 Português
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All cells undergo rapid remodeling of their actin networks to regulate such critical processes as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. These events are driven by the coordinated activities of a set of 20 to 30 highly conserved actin-associated proteins, in addition to many cell-specific actin-associated proteins and numerous upstream signaling molecules. The combined activities of these factors control with exquisite precision the spatial and temporal assembly of actin structures and ensure dynamic turnover of actin structures such that cells can rapidly alter their cytoskeletons in response to internal and external cues. One of the most exciting principles to emerge from the last decade of research on actin is that the assembly of architecturally diverse actin structures is governed by highly conserved machinery and mechanisms. With this realization, it has become apparent that pioneering efforts in budding yeast have contributed substantially to defining the universal mechanisms regulating actin dynamics in eukaryotes. In this review, we first describe the filamentous actin structures found in Saccharomyces cerevisiae (patches, cables, and rings) and their physiological functions, and then we discuss in detail the specific roles of actin-associated proteins and their biochemical mechanisms of action.

‣ Role and Localization of Urokinase Receptor in the Formation of New Microvascular Structures in Fibrin Matrices

Kroon, Marielle E.; Koolwijk, Pieter; van Goor, Harry; Weidle, Ulrich H.; Collen, Annemie; van der Pluijm, Gabri; van Hinsbergh, Victor W. M.
Fonte: American Society for Investigative Pathology Publicador: American Society for Investigative Pathology
Tipo: Artigo de Revista Científica
Publicado em /06/1999 Português
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Fibrin or a fibrinous exudate can facilitate angiogenesis in many pathological conditions. In vitro, the outgrowth of capillary-like structures in fibrin can be mimicked by exposing human microvascular endothelial cells (hMVECs) to an angiogenic growth factor and tumor necrosis factor (TNF)-α. Urokinase-type plasminogen activator (u-PA) and plasmin activities are required for this angiogenic process. This study focuses on the role and localization of the u-PA receptor (u-PAR) in newly formed microvascular structures. The u-PAR-blocking monoclonal antibody (MAb) H-2 completely inhibited the formation of capillary-like tubular structures induced by exposure of hMVECs to basic fibroblast growth factor and TNF-α. This was accompanied by a several-fold increase in u-PA accumulation in the conditioned medium. The effect of MAb H-2 was not caused by blocking cellular activation by u-PA/u-PAR interaction, as the amino-terminal fragment (ATF) of u-PA, which also activates u-PAR, prevented tube formation. In addition, the inhibition by MAb H-2 was not due to an effect of the antibody on u-PAR-vitronectin binding. These data show that inhibition of tube formation can be caused not only by inhibition of u-PA or plasmin activities but also by unavailability of the u-PAR for cell-bound proteolysis. Immunohistochemical analysis showed that in in vitro angiogenesis u-PAR and u-PA were localized on the invading...

‣ Basal bodies and associated structures are not required for normal flagellar motion or phototaxis in the green alga Chlorogonium elongatum

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/01/1985 Português
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The interphase flagellar apparatus of the green alga Chlorogonium elongatum resembles that of Chlamydomonas reinhardtii in the possession of microtubular rootlets and striated fibers. However, Chlorogonium, unlike Chlamydomonas, retains functional flagella during cell division. In dividing cells, the basal bodies and associated structures are no longer present at the flagellar bases, but have apparently detached and migrated towards the cell equator before the first mitosis. The transition regions remain with the flagella, which are now attached to a large apical mitochondrion by cross-striated filamentous components. Both dividing and nondividing cells of Chlorogonium propagate asymmetrical ciliary-type waveforms during forward swimming and symmetrical flagellar-type waveforms during reverse swimming. High- speed cinephotomicrographic analysis indicates that waveforms, beat frequency, and flagellar coordination are similar in both cell types. This indicates that basal bodies, striated fibers, and microtubular rootlets are not required for the initiation of flagellar beat, coordination of the two flagella, or determination of flagellar waveform. Dividing cells display a strong net negative phototaxis comparable to that of nondividing cells; hence...

‣ Formation and alignment of Z lines in living chick myotubes microinjected with rhodamine-labeled alpha-actinin

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/12/1986 Português
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We have used fluorescence analogue cytochemistry in conjunction with time lapse recording to study the dynamics of alpha-actinin, a major component of the Z line, during myofibrillogenesis. Rhodamine-labeled alpha-actinin microinjected into living cultured chick skeletal myotubes became localized in discrete cellular structures within 1 h and remained specifically associated with structures for up to 4 d, allowing individual identified structures to be followed during development. In the most immature cells used, alpha-actinin was found in diffuse aggregates, some of which displayed sarcomeric periodicity. Aggregates were observed to coalesce into better defined structures (Z bands) that were approximately 1.0-micron wide. Z bands condensed into narrow, more intensely fluorescent Z lines in 4-48 h. During this period, Z lines grew laterally, primarily by the addition of small beads of alpha-actinin to existing Z lines or by the merging of small Z lines. In more mature cells, alpha-actinin added to Z lines without going through a visible intermediary structure. Mean sarcomere length did not change significantly during the stages examined, although the variability of sarcomere length did decrease markedly over time for identified sets of sarcomeres. At early stages...

‣ Tetraspanins: Small transmembrane proteins with big impact on membrane microdomain structures

Singethan, Katrin; Schneider-Schaulies, Jürgen
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
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Members of the tetraspanin family of transmembrane proteins including CD9, CD37, CD53, CD63, CD81, CD82, CD151, etc., contribute to the structural organization of the plasma membrane by forming microdomain structures, influencing cell fusion and regulating cell motility. Interestingly, K41, a CD9-specific monoclonal antibody (mAb), inhibits the release of human immunodeficiency virus (HIV-1), and the canine distemper virus (CDV)-, but not measles virus (MV)-induced cell-cell fusion. This mAb, which recognizes a conformational epitope on the large extracellular loop (LEL) of CD9, induced rapid relocation and clustering of CD9 in net-like structures at cell-cell contact areas.1 High-resolution analyses revealed that CD9 clustering is accompanied by the formation of microvilli that protrude from either side of adjacent cell surfaces, thus forming structures like microvilli zippers. While the cellular CD9-associated proteins β1-integrin and EWI-F were co-clustered with CD9 at cell-cell interfaces, viral proteins in infected cells were differentially affected. MV envelope proteins were detected within, whereas CDV proteins were excluded from CD9 clusters, and thus, the tetraspanin CD9 can regulate cell-cell fusion by controlling the access of the viral fusion machinery to cell contact areas.

‣ Self-assembly of 3D prestressed tensegrity structures from DNA

Liedl, Tim; Högberg, Björn; Tytell, Jessica; Ingber, Donald E.; Shih, William M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Tensegrity or tensional integrity is a property of a structure that relies on a balance between components that are either in pure compression or in pure tension for its stability [1,2]. Tensegrity structures exhibit extremely high strength-to-weight ratios and great resilience, and are therefore widely used in engineering, robotics and architecture [3,4]. Here we report nanoscale, prestressed, three-dimensional tensegrity structures in which rigid bundles of DNA double helices resist compressive forces exerted by segments of single-stranded DNA that act as tension-bearing cables. Our DNA tensegrity structures can self-assemble against forces up to 14 pN, which is twice the stall force of powerful molecular motors such as kinesin or myosin [5,6]. The forces generated by this molecular prestressing mechanism can be employed to bend the DNA bundles or to actuate the entire structure through enzymatic cleavage at specific sites. In addition to being building blocks for nanostructures, tensile structural elements made of single-stranded DNA could be used to study molecular forces, cellular mechanotransduction, and other fundamental biological processes.

‣ RNA Structures Required for Production of Subgenomic Flavivirus RNA▿

Funk, Anneke; Truong, Katherine; Nagasaki, Tomoko; Torres, Shessy; Floden, Nadia; Balmori Melian, Ezequiel; Edmonds, Judy; Dong, Hongping; Shi, Pei-Yong; Khromykh, Alexander A.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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Flaviviruses are a group of single-stranded, positive-sense RNA viruses causing ∼100 million infections per year. We have recently shown that flaviviruses produce a unique, small, noncoding RNA (∼0.5 kb) derived from the 3′ untranslated region (UTR) of the genomic RNA (gRNA), which is required for flavivirus-induced cytopathicity and pathogenicity (G. P. Pijlman et al., Cell Host Microbe, 4: 579-591, 2008). This RNA (subgenomic flavivirus RNA [sfRNA]) is a product of incomplete degradation of gRNA presumably by the cellular 5′-3′ exoribonuclease XRN1, which stalls on the rigid secondary structure stem-loop II (SL-II) located at the beginning of the 3′ UTR. Mutations or deletions of various secondary structures in the 3′ UTR resulted in the loss of full-length sfRNA (sfRNA1) and production of smaller and less abundant sfRNAs (sfRNA2 and sfRNA3). Here, we investigated in detail the importance of West Nile virus Kunjin (WNVKUN) 3′ UTR secondary structures as well as tertiary interactions for sfRNA formation. We show that secondary structures SL-IV and dumbbell 1 (DB1) downstream of SL-II are able to prevent further degradation of gRNA when the SL-II structure is deleted, leading to production of sfRNA2 and sfRNA3, respectively. We also show that a number of pseudoknot (PK) interactions...

‣ Podosomes and Invadopodia: Related structures with Common Protein Components that May Promote Breast Cancer Cellular Invasion

Flynn, Daniel C.; Cho, YoungJin; Vincent, Deanne; Cunnick, Jess M.
Fonte: Libertas Academica Publicador: Libertas Academica
Tipo: Artigo de Revista Científica
Publicado em 29/05/2008 Português
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A rate-limiting step in breast cancer progression is acquisition of the invasive phenotype, which can precede metastasis. Expression of cell-surface proteases at the leading edge of a migrating cell provides cells with a mechanism to cross tissue barriers. A newly appreciated mechanism that may be relevant for breast cancer cell invasion is the formation of invadopodia, well-defined structures that project from the ventral membrane and promote degradation of the extracellular matrix, allowing the cell to cross a tissue barrier. Recently, there has been some controversy and discussion as to whether invadopodia, which are associated with carcinoma cells, are related to a similar structure called podosomes, which are associated with normal cells. Invadopodia and podosomes share many common characteristics, including a similar size, shape, subcellular localization and an ability to promote invasion. These two structures also share many common protein components, which we outline herein. It has been speculated that podosomes may be precursors to invadopodia and by extension both structures may be relevant to cancer cell invasion. Here, we compare and contrast the protein components of invadopodia and podosomes and discuss a potential role for these proteins and the evidence that supports a role for invadopodia and podosomes in breast cancer invasion.

‣ Limited Transferrin Receptor Clustering Allows Rapid Diffusion of Canine Parvovirus into Clathrin Endocytic Structures

Cureton, David K.; Harbison, Carole E.; Cocucci, Emanuele; Parrish, Colin R.; Kirchhausen, Tom
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /05/2012 Português
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Viral pathogens usurp cell surface receptors to access clathrin endocytic structures, yet the mechanisms of virus incorporation into these structures remain incompletely understood. Here we used fluorescence microscopy to directly visualize the association of single canine parvovirus (CPV) capsids with cellular transferrin receptors (TfR) on the surfaces of live feline cells and to monitor how these CPV-TfR complexes access endocytic structures. We found that most capsids associated with fewer than five TfRs and that ∼25% of TfR-bound capsids laterally diffused into assembling clathrin-coated pits less than 30 s after attachment. Capsids that did not encounter a coated pit dissociated from the cell surface with a half-life of ∼30 s. Together, our results show how CPV exploits the natural mechanism of TfR endocytosis to engage the clathrin endocytic pathway and reveal that the low affinity of capsids for feline TfRs limits the residence time of capsids on the cell surface and thus the efficiency of virus internalization.

‣ Discovery of Protein Complexes with Core-Attachment Structures from Tandem Affinity Purification (TAP) Data

Wu, Min; Li, Xiao-li; Kwoh, Chee-Keong; Ng, See-Kiong; Wong, Limsoon
Fonte: Mary Ann Liebert, Inc. Publicador: Mary Ann Liebert, Inc.
Tipo: Artigo de Revista Científica
Publicado em /09/2012 Português
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Many cellular functions involve protein complexes that are formed by multiple interacting proteins. Tandem Affinity Purification (TAP) is a popular experimental method for detecting such multi-protein interactions. However, current computational methods that predict protein complexes from TAP data require converting the co-complex relationships in TAP data into binary interactions. The resulting pairwise protein-protein interaction (PPI) network is then mined for densely connected regions that are identified as putative protein complexes. Converting the TAP data into PPI data not only introduces errors but also loses useful information about the underlying multi-protein relationships that can be exploited to detect the internal organization (i.e., core-attachment structures) of protein complexes. In this article, we propose a method called CACHET that detects protein complexes with Core-AttaCHment structures directly from bipartitETAP data. CACHET models the TAP data as a bipartite graph in which the two vertex sets are the baits and the preys, respectively. The edges between the two vertex sets represent bait-prey relationships. CACHET first focuses on detecting high-quality protein-complex cores from the bipartite graph. To minimize the effects of false positive interactions...

‣ Engineering of polarized tubular structures in a microfluidic device to study calcium phosphate stone formation†

Wei, Zengjiang; Amponsah, Prince K.; Al-Shatti, Mariyam; Nie, Zhihong; Bandyopadhyay, Bidhan C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 21/10/2012 Português
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This communication describes the formation of tubular structures with a circular cross-section by growing epithelial cells in a microfluidic (MF) device. Here we show for the first time that it is possible to form a monolayer of polarized cells, embedded within the MF device which can function as an in vivo epithelia. We showed: i) the overexpression of specific protein(s) of interest (i.e., ion channel and transport proteins) is feasible inside tubular structures in MFs; ii) the functional kinetic information of Ca2+ in cells can be measured by microflurometry using cell permeable Ca2+ probe under confocal microscope; and iii) calcium phosphate stones can be produced in real time in MFs with Ca2+ transporting epithelia. These data suggest that tubular structures inside this MF platform can be used as a suitable model to understand the molecular and pharmacological basis of calcium phosphate stone formation in the epithelial or other similar cellular micro environments.

‣ PcG-Mediated Higher-Order Chromatin Structures Modulate Replication Programs at the Drosophila BX-C

Lo Sardo, Federica; Lanzuolo, Chiara; Comoglio, Federico; De Bardi, Marco; Paro, Renato; Orlando, Valerio
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
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Polycomb group proteins (PcG) exert conserved epigenetic functions that convey maintenance of repressed transcriptional states, via post-translational histone modifications and high order structure formation. During S-phase, in order to preserve cell identity, in addition to DNA information, PcG-chromatin-mediated epigenetic signatures need to be duplicated requiring a tight coordination between PcG proteins and replication programs. However, the interconnection between replication timing control and PcG functions remains unknown. Using Drosophila embryonic cell lines, we find that, while presence of specific PcG complexes and underlying transcription state are not the sole determinants of cellular replication timing, PcG-mediated higher-order structures appear to dictate the timing of replication and maintenance of the silenced state. Using published datasets we show that PRC1, PRC2, and PhoRC complexes differently correlate with replication timing of their targets. In the fully repressed BX-C, loss of function experiments revealed a synergistic role for PcG proteins in the maintenance of replication programs through the mediation of higher-order structures. Accordingly, replication timing analysis performed on two Drosophila cell lines differing for BX-C gene expression states...

‣ In vivo three-photon microscopy of subcortical structures within an intact mouse brain

Horton, Nicholas G.; Wang, Ke; Kobat, Demirhan; Clark, Catharine G.; Wise, Frank W.; Schaffer, Chris B.; Xu, Chris
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Two-photon fluorescence microscopy (2PM)1 enables scientists in various fields including neuroscience2,3, embryology4, and oncology5 to visualize in vivo and ex vivo tissue morphology and physiology at a cellular level deep within scattering tissue. However, tissue scattering limits the maximum imaging depth of 2PM within the mouse brain to the cortical layer, and imaging subcortical structures currently requires the removal of overlying brain tissue3 or the insertion of optical probes6,7. Here we demonstrate non-invasive, high resolution, in vivo imaging of subcortical structures within an intact mouse brain using three-photon fluorescence microscopy (3PM) at a spectral excitation window of 1,700 nm. Vascular structures as well as red fluorescent protein (RFP)-labeled neurons within the mouse hippocampus are imaged. The combination of the long excitation wavelength and the higher order nonlinear excitation overcomes the limitations of 2PM, enabling biological investigations to take place at greater depth within tissue.

‣ Palladin regulation of the actin structures needed for cancer invasion

Najm, Paul; El-Sibai, Mirvat
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Português
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Cell migration and invasion involve the formation of cell adhesion structures as well as the dynamic and spatial regulation of the cytoskeleton. The adhesive structures known as podosomes and invadopodia share a common role in cell motility, adhesion, and invasion, and form when the plasma membrane of motile cells undergoes highly regulated protrusions. Palladin, a molecular scaffold, co-localizes with actin-rich structures where it plays a role in their assembly and maintenance in a wide variety of cell lines. Palladin regulates actin cytoskeleton organization as well as cell adhesion formation. Moreover, palladin contributes to the invasive nature of cancer metastatic cells by regulating invadopodia formation. Palladin seems to regulate podosome and invodopodia formation through Rho GTPases, which are known as key players in coordinating the cellular responses required for cell migration and metastasis.