scholarly journals Anne Elizabeth Warner. 25 August 1940—16 May 2012

2021 ◽  
Author(s):  
Sarah Guthrie
Keyword(s):  
Gap Junctions ◽  
Marine Biology ◽  
Multiple Scales ◽  
Cell Interaction ◽  
Early Embryo ◽  
Muscle Physiology ◽  
Gap Junction Communication ◽  
Junctional Communication ◽  
High Standards ◽  
Biology Laboratory

Anne Warner applied physiological techniques to developmental biology, elucidating the mechanisms of cell interaction and communication that pattern the early embryo. Through her determination and passion for science, she contributed crucial discoveries in the fields of muscle physiology, cellular differentiation and gap junction communication. She spent the majority of her career at University College London, which became her intellectual home and where she acquired a Royal Society Foulerton Research Professorship, becoming a highly respected and influential figure. In her work on gap junctions, Anne was the first to show that embryonic development and patterning required gap junctions, and that the restriction of junctional communication between cells played a key role in tissue differentiation. Anne excelled in her breadth of vision across research and its interdisciplinary possibilities. In 1998 she established the CoMPLEX Centre for systems biology at UCL, bringing her own group together with scientists from across the STEM subjects to build testable mathematical models of biological systems across multiple scales. Indefatigable in her capacity for leadership and committee work, she assumed an eclectic set of roles across a large span of research organizations and professional societies, and had a lifelong association with the Physiological Society. In 1984 she founded the Microelectrodes course at the Plymouth Marine Biology Laboratory, which has trained generations in the art of electrophysiology and still continues today. With uncompromisingly high standards, she inspired her mentees to be ambitious and fearless, and established postdoctoral fellowships to help the young scientists who followed after her.

scholarly journals Role of gap junctions during early embryo development

Reproduction ◽  
2005 ◽  
Vol 129 (2) ◽  
pp. 129-135 ◽  
Author(s):  
Franchesca D Houghton
Keyword(s):  
Gap Junctions ◽  
Embryo Development ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Early Embryo ◽  
Preimplantation Development ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional

Gap junctional communication plays a central role in the maintenance of cellular homeostasis by allowing the passage of small molecules between adjacent cells. Gap junctions are composed of a family of proteins termed connexins. During preimplantation development several connexin proteins are expressed and assembled into gap junctions in the plasma membrane at compaction but the functional significance of connexin diversity remains controversial. Although, many of the connexin genes have been disrupted using homologous recombination in embryonic stem cells to obtain unique phenotypes, none of these studies has demonstrated a specific role for connexins during preimplantation development in the null mutants. This review surveys evidence for the involvement of gap junctional communication during embryo development highlighting discrepancies in the literature. Although some evidence suggests that gap junctions may be dispensable during preimplantation development this is difficult to envisage particularly for the process of cavitation and the maintenance of homeostasis between the differentiated trophectoderm cells and the pluripotent inner cell mass cells of the blastocyst.

scholarly journals Tyrosine phosphorylation of the gap junction protein connexin43 is required for the pp60v-src-induced inhibition of communication.

1990 ◽  
Vol 1 (13) ◽  
pp. 989-1002 ◽  
Author(s):  
K I Swenson ◽  
H Piwnica-Worms ◽  
H McNamee ◽  
D L Paul
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Kinase ◽  
Expression System ◽  
Functional Expression ◽  
Gap Junction Communication ◽  
Junctional Communication ◽  
Junction Protein ◽  
Gap Junction Protein

Gap junction communication in some cells has been shown to be inhibited by pp60v-src, a protein tyrosine kinase encoded by the viral oncogene v-src. The gap junction protein connexin43 (Cx43) has been shown to be phosphorylated on serine in the absence of pp60v-src and on both serine and tyrosine in cells expressing pp60v-src. However, it is not known if the effect of v-src expression on communication results directly from tyrosine phosphorylation of the Cx43 or indirectly, for example, by activation of other second-messenger systems. In addition, the effect of v-src expression on communication based on other connexins has not been examined. We have used a functional expression system consisting of paired Xenopus oocytes to examine the effect of v-src expression on the regulation of communication by gap junctions comprised of different connexins. Expression of pp60v-src completely blocked the communication induced by Cx43 but had only a modest effect on communication induced by connexin32 (Cx32). Phosphoamino acid analysis showed that pp60v-src induced tyrosine phosphorylation of Cx43, but not Cx32. A mutation replacing tyrosine 265 of Cx43 with phenylalanine abolished both the inhibition of communication and the tyrosine phosphorylation induced by pp60v-src without affecting the ability of this protein to form gap junctions. These data show that the effect of pp60v-src on gap junctional communication is connexin specific and that the inhibition of Cx43-mediated junctional communication by pp60v-src requires tyrosine phosphorylation of Cx43.

Phosphorylation of connexin43 gap junction protein in uninfected and Rous sarcoma virus-transformed mammalian fibroblasts

1990 ◽  
Vol 10 (4) ◽  
pp. 1754-1763
Author(s):  
D S Crow ◽  
E C Beyer ◽  
D L Paul ◽  
S S Kobe ◽  
A F Lau
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Rous Sarcoma Virus ◽  
Gap Junctional Communication ◽  
Rous Sarcoma ◽  
Junctional Communication ◽  
Junction Protein ◽  
Sarcoma Virus ◽  
Gap Junction Protein ◽  
Gap Junctional

Gap junctions are membrane channels that permit the interchange of ions and other low-molecular-weight molecules between adjacent cells. Rous sarcoma virus (RSV)-induced transformation is marked by an early and profound disruption of gap-junctional communication, suggesting that these membrane structures may serve as sites of pp60v-src action. We have begun an investigation of this possibility by identifying and characterizing putative proteins involved in junctional communication in fibroblasts, the major cell type currently used to study RSV-induced transformation. We found that uninfected mammalian fibroblasts do not appear to contain RNA or protein related to connexin32, the major rat liver gap junction protein. In contrast, vole and mouse fibroblasts contained a homologous 3.0-kilobase RNA similar in size to the heart tissue RNA encoding the gap junction protein, connexin43. Anti-connexin43 peptide antisera specifically reacted with three proteins of approximately 43, 45 and 47 kilodaltons (kDa) from communicating fibroblasts. Gap junctions of heart cells contained predominantly 45- and 47-kDa species similar to those found in fibroblasts. Uninfected fibroblast 45- and 47-kDa proteins were phosphorylated on serine residues. Phosphatase digestions of 45- and 47-kDa proteins and pulse-chase labeling studies indicated that these proteins represented phosphorylated forms of the 43-kDa protein. Phosphorylation of connexin protein appeared to occur shortly after synthesis, followed by an equally rapid dephosphorylation. In comparison with these results, connexin43 protein in RSV-transformed fibroblasts contained both phosphotyrosine and phosphoserine. Thus, the presence of phosphotyrosine in connexin43 correlates with the loss of gap-junctional communication observed in RSV-transformed fibroblasts.

Gap Junctions and Osteoblast-like Cell Gene Expression in Response to Fluid Flow

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Michael G. Jekir ◽  
Henry J. Donahue
Keyword(s):  
Fluid Flow ◽  
Gap Junctions ◽  
Gap Junction ◽  
Bone Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Mrna Levels ◽  
Mechanical Stimuli ◽  
Junctional Communication ◽  
Osteogenic Response

Bone formation occurs in vivo in response to mechanical stimuli, but the signaling pathways involved remain unclear. The ability of bone cells to communicate with each other in the presence of an applied load may influence the overall osteogenic response. The goal of this research was to determine whether inhibiting cell-to-cell gap junctional communication between bone-forming cells would affect the ensemble cell response to an applied mechanical stimulus in vitro. In this study, we investigated the effects of controlled oscillatory fluid flow (OFF) on osteoblastic cells in the presence and the absence of a gap-junction blocker. MC3T3-E1 Clone 14 cells in a monolayer were exposed to 2h of OFF at a rate sufficient to create a shear stress of 20dynes∕cm2 at the cell surface, and changes in steady-state mRNA levels for a number of key proteins known to be involved in osteogenesis were measured. Of the five proteins investigated, mRNA levels for osteopontin (OPN) and osteocalcin were found to be significantly increased 24h postflow. These experiments were repeated in the presence of 18β-glycyrrhetinic acid (BGA), a known gap-junction blocker, to determine whether gap-junction intercellular communication is necessary for this response. We found that the increase in OPN mRNA levels is not observed in the presence of BGA, suggesting that gap junctions are involved in the signaling process. Interestingly, enzyme linked immunosorbent assay data showed that levels of secreted OPN protein increased 48h postflow and that this increase was unaffected by the presence of intact gap junctions.

scholarly journals Morphofunctional integration between skeletal myoblasts and adult cardiomyocytes in coculture is favored by direct cell-cell contacts and relaxin treatment

2005 ◽  
Vol 288 (4) ◽  
pp. C795-C804 ◽  
Author(s):  
Lucia Formigli ◽  
Fabio Francini ◽  
Alessia Tani ◽  
Roberta Squecco ◽  
Daniele Nosi ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Lucifer Yellow ◽  
Myoblast Differentiation ◽  
Cell Contact ◽  
Cx43 Expression ◽  
Gap Junctional Communication ◽  
Skeletal Myoblasts ◽  
Junctional Communication ◽  
Direct Cell ◽  
Gap Junctional

The success of cellular cardiomyoplasty, a novel therapy for the repair of postischemic myocardium, depends on the anatomical integration of the engrafted cells with the resident cardiomyocytes. Our aim was to investigate the interaction between undifferentiated mouse skeletal myoblasts (C2C12 cells) and adult rat ventricular cardiomyocytes in an in vitro coculture model. Connexin43 (Cx43) expression, Lucifer yellow microinjection, Ca2+ transient propagation, and electrophysiological analysis demonstrated that myoblasts and cardiomyocytes were coupled by functional gap junctions. We also showed that cardiomyocytes upregulated gap junctional communication and expression of Cx43 in myoblasts. This effect required direct cell-to-cell contact between the two cell types and was potentiated by treatment with relaxin, a cardiotropic hormone with potential effects on cardiac development. Analysis of the gating properties of gap junctions by dual cell patch clamping showed that the copresence of cardiomyocytes in the cultures significantly increased the transjunctional current and conductance between myoblasts. Relaxin enhanced this effect in both the myoblast-myoblast and myoblast-cardiomyocyte cell pairs, likely acting not only on gap junction formation but also on the electrical properties of the preexisting channels. Our findings suggest that myoblasts and cardiomyocytes interact actively through gap junctions and that relaxin potentiates the intercellular coupling. A potential role for gap junctional communication in favoring the intercellular exchange of regulatory molecules, including Ca2+, in the modulation of myoblast differentiation is discussed.

scholarly journals The Sleep-inducing Lipid Oleamide Deconvolutes Gap Junction Communication and Calcium Wave Transmission in Glial Cells

1997 ◽  
Vol 139 (7) ◽  
pp. 1785-1792 ◽  
Author(s):  
Xiaojun Guan ◽  
Benjamin F. Cravatt ◽  
George R. Ehring ◽  
James E. Hall ◽  
Dale L. Boger ◽  
...  
Keyword(s):  
Gap Junction ◽  
Glial Cells ◽  
Wave Transmission ◽  
Calcium Wave ◽  
Mediated Communication ◽  
Gap Junctional Communication ◽  
Gap Junction Communication ◽  
Junctional Communication ◽  
Nervous System Function ◽  
Gap Junctional

Oleamide is a sleep-inducing lipid originally isolated from the cerebrospinal fluid of sleep-deprived cats. Oleamide was found to potently and selectively inactivate gap junction–mediated communication between rat glial cells. In contrast, oleamide had no effect on mechanically stimulated calcium wave transmission in this same cell type. Other chemical compounds traditionally used as inhibitors of gap junctional communication, like heptanol and 18β-glycyrrhetinic acid, blocked not only gap junctional communication but also intercellular calcium signaling. Given the central role for intercellular small molecule and electrical signaling in central nervous system function, oleamide- induced inactivation of glial cell gap junction channels may serve to regulate communication between brain cells, and in doing so, may influence higher order neuronal events like sleep induction.

scholarly journals Topological distribution of two connexin32 antigenic sites in intact and split rodent hepatocyte gap junctions.

1988 ◽  
Vol 107 (5) ◽  
pp. 1817-1824 ◽  
Author(s):  
D A Goodenough ◽  
D L Paul ◽  
L Jesaitis
Keyword(s):  
Amino Acids ◽  
Gap Junctions ◽  
Keyhole Limpet Hemocyanin ◽  
Cell Types ◽  
Cell Interaction ◽  
Amino Acid Sequences ◽  
Membrane Topology ◽  
Cdna Clones ◽  
Cleavage Sites ◽  
Mouse Hepatocyte

The membrane topology of connexin32, a principal polypeptide of gap junctions in diverse cell types, has been studied in rat and mouse hepatocyte gap junctions using site-specific antisera raised against synthetic oligopeptides corresponding to amino acid sequences deduced from cDNA clones. Based on published hydropathicity maps and identified protease-sensitive cleavage sites, oligopeptides were synthesized corresponding to two hydrophilic domains of connexin32, one predicted to face the cytoplasm, the other predicted to be directed extracellularly. Antisera were raised to keyhole limpet hemocyanin conjugates of the oligopeptides and used to map the distribution of their antigens using indirect immunocytochemistry on isolated gap junctions. The results directly demonstrated the cytoplasmic orientation of an antigen contained within amino acids 98-124 of the connexin32 sequence. The extracellular space in intact, isolated gap junctions is too small to permit binding of antibody molecules, necessitating the experimental separation of the junctional membranes to expose their extracellular surfaces using a urea/alkali procedure. While an antigen contained within amino acids 164-189 was visualized on the extracellular surfaces of some of the separated junctional membranes, variability in the observations and in the splitting procedure left ambiguities concerning the biological relevance of the observations after the denaturing conditions necessary to separate the junctional membranes. Using a different approach, however, the antigen could be exposed in intact liver using a hypertonic disaccharide junction-splitting procedure. The period of time of antigen exposure at the cell surface appears to peak at 30 s and disappear by 2-4 min. Taken together, these data demonstrate the extracellular orientation of an antigen contained within amino acids 164-189, which may be involved in cell-cell interaction within the gap junction.

Polyamines regulate gap junction communication in connexin 43-expressing cells

2001 ◽  
Vol 357 (2) ◽  
pp. 489-495 ◽  
Author(s):  
Leonard SHORE ◽  
Pauline McLEAN ◽  
Susan K. GILMOUR ◽  
Malcolm B. HODGINS ◽  
Malcolm E. FINBOW
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Ornithine Decarboxylase ◽  
Normal Tissue ◽  
Connexin 43 ◽  
Cell Communication ◽  
Cell Types ◽  
Decarboxylase Activity ◽  
Gap Junction Communication ◽  
Different Cell Types

The control of cell–cell communication through gap junctions is thought to be crucial in normal tissue function and during various stages of tumorigenesis. However, few natural regulators of gap junctions have been found. We show here that increasing the activity of ornithine decarboxylase, or adding polyamines to the outside of cells, increases the level of gap junction communication between various epithelial cells. Conversely, reduction of ornithine decarboxylase activity decreases the level of gap junction communication. This regulation is dependent upon the expression of connexin 43 (Cx43 or Cxα1), which is a major connexin expressed in many different cell types, and involves an increase in Cx43 and its cellular re-distribution.

scholarly journals Differential phosphorylation of the gap junction protein connexin43 in junctional communication-competent and -deficient cell lines.

1990 ◽  
Vol 111 (5) ◽  
pp. 2077-2088 ◽  
Author(s):  
L S Musil ◽  
B A Cunningham ◽  
G M Edelman ◽  
D A Goodenough
Keyword(s):  
Cell Adhesion ◽  
Gap Junctions ◽  
Gap Junction ◽  
Cell Lines ◽  
Gap Junctional Communication ◽  
Competent Cells ◽  
Deficient Cell ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Cell Cell

Connexin43 is a member of the highly homologous connexin family of gap junction proteins. We have studied how connexin monomers are assembled into functional gap junction plaques by examining the biosynthesis of connexin43 in cell types that differ greatly in their ability to form functional gap junctions. Using a combination of metabolic radiolabeling and immunoprecipitation, we have shown that connexin43 is synthesized in gap junctional communication-competent cells as a 42-kD protein that is efficiently converted to a approximately 46-kD species (connexin43-P2) by the posttranslational addition of phosphate. Surprisingly, certain cell lines severely deficient in gap junctional communication and known cell-cell adhesion molecules (S180 and L929 cells) also expressed 42-kD connexin43. Connexin43 in these communication-deficient cell lines was not, however, phosphorylated to the P2 form. Conversion of S180 cells to a communication-competent phenotype by transfection with a cDNA encoding the cell-cell adhesion molecule L-CAM induced phosphorylation of connexin43 to the P2 form; conversely, blocking junctional communication in ordinarily communication-competent cells inhibited connexin43-P2 formation. Immunohistochemical localization studies indicated that only communication-competent cells accumulated connexin43 in visible gap junction plaques. Together, these results establish a strong correlation between the ability of cells to process connexin43 to the P2 form and to produce functional gap junctions. Connexin43 phosphorylation may therefore play a functional role in gap junction assembly and/or activity.

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