Kegg Pathway: Gap junction

PLoS One. 2009; 4(11): e7837
Mallick B, Ghosh Z, Chakrabarti J

Severe acute respiratory syndrome (SARS), caused by the coronavirus SARS-CoV, is an acute infectious disease with significant mortality. A typical clinical feature associated with SARS is pulmonary fibrosis and associated lung failure. In the aftermath of the SARS epidemic, although significant progress towards understanding the underlying molecular mechanism of the infection has been made, a large Gap still remains in our knowledge regarding how SARS-CoV interacts with the host cell at the onset of infection. The rapidly changing viral genome adds another variable to this equation. We have focused on a novel concept of microRNA (miRNA)-mediated host-virus interactions in bronchoalveolar stem cells (BASCs) at the onset of infection by correlating the "BASC-microRNome" with their targets within BASCs and viral genome. This work encompasses miRNA array data analysis, target prediction, and miRNA-mRNA enrichment analysis and develops a complex interaction map among disease-related factors, miRNAs, and BASCs in SARS pathway, which will provide some clues for diagnostic markers to view an overall interplay leading to disease progression. Our observation reveals the BASCs (Sca-1+ CD34+ CD45- Pecam-), a subset of Oct-4+ ACE2+ epithelial colony cells at the broncho-alveolar duct junction, to be the prime target cells of SARS-CoV infection. Upregulated BASC miRNAs-17*, -574-5p, and -214 are co-opted by SARS-CoV to suppress its own replication and evade immune elimination until successful transmission takes place. Viral Nucleocapsid and Spike protein targets seem to co-opt downregulated miR-223 and miR-98 respectively within BASCs to control the various stages of BASC differentiation, activation of inflammatory chemokines, and downregulation of ACE2. All these effectively accounts for a successful viral transmission and replication within BASCs causing continued deterioration of lung tissues and apparent loss of capacity for lung repair. Overall, this investigation reveals another mode of exploitation of cellular miRNA machinery by virus to their own advantage.

Reprod Domest Anim. 2009 Nov 12;
Romek M, Karasinski J

Contents The aim of this study was to quantify the number and size of connexin43 (Cx43) Gap junctions in the circular and longitudinal layers of myometrium of the non-pregnant pig. We developed a novel approach to measure the mean surface area (), numerical density (N(v)) and surface density (S(v)) of Gap junctions using confocal microscopy and stereological analysis. Immunolabelled Cx43 Gap junctions were measured in the subendometrial and deep regions of the circular layer and in the longitudinal layer of the myometrium of pre-pubertal pig and mature pig at pre-ovulatory and secretory stages of the oestrous cycle. In the circular subendometrial region, all investigated stereological parameters of Cx43 Gap junctions (, N(v) and S(v)) were significantly higher (p < 0.05) than those of the circular deep region and the longitudinal layer in all three groups of animals. These results indicate the large-scale heterogeneity of the number and size of Cx43 Gap junctions across the myometrium in non-pregnant pig and emphasize the existence of functional diversity among myometrial cells.

Leuk Res. 2009 Nov 10;
Liu Y, Zhang X, Li ZJ, Chen XH

Gap junction intercellular communication (GJIC) among bone marrow stromal cells (BMSCs) most frequently occurs through a channel composed of connexin43 (Cx43). Dysregulation of connexin expression is believed to have a role in carcinogenesis. In earlier work, we found that in acute leukemia BMSCs, expression of Cx43 and functioning GJIC declined. However, there has been no evaluation of whether GJIC in BMSCs in complete remission (CR) post-chemotherapy is different from GJIC pre-chemotherapy. We studied Cx43 expression and tested GJIC function in human bone marrow cultures under different physiological and pathological conditions. To assay Cx43 expression we used immunocytochemistry, laser scan confocal microscopy (LSCM), flow cytometry and RT-PCR. The results showed that the expression level of Cx43 and its mRNA in acute leukemia BMSCs post-chemotherapy was significantly higher and similar to normal levels than in primary acute leukemia BMSCs (p<0.01). Functional tests in cultures using dye transfer and fluorescence recovery after photobleaching (FRAP) assays showed that the function of GJIC in acute leukemia BMSCs was significantly improved following effective chemotherapy. Our findings suggest Cx43 and GJIC might be involved in the courses of occurrence, development and termination of acute leukemia, and effective chemotherapy could improve Cx43 expression and GJIC function that were dysfunctional prior to treatment.

Nano Lett. 2009 Nov 12;
Chen X, Yeganeh S, Qin L, Li S, Xue C, Braunschweig AB, Schatz GC, Ratner MA, Mirkin CA

We report a simple and reproducible method for fabricating heterometallic nanoGaps, which are made of two different metal nanorods separated by a nanometer-sized Gap. The method is based upon on-wire lithography, which is a chemically enabled technique used to synthesize a wide variety of nanowire-based structures (e.g., nanoGaps and disk arrays). This method can be used to fabricate pairs of metallic electrodes, which exhibit distinct work functions and are separated by Gaps as small as 2 nm. Furthermore, we demonstrate that a symmetric thiol-terminated molecule can be assembled into such heterometallic nanoGaps to form molecular transport junctions (MTJs) that exhibit molecular diode behavior. Theoretical calculations demonstrate that the coupling strength between gold and sulfur (Au-S) is 2.5 times stronger than that of Pt-S. In addition, the structures form Raman hot spots in the Gap, allowing the spectroscopic characterization of the molecules that make up the MTJs.

Methods Mol Biol. 2010; 585: 313-34
Langlois S, Churko JM, Laird DW

The epidermis is a complex tissue composed principally of differentiated keratinocytes that form a keratinized stratified squamous epithelium. The Gap junction proteins, connexins (Cx), are differentially expressed throughout the stratified layers of the epidermis and their exquisite regulation appears to govern the delicate balance between cell proliferation and differentiation in normal skin homeostasis and in wound healing. In the last 10 years, germ line mutations in the genes encoding five connexin family members have been linked to various types of skin diseases that appear to offset the balance between keratinocyte differentiation and proliferation. Consequently, in order to determine how these connexin gene mutations manifest as skin disease, disease-linked mutants must be expressed in 3D organotypic epidermis reference models that attempt to mimic the human condition. Given the complexity of organotypic epidermis, confocal optical and biochemical dissection of connexin or disease-linked connexin mutants within the regenerated epidermal layer is required. The procedures necessary to assess the architectural characteristics of genetically modified organotypic epidermis and its state of differentiation will be described in this chapter.

Methods Mol Biol. 2010; 584: 211-28
Wong RC, Pébay A

Gap junctional intercellular communication (GJIC) has been described in different cell types including stem cells and has been involved in different biological events. GJIC is required for mouse embryonic stem cell maintenance and proliferation, and various studies suggest that functional GJIC is a common characteristic of human embryonic stem cells (hESC) maintained in different culture conditions. This chapter introduces methods to study Gap junctions in hESC, from expression of Gap junction proteins to functional study of GJIC in hESC proliferation, apoptosis, colony growth, and pluripotency.

G Ital Dermatol Venereol. 2009 Dec; 144(6): 689-700
Jensen JM, Proksch E

The skin provides an effective barrier between the organism and the environment, preventing the invasion of pathogens and fending off chemical and physical assaults, as well as the unregulated loss of water and solutes. In this review we provide an overview of several components of the physical barrier, as well as how barrier function is regulated and altered in association with dermatoses. The physical barrier localized primarily in the stratum corneum (SC) and consists of protein-enriched cells (corneocytes with cornified envelope and cytoskeletal elements, as well as corneodesmosomes) and lipid-enriched intercellular domains. The nucleated epidermis, with its tight, Gap and adherens junctions, additional desmosomes and cytoskeletal elements, also contributes to the barrier. Lipids are synthesized in the keratinocytes during epidermal differentiation and are then extruded into the extracellular domains, where they form lipid-enriched extracellular layers. The cornified cell envelope, a robust protein/lipid polymer structure, is located below the cytoplasmic membrane on the exterior of the corneocytes. Ceramides A and B, forming the backbone for the subsequent addition of free ceramides, free fatty acids and cholesterol in the SC, are covalently bound to cornified envelope proteins. Filaggrin is cross-linked to the cornified envelope and aggregates keratin filaments into macrofibrils. Cytokines, cAMP and calcium influence the formation and maintenance of barrier function. Changes in lipid composition and epidermal differentiation lead to a disturbed skin barrier, which allows the entry of environmental allergens, immunological reaction and inflammation in atopic dermatitis. A disturbed skin barrier is an important component in the pathogenesis of contact dermatitis, ichthyosis, psoriasis, and atopic dermatitis.

Invest Ophthalmol Vis Sci. 2009 Nov 11;
Kimura K, Nishida T

Purpose: Fibroblasts in the corneal stroma communicate with each other via Gap junctions and form a three-dimensional network structure. The proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) down-regulates the Gap-junction protein connexin43 (Cx43) and thereby inhibits Gap-junctional intercellular communication (GJIC) in corneal fibroblasts. We have now examined the role of the ubiquitin-proteasome system in the TNF-alpha-induced degradation of Cx43 in these cells. Methods: Human corneal fibroblasts were cultured with TNF-alpha in the absence or presence of the proteasome inhibitor MG132. The expression of Cx43 was detected by immunofluorescence and immunoblot analyses. GJIC was monitored by observing the intercellular diffusion of the fluorescent dye Lucifer yellow. The ubiquitination of Cx43 was evaluated by immunoprecipitation and immunoblot analysis. Results: TNF-alpha induced a decrease both in the amount of Cx43 as detected by immunoblot analysis and in the extent of specific staining for this protein as revealed by immunofluorescence analysis in corneal fibroblasts. These effects of TNF-alpha were inhibited by MG132. MG132 also attenuated the TNF-alpha-induced inhibition of GJIC in these cells. In addition, TNF-alpha induced the ubiquitination of Cx43 in corneal fibroblasts. Conclusions: The ubiquitin-proteasome pathway contributes to the degradation of Cx43 and inhibition of GJIC induced by TNF-alpha in corneal fibroblasts. The ubiquitin-proteasome system may thus play an important role in the disruption of corneal homeostasis associated with corneal inflammation.

Med Hypotheses. 2009 Nov 7;
Mitterauer BJ

Astrocytes interconnected via Gap junctions build an astrocytic syncytium. Gap junctions are composed of connexin proteins that are activated by substances of the neuronal system. It is hypothesized that disorders in the astrocytic syncytium may represent a main component of the pathophysiology of depression, called syncytiopathy. If the expression of connexin proteins is downregulated, a compensatory upregulation of astrocytic receptors may occur leading to an overproduction of these. Such an excess of astrocytic receptors exerts an imbalance of synaptic neurotransmission, because of a relative lack of neurotransmitters for the occupancy of astrocytic receptors so that neurotransmission is protracted. This delay of information processing may be responsible for the main symptoms of depression. In addition, the downregulation of connexin expression may also lead to an incomplete syncytium formation, responsible for memory impairment in severe depression. Finally, general approaches for testing the hypothesis are outlined.

Cell Commun Adhes. 2009 Nov; 16(4): 39
Lampe PD, Simon AM, Boitano S, Burt JM

Curr Eye Res. 2009 Jun; 34(6): 454-65
D'hondt C, Ponsaerts R, Srinivas SP, Vereecke J, Himpens B

PURPOSE: Mechanical stimulation induces intercellular Ca(2 +) waves in the corneal endothelium. The extent of the wave propagation is dependent on the activity of Gap junctions, hemichannels, and ectonucleotidases. To further establish the use of a cell culture model to investigate intercellular communication, in this study, we have characterized the changes in the Ca(2 +) wave propagation in bovine corneal endothelial cells with prolonged time in culture. MATERIALS AND METHODS: Freshly isolated BCEC were cultured for a short term (8 to 14 days; referred to as "short term") and a long term (21 to 30 days; referred to as "long term"). Cell surface area and size were measured by confocal microscopy and flow cytometry, respectively. Calcium wave propagation was assayed by imaging spread of the Ca(2 +) waves elicited by mechanical stimulation. ATP release was assayed using Luciferin-Luciferase bioluminescence technique. RESULTS: Cells cultured for a long term showed larger surface area and size compared to those cultured for a short term, but a reduced spread of the Ca(2 +) wave. Exposure to exogenous apyrases, which can rapidly hydrolyze extracellular ATP, reduced the spread of the Ca(2 +) wave in both groups. The fractional decrease, however, was smaller in cells cultured for a long term. Exposure to ARL-67156 to inhibit the ectonucleotidases led to a larger enhancement of the active area in cells cultured for a long term. However, the active areas of the two groups were not significantly different in the presence of the drug. Furthermore, ATP release in response to mechanical stimulation was lower in cells cultured for a long term in the absence of ARL-67156 but not in its presence. CONCLUSIONS: BCEC cultured for a long term show an increase in cell surface area and cell size similar to the effect of aging in human corneas. Moreover, the cells cultured for a long term showed a reduced ATP-dependent paracrine intercellular communication, largely due to an increase in the activity of the ectonucleotidases.

J Hazard Mater. 2009 Oct 13;
Yang X, Ma F, Li K, Guo Y, Hu J, Li W, Huo M, Guo Y

Titania nanocomposite codoped with metallic silver and vanadium oxide was prepared by a one-step sol-gel-solvothermal method in the presence of a triblock copolymer surfactant (P123). The resulting Ag/V-TiO(2) three-component junction system exhibited an anatase/rutile (weight ratio of 73.8:26.2) mixed phase structure, narrower band Gap (2.25eV), and extremely small particle sizes (ca. 12nm) with metallic Ag particles well distributed on the surface of the composite. The Ag/V-TiO(2) nanocomposite was used as the visible- and UV-light-driven photocatalyst to degrade dyes rhodamine B (RB) and coomassie brilliant blue G-250 (CBB) in an aqueous solution. At 1.8% Ag and 4.9% V doping, the Ag/V-TiO(2) system exhibited the highest visible- as well as UV-light photocatalytic activity; additionally, the activity of the three-component system exceeded that of Degussa P25, pure TiO(2), single-doped TiO(2) system (Ag/TiO(2) or V-TiO(2)) as well as P123-free-Ag/V-TiO(2) codoped system. The reasons for this enhanced photocatalytic activity were revealed.

FEBS J. 2009 Nov 6;
Imtiaz MS, von der Weid PY, van Helden DF

Entrained oscillations in Ca(2+) underlie many biological pacemaking phenomena. In this article, we review a long-range signaling mechanism in smooth muscle that results in global outcomes of local interactions. Our results are derived from studies of the following: (a) slow-wave depolarizations that underlie rhythmic contractions of gastric smooth muscle; and (b) membrane depolarizations that drive rhythmic contractions of lymphatic smooth muscle. The main feature of this signaling mechanism is a coupled oscillator-based synchronization of Ca(2+) oscillations across cells that drives membrane potential changes and causes coordinated contractions. The key elements of this mechanism are as follows: (a) the Ca(2+) release-refill cycle of endoplasmic reticulum Ca(2+) stores; (b) Ca(2+)-dependent modulation of membrane currents; (c) voltage-dependent modulation of Ca(2+) store release; and (d) cell-cell coupling through Gap junctions or other mechanisms. In this mechanism, Ca(2+) stores alter the frequency of adjacent stores through voltage-dependent modulation of store release. This electrochemical coupling is many orders of magnitude stronger than the coupling through diffusion of Ca(2+) or inositol 1,4,5-trisphosphate, and thus provides an effective means of long-range signaling.

FEBS J. 2009 Nov 6;
Yamashita M

Increases in intracellular [Ca(2+)] occur synchronously between cells in the neuroepithelium. If neuroepithelial cells were capable of generating action potentials synchronized by Gap junctions (direct current electrical coupling), the influx of Ca(2+) through voltage-activated Ca(2+) channels would lead to a synchronous increase in intracellular [Ca(2+)]. However, no action potential is generated in neuroepithelial cells, and the [Ca(2+)] increase is instead produced by the release of Ca(2+) from intracellular Ca(2+) stores. Recently, synchronous fluctuations in the membrane potential of Ca(2+) stores were recorded using an organelle-specific voltage-sensitive dye. On the basis of these recordings, a capacitative [alternating current (AC)] electrical coupling model for the synchronization of voltage fluctuations of Ca(2+) store potential was proposed [Yamashita M (2006) FEBS Lett580, 4979-4983; Yamashita M (2008) FEBS J275, 4022-4032]. Ca(2+) efflux from the Ca(2+) store and K(+) counterinflux into the store cause alternating voltage changes across the store membrane, and the voltage fluctuation induces ACs. In cases where the store membrane is closely apposed to the plasma membrane and the cells are tightly packed, which is true of neuroepithelial cells, the voltage fluctuation of the store membrane is synchronized between the cells by the AC currents through the series capacitance of these membranes. This article provides a short review of the model and its relationship to the structural organization of the Ca(2+) store. This is followed by a discussion of how the mode of synchronization of [Ca(2+)] increase may change during central nervous system development and new molecular insights into the synchronicity of [Ca(2+)] increase.

Nat Nanotechnol. 2009 Nov 5;
Bhabra G, Sood A, Fisher B, Cartwright L, Saunders M, Evans WH, Surprenant A, Lopez-Castejon G, Mann S, Davis SA, Hails LA, Ingham E, Verkade P, Lane J, Heesom K, Newson R, Case CP

The increasing use of nanoparticles in medicine has raised concerns over their ability to gain access to privileged sites in the body. Here, we show that cobalt-chromium nanoparticles (29.5 +/- 6.3 nm in diameter) can damage human fibroblast cells across an intact cellular barrier without having to cross the barrier. The damage is mediated by a novel mechanism involving transmission of purine nucleotides (such as ATP) and intercellular signalling within the barrier through connexin Gap junctions or hemichannels and pannexin channels. The outcome, which includes DNA damage without significant cell death, is different from that observed in cells subjected to direct exposure to nanoparticles. Our results suggest the importance of indirect effects when evaluating the safety of nanoparticles. The potential damage to tissues located behind cellular barriers needs to be considered when using nanoparticles for targeting diseased states.

Am J Physiol Gastrointest Liver Physiol. 2009 Nov 5;
Goyal RK, Chaudhury A

How nerves transmit their signals to regulate activity of smooth muscle is of fundamental importance to autonomic and enteric physiology, clinical medicine and therapeutics. A traditional view of neurotransmission to smooth muscles has been that motor nerve varicosities release neurotransmitters that act on receptors on smooth muscles to cause their contraction or relaxation via electromechanical and phamacomechanical signaling pathways in the smooth muscle. In recent years, an old hypothesis that certain interstitial cells of Cajal (ICC) may transduce neural signals to smooth muscle cells has been resurrected. This later hypothesis is based on indirect evidence of closer proximity and presence of synapses between the nerve varicosities and ICC, Gap junctions between ICC and smooth muscles and presence of receptors and signaling pathways for the neurotransmitters and ICC. This indirect evidence is at best circumstantial. The direct evidence is based on the reports of loss of neurotransmission in mutant animals lacking ICC due to c-kit receptor deficiency. However, a critical analysis of the recent data show that animals lacking ICC have normal cholinergic and purinergic neurotransmission and tachykinergic neurotransmission is actually increased. The status of nitrergic neurotransmission in in c-kit deficient animals has been controversial. However, reports suggest that 1) nitrergic neurotransmission in the internal anal sphincter does not require ICC. 2) in vivo phenotype of ICC deficiency does not resemble nNOS deficiency. 3) Most recent report in this issue of the Journal concludes that impaired nitrergic neurotransmission may be due to smooth muscle defects associated with c-kit receptor deficiency.

Handb Clin Neurol. 2009; 95: 361-72
Smith CU

Although the chemical study of the nervous system dates back well into the 19th century, molecular biology and especially molecular neurobiology only began to be established in the second half of the 20th century. This chapter reviews their impact on clinical neuroscience during the 50 years since Watson and Crick published their seminal paper. After a short review of the part played by F.O. Schmitt in establishing molecular neuroscience the chapter outlines work that led to a detailed understanding of the biochemical structure and function of nerve cell membranes and their embedded channel proteins, receptors, and other molecules. The chapter then turns to the numerous pathologies that result from disorders of these elements: the various channel and Gap-junction pathologies. The chapter continues with a discussion of some of the diseases caused by defective DNA, especially the trinucleotide repeat expansion diseases (TREDs) and ends with a short account of the development of molecular approaches to prion diseases, myasthenia gravis, and the neurodegenerative diseases of old age. Francis Bacon said long ago that "knowledge is power." The hope is that increasing molecular knowledge will help cure some of the human suffering seen in the neurological ward and clinic.

Neuron Glia Biol. 2009 Nov 6; 1-9
Suadicani SO, Cherkas PS, Zuckerman J, Smith DN, Spray DC, Hanani M

Astrocytes communicate with neurons, endothelial and other glial cells through transmission of intercellular calcium signals. Satellite glial cells (SGCs) in sensory ganglia share several properties with astrocytes, but whether this type of communication occurs between SGCs and sensory neurons has not been explored. In the present work we used cultured neurons and SGCs from mouse trigeminal ganglia to address this question. Focal electrical or mechanical stimulation of single neurons in trigeminal ganglion cultures increased intracellular calcium concentration in these cells and triggered calcium elevations in adjacent glial cells. Similar to neurons, SGCs responded to mechanical stimulation with increase in cytosolic calcium that spread to the adjacent neuron and neighboring glial cells. Calcium signaling from SGCs to neurons and among SGCs was diminished in the presence of the broad-spectrum P2 receptor antagonist suramin (50 muM) or in the presence of the Gap junction blocker carbenoxolone (100 muM), whereas signaling from neurons to SGCs was reduced by suramin, but not by carbenoxolone. Following induction of submandibular inflammation by Complete Freund's Adjuvant injection, the amplitude of signaling among SGCs and from SGCs to neuron was increased, whereas the amplitude from neuron to SGCs was reduced. These results indicate for the first time the presence of bidirectional calcium signaling between neurons and SGCs in sensory ganglia cultures, which is mediated by the activation of purinergic P2 receptors, and to some extent by Gap junctions. Furthermore, the results indicate that not only sensory neurons, but also SGCs release ATP. This form of intercellular calcium signaling likely plays key roles in the modulation of neuronal activity within sensory ganglia in normal and pathological states.

Langmuir. 2009 Nov 5;
Fu N, Wu Y, Jin Z, Lu G

Bicrystalline dehydrated nanoribbon (DNR) with alternate structure of TiO(2)(B) and anatase has been prepared by a short-time annealing method. It is photoactive for photocatalytic H(2) evolution from water in the visible region sensitized by a novel heteropoly blue sensitizer. The effects of annealing temperature and time on the DNR phase transformation process have been investigated. These results reveal that the nanocavity structure of TiO(2)(B) exhibits a narrow band Gap and improves its absorbance coefficient in the visible region. The alternate structures of TiO(2)(B) and anatase improve interfacial electron separation and transfer. Compared with normal phase junction, the smoothing alternate joints in the band structure of DNR-600-30 provide an effective route for the movement of holes and electrons. This unique alternate bicrystalline structure has a significant advantage on its applications in photocatalysis and nanodevices.

Cell Mol Bioeng. 2009 Mar 1; 2(1): 144-155
Yu D, Buibas M, Chow SK, Lee IY, Singer Z, Silva GA

Retinal Müller glial cells, in addition to providing homeostatic support to retinal neurons, have been shown to engage in modulation of neuronal activity and regulate vasomotor responses in the retina, among other functions. Calcium-mediated signaling in Müller cells has been implicated to play a significant role in the intracellular and intercellular interactions necessary to carry out these functions. Although the basic molecular mechanisms of calcium signaling in Müller cells have been described, the dynamics of calcium responses in Müller cells have not been fully explored. Here, we provide a quantitative characterization of calcium signaling in an in vitro model of Müller cell signaling using the rMC-1 cell line, a well-established line developed from rat Müller cells. rMC-1 cells displayed robust intracellular calcium transients and the capacity to support calcium transient-mediated intercellular calcium waves with signaling dynamics similar to that reported for Müller cells in in situ retinal preparations. Furthermore, pharmacological perturbations of intracellular calcium transients with thapsigargin and intercellular calcium waves with purinergic receptor antagonists and Gap junction blockers (PPADS and FFA, respectively) suggest that the molecular mechanisms that underlie calcium signaling in rMC-1 cells has been conserved with those of Müller cells. This model provides a robust in vitro system for investigating specific mechanistic hypotheses of intra- and intercellular calcium signaling in Müller cells.