An overview of the focus of the International Gap Junction Conference 2017 and Future Perspectives

n/

ENVIRONMENTAL QUALITY, ENVIRONMENTAL REGULATION AND THE STRUCTURE OF ANIMAL AGRICULTURE

Environmental Economics and Policy,

Connexin communication compartments and wound repair in epithelial tissue

Epithelial tissues line the lumen of tracts and ducts connecting to the external environment. They are critical in forming an interface between the internal and external environment and, following assault from environmental factors and pathogens, they must rapidly repair to maintain cellular homeostasis. These tissue networks, that range from a single cell layer, such as in airway epithelium, to highly stratified and differentiated epithelial surfaces, such as the epidermis, are held together by a junctional nexus of proteins including adherens, tight and gap junctions, often forming unique and localised communication compartments activated for localised tissue repair. This review focuses on the dynamic changes that occur in connexins, the constituent proteins of the intercellular gap junction channel, during wound-healing processes and in localised inflammation, with an emphasis on the lung and skin. Current developments in targeting connexins as corrective therapies to improve wound closure and resolve localised inflammation are also discussed. Finally, we consider the emergence of the zebrafish as a concerted whole-animal model to study, visualise and track the events of wound repair and regeneration in real-time living model systems

New insights into pulmonary hypertension: a role for connexin-mediated signalling

Pulmonary hypertension is a serious clinical condition characterised by increased pulmonary arterial pressure. This can lead to right ventricular failure which can be fatal. Connexins are gap junction-forming membrane proteins which serve to exchange small molecules of less than 1 kD between cells. Connexins can also form hemi-channels connecting the intracellular and extracellular environments. Hemi-channels can mediate adenosine triphosphate release and are involved in autocrine and paracrine signalling. Recently, our group and others have identified evidence that connexin-mediated signalling may be involved in the pathogenesis of pulmonary hypertension. In this review, we discuss the evidence that dysregulated connexin-mediated signalling is associated with pulmonary hypertension

Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

Energy filtering has been suggested by many authors as a means to improve thermoelectric properties. The idea is to filter away low-energy charge carriers in order to increase Seebeck coefficient without compromising electronic conductivity. This concept was investigated in the present paper for a specific material (ZnSb) by a combination of first-principles atomic-scale calculations, Boltzmann transport theory, and experimental studies of the same system. The potential of filtering in this material was first quantified, and it was as an example found that the power factor could be enhanced by an order of magnitude when the filter barrier height was 0.5~eV. Measured values of the Hall carrier concentration in bulk ZnSb were then used to calibrate the transport calculations, and nanostructured ZnSb with average grain size around 70~nm was processed to achieve filtering as suggested previously in the literature. Various scattering mechanisms were employed in the transport calculations and compared with the measured transport properties in nanostructured ZnSb as a function of temperature. Reasonable correspondence between theory and experiment could be achieved when a combination of constant lifetime scattering and energy filtering with a 0.25~eV barrier was employed. However, the difference between bulk and nanostructured samples was not sufficient to justify the introduction of an energy filtering mechanism. The reasons for this and possibilities to achieve filtering were discussed in the paper

Connexins and the epithelial tissue barrier: a focus on Connexin 26

Epithelial tissue responds rapidly to environmental triggers and is constantly renewed. This tissue is also highly accessible for therapeutic targeting. This review highlights the role of connexin mediated communication in avascular epithelial tissue. These proteins form communication conduits with the extracellular space (hemichannels) and between neighboring cells (gap junctions). Regulated exchange of small metabolites less than 1kDa aide the co-ordination of cellular activities and in spatial communication compartments segregating tissue networks. Dysregulation of connexin expression and function has profound impact on physiological processes in epithelial tissue including wound healing. Connexin 26, one of the smallest connexins, is expressed in diverse epithelial tissue and mutations in this protein are associated with hearing loss, skin and eye conditions of differing severity. The functional consequences of dysregulated connexin activity is discussed and the development of connexin targeted therapeutic strategies highlighted

Type III collagen is required for adipogenesis and actin stress fibre formation in 3T3-L1 preadipocytes

GPR56 is required for the adipogenesis of preadipocytes, and the role of one of its ligands, type III collagen (ColIII), was investigated here. ColIII expression was examined by reverse transcription quantitative polymerase chain reaction, immunoblotting and immunostaining, and its function investigated by knockdown and genome editing in 3T3-L1 cells. Adipogenesis was assessed by oil red O staining of neutral cell lipids and production of established marker and regulator proteins. siRNA-mediated knockdown significantly reduced Col3a1 transcripts, ColIII protein and lipid accumulation in 3T3-L1 differentiating cells. Col3a1−/− 3T3-L1 genome-edited cell lines abolished adipogenesis, demonstrated by a dramatic reduction in adipogenic moderators: Pparγ2 (88%) and C/ebpα (96%) as well as markers aP2 (93%) and oil red O staining (80%). Col3a1−/− 3T3-L1 cells displayed reduced cell adhesion, sustained active β-catenin and deregulation of fibronectin (Fn) and collagen (Col4a1, Col6a1) extracellular matrix gene transcripts. Col3a1−/− 3T3-L1 cells also had dramatically reduced actin stress fibres. We conclude that ColIII is required for 3T3-L1 preadipocyte adipogenesis as well as the formation of actin stress fibres. The phenotype of Col3a1−/− 3T3-L1 cells is very similar to that of Gpr56−/− 3T3-L1 cells, suggesting a functional relationship between ColIII and Gpr56 in preadipocytes

Control of protein synthesis by the reovirus S4 gene

Mammalian reoviruses have been used as a model to study the control of host cell protein synthesis following infection. The reovirus genome is composed of 10 segments of double stranded RNA each of which, with one exception, encodes a single protein. The three serotypes of the virus show marked differences in their effects on host cell protein synthesis following viral infection. Serotypes 2 and 3 give pronounced inhibition and serotype 1 has little effect. Genetic studies using intertypic reassortants have mapped this property to the S4 gene of the virus which encodes the major outer capsid polypeptide σ3. The S4 gene of serotypes 1 and 3 have been sequenced and show 96 % homology at the amino acid level. Full length cDNA clones of the S4 gene of serotypes 1 and 3 (S4-1 and S4-3) were used to develop in vitro and in vivo assay systems to study the mechanism underlying the differential effects on host cell protein synthesis of the corresponding σ3 proteins. The ability of σ3 to inhibit host cell protein synthesis was investigated in two in vitro translation systems: the rabbit reticulocyte lysate system and S-10 cell extracts prepared from uninfected and type 1 and type 3 infected L-cells. Σ3 had no effect on either the translation of B-actin when used as a marker for eukaryotic protein synthesis, or endogenous protein synthesis in either of these systems. In vivo assay systems made use of the HIVLTR/tat inducible reporter system to drive σ3 expression. The effects of σ3 on the expression of two reporter genes, chloramphenicol acetyltransferase (CAT) and B-galactosidase were investigated in transient in vivo assay systems. Σ3 expressed from S4-3 cDNA caused a significant stimulation of reporter gene expression. In contrast σ3 from S4-1 cDNA had no effect on gene expression, suggesting a domain of S4-3 was responsible for this stimulation. In an attempt to domain map this property two hybrids were constructed, one containing the S' 800 base pairs of S4-1 and the 3' 400 base pairs of S4-3 (HY-1), and the other, HY-3, the converse of this. Σ3 synthesised from HY-1 stimulated reporter gene expression whereas that from HY-3 had no effect. Σ3 was readily detected in cells transiently expressing either the parental type 3 S4 cDNA or the HY-1 hybrid by immunoprecipitation and immunofluorescence. By contrast only very small amounts of oi were detected when either the S4 cDNA from type 1 or the HY-3 were used. Pulse-chase experiments indicated that the σ3 from type 1 virus is less stable than the type 3 protein and that the domain responsible for this stability is in the 3' terminus of the S4 gene. This domain is also that shown by others to be responsible for the ability of σ3 to bind dsRNA