Cell communication, cell union, and initiation of meiosis in ciliate conjugation.
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Bioenergetics and cell communication; cell uncoupling seen as a protective mechanism in cardiac muscle.
Differences in rate of ATP resynthesis between apposing heart cells were created by dialysing 2-4-dinitrophenol (0.01-0.05 mM) into just one cell of isolated heart cell pairs. When 0.01 mM of dinitrophenol was used the junctional conductance (gj) remained unchanged for at least 8 min if cell 1 (normal) was pulsed at low rate (0.04 Hz). The increment in rate of pulsing to 4 Hz caused a fast decrease (13%) of gj within 30 sec. This change in gj was spontaneously reversed. With 0.05 mM of dinitrophenol cell uncoupling was produced if cell 1 (normal) was stimulated at 4 Hz for 25-30 sec. Despite the suppression of electrical coupling (which was not reversed within 8 min.) no contracture or signs of deterioration of the experimental conditions were found. Cell uncoupling can be seen as a protective mechanism providing opportunity to energy-depleted cells to re-establish their ATP stores.
2,4-Dinitrophenol↗
Notch signaling: control of cell communication and cell fate.
Notch is a transmembrane receptor that mediates local cell-cell communication and coordinates a signaling cascade present in all animal species studied to date. Notch signaling is used widely to determine cell fates and to regulate pattern formation; its dysfunction results in a tremendous variety of developmental defects and adult pathologies. This primer describes the mechanism of Notch signal transduction and how it is used to control the formation of biological patterns.
Animals↗
Expression of a Cx43 deletion mutant in 3T3 A31 fibroblasts prevents PDGF-induced inhibition of cell communication and suppresses cell growth.
Communication through gap junctions was first suggested to have a role in the social control of cell growth over 30 years ago. However, despite extensive experimentation, the importance of gap junctions as a general mechanism of growth control remains to be established. A number of different studies have shown that a common early response of cells in culture to polypeptide growth factors such as PDGF is a rapid and transient inhibition of cell communication suggesting that a cell may have to lose communication with its neighbors before it can undergo cell division. Here we show that 3T3 A31 fibroblasts exposed to PDGF exhibit a 50% decrease in cell communication as measured by dye transfer in the absence of significant changes in the cellular content and distribution of Cx43. Likewise, PDGF inhibited cell communication in cells transfected either with a vector which did not contain a cDNA or with an expression vector encoding full-length Cx43 fused to a c-myc tag (Cx43-M). In contrast, 3T3 A31 fibroblasts transfected with an expression construct encoding a deletion mutant of Cx43 (Cx43-256M) consisting of amino acids 1-256 of Cx43 fused to a c-myc tag maintain high levels of gap junction activity following exposure to PDGF. These results suggest that sites which trigger loss of cell communication in response to PDGF are located within amino acids 257 to 382 of the Cx43 molecule. Cells transfected with an expression vector encoding full-length Cx43 fused to a c-myc tail exhibited a reduced basal growth rate compared to both parent cells and cells transfected with a control vector but maintained a strong mitogenic response to PDGF. In contrast, both the basal growth rate and the mitogenic response to PDGF was markedly reduced in cells which expressed Cx43-256M consistent with the hypothesis that loss of cell communication is required before a cell can respond to mitogenic stimuli.
3T3 Cells↗
Quantitative evaluation of cell-to-cell communication effects in cell group class using on-chip individual-cell-based cultivation system.
Cell-to-cell communication is considered to underlie the coordinated behavior and the multicellularity of cell group class, which cannot be explained only by the knowledge of lower class of life system from molecule to individual cell, because they are determined by at least two different ways: diffusible chemical signals and their direct physical contacts. We show in this paper a new method of individual-cell-based cell observation that can estimate the role of cell-to-cell communication, diffusible chemical signals, and physical contacts as separated properties, by applying an on-chip individual-cell-based cultivation system. The exchange of stationary phase medium on isolated individual Escherichia coli from exponential phase medium and the control of physical contacts indicated that the cell-to-cell direct contact did not affect the growth rate; only the communication through diffusible signals affects the growth rates as Hill's equation manner.
Cell Communication↗
Cell Communication, Stochastic Cell Responses, and Anthocyanin Pattern in Mustard Cotyledons.
The role of intercellular signals in plant development was investigated using phytochrome-induced formation of anthocyanin in cotyledons of white mustard as a model system. The problem was approached by irradiating different subregions of the cotyledon with a microbeam. This technique was combined with in situ hybridization of chalcone synthase mRNA after irradiation of the entire cotyledon. Individual cells that exhibited all-or-none responses with a resultant stochastic, patchy pattern were examined during early stages of anthocyanin synthesis. It was demonstrated that the responses of individual cells were subsequently integrated by long-range inhibitory signals. This process led to ordered and gradually developing patterns that could be detected when final stages were analyzed at the whole-organ level. The significance of these findings is discussed in terms of efforts toward a general understanding of photomorphogenesis in plants.
Journal Article↗
Tyrosine phosphorylation of a gap junction protein correlates with inhibition of cell-to-cell communication.
Cell-to-cell communication is achieved by passage of small molecules through gap junction membrane channels. The expression of the transforming gene from Rous sarcoma virus, v-src, induces a rapid and dramatic reduction in cell-to-cell communication in cultured cells. To determine whether connexin43, a major gap junction protein expressed in fibroblasts, is a target for the v-src protein tyrosine kinase activity, we examined the phosphorylation state of connexin43 in cells expressing variants of src. Using an antipeptide serum that recognizes connexin43, we demonstrate that this protein is phosphorylated on serine and tyrosine residues in avian and mammalian cells expressing activated src proteins. Connexin43 from control cells and cells expressing nonactivated variants of the src protein was phosphorylated solely on serine residues. In lysates from v-src-transformed cells, all phosphorylated connexin43 molecules were cleared from the lysate by sequential immunoprecipitations using the phosphotyrosine antibodies, suggesting that each molecule of phosphorylated connexin43 contains both phosphoserine and phosphotyrosine. We have also examined junctional permeability in cells expressing src variants and find that loss of cell-to-cell communication correlates with tyrosine phosphorylation of connexin43.
Animals↗
Mutations of connexin32 in Charcot-Marie-Tooth disease type X interfere with cell-to-cell communication but not cell proliferation and myelin-specific gene expression.
Connexin32 (Cx32) is a gap junction protein and its mutations are responsible for X-linked Charcot-Marie-Tooth disease. We examined the functional abnormality of C6 glioma cells transfected with mutant (C53S and P172R) Cx32 genes. Nontransfected C6 did not express Cx32. Northern and Western blot analyses showed Cx32 mRNA and protein in cells with the wild-type gene as well as with the mutant Cx32 genes. An immunocytochemical study of cells with the wild-type gene showed the immunoreactive spots in the cell membrane. In cells with C53S or P172R mutant gene, however, the immunoreactivity was found in the cytoplasm. The scrape-loading method produced effective dye transfer in cells with the wild-type gene but not in those with mutant genes. A cell proliferation assay showed no differences in nontransfected cells, cells with the wild-type gene and those with the mutant genes. Messenger RNA expression for proteolipid protein did not change. These findings suggest that Cx32 gene mutation results in loss of cell-to-cell communication because of failure to incorporate Cx32 protein in the cell membrane. The mutations do not, however, interfere with cell proliferation or myelin-specific gene expression, at least myelin proteolipid protein expression in C6 glioma cells.
Blotting, Northern↗
Restoration of cell-to-cell communication in thyroid cell lines by transfection with and stable expression of the connexin-32 gene. Impact on cell proliferation and tissue-specific gene expression.
Normal thyroid epithelial cells coexpress connexin-32 and connexin-43, which form distinct gap junctions. In primary culture, connexin-43 is expressed by thyrocytes in monolayers or reorganized into follicles, whereas the expression of connexin-32 is dependent upon the reconstitution of follicles. To study the functional impact of connexin-32 gap junctions in thyroid cells, we transfected connexin-32 cDNA in two thyroid-derived communication-deficient cell lines, FRT and FRTL-5. The selected clones, which stably expressed connexin-32 at high levels and exhibited high gap junction-mediated dye-coupling, presented a reduced proliferation rate as compared with that of the corresponding wild-type FRT and FRTL-5 cells; the mean population doubling time was increased by approximately 35%. The proliferation of connexin-32-transfected FRTL-5 cells remained thyrotropin-dependent; the range of thyrotropin concentrations that stimulated growth was the same in transfected and control cells. The expression of connexin-32 led to an increase of thyroglobulin gene expression in FRTL-5 cells. The expression of two other tissue-specific proteins, thyroid transcription factor-1 and Pax-8, was unchanged. These findings provide evidence that connexin-32 gap junction-mediated cell-to-cell communication participates in the control of growth and differentiation of thyroid cells.
Animals↗
Cell-to-cell communication in the heart: structure-function correlations.
The communicating cell junctions that ensure the electrical and diffusional continuity of the intracellular space in the heart fibres can be switched from their normal conducting, or opened state, to an exceptional non-conducting, or closed state. This electrical uncoupling is observed after cell injury in the presence of Ca2+ ions in the extracellular fluid, after metabolic inhibition and in the presence of aliphatic alcohols (C6 to C9). The correlations between electrical uncoupling and gap junction morphology in the heart are briefly reviewed. A decrease of the distance between P-face particles and between the E-face pits has been found in all investigations, but the functional significance of this observation is not understood at present. A quantitatively very similar decrease of the average particle diameter (about -0.7 nm) has been measured in glutaraldehyde-fixed sheep Purkinje fibres and in unfixed, quickly frozen rat auricles that had been electrically uncoupled by three different procedures. About half of this decrease was reversible on short-term electrical recoupling (within 20 min). It is concluded that a measurable decrease of the connexon diameter correlates with electrical uncoupling.
Animals↗
Effect of various polybrominated biphenyls on cell-cell communication in cultured human teratocarcinoma cells.
Firemaster BP-6 (FM), a mixture of polybrominated biphenyls (PBB), and the congeners 2,2',4,4',5,5'-hexabromobiphenyl (245-HBB), 3,3',4,4',5,5'-hexabromobiphenyl (345-HBB), and 3,3',4,4'-tetrabromobiphenyl (34-TBB) were tested for their ability to inhibit cell-cell communication between human teratocarcinoma cells in culture. Both FM and 245-HBB were capable of inhibiting cell-cell communication in these cells, with only slight effects on cell survival. 345-HBB was highly cytotoxic, but did not show the ability to interrupt cell-cell communication. 34-TBB was moderately cytotoxic and was also ineffective at blocking cell-cell communication. The results agree with previously published findings in Chinese hamster V79 cells, and are in accordance with proposed structure-activity relationships for these compounds. Inhibition of cell-cell communication, either directly (FM and 245-HBB) or indirectly through necrosis-induced compensatory hyperplasia (345-HBB), may be involved in the promotion of hepatocellular neoplasms by these compounds.
Cell Communication↗
Short term regulation of cell-cell communication in TM3 Leydig cells. A perforated patch study.
Determination of the junctional conductance (g(j)) in TM3 Leydig cells by the dual whole cell patch clamp technique (DWCPC) shows that coupling undergoes a rapid and irreversible run down. Addition of ATP or cAMP derivatives to the pipette solution has been shown to prevent this phenomenon in several tissues, but this same treatment is unable to inhibit run down in Leydig cells. Because the run down in junctional conductance may pose serious problems to the interpretation of results, we also measured g(j) by using the double perforated patch clamp technique (DPPT). Access to the cell interior was achieved by adding 200 microgram/ml of nystatin to the pipette solution. With this method, run down in g(j) was greatly reduced, amounting to no more than 5% of the initial value. Exposure of the cells, under DWCPC or DPPT, to dibutyryl cAMP or to tumor promoting agent (TPA) led to a decrease in cell to cell communication. Staurosporine, a PKC inhibitor, increased g(j) and was able to prevent and reverse the uncoupling action of cAMP or TPA. Our results indicate that cell-cell communication in Leydig cells is down regulated by both protein kinases A and C, interacting in a complex manner.
Animals↗
Retinoids and carotenoids as inhibitors of carcinogenesis and inducers of cell-cell communication.
In cell cultures of carcinogen-initiated fibroblasts, a number of retinoids and carotenoids can reversibly inhibit progression to the transformed state. The anticarcinogenic action of retinoids and carotenoids is closely correlated with enhanced gap-junction cell-to-cell communication and with increased synthesis of the gap-junction protein, connexin.
Animals↗
Interaction of c-Src with gap junction protein connexin-43. Role in the regulation of cell-cell communication.
Cell-cell communication via connexin-43 (Cx43)-based gap junctions is transiently inhibited by certain mitogens, but the underlying regulatory mechanisms are incompletely understood. Our previous studies have implicated the c-Src tyrosine kinase in mediating transient closure of Cx43-based gap junctions in normal fibroblasts. Here we show that activated c-Src (c-SrcK(+)) phosphorylates the COOH-terminal tail of Cx43, both in vitro and in intact cells. Coimmunoprecipitation experiments reveal that Cx43 associates with c-SrcK(+) and, to a lesser extent, with wild-type c-Src, but not with kinase-dead c-Src. Mutation of residue Cx43 Tyr(265) (Cx43-Y265F mutant) abolishes both tyrosine phosphorylation of Cx43 and its coprecipitation with c-Src. Expression of c-SrcK(+) in Rat-1 cells disrupts gap junctional communication. Strikingly, the communication-defective phenotype is bypassed after coexpression of the Cx43-Y265F mutant or a COOH-terminally truncated version of Cx43 (Cx43Delta263) that lacks residue Tyr(265). Our results support a model in which activated c-Src phosphorylates the COOH-terminal tail of Cx43 on residue Tyr(265), resulting in a stable interaction between both proteins leading to inhibition of gap junctional communication.
Animals↗
Effects of denervation on cell-to-cell communication between acinar cells of rat submandibular salivary gland.
Communication measured by electrical cell coupling and dye transfer decreased transiently 1 day after parasympathectomy and then recovered 2 days later. Parasympathectomy decreased communication again 2 weeks later, coinciding with a decrease in the wet weight of the gland, but sympathectomy did not affect it. Thus parasympathetic nerve activity may be required for the regulation and maintenance of cell-to-cell communication in the rat submandibular gland.
Animals↗
Differential cell signaling testing for cell-cell communication inference from single-cell data by dominoSignal.
MOTIVATION: Algorithms for ligand-receptor network inference have emerged as commonly used tools to estimate cell-cell communication from reference single-cell data. Many studies employ these algorithms to compare signaling between conditions and lack methods to statistically identify signals that are significantly different. We previously developed the cell communication inference algorithm Domino, which considers ligand and receptor gene expression in association with downstream transcription factor activity scoring. We developed the dominoSignal software to innovate upon Domino and extend its functionality to test statistically differential cellular signaling. RESULTS: This new functionality includes the compilation of active signals as linkages from multiple subjects in a single-cell data set and testing condition-dependent signaling linkage. The software is applicable for analysis of single-cell data sets with multiple subjects as biological replicates as well as with bootstrapped replicates from data sets with few or pooled subjects. We use simulation studies to benchmark the number of subjects in compared groups and cells within an annotated cell type sufficient to accurately identify differential linkages. We demonstrate the application of the Differential Cell Signaling Test (DCST) in the dominoSignal software to investigate consequences of cancer cell phenotypes and immunotherapy on cell-cell communication in tumor microenvironments. These applications in cancer studies demonstrate the ability of differential cell signaling analysis to infer changes to cell communication networks from therapeutic or experimental perturbations, which is broadly applicable across biological systems. AVAILABILITY: dominoSignal is available through Bioconductor at https://www.bioconductor.org/packages/release/bioc/html/dominoSignal.html.
Cell Communication↗
Human papillomavirus type 16 E5 protein affects cell-cell communication in an epithelial cell line.
The human papillomavirus type 16 (HPV16) E5 protein is considered to have weak oncogenic properties, and its function in infected human keratinocytes is unknown. HPV16 E5 protein has been found to localize to the Golgi apparatus and the plasma membrane. To analyze the effect of E5 on plasma membrane properties, cells from the human keratinocyte cell line HaCaT were transfected with the HPV16 E5 open reading frame under the control of an inducible promoter. The gap junction-mediated cell-cell communication of E5- and vector-transfected cells was analyzed by microinjection of Lucifer yellow to measure dye coupling of the cells. A strong impairment of dye transfer in E5-transfected cells but not in vector-transfected cells was observed, with more than 80% dye transfer inhibition 40 min after injection. This impairment correlated with dephosphorylation of connexin 43, the major gap junctional protein in HaCaT cells. Furthermore, the dye coupling inhibition was not the result of differentiation of the E5-expressing cells, since no overexpression of cytokeratin 1 or filaggrin, markers of HaCaT cell differentiation, could be observed. These results therefore strongly suggest a correlation between expression of the HPV16 E5 open reading frame, impairment of gap junction-mediated dye coupling, and dephosphorylation of connexin 43.
Cell Communication↗
[The electrical cell communication between acinar cells of rat submandibular gland after parasympathectomy].
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