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PubMed2002

G protein-coupled receptors: dominant players in cell-cell communication.

The G protein-coupled receptors (GPCRs) are the most numerous and the most diverse type of receptors (1-5% of the complete invertebrate and vertebrate genomes). They transduce messages as different as odorants, nucleotides, nucleosides, peptides, lipids, and proteins. There are at least eight families of GPCRs that show no sequence similarities and that use different domains to bind ligands and activate a similar set of G proteins. Homo- and heterodimerization of GPCRs seem to be the rule, and in some cases an absolute requirement, for activation. There are about 100 orphan GPCRs in the human genome which will be used to find new message molecules. Mutations of GPCRs are responsible for a wide range of genetic diseases. The importance of GPCRs in physiological processes is illustrated by the fact that they are the target of the majority of therapeutical drugs and drugs of abuse.

Animals↗
PubMed1997

Physiology and cell biology of the endothelium: a dynamic interface for cell communication.

This manuscript presents a brief overview of the physiology and cell biology of the endothelium, which is the basis for understanding the role of endothelial cells in pathological processes as diverse as atherosclerosis, tumour intravasation and multiple organ failure. Following consideration of general aspects of endothelial function in regulating haemostasis, vascular tone and growth, special emphasis will be placed on endothelial regulation of the inflammatory response, which centres on the microcirculation. A particular role in inflammation is played by cell adhesion molecules (CAM), expressed both on endothelial and blood cells. Cell and molecular biological methods to investigate the expression of CAM in endothelial cells in vitro will be presented, as well as novel data, indicating that cytokine-induced up-regulation of CAM in the endothelium may involve signal transduction pathways other than those culminating in the activation of NF-kappa B. Finally, the phenomenon of angiogenesis will be briefly reviewed as a characteristic of endothelial cell activity of central importance to both physiology and pathology and new experimental data presented from an in vitro model to study the ability of individual endothelial cells to form vessel-like structures. In comparative studies to investigate the roles of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor, the dominant role of VEGF in the formation of capillary networks could be unequivocally demonstrated.

Animals↗
PubMed1994

Mesodermal patterning by an inducer gradient depends on secondary cell-cell communication.

BACKGROUND: Gradients of inducing molecules, or morphogens, could impose pattern on early embryos. Although there are candidates for morphogens in several systems, it is not well understood how cells might translate differences in extracellular inducer concentration into an orderly arrangement of cell types. With this question in mind, we have re-examined mesodermal patterning in Xenopus in response to the secreted growth factor activin. Previous work has shown that activin can initiate the formation of a variety of mesodermal tissues in a concentration-dependent fashion. We have sought to disentangle the roles played by individual cell responses to activin and subsequent interactions among induced cells in producing this outcome. RESULTS: We find that the initial response of dispersed cells to activin concentration is unexpectedly simple, showing neither the thresholds of activin concentration nor the distinct domains of gene expression that characterize the later response. The eventual emergence of an ordered series of coherent differentiation steps requires the reaggregation of the induced cells, implying that secondary interactions occur. Furthermore, when cells induced at different doses of activin are mixed, the final response apparently represents a consensus, rather than a mosaic, of the mixed populations. CONCLUSIONS: We conclude that communication among responding cells underlies much of the remarkable patterning influence of activin. Moreover, we suggest that these findings can inform thinking about how inducer gradients might act in other systems, shifting emphasis from the initial response of cells to inducer concentration toward the elaboration of complex pattern by secondary interactions.

Actins↗
PubMed2001

Effects of ginsenosides from Panax ginseng on cell-to-cell communication function mediated by gap junctions.

Gap junctions have been shown or are believed to be involved in the pathogenesis of many inherited and acquired human diseases. Agents that regulate the gap junction-mediated intercellular communication (GJIC) function may facilitate prevention and treatment of GJIC-involved diseases. In the present study we examined the effects of 27 ginsenosides isolated from Panax ginseng on GJIC. The results show that compounds 1 (oleanolic acid), 2 (ginsenoside-R0), 3 (ginsenoside-Rb1), 5 (ginsenoside-Rb2), 7 (ginsenoside-Rd), 8 (ginsenoside-Rg3), 12 (panaxadial), 13 (notoginsenoside-R4), 17 [ginsenoside-Rg2 (20S)], 18 (ginsenoside-Rf), and 26 (ginsenoside-F3) did not obviously affect GJIC, whereas compounds 4 (ginsenoside-Rc), 6 (ginsenoside-Rb3), 9 (ginsenoside-Rd2), 10 (notoginsenoside-Fe), 11 (ginsenoside-Rh2),14 (ginsenoside-Ra1), 15 (ginsenoside-Re), 16 [ginsenoside-Rg2 (20R)], 19 (ginsenoside-Ia), 20 [ginsenoside-Rh1 (20S)], 21 [ginsenoside-Rh1 (20R)], 22 (ginsenoside-F1), 23 (protopanaxatriol), 24 (panaxatriol), 25 (ginsenoside-Rg1), and 27 (chikusetsaponin-L8) induced GJIC reductions at various degrees. Compounds 2, 7, and 8 protected against the tyrosine phosphatase inhibitor vanadate-induced GJIC reduction, while compounds 1, 5, 7, and 17 inhibited the cytokine interleukin 1 alpha (IL-1alpha)-induced reduction in GJIC. Nevertheless, no compounds protected against the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced GJIC inhibition. On the other hand, GJIC reductions induced by compounds 6, 9,10, 20, 21, 22, 24, and 25 were inhibited by the tyrosine kinase (TK) inhibitor genistein, while GJIC reductions induced by compounds 6, 9, 14, 16, 19, 21, and 24 were attenuated in the presence of the PKC inhibitor calphostin C. However, GJIC reductions induced by compounds 4, 23, and 27 were not inhibited either by genistein or by calphostin C. These data indicate that various mechanisms are responsible for effects of ginsenosides on GJIC.

Cell Communication↗
PubMed2005

The role of human adult stem cells and cell-cell communication in cancer chemoprevention and chemotherapy strategies.

Since carcinogenesis is a multi-stage, multi-mechanism process, involving mutagenic, cell death and epigenetic mechanisms, during the "initiation/promotion/and progression" phases, chemoprevention must be based on understanding the underlying mechanism(s) of each phase, In principle, prevention of each of these phases could reduce the risk to cancer. However, because reducing the mutagenic/initiation phase to a zero level is impossible, the most efficacious intervention would be at the promotion phase that requires a sustained exposure to promoting conditions/agents. In addition, assuming the "target" cells for carcinogenesis are the pluri-potent stem cells and their early progenitor or transit cells, chemoprevention strategies for inhibiting the promotion of these two types of pre-malignant "initiated" cells will require different kinds of agents. A hypothesis will be proposed that involves adult stem cells, which express Oct-4 gene and lack gap junctional intercellular communication (GJIC-) or the early progenitor cells which express GJIC+ and are partially-differentiated, if initiated, will be promoted by agents that either inhibit secreted negative growth regulators or by inhibitors of GJIC. Consequently, anti-tumor promoting chemopreventing agents to each of these two types of initiated cells must have different mechanisms of action and work on different target cells. Assuming stem cells are target cells for carcinogenesis, an alternative method of chemoprevention would be to reduce the stem cell pool. Many classes of anti-tumor promoter chemopreventive agents, such as green tea components, resveratrol, caffeic acid phenethylene ester, either up-regulate GJIC in stem cells or prevent the down regulation of GJIC by tumor promoters in early progenitor cells.

Adult↗
PubMed2001

Selective loss of Sertoli cell and germ cell function leads to a disruption in sertoli cell-germ cell communication during aging in the Brown Norway rat.

We investigated the effects of aging on Sertoli cell-germ cell interactions from Brown Norway rats using the induction of four specific mRNAs as markers. The testes from aging (24 mo old) Brown Norway rats can be normal size or regressed. One marker, a von Ebner's-like protein, is expressed in coculture and "in vivo" in germ cells from normal testes of 6- and 24-mo-old rats but not in germ cells from regressed testes of 24-mo-old rats. A second germ cell marker, the Huntington disease protein, is expressed in all germ cells. Two Sertoli cell markers, a serotonin receptor and a novel gene, are induced in Sertoli cells by meiotic germ cells. The serotonin receptor mRNA is expressed in Sertoli cells from 20-day, 6-mo, and 24-mo normal testes but not in those from 24-mo regressed testes. The novel gene is induced in Sertoli cells from all testes. We conclude that Sertoli cells from aged regressed testes are unable to respond to selective signals from germ cells from young rats, and germ cells from regressed testes show a similar selective loss. Such disruptions in communication between Sertoli cells and germ cells likely contribute to germ cell loss during aging.

Actins↗
PubMed1999

Cell-to-cell communication and expression of gap junctional proteins in human diabetic and nondiabetic skin fibroblasts: effects of basic fibroblast growth factor.

Wound healing involves the interactions of many cell types, and is controlled in part by growth factors. Intercellular communication mediated by gap junctions is considered to play an important role in the coordination of cellular metabolism duringthe growth and development of tissues and organs. Basic fibroblast growth factor (bFGF), known to be important in wound healing, has been found to increase Cx43 expression and intercellular communication in endothelial cells and cardiac fibroblasts. It has been proposed that an increased coupling is necessary for the coordination of these cells in wound healing and angiogenesis, and that one of the actions of bFGF is to modulate intercellular communication. The aim of our study was to evaluate the effects of bFGF on gap junctional intercellular communication (GJIC) in vitro, and the presence of gap junctional proteins connexin (Cx) 26, Cx32, and Cx43 in fibroblasts of diabetic and nondiabetic individuals. Fibroblast cell lines (n = 10) were cultured for 3 d in serum-free media with or without bFGF (3 ng/mL). Cells were evaluated for the rate of GJIC by using laser cytometry, and for the presence of Cx26, Cx32, and Cx43 by immunohistochemical and Western analyses. All cell types communicated via contact-dependent mechanisms. The rate of GJIC was greater (p < 0.01) for diabetic than for nondiabetic fibroblasts (4.1 +/- 0.01 vs 3.3 +/- 0.01%/min). bFGF increased (p < 0.01) the rate of GJIC for diabetic (4.9 +/- 0.01 vs 4.1 +/- 0.01%) and nondiabetic (4.1 +/- 0.01 vs 3.3 +/- 0.01%) fibroblasts. Immunohistochemistry identified Cx26 in the cytoplasm, Cx32 was not detected, and Cx43 was present on the cellular borders in all cultures. Image analysis of immunofluorescent staining demonstrated that bFGF increased (p < 0.05) Cx43 expression in diabetic and nondiabetic fibroblasts. Western immunoblot analysis revealed bands at 43-46 kD that were similar in volume for diabetic and nondiabetic fibroblasts. Thus, gap junctions involving Cx43 and GJIC among fibroblasts appear to be targets for bFGF. Fibroblasts of diabetic individuals appear to have an increased rate of cell-cell coupling, correlating with a decreased rate of proliferation.

Adult↗
PubMed1993

Neighboring cerebellar Purkinje cells communicate via retrograde inhibition of common presynaptic interneurons.

Paired tight-seal whole-cell recordings were obtained from neighboring Purkinje cells in cerebellar slices. Under voltage clamp, spontaneous inhibitory postsynaptic currents resulted from the activity of GABAergic interneurons, stellate and basket cells. Up to 80% of inhibitory postsynaptic currents in paired recordings were in register. This correlation was not affected by antagonists of glutamate receptors, faded with distance, and was abolished by tetrodotoxin. Earlier work showed that voltage-gated Ca2+ entry into a Purkinje cell elicits a transient presynaptic inhibition of inhibitory postsynaptic currents. It is now shown that this inhibition is not restricted to the stimulated cell, but that it is transmitted to its neighbors. The results indicate that Purkinje cells exchange information by an unconventional mechanism involving retrograde control of inhibitory synapses.

Animals↗
PubMed1993

An in vitro model of ovarian epithelial carcinogenesis: changes in cell-cell communication and adhesion occurring during neoplastic progression.

To investigate the cellular mechanisms of ovarian epithelial carcinogenesis, a series of progressively transformed rat ovarian surface epithelial (ROSE) cell lines were developed and studied. Transfection of primary ROSE cells and an immortalized ROSE line (ROSE 199) with the pSV3neo plasmid (SV40 T-antigen) yielded transformed lines which retained epithelial morphology. In vivo selection of these pSV3neo cell populations resulted in further phenotypic transformation. Transfection of ROSE 199 with pSV2neo/c-H-rasEJ (rasEJp21) resulted in a malignant line which appeared fibroblast-like and formed invasive sarcomas both in athymic mice and in immunocompetent rats. Gap junctional intercellular communication (GJIC) and cell-cell adhesion were studied in this series of ROSE lines. Both c-H-rasEJ-transformation and in vivo selection resulted in a significant reduction of GJIC between adjoining cells and a transition of in vitro migration as continuous epithelial sheets to the dissociation of individual cells. This apparent shift in cell adhesiveness was associated with reduced expression of the E-cadherin adhesion molecule. Our data suggest that neoplastic progression of the ovarian surface epithelium may be associated with concomitant reductions in GJIC, E-cadherin expression and functional adhesiveness.

Animals↗
PubMed2003

Oocyte-somatic cell communication.

The physical interface between the female germ line and enveloping somatic cells is dynamically modified throughout the course of folliculogenesis. How selective pathways for communication between the oocyte and granulosa cell are established and regulated remains to be determined, but insights into the structural basis for this communication are emerging. This review summarizes the available evidence that supports the notion that the integration of oogenesis with folliculogenesis is achieved by regulated cell interactions between oocytes and granulosa cells.

Animals↗
PubMed1981

Sertoli-Leydig cell communication via an LHRH-like factor.

The primary function of the testosterone secreted by Leydig cells is the maintenance of spermatogenesis and hence fertility. This action of testosterone is mediated by the Sertoli cells which nourish and support the developing spermatozoa. As normal Sertoli cell function is so critically dependent on normal Leydig cell function, a regulatory influence of the Sertoli cells on the Leydig cells has been suggested. Indeed, follicle-stimulating hormone (FSH), which acts only on Sertoli cells, can also cause profound changes in Leydig cell function, although how this is effected is unknown. We recently hypothesized that the Sertoli cell might be the source of a luteinizing hormone releasing hormone (LHRH)-like factor which we detected in the interstitial fluid surrounding the Leydig cells. As injected LHRH agonists cause impairment of gonadal function and directly inhibit FSH-induced changes in Leydig cell function through specific membrane receptors, this 'LHRH-like' factor has all the correct credentials for the postulated messenger between the Sertoli and Leydig cells. Here, we strengthen this case by demonstrating that seminiferous tubules from both the rat and the stumptailed macaque (Macaca arctoides) contain a factor which has LHRH-like receptor-binding and biological activity in vitro, but which is immunologically distinct from native LHRH. We have also shown that this factor is secreted in vitro by cultured rat Sertoli cells.

Animals↗
PubMed1980

Cell communication in breast cancer.

Direct intercellular communication is the transfer of ions and small molecules between cells in contact. Cells derived from human breast tissue have been examined to determine their pattern of direct communication, which was measured by the 3H-uridine nucleotide transfer method. The behaviour of mammary epithelium from normal and pathological sources has been compared with that of malignant mammary epithelium. Normal human mammary fibroblasts and epithelium demonstrate selectivity in direct communication. Thus although both transfer nucleotide to and from their own cell type, they do not transfer nucleotide between one another in heterologous co-culture. Further study of a variety of non-human fibroblasts and epithelium showed that cells may be functionally subdivided into selective communicators, non-selective communicators, and non-communicators. None of the malignant human breast cells examined showed selectivity in communication. Thus both primary cultures and established lines were either non-communicators or non-selective communicators. This loss of selectivity could favour the metastasis of malignant cells, enabling them either to ignore inhibitory growth control signals or alternatively to receive stimulatory signals from abnormal sources.

Breast↗
PubMed1998

The polarized hepatic human/rat hybrid WIF 12-1 and WIF-B cells communicate efficiently in vitro via connexin 32-constituted gap junctions.

Gap junction intercellular communication (GJIC) plays an essential role in the control of growth, differentiation, and functions of different tissues. The expression of connexins (Cxs), the structural proteins of gap junctions, is developmentally regulated and tissue-specific. In vivo hepatocytes express Cx32 and Cx26. Most currently available in vitro hepatic cell systems express Cx43 instead of the expected Cxs. This work analyzes the GJIC competence and Cx expression of the highly differentiated and polarized hepatoma-derived hybrid cell lines, WIF 12-1 and WIF-B. It shows (using two dye transfer assays) that both lines communicate efficiently and that the acquisition of GJIC competence precedes the formation of bile canaliculi. Interestingly, these cells communicate via Cx32 expression, whereas Cx26 and Cx43 are not expressed, as demonstrated by Western and Northern blotting, immunocytochemistry, and confocal microscopy. The human fibroblast W138 parent communicates via Cx43, whereas the rat hepatoma parent Fao and the subclone WIF 12-1 TGdelta, that has lost the human X chromosome, do not communicate, the expression of Cx32 being restricted to the mRNA in these two lines. The GJIC competence of WIF cells could thus result from the activation of the human X chromosome-linked Cx32 gene.

Animals↗