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R Le Panse

Publications and source records attributed to R Le Panse.

8 recordsLinked to original sources
PubMed2005

Thymic myoid cells protect thymocytes from apoptosis and modulate their differentiation: implication of the ERK and Akt signaling pathways.

Thymic myoid cells correspond to a muscle-like cell population present in the thymic medulla. They are well conserved throughout species evolution, but their biological role is not known. We demonstrated that myoid cells protected thymocytes from apoptosis as evidenced by a strong decrease of annexin-V-FITC positive thymocytes. This effect was (1) specific of myoid cells compared to thymic epithelial cells; (2) dependent on direct cell-to-cell contacts and (3) triggered rapidly after 2 h in cocultures. This protective phenomenon was due to the activation of prosurvival mechanisms. Indeed, myoid cells activated extracellular-regulated kinases (ERK1/2) and Akt in thymocytes. Myoid cells also influenced thymocyte maturation. We observed an increase in CD4(+) and a decrease in CD8(+) single positive (SP) thymocytes when cocultured with myoid cells, independently of a CD8(+)SP increased death or a CD4(+)SP overproliferation. Consequently, thymic myoid cells protect thymocytes from apoptosis and could also modulate their differentiation process.

Annexin A5↗
PubMed1998

Anisomycin selectively desensitizes signalling components involved in stress kinase activation and fos and jun induction.

Anisomycin, a translational inhibitor secreted by Streptomyces spp., strongly activates the stress-activated mitogen-activated protein (MAP) kinases JNK/SAPK (c-Jun NH2-terminal kinase/stress-activated protein kinase) and p38/RK in mammalian cells, resulting in rapid induction of immediate-early (IE) genes in the nucleus. Here, we have characterized this response further with respect to homologous and heterologous desensitization of IE gene induction and stress kinase activation. We show that anisomycin acts exactly like a signalling agonist in eliciting highly specific and virtually complete homologous desensitization. Anisomycin desensitization of a panel of IE genes (c-fos, fosB, c-jun, junB, and junD), using epidermal growth factor (EGF), basic fibroblast growth factor, (bFGF), tumor necrosis factor alpha (TNF-alpha), anisomycin, tetradecanoyl phorbol acetate (TPA), and UV radiation as secondary stimuli, was found to be extremely specific both with respect to the secondary stimuli and at the level of individual genes. Further, we show that anisomycin-induced homologous desensitization is caused by the fact that anisomycin no longer activates the JNK/SAPK and p38/RK MAP kinase cascades in desensitized cells. In anisomycin-desensitized cells, activation of JNK/SAPKs by UV radiation and hyperosmolarity is almost completely lost, and that of the p38/RK cascade is reduced to about 50% of the normal response. However, all other stimuli produced normal or augmented activation of these two kinase cascades in anisomycin-desensitized cells. These data show that anisomycin behaves like a true signalling agonist and suggest that the anisomycin-desensitized signalling component(s) is not involved in JNK/SAPK or p38/RK activation by EGF, bFGF, TNF-alpha, or TPA but may play a significant role in UV- and hyperosmolarity-stimulated responses.

Animals↗
PubMed1996

Protein kinase C-independent activation of mitogen-activated protein kinase by epidermal growth factor in skin fibroblasts.

In this study, we demonstrated that epidermal growth factor (EGF) stimulated the phosphorylation of myelin basic protein (MBP), a mitogen-activated protein kinase (MAPK) substrate, in crude extracts of human dermal fibroblasts. Moreover, using a selective protein kinase C inhibitor, GF 109203X (3-[1-[3-(dimethylamino)propyl]-1 H-indol-3-yl]-4 (1 H-indol-3-yl)-1 H-pyrrole-2,5-dione monohydrochloride), we observed that protein kinase C was partially involved in the total MBP phosphorylation. To determine the role of protein kinase C in the MBP phosphorylation, we separated, using fast protein liquid chromatography, the proteins present in the fibroblast crude extracts; we thus detected two distinct MBP kinase activities. The first one was stimulated by EGF and corresponded to p42mapk and p44mapk isoforms; this stimulation was not modified by GF 109203X. The second MBP kinase activity was not stimulated by EGF and was due to two protein kinase C isoforms reacting with an anti-protein kinase C zeta antibody. These results show that, in human dermal fibroblasts, EGF stimulates p42mapk and p44mapk isoforms in a protein kinase C-independent manner.

Adult↗
PubMed1996

Modulation of keratinocyte growth factor (KGF) mRNA expression in human dermal fibroblasts grown in monolayer or within a collagen matrix.

In this study, we analysed the modulation of keratinocyte growth factor (KGF) mRNA expression in human dermal fibroblasts cultured either in monolayer or within a collagen matrix (dermal equivalent). In monolayer cultures, KGF expression by quiescent fibroblasts was stimulated by different growth substances such as serum, epidermal growth factor and basic fibroblast growth factor. Moreover, we demonstrated that the induction of this gene was mediated by at least 2 different signalling pathways involving protein kinase C (PKC) and cAMP. In dermal equivalents, we observed that the collagen matrix negatively modulated KGF mRNA expression. Indeed, among the growth substances used, only the serum slightly stimulated KGF expression. Nevertheless, as in monolayers, this induction involved at least PKC and cAMP signalling pathways. As the collagen matrix can modulate fibroblast growth, we also studied KGF expression in growing fibroblasts from either monolayer cultures or dermal equivalents. We then showed that this collagen matrix negatively influenced KGF expression independently of the proliferative state of fibroblasts. All these results underline the fact that KGF mRNA expression by human dermal fibroblasts is induced by different substances; however this expression can be modulated by fibroblast-matrix interactions.

Adolescent↗
PubMed1995

Epidermal growth factor stimulates mitogen-activated protein kinase by a PKC-dependent pathway in human keratinocytes.

Epidermal growth factor (EGF), 20 ng/ml, stimulated myelin basic protein (MBP) phosphorylation in crude extracts from human keratinocyte primary cultures. In order to identify the involved kinases, we separated by fast protein liquid chromatography proteins participating in MBP phosphorylation. We detected three MBP kinase activities in the keratinocyte crude extracts. The first MBP kinase activity was the only one stimulated by EGF and reacted with anti-mitogen-activated protein kinase (MAPK) antiserum recognising p42mapk and p44mapk isoforms. However, when protein kinase C (PKC) was either inhibited by the PKC inhibitor GF 109203X or depleted by a prolonged TPA treatment, the stimulation of MBP phosphorylation by EGF was strongly inhibited. The second MBP kinase activity eluted was due to a PKC isoform reacting with an anti-PKC zeta antibody, and the third was not identified. With this work, we have thus shown that, in human keratinocytes, EGF activates MAPK activity by a PKC-dependent pathway.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1994

Modulation of epidermal growth factor and keratinocyte growth factor effects on human keratinocyte growth by protein kinase C inhibitor, GF 109203X: comparison to fibroblast growth modulation.

In this study, epidermal growth factor (EGF), 20 ng/ml, and keratinocyte growth factor (KGF), 10 ng/ml, were able to stimulate human keratinocyte growth only in presence of GF 109203X 1 microM, a selective PKC inhibitor. This suggests that PKC negatively controls keratinocyte growth in response to EGF and KGF. On the other hand, EGF and KGF have no significant effect on PKC activity. In contrast, in human fibroblasts, EGF stimulated fibroblast growth in the presence or not of GF 109203X. Thus, EGF seems to stimulate fibroblast growth in a PKC independent manner. Moreover, EGF didn't modify significantly PKC activity in fibroblasts. KGF had no effect on fibroblasts. These results show differences in the interconnections between PKC and EGF transduction pathway in the modulation of human keratinocyte and fibroblast growth. Moreover, they especially demonstrate that PKC would negatively control human keratinocyte growth in response to EGF and also to KGF.

Adult↗
PubMed1994

Differential modulation of human fibroblast and keratinocyte growth by the protein kinase C inhibitor GF 109203X.

Protein kinase C (PKC) is known to be involved in cellular proliferation and differentiation. In this work, we have investigated the effects of a novel PKC inhibitor, GF 109203X, on normal human fibroblast and keratinocyte growth. GF 109203X selectively inhibited PKC activity extracted from either fibroblasts (IC50 = 0.01 microM) or keratinocytes (IC50 = 0.4 microM). The inhibitory effects of GF 109203X on total PKC activity and Ca(2+)-independent PKC activity were similar. Nevertheless, in keratinocytes Ca(2+)-independent PKC activity represented 95% of total PKC activity, whereas in fibroblasts it corresponded to only 32% of total PKC activity. GF 109203X also inhibited a cellular function related to PKC activity in living fibroblasts and keratinocytes; it blocked the inhibitory effect of 12-O-tetradecanoylphorbol-13-acetate on 125I-epidermal growth factor binding. GF 109203X inhibited fibroblast growth, in terms of tritiated thymidine incorporation and cell counts, in a dose-dependent manner. We also observed that GF 109203X at 1 microM inhibited serum stimulation of expression of mRNA for c-fos and c-jun, which are usually involved in cellular proliferation. These results suggest that PKC stimulates fibroblast growth. In contrast, GF 109203X stimulated keratinocyte growth. We also observed that GF 109203X inhibited c-fos and c-jun mRNA expression in these cells. In fact, in keratinocytes these proto-oncogenes would be involved in the cellular differentiation process rather than in cellular proliferation. This suggests that the inhibition of PKC favors keratinocyte proliferation probably by inhibiting their differentiation. Thus, using GF 109203X, we show that PKC is involved differently in human fibroblast and keratinocyte growth.

Adolescent↗