Antagonistic effects of thyrotropin and epidermal growth factor on thyroglobulin mRNA level in cultured thyroid cells

Experimental Cell Research

Demartin

Dumont

1999

This study addresses the nature of the critical labile event that couples at restriction point mitogenic cascades with the autonomous part of the cell cycle. In primary cultures of dog thyroid epithelial cells, kinetic experiments indicate that a labile cAMP-dependent event positively controls a late G1 commitment to DNA replication and RB phosphorylation. As previously shown in this system, the cAMP-dependent mitogenic pathway differs from the most generally envisaged growth factor cascades as it stimulates the accumulation of p27 kip1 but not of cyclins D. Nevertheless, cyclin D3 and CDK4 activity are essential in the cAMP-dependent mitogenesis, and cAMP unmasks the DCS-22 epitope of cyclin D3 and induces the nuclear translocations and assembly of cyclin D3 and CDK4 in a complex that also contains p27 kip1 . Unexpectedly, the washing out of forskolin rapidly arrested S phase entry and the accumulation of hyperphosphorylated RB, but did not reverse any of the above events associated with cyclin D3-CDK4 activation. This implies that even after induction of stable nuclear cyclin D3-CDK4 complexes, dog thyrocytes still depend on cAMP for RB phosphorylation and commitment to DNA synthesis, which suggests that a key labile event responsible for a last control of restriction point passage remains to be uncovered, in the cAMP-dependent cell cycle of dog thyrocytes and possibly other systems.

Section: Resultsmentioning

confidence: 99%

Nature of the Critical Labile Event That Controls RB Phosphorylation in the Cyclic AMP-Dependent Cell Cycle of Thyrocytes in Primary Culture

Experimental Cell Research

Demartin

Dumont

1999

“…1B). TSH and cAMP induce differentiation expression, whereas growth factors and more potently EGF reversibly inhibit the expression of all differentiation markers while inducing a morphological transformation analogous to an epithelium/mesenchyme transition (EMT) (Roger and Dumont, 1984;Pohl et al, 1990;Roger et al, 1985;Coclet et al, 1991;Hebrant et al, 2007). Both TSH and EGF mitogenic stimulations are permitted or facilitated by the comitogenic activity of IGF -I (reproduced in vitro by high insulin concentrations) acting through IGF-I tyrosine kinase receptors (Roger et al, 1987;Burikhanov et al, 1996).…”

Section: Our Present Knowledge Of Signal Transduction Pathways Comentioning

confidence: 99%

Signal transduction in the human thyrocyte and its perversion in thyroid tumors

Molecular and Cellular Endocrinology

Staveren

Coulonval

et al. 2010

Self Cite

The study of normal signal transduction pathways regulating the proliferation and differentiation of a cell type allows to predict and to understand the perversions of these pathways which lead to tumorigenesis. In the case of the human thyroid cell, three cascades are mostly involved in tumorigenesis:the TSH receptor-cyclic AMP cascade, the constitutive activation of which leads to autonomous adenomas and congenital hyperthyroidism.the growth factor-Ras-MAP kinase pathway, whose constitutive activation causes follicular and papillary carcinomas.the PI-3Kinase-PKB pathway, the activity of which is necessary for both pathways and the corresponding tumors.The pathways and genetic events affecting them are described. Caveats in the use of models and the interpretation of results are formulated and the still pending questions are outlined.

“…When [15,17]; in such a system the hormone enhanced the synthesis of most proteins (2 -6, 8 and 9) but not of protein 7. In the same way, when thyroid cells were cultured for 12 days with EGF and were no longer proliferating but still sensitive to this agent [15,17], protein 1 was not induced (data not shown).…”

Section: Resultsmentioning

confidence: 99%

“…Maximal stimulation of DNA synthesis and proliferation is obtained when these factors are added together. While TSH also induces differentiation expression, serum has no effect, while EGF inhibits this process [15,17,181. We have studied the effects of these agents acting alone or in combination on the pattern of protein synthesis during the induction of proliferation with the working hypothesis that the new synthesis or the repression of a common set of proteins could be the final common pathway of these different mitogenic stimuli.…”

mentioning

confidence: 99%

Differential protein synthesis in the induction of thyroid cell proliferation by thyrotropin, epidermal growth factor or serum

Lamy

European Journal of Biochemistry

Lecocq

et al. 1986

Self Cite

Protein synthesis in the G1 period of the cell cycle has been investigated using two-dimensional gel electrophoresis in primary cultures of dog quiescent thyroid cells, incubated in defined medium and induced to proliferate by the combined action of thyrotropin (TSH), epidermal growth factor (EGF) and serum or by each of these agents, acting alone.1. The analysis of the proteins, pulse-labeled for 3 h with [35S]methionine, in quiescent cells deprived of serum and in cells that had been stimulated for various periods of time by the addition of TSH, EGF and serum showed maximal modifications before entry into S phase: the labeling of at least ten proteins was enhanced while that of at least six proteins was decreased. The synthesis of one of these proteins (protein 1 ; M , z 81 000) was maximal 9 -3 2 h after stimulation by the proliferative agents but began to decrease at 15 -18 h and was still decreased at 2. The study of the effect of each of the proliferation agents alone on the labeling of these sixteen proteins showed that TSH specifically stimulated the labeling of eight polypeptides (proteins 2 -9) and that, in contrast, EGF and serum specifically increased the labeling of two other proteins (proteins 1 and 10). The labeling of one protein was decreased by each of the different agents (protein 6') while TSH specifically decreased the labeling of four polypeptides (proteins 1' -4 ) and increased the labeling of one polypeptide (protein 5') whose synthesis was decreased by EGF and serum.3. The specific effect of TSH on one protein labeling (protein 7; MI 2 39000) was potentiated by EGF and serum while the specific effect of EGF and serum on another protein labeling (protein 1) was potentiated by TSH.There is thus a correlation between the level of synthesis of these two proteins and the proliferative state of the cells, which is much greater when the stimulating agents are acting together.4. The induction of protein 1 synthesis by EGF was no longer observed when the cells were no longer proliferating. In the same way, TSH no longer stimulated the synthesis of protein 7 in thyroid cells at confluence.In conclusion, the present study has identified some proteins (proteins 1 and 7) which, as judged by the peculiar stimulation and the kinetics of their synthesis, could be part of the final key events triggering DNA replication in thyroid cells. Our findings are discussed within the framework of the previously described coexistence of cyclic-AMP-dependent (stimulated by TSH) and cyclic-AMP-independent (stimulated by serum or EGF) regulatory pathways leading to the initiation of DNA synthesis.