h-89 and Choriocarcinoma

The env region of the human endogenous retrovirus ERV-3 is expressed during differentiation of trophoblast and the choriocarcinoma BeWo. Stable transfectants with ERV-3 env exhibit most aspects of trophoblast differentiation, including inhibition of cell proliferation, changes in cell morphology, and increased production of beta-hCG mRNA. In this study, the cellular mechanism of induction of BeWo cell differentiation by ERV-3 env was investigated. In BeWo cells stably transfected with ERV-3 env, the production of beta-hCG mRNA and hCG protein was increased. Intracellular cAMP level was markedly increased over that of vector transfected cells. The effect on beta-hCG protein production was inhibited by H89, a protein kinase A (PKA) inhibitor, while protein kinase C (PKC) and protein tyrosine kinase (PTK) inhibitors had no effect. The expression of a major cell cycle promoter, cyclin B, was markedly reduced while expression of p21, a negative regulator of the cell cycle, was up-regulated. Inhibition of ERV-3 env induced hCG production with H89 had no significant effect on cell growth when compared with cells transfected with vector alone.

Topics: Cell Differentiation; Cell Division; Choriocarcinoma; Chorionic Gonadotropin; Cyclic AMP-Dependent Protein Kinases; Cyclin B; Endogenous Retroviruses; Enzyme Inhibitors; Female; Gene Expression; Genes, env; Humans; Isoquinolines; Pregnancy; rho GTP-Binding Proteins; Sulfonamides; Transfection; Trophoblasts; Tumor Cells, Cultured; Uterine Neoplasms

Treatment of confluent cultures of JAR human placental choriocarcinoma cells with staurosporine caused a marked stimulation of serotonin transport activity in these cells. The stimulatory effect was noticeable at nanomolar concentrations of staurosporine, and a treatment time of > 4 h was required for staurosporine to elicit the effect. At 40 nM and with a treatment time of 16 h, the stimulation of the transport activity was 3.5-6.0-fold. None of the several other protein kinase inhibitors tested had similar effect except KT 5720, a protein kinase A inhibitor, which showed a small but significant (approximately 1.4-fold) stimulatory effect at a concentration of 5 microM. Blockade of RNA synthesis and protein synthesis in the cells prevented completely the stimulation of the transport activity induced by staurosporine. The stimulation was observed not only in intact cells but also in plasma membrane vesicles prepared from staurosporine-treated cells. The stimulation was accompanied by a 5-7-fold increase in the steady state levels of the transporter-specific mRNAs, by a 7-fold increase in the maximal velocity of the transport process, and by a 6-fold increase in the transporter density in the plasma membrane. Even though both staurosporine and cholera toxin had similar effects on the serotonin transport activity in these cells, the effect was not additive when the cells were treated with both reagents together. While treatment of the cells with cholera toxin markedly elevated intracellular levels of cAMP, staurosporine did not have any effect on the cellular levels of this cyclic nucleotide. It is concluded that staurosporine up-regulates the serotonin transport activity in JAR cells by increasing the steady state levels of the serotonin transporter mRNA and by the consequent increase in the transporter density in the plasma membrane and that the process involves a cAMP-independent signaling pathway.

Topics: Alkaloids; Carrier Proteins; Cholera Toxin; Choriocarcinoma; Cocaine; Cyclic AMP; Cyclic GMP; Cycloheximide; Dactinomycin; Female; Humans; Isoquinolines; Membrane Glycoproteins; Membrane Transport Proteins; Nerve Tissue Proteins; Pregnancy; RNA, Messenger; Serotonin; Serotonin Plasma Membrane Transport Proteins; Staurosporine; Sulfonamides; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; Up-Regulation