tacrolimus and Choriocarcinoma

The post-translational regulation of aromatase has not been well characterized as compared with transcriptional regulation. Several studies of post-translational regulation have focused on decreases in catalytic activity following phosphorylation. We report here dual post-translational regulation of aromatase, at the catalytic activity and protein levels. Microsomal aromatase prepared from JEG-3 cells was rapidly inactivated and subsequently degraded in the presence of a cytosolic fraction with calcium, magnesium, and ATP. In a reconstituted system consisting of microsomal and cytosolic fractions, aromatase was protected from protein degradation by treatment with alkaline phosphatase, whereas degradation was enhanced by treatment with calcineurin inhibitors (FK506 and cyclosporin A). Furthermore, aromatase was protected from degradation by treatment with kinase inhibitors, especially the calcium/calmodulin kinase inhibitors KN62 and KN93. Similarly to the reconstituted system, aromatase in cultured JEG-3 cells was protected from degradation by KN93, whereas FK503 increased degradation in the presence of cycloheximide, although cellular aromatase mRNA levels were unchanged by these reagents. Knockdown of calcineurin and calcium/calmodulin kinase II (CaMKII) with small interfering RNAs resulted in a dose-dependent increase in aromatase degradation and protection from degradation, respectively. The cytosol fraction-dependent phosphorylation of microsomal aromatase was inhibited by calcineurin, KN62, and KN93, and promoted by CaMKII and FK506. These results indicate that aromatase is regulated acutely at the catalytic activity level and subsequently at the enzyme content level by CaMKII/calcineurin-dependent phosphorylation/dephosphorylation.

Topics: Adenosine Triphosphate; Alkaline Phosphatase; Aromatase; Calcium; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Catalysis; Cell Line, Tumor; Cell-Free System; Choriocarcinoma; Cyclosporine; Cytosol; Female; Humans; Magnesium; Microsomes; Neoplasm Proteins; Phosphorylation; Protein Kinase Inhibitors; Protein Processing, Post-Translational; Proteolysis; Recombinant Fusion Proteins; RNA Interference; RNA, Small Interfering; Tacrolimus

We investigated, using a human placental choriocarcinoma cell line as a model, the effects of the immunosuppressive drug cyclosporin A on several placental transport systems mediating the transfer of glucose and amino acids from mother to fetus. The results of the investigation show that the transport system responsible for the transfer of taurine is selectively impaired by the drug, whereas the other transport systems are either stimulated or not affected. The inhibitory effect of the drug on taurine transport appears to be due to interference with calmodulin-dependent processes because calmodulin antagonists such as W-7, calmidazolium, and CGS 9343B mimic the effects of cyclosporin A. FK506, another immunosuppressive drug that is currently undergoing clinical trials, does not have this inhibitory effect.

Topics: Biological Transport, Active; Cell Line; Choriocarcinoma; Cyclosporine; Female; Humans; Placenta; Pregnancy; Tacrolimus; Taurine; Tumor Cells, Cultured; Uterine Neoplasms