Steroidogenesis in BeWo cells: role of protein kinase A and benzodiazepines.
The peripheral benzodiazepine receptor and protein kinase A have been proposed to modulate placental steroidogenesis. Binding of the radioactive benzodiazepine PK 11195 has been observed in membranes isolated from whole human placenta, but the presence of the peripheral benzodiazepine receptors, now called translocator protein, does not seem to be indispensable. We hypothesized that cAMP analogs could induce the translocator protein expression in BeWo cells increasing steroidogenesis in the presence of benzodiazepines. The effect of two benzodiazepines and of 8-Br-cAMP on steroidogenesis in BeWo cells or in isolated human placental mitochondria was studied. Benzodiazepines did not modify progesterone synthesis in either system. Progesterone increased three times in BeWo cells incubated in the presence of 8-Br-cAMP. The translocator protein was not identified by western blot in mitochondria isolated from either the human placenta or BeWo cells but it was present in isolated rat testicular mitochondria. Neither was it observed in isolated mitochondria from BeWo cells incubated with 8-Br-cAMP. An inhibitor of protein kinase A activity, H89, at 25 microM inhibited 90% the steroidogenesis in BeWo cells, even in the presence of 8-Br-cAMP, but protein phosphorylation in mitochondria increased in the presence of H89, suggesting that protein kinase A modulates the phosphorylation cycle of mitochondrial proteins. The results suggest that placental steroidogenesis is regulated via activation of protein kinase A modulated by cAMP.
Maldonado-Mercado
María Guadalupe
MG
Departamento de Bioquimica, Facultad de Medicina, UNAM, PO Box 70 158, Coyoacan, 04510, Mexico City, Mexico.
Espinosa-García
María Teresa
MT
Gómez-Concha
Cuauhtémoc
C
Monreal-Flores
Jessica
J
Martinez
Federico
F
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D001570:Benzodiazepinones / Q000494:pharmacology; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D010920:Placenta / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D011374:Progesterone / Q000096:biosynthesis*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology
D001570:Benzodiazepinones; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D011963:Receptors, GABA-A; D013449:Sulfonamides; D015124:8-Bromo Cyclic Adenosine Monophosphate; C028513:4'-chlorodiazepam; D011374:Progesterone; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C037850:PK 11195