Expression of aromatase in the ovary: down-regulation of mRNA by the ovulatory luteinizing hormone surge.
Aromatase (CYP19) mRNA is induced by follicle-stimulating hormone (FSH) in granulosa cells of preovulatory follicles and subsequently is rapidly diminished as a consequence of the luteinizing hormone (LH) surge. Primary cultures of rat granulosa cells were used to identify some of the cellular mechanisms by which FSH increases and LH decreases steady-state levels of aromatase mRNA. Induction of aromatase mRNA by FSH was increased by cycloheximide but was blocked by alpha-amanitin and the C-kinase activators gonadotropin-releasing hormone (GnRH) and phorbol 12-myristate 13-acetate (PMA). In contrast, the decrease in steady-state levels of aromatase mRNA by LH was mimicked by A-kinase (forskolin) and C-kinase (PMA or GnRH) activators. The decrease in aromatase mRNA was associated with decreased amounts of mRNA and protein for steroidogenic factor-1 (SF-1), a nuclear orphan receptor that binds and trans-activates the aromatase promoter, and with the A-kinase subunit type II (RII beta), which is required for mediating cAMP action in these cells. The down-regulation of aromatase, SF-1, and RII beta by each kinase activator and alpha-amanitin was prevented by cycloheximide when the drug was added in combination with the activator. If, however, cycloheximide was added 2 h after PMA (or LH), the drug did not prevent the rapid loss of mRNA. When granulosa cells were transfected with an aromatase CAT transgene, CAT activity was stimulated 10- to 20-fold by FSH and forskolin but not by PMA. Taken together, these results indicate that the A-kinase but not the C-kinase pathway can trans-activate the aromatase gene in immature granulosa cells, whereas the C-kinase, as well as A-kinase pathways, mimic the LH surge to decrease aromatase mRNA in preovulatory cells. By increasing degradation of aromatase mRNA and by inhibiting transcription, the LH surge rapidly terminates the granulosa cell pattern of gene expression while reprogramming the cells to express genes associated with ovulation and luteinization.
Fitzpatrick
S L
SL
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Carlone
D L
DL
Robker
R L
RL
Richards
J S
JS
D000546:Amanitins / Q000494:pharmacology; D000818:Animals; D001141:Aromatase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D051717:Fushi Tarazu Transcription Factors; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism; D018398:Homeodomain Proteins; D007986:Luteinizing Hormone / Q000378:metabolism* / Q000494:pharmacology; D010053:Ovary / Q000201:enzymology*; D010060:Ovulation / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D054339:Steroidogenic Factor 1; D013739:Testosterone / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D000546:Amanitins; D006063:Chorionic Gonadotropin; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; C517839:Prkar2b protein, rat; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515060:steroidogenic factor 1, rat; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D003513:Cycloheximide; D001141:Aromatase; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate