Progesterone regulation of human granulosa/luteal cell viability by an RU486-independent mechanism.
BACKGROUND
Progesterone (P4) inhibits human granulosa/luteal cell apoptosis by an unknown mechanism.


OBJECTIVE
Our objective was to assess the role of the nuclear P4 receptor (PGR) and PGR membrane component 1 (PGRMC1) in mediating P4's antiapoptotic action in human granulosa/luteal cells.


METHODS
In vitro laboratory studies were designed in which human granulosa/luteal cells were harvested from in vitro fertilization patients from 2004-2006.


METHODS
Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assays and DNA staining. Protein expression was observed by Western blot and immunocytochemistry.


RESULTS
PGR was detected in 20% of the human granulosa/luteal cells, and 25 and 50 microM RU486 induced at least 70% of the cells to undergo apoptosis. Five micromolar RU486 neither induced apoptosis nor attenuated the antiapoptotic action of 1 microM P4. PGRMC1 and its binding partner, plasminogen activator inhibitor RNA-binding protein-1 (PAIRBP1), were detected in human granulosa/luteal cells. Antibodies to either PGRMC1 or PAIRBP1 completely attenuated P4's action.


CONCLUSIONS
PGR does not exclusively mediate P4's action because 1) 5 microM RU486 should have been able to override the antiapoptotic action of 1 microM P4 because RU486 binds to the PGR at a greater affinity than P4; 2) 25 and 50 microM RU486 induce three to four times more cells to undergo apoptosis than express PGR; 3) P4 must be continuously present to prevent apoptosis, which implies a rapid, possibly membrane-initiated mechanism of action; and 4) expression and blocking antibody studies suggest that PGRMC1 and PAIRBP1 account in part for P4's action in human granulosa/luteal cells.
Engmann
Lawrence
L
Department of Obstetrics and Gynecology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
Losel
Ralf
R
Wehling
Martin
M
Peluso
John J
JJ
D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects*; D006801:Humans; D008184:Luteal Cells / Q000187:drug effects*; D008565:Membrane Proteins / Q000378:metabolism; D015735:Mifepristone / Q000494:pharmacology*; D011374:Progesterone / Q000494:pharmacology*; D016601:RNA-Binding Proteins / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism
D016895:Culture Media, Serum-Free; D008565:Membrane Proteins; C115296:PGRMC1 protein, human; D016601:RNA-Binding Proteins; D011980:Receptors, Progesterone; C428129:SERBP1 protein, human; D015735:Mifepristone; D011374:Progesterone