Role of adiponectin receptors, AdipoR1 and AdipoR2, in the steroidogenesis of the human granulosa tumor cell line, KGN.
BACKGROUND
Adiponectin is involved in the regulation of energy homeostasis and more recently in the reproductive functions. We have previously shown that adiponectin receptors (AdipoR1 and AdipoR2) are expressed in human granulosa cells. However, it remains to be investigated whether both AdipoR1 and AdipoR2 or only one of these receptors serve as the major receptor(s) for adiponectin in human granulosa cells.


METHODS
The RNA interference (RNAi) technology was used to specifically knockdown the expression of either AdipoR1 or AdipoR2. Progesterone and estradiol levels in the conditioned media were measured by radioimmunoassay, and determination of cell proliferation by tritiated thymidine incorporation. The levels of adiponectin receptors and proteins involved in the steroidogenesis and in the signalling pathways were examined by western blot.


RESULTS
We generated AdipoR1 (R1) and AdipoR2 (R2) knockdown KGN cell lines. R1 cells were apoptotic and had increased expression levels of cleaved caspase 3 and decreased levels of BAD phosphorylation and PCNA as compared with control or parental KGN cells. R2 cells had similar morphology to control or KGN cells. However, they produced less progesterone and estradiol and expressed lower levels of StAR protein in response to FSH or IGF-1 stimulation compared with control cells. Furthermore, the increase of MAPK ERK1/2 phosphorylation in response to human recombinant adiponectin and FSH was lower in R2 than control cells.


CONCLUSIONS
In the human granulosa KGN cell-line, AdipoR1 seems to be involved in the cell survival whereas AdipoR2, through MAPK ERK1/2 activation, may be implicated in the regulation of steroid production.
Pierre
P
P
INRA, UMR 85, Unité de Physiologie de la Reproduction et des Comportements F-37 380, Nouzilly, France.
Froment
P
P
Nègre
D
D
Ramé
C
C
Barateau
V
V
Chabrolle
C
C
Lecomte
P
P
Dupont
J
J
D052242:Adiponectin / Q000494:pharmacology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D017077:Culture Media, Conditioned; D004958:Estradiol / Q000096:biosynthesis*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000096:biosynthesis; D006107:Granulosa Cells; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis; D048370:MAP Kinase Kinase 2 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D011374:Progesterone / Q000096:biosynthesis*; D034622:RNA Interference; D054419:Receptors, Adiponectin / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction
C475418:ADIPOR1 protein, human; C475420:ADIPOR2 protein, human; D052242:Adiponectin; D017077:Culture Media, Conditioned; D054419:Receptors, Adiponectin; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D005640:Follicle Stimulating Hormone; D048052:Mitogen-Activated Protein Kinase 3; D048370:MAP Kinase Kinase 2