Expression of progesterone receptor (PR) A and B isoforms in mouse granulosa cells: stage-dependent PR-mediated regulation of apoptosis and cell proliferation.

• The intracellular progesterone receptor (PR) in the mammalian ovary is a part of the physiological pathway that facilitates ovulation. Two PR isoforms (A and B) exist, with different molecular and biological functions. Previous studies have revealed that the cellular ratio of the PR isoforms is important for progesterone-responsive tissues and is under developmental control in different species. However, the relative expression of PR isoforms in the ovary is unknown. In this study we have demonstrated first that the expression of both PR isoforms in mouse granulosa cells was rapidly up-regulated by hCG treatment and dramatically down-regulated when the granulosa cells were undergoing luteinization. The relative level of protein expression of the A and B forms was 2:1 and the highest total PR protein expression was found after hCG stimulation. Second, we demonstrated that the expression of PR protein was specific to granulosa cells of periovulatory follicles and was absent in undifferentiated granulosa cells of growing follicles. It was not detected in other cell types (i.e., corpora lutea or any stage of follicles with features of apoptosis). Third, we demonstrated that treatment with the PR antagonist RU 486 in vivo resulted in down-regulation of both isoforms in parallel with increased activation of caspase-3, a decreased level of proliferating cell nuclear antigen, and a reduced rate of ovulation. Fourth, we demonstrated, in vitro, that the PR antagonists RU 486 and Org 31710 increased internucleosomal DNA fragmentation parallel with a decrease in DNA synthesis in granulosa cells, which express PR. These results indicate that PR and its isoforms participate in regulation of ovulation, along with suppression of granulosa cell apoptosis and promotion of cell survival in the mouse ovary.

Nyckelord

Animals

Apoptosis

physiology

Blotting

Western

Caspase 3

Caspases

metabolism

Cell Division

physiology

Chorionic Gonadotropin

pharmacology

Estrenes

pharmacology

Female

Furans

pharmacology

Granulosa Cells

cytology

metabolism

Hormone Antagonists

pharmacology

Immunohistochemistry

Mice

Mice

Inbred C57BL

Mifepristone

pharmacology

Ovarian Follicle

cytology

metabolism

Proliferating Cell Nuclear Antigen

metabolism

pharmacology

Protein Isoforms

Random Allocation

Receptors

Progesterone

biosynthesis

physiology

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)