Qualitative and quantitative changes in protein sythesis of bovine follicular cells during the preovulatory period

Abstract

To understand the mechanisms governing oocyte maturation better, the effects of the gonadotropin surge were studied on follicular cells of bovine preovulatory follicles. For this purpose, qualitative and quantitative changes in protein synthesis by both granulosa cells and cumulus cells were compared relative to the luteinizing hormone (LH) surge and the resumption of meiosis in the oocyte. Follicular cells were collected at different times before and up to 25 hr after the LH surge. For each individual preovulatory follicle, granulosa and cumulus cells were incubated separately for 3 hr with 3H-methionine or with 35S-methionine. Newly synthesized cytosolic proteins from granulosa and cumulus cells and proteins secreted into the medium were analyzed by polyacrylamide gel electrophoresis. The radioactivity was measured by liquid scintillation counting after slicing of the gels or revealed by fluorography. Three major peaks of the newly synthesized proteins, with molecular weights of 76, 56, and 30 kDa, were studied throughout the preovulatory period. After the LH surge, the overall level of protein synthesis increased in granulosa cells. In addition, the pattern of cytosolic proteins in granulosa cells changed, and, in particular, the relative synthesis of the 30 kDa peak decreased. These changes in cytosolic protein synthesis may be due to the action of LH since they could be reproduced in vitro in LH-stimulated granulosa cells. A predominant peak of 56 kDa was secreted by granulosa cells throughout the experimental period. No significant change was observed in proteins synthesized by cumulus cells under the same experimental conditions. The amounts of radioactivity incorporated into the three major proteins secreted by granulosa cells, however, were correlated significantly with the amounts of radioactivity incorporated by similar proteins synthesized by cumulus cells. These results indicate that cumulus cells respond differently from granulosa cells to the gonadotropin surge but not in an independent manner.

High Expression of Bovine Glutathione S-Transferase (GSTA1, GSTA2) Subunits Is Mainly Associated with Steroidogenically Active Cells and Regulated by Gonadotropins in Bovine Ovarian Follicles

“…GSTAs were found to be major cytosolic proteins in the bovine adrenal cortex (28). Similarly, we have observed a major group of 28 kDa proteins as demonstrated herein and a previous study (4). In the bovine adrenal gland study (28), two GSTAs were observed: a major protein band at 25.9 kDa estimated to contribute to 1.3% of the cytosolic protein content, and a minor protein band at 26.5 kDa.…”

“…A group of 28 kDa proteins was shown to constitute one of the conspicuous groups of proteins in bovine granulosa cells (4). In this latter study, it was shown that the expression of the 28 kDa protein group was reduced when granulosa cells from bovine preovulatory follicles were treated with LH.…”

“…The pattern of proteins synthesized in mural/antral granulosa cells was shown to be modified in response to the LH surge. Rabahi et al (1991) have shown by SDS-PAGE analysis that the de novo synthesized 28 -30 kDa protein group was decreased relative to total granulosa cell proteins after the LH surge. Thus, we have pursued the characterization of these proteins synthesized by granulosa cells that could modulate follicular development and/or COC maturation in the bovine species.…”

“…The importance of the cumulus cells for the final maturation and developmental competence of immature oocytes has been well established (1)(2)(3). The relationship that exists in vivo between the mural granulosa cells and the cumulus-oocyte complexes (COCs) has been studied throughout the preovulatory period in cattle (4). Three major protein groups of approximately 76 kDa, 56 -58 kDa, and 28 -30 kDa were identified by de novo 35 Smetabolic labeling and SDS-PAGE gel analysis.…”

Vacuolar System-Associated Protein-60: A Protein Characterized from Bovine Granulosa and Luteal Cells That Is Associated with Intracellular Vesicles and Related to Human 80K-H and Murine β-Glucosidase II1

“…The importance of the cumulus cells for the final maturation and developmental competence of immature oocytes has been well established (reviews [1][2][3]). The relationship that exists in vivo between the mural granulosa cells and the cumulus-oocyte complexes has been studied throughout the preovulatory period in cattle [4]. Three major protein groups of approximately 76 kDa, 56-58 kDa, and 28-30 kDa were identified on SDS-PAGE analysis following de novo 35 S-metabolic labeling of granulosa cells collected from preovulatory follicles.…”