HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 75/1/140    most recent biolreprod.105.050294v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Yang, P. Articles by Roy, S. K. Search for Related Content PubMed PubMed Citation Articles by Yang, P. Articles by Roy, S. K. Agricola Articles by Yang, P. Articles by Roy, S. K.

Transforming Growth Factor B1 Stimulated DNA Synthesis in the Granulosa Cells of Preantral Follicles: Negative Interaction with Epidermal Growth Factor¹

Departments of OB/GYN⁴ and Cellular and Integrative Physiology,⁵ University of Nebraska Medical Center, Omaha, Nebraska 68198-4515

ABSTRACT

EGF or TGFB1 alone stimulates but together attenuate granulosa cell DNA synthesis. Intact preantral follicles from hamsters were cultured with TGFB1, EGF, or both to reveal the mechanisms of such unique regulation. Follicular CCND2 (also known as cyclin D2), CDKN1B (also known as p27^kip1), and the involvement of appropriate signaling intermediaries and kinases were examined. TGFB1, acting via SMAD2 and SMAD3, antagonized the degradation of CCND2 protein by blocking its phosphorylation. In contrast, TGFB1 supported CDKN1B degradation by involving MAPK14 (also known as p38 Map Kinase) and PKC, resulting in CDK4 activation and DNA synthesis. EGF via MAPK3/1 maintained functional levels of CCND2 through CCND2 synthesis as well as degradation. EGF and TGFB1 together inhibited CDK4 activation and DNA synthesis. EGF attenuated TGFB1 stimulated phosphorylation of SMAD3, TGFB1-induced activation of MAPK14 and PKC, and TGFB1 suppression of CCND2 degradation. In contrast, TGFB1 suppressed EGF-induced increase in CCND2 mRNA levels. The final outcome was CCND2 degradation without replenishment and decreased activities of MAPK14 and PKC leading to suppression of CDK4 activation. The results indicate that each growth factor involves a separate mechanism to maintain an effective level of CCND2 in granulosa cells for the activation of CDK4 and induction of DNA synthesis. However, their simultaneous action is inhibitory to follicular DNA synthesis because they counteract each other's activity by interfering at specific sites. Because both EGF and TGFB1 are present in granulosa cells, this mechanism may explain how their effects are temporally modulated for granulosa cell proliferation and folliculogenesis.

DNA synthesis, EGF, follicle, granulosa cells, growth factors, ovary, signal transduction, TGFB1

¹ Supported by a grant (HD 28165) to S.K.R. P.Y. was a Lalor Foundation fellow.

² Correspondence: Shyamal K. Roy, DRC 5013, Departments of OB/GYN and Cellular and Integrative Physiology, University of Nebraska Medical Center, 984515 Nebraska Medical Center, Omaha, NE 68198-4515. FAX: 402 559 6164; skroy{at}unmc.edu

³ Current address: Department of Internal Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Little Rock, AR 72205.