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: 68/3/968    most recent biolreprod.102.008839v1 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 Fan, H.-Y. Articles by Sun, Q.-Y. Search for Related Content PubMed PubMed Citation Articles by Fan, H.-Y. Articles by Sun, Q.-Y. Agricola Articles by Fan, H.-Y. Articles by Sun, Q.-Y.

Characterization of Ribosomal S6 Protein Kinase p90rsk During Meiotic Maturation and Fertilization in Pig Oocytes: Mitogen-Activated Protein Kinase-Associated Activation and Localization¹

^a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, People's Republic of China ^b Department of Veterinary Pathobiology, University of Missouri-Columbia, Columbia, Missouri 65211

Mitogen-activated protein kinase (MAPK) becomes activated during the meiotic maturation of pig oocytes, but its physiological substrate is unknown. The 90-kDa ribosome S6 protein kinase (p90rsk) is the best known MAPK substrate in Xenopus and mouse oocytes. The present study was designed to investigate the expression, phosphorylation, subcellular localization, and possible roles of p90rsk in porcine oocytes during meiotic maturation, fertilization, and parthenogenetic activation. This kinase was partially phosphorylated in oocytes at germinal vesicle (GV) stage through a MAPK-independent mechanism, but its full phosphorylation is dependent on MAPK activity. After fertilization or electrical activation, p90rsk was dephosphorylated shortly before pronucleus formation, which coincided with the inactivation of MAPK. A protein phosphatase inhibitor, okadaic acid, accelerated the phosphorylation of p90rsk during meiotic maturation and induced its rephosphorylation in activated eggs. MAPK kinase (MAPKK or MEK) inhibitor U0126 inhibited the activation of MAPK and p90rsk in both cumulus-enclosed and denuded pig oocytes, but prevented GV breakdown (GVBD) only in cumulus-enclosed oocytes. Active MAPK and p90rsk were detected in pig cumulus cells, and U0126 induced their dephosphorylation. In meiosis II arrested eggs, U0126 led to the inactivation of MAPK and p90rsk, as well as the interphase transition of the eggs. P90rsk was distributed evenly in GV oocytes, but it accumulated in the nucleus before GVBD. It was localized to the meiotic spindle after GVBD and concentrated in the spindle mid zone during emission of the polar bodies. All these results suggest that p90rsk is downstream of MAPK and plays functional roles in the regulation of nuclear status and microtubule organization. Although MAPK and p90rsk activity are not essential for the spontaneous meiotic resumption in denuded oocytes, activation of this cascade in cumulus cells is indispensable for the gonadotropin-induced meiotic resumption of pig oocytes.

¹ This study was supported by grants from the Special Funds for Major State Basic Research (973) Project (G1999055902), Knowledge Innovation Program of the Chinese Academy of Sciences (KSCX2-SW-303), and Grant for Outstanding Young Scientists from the National Natural Science Foundation of China (30225010).

² Correspondence. FAX: 8610 6256 5689; e-mail: sunqy{at}panda.ioz.ac.cn