Distribution and association of mTOR with its cofactors, raptor and rictor, in cumulus cells and oocytes during meiotic maturation in mice

Yuhei Kogasaka, Yumi Hoshino, Yuuki Hiradate, Kentaro Tanemura, Eimei Sato

    Research output: Contribution to journalArticlepeer-review

    22 Citations (Scopus)

    Abstract

    Mammalian target of rapamycin (mTOR), a Ser/Thr protein kinase, is the catalytic component of two distinct signaling complexes, mTOR-raptor complex (mTORC1) and mTOR-rictor complex (mTORC2). Recently, studies have demonstrated mitosis-specific roles for mTORC1, but the functions and expression dynamics of mTOR complexes during meiotic maturation remain unclear. In the present study, to evaluate the roles of respective mTOR complexes in maternal meiosis and compare them with those in mitosis, we sought to elucidate the spatiotemporal immunolocalization of mTOR, the kinase-active Ser2448- and Ser2481-phosphorylated mTOR, and raptor and rictor during cumulus-cell mitosis and oocyte meiotic maturation in mice. mTOR principally accumulated around the chromosomes and on the spindle. Phosphorylated mTOR (Ser2448 and Ser2481) exhibited elevated fluorescence intensities in the cytoplasm and punctate localization adjacent to the chromosomes, on the spindle poles, and on the midbody during mitotic and meiotic maturation, suggesting functional homology of mTOR between the two cell division systems, despite their mechanistically distinctive spindles. Raptor colocalized with mTOR during both types of cell division, indicating that mTORC1 is predominantly associated with these events. Mitotic rictor uniformly distributed through the cytoplasm, and meiotic rictor localized around the spindle poles of metaphase-I oocytes, suggesting functional divergence of mTORC2 between mitosis and female meiosis. Based on the general function of mTORC2 in the organization of the actin cytoskeleton, we propose that mTORC1 controls spindle function during mitosis and meiosis, while mTORC2 contributes to actin-dependent asymmetric division during meiotic maturation in mice.

    Original languageEnglish
    Pages (from-to)334-348
    Number of pages15
    JournalMolecular reproduction and development
    Volume80
    Issue number4
    DOIs
    Publication statusPublished - 2013 Apr

    Keywords

    • Actin
    • Centrosome, midbody
    • GVBD
    • MTOCs
    • Spindle

    ASJC Scopus subject areas

    • Genetics
    • Developmental Biology
    • Cell Biology

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