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Rapamycin‐sensitive Co‐localization of mTOR to the Mitotic Spindle
Author(s) -
Shenberger Jeffrey S,
Zhang Lianqin
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.507.2
Subject(s) - pi3k/akt/mtor pathway , mtorc2 , microbiology and biotechnology , mitosis , mtorc1 , rptor , hela , cell cycle , biology , spindle apparatus , chemistry , cell , cell division , signal transduction , biochemistry
Protein synthesis and mTOR (mammalian target of rapamycin) activity are suppressed during mitosis. Recently, phosphorylated mTOR has been localized to the mitotic spindle. To investigate functions of mTOR during mitosis, we examined the impact of rapamycin (RAP) on mTOR localization and mTOR complex (mTORC1/2) assembly. Using immunofluorescence we observed that mTOR co‐localizes to mitotic spindle fibers and the mid‐body in normal, transformed, and cancer cells. Incubation of HeLa cells with mTOR activity‐suppressing concentrations of RAP (0.1–3 μM) for 30 min failed to alter the localization of mTOR. In A549 cells, 0.1 μM RAP dispersed mTOR from spindle fibers. Pre‐treatment with the kinesin inhibitor monastrol (ML) prior to RAP stabilized mTOR on monopolar asters in A549 cells. Immunoprecipitation of mTORC1/2 revealed similar raptor/mTOR/rictor interactions in mitotic and interphase HeLa and A549 cells. In both cell types, RAP reduced raptor in mTORC1 from mitotic and interphase fractions even in the presence of ML, while the content of rictor in mTORC2 was unaffected by RAP or ML. Our findings reveal that the association of mTOR with the mitotic spindle in A549 cells is not exclusively mediated by raptor interactions, though these interactions are sensitive to RAP. Differences in the avidity of mTOR for the spindle fibers may have implications for the cell‐specific anti‐proliferative effects of RAP.