Rapamycin-sensitive pathway regulates mitochondrial membrane potential, autophagy, and survival in irradiated MCF-7 cells Journal Article
| Authors: | Paglin, S.; Lee, N. Y.; Nakar, C.; FitzGerald, M.; Plotkin, J.; Deuel, B.; Hackett, N.; McMahill, M.; Sphicas, E.; Lampen, N.; Yahalom, J. |
| Article Title: | Rapamycin-sensitive pathway regulates mitochondrial membrane potential, autophagy, and survival in irradiated MCF-7 cells |
| Abstract: | Radiation-induced inhibition of rapamycin-sensitive pathway and its effect on the cellular response to radiation were studied in the human breast cancer cell line MCF-7. Both radiation and rapamycin shared molecular targets and induced similar physiologic responses. Each of these treatments increased immunostaining of mammalian target of rapamycin (mTOR) in the nucleus, and radiation led to decreased phosphorylation of its autophosphorylation site Ser 2481. In addition to dephosphorylation of established mTOR downstream effectors 4E-binding protein 1 and p70 ribosomal S6 kinase, both treatments decreased the level of eukaryotic initiation factor 4G. Experiments with the potentiometric dye, JC-1, revealed an oligomycin-dependent increase in mitochondrial membrane potential following radiation or rapamycin treatment, suggesting that both lead to reversal of F 0F 1ATPase activity. Both radiation and rapamycin induced sequestration of cytoplasmic material in autophagic vacuoles. In both cases, appearance of autophagic vacuoles involved the participation of microtubule-associated protein 1 light chain 3 (LC3). Transient cotransfection of green fluorescent protein-LC3 with either wild-type or dominant-negative mTOR further showed that inactivation of mTOR pathway is sufficient to induce autophagy in these cells. Finally, administration of rapamycin in combination with radiation led to enhanced mitochondria hyperpolarization, p53 phosphorylation, and increased cell death. Taken together, these experiments show that radiation-induced inhibition of rapamycin-sensitive pathway in MCF-7 cells causes changes in mitochondria metabolism, development of autophagy, and an overall decrease in cell survival. ©2005 American Association for Cancer Research. |
| Keywords: | immunohistochemistry; s6 kinase; controlled study; protein phosphorylation; unclassified drug; human cell; cancer radiotherapy; adenocarcinoma; cell survival; breast cancer; protein kinases; serine; green fluorescent protein; mitochondrial membrane potential; enzyme activity; cell line, tumor; autophosphorylation; breast neoplasms; phosphorylation; protein p53; genetic transfection; intracellular signaling peptides and proteins; mammalian target of rapamycin; enzyme inactivation; initiation factor 4e binding protein 1; tumor suppressor protein p53; cytoplasm; cell nucleus; dye; autophagy; antibiotics, antineoplastic; mitochondrial membrane; cell strain mcf 7; mitochondria; rapamycin; sirolimus; cell vacuole; dephosphorylation; mitochondrial respiration; intracellular membranes; membrane potentials; vacuoles; microtubule associated protein 1; initiation factor 4g; membrane potential; microtubule associated protein 1 light chain 3; oligomycin; proton transporting adenosine triphosphate synthase; hyperpolarization |
| Journal Title: | Cancer Research |
| Volume: | 65 |
| Issue: | 23 |
| ISSN: | 0008-5472 |
| Publisher: | American Association for Cancer Research |
| Date Published: | 2005-12-01 |
| Start Page: | 11061 |
| End Page: | 11070 |
| Language: | English |
| DOI: | 10.1158/0008-5472.can-05-1083 |
| PUBMED: | 16322256 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | --- - "Cited By (since 1996): 93" - "Export Date: 24 October 2012" - "CODEN: CNREA" - "Source: Scopus" |
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