title: Disruption of an hTERT-mTOR-RAPTOR protein complex by a phytochemical perillyl alcohol and rapamycin.
abstract: We previously demonstrated in prostate cancer cells that a phytochemical-perillyl alcohol-and the mechanistic target of rapamycin (mTOR) inhibitor rapamycin rapidly attenuated telomerase activity. Protein levels of the telomerase catalytic subunit reverse transcriptase (hTERT) were diminished in the absence of an effect on hTERT mRNA, supporting an effect on 4E-BP1 phosphorylation and reduced initiation of protein translation. The decline in hTERT protein did not coincide wholly, however, with loss of telomerase activity suggesting a further level of regulation. We hypothesized that a hTERT-mTOR-S6K (S6 kinase)-Hsp90 (Heat shock protein 90)-Akt complex previously detected in activated NK cells was present in DU145 prostate cancer cells. Furthermore, we postulated that both perillyl alcohol and rapamycin disrupted this complex to control telomerase activity post-translationally. Antibodies directed against either RAPTOR, a binding partner of mTOR, or mTOR itself co-immunoprecipitated Hsp90, hTERT, and S6K confirming a similar TERT complex in prostate cancer cells. Perillyl alcohol or rapamycin caused rapid dissociation of the captured hTERT-mTOR-RAPTOR complex, establishing an additional mechanism by which these agents decrease telomerase activity. These findings provide convincing evidence for mTOR-mediated regulation of hTERT in DU145 cells.
authors.affiliation: Department of Medical Diagnostic and Translational Sciences, Old Dominion University, 4608 Hampton Blvd., Norfolk, VA 23529, USA.
authors.forename: Tabetha
authors.initials: T
authors.lastname: Sundin
authors.forename: Dennis M
authors.initials: DM
authors.lastname: Peffley
authors.forename: Patricia
authors.initials: P
authors.lastname: Hentosh
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D002460:Cell Line; D015536:Down-Regulation / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D039821:Monoterpenes / Q000494:pharmacology*; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D000076223:Regulatory-Associated Protein of mTOR; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D019098:Telomerase / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000903:Antibiotics, Antineoplastic; D018841:HSP90 Heat-Shock Proteins; D039821:Monoterpenes; D046912:Multiprotein Complexes; C463659:RPTOR protein, human; D000076223:Regulatory-Associated Protein of mTOR; C032208:perillyl alcohol; C546842:MTOR protein, human; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; C509186:TERT protein, human; D019098:Telomerase; D020123:Sirolimus