title: Rapamycin induces transactivation of the EGFR and increases cell survival.
abstract: The mammalian target of rapamycin (mTOR) signaling network regulates cell growth, proliferation and cell survival. Deregulated activation of this pathway is a common event in diverse human diseases such as cancers, cardiac hypertrophy, vascular restenosis and nephrotic hypertrophy. Although mTOR inhibitor, rapamycin, has been widely used to inhibit the aberrant signaling due to mTOR activation that plays a major role in hyperproliferative diseases, in some cases rapamycin does not attenuate the cell proliferation and survival. Thus, we studied the mechanism(s) by which cells may confer resistance to rapamycin. Our data show that in a variety of cell types the mTOR inhibitor rapamycin activates extracellularly regulated kinases (Erk1/2) signaling. Rapamycin-mediated activation of the Erk1/2 signaling requires (a) the epidermal growth factor receptor (EGFR), (b) its tyrosine kinase activity and (c) intact autophosphorylation sites on the receptor. Rapamycin treatment increases tyrosine phosphorylation of EGFR without the addition of growth factor and this transactivation of receptor involves activation of c-Src. We also show that rapamycin treatment triggers activation of cell survival signaling pathway by activating the prosurvival kinases Erk1/2 and p90RSK. These studies provide a novel paradigm by which cells escape the apoptotic actions of rapamycin and its derivatives that inhibit the mTOR pathway.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Stritch School of Medicine, Loyola University Medical Center, Maywood, IL 60153, USA. dchaturvedi@lumc.edu
authors.forename: D
authors.initials: D
authors.lastname: Chaturvedi
authors.forename: X
authors.initials: X
authors.lastname: Gao
authors.forename: M S
authors.initials: MS
authors.lastname: Cohen
authors.forename: J
authors.initials: J
authors.lastname: Taunton
authors.forename: T B
authors.initials: TB
authors.lastname: Patel
mesh_terms: D002470:Cell Survival / Q000187:drug effects*; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology*; D015533:Transcriptional Activation / Q000187:drug effects*
chemical_list: D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D020123:Sirolimus