title: Rapamycin inhibits IGF-1 stimulated cell motility through PP2A pathway.
abstract: Serine/threonine (Ser/Thr) protein phosphatase 2A (PP2A) has been implicated as a novel component of the mammalian target of rapamycin (mTOR) signaling pathway. Recently we have demonstrated that mTOR regulates cell motility in part through p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1) pathways. Little is known about the role of PP2A in the mTOR-mediated cell motility. Here we show that rapamycin inhibited the basal or insulin-like growth factor 1 (IGF-1)-induced motility of human Ewing sarcoma (Rh1) and rhabdomyosarcoma (Rh30) cells. Treatment of the cells with rapamycin activated PP2A activity, and concurrently inhibited IGF-1 stimulated phosphorylation of Erk1/2. Inhibition of Erk1/2 with PD98059 did not significantly affect the basal mobility of the cells, but dramatically inhibited IGF-1-induced cell motility. Furthermore, inhibition of PP2A with okadaic acid significantly attenuated the inhibitory effect of rapamycin on IGF-1-stimulated phosphorylation of Erk1/2 as well as cell motility. Consistently, expression of dominant negative PP2A conferred resistance to IGF-1-stimulated phosphorylation of Erk1/2 and cell motility. Expression of constitutively active MKK1 also attenuated rapamycin inhibition of IGF-1-stimulated phosphorylation of Erk1/2 and cell motility. The results suggest that rapamycin inhibits cell motility, in part by targeting PP2A-Erk1/2 pathway.
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Long
authors.initials: L
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Luo
authors.forename: Wenxing
authors.initials: W
authors.lastname: Chen
authors.forename: Hongyu
authors.initials: H
authors.lastname: Zhou
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xu
authors.forename: Xiuzhen
authors.initials: X
authors.lastname: Han
authors.forename: Tao
authors.initials: T
authors.lastname: Shen
authors.forename: Shile
authors.initials: S
authors.lastname: Huang
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D005799:Genes, Dominant / Q000235:genetics; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases
chemical_list: D005419:Flavonoids; D047908:Intracellular Signaling Peptides and Proteins; D019319:Okadaic Acid; D007334:Insulin-Like Growth Factor I; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D054648:Protein Phosphatase 2; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D020123:Sirolimus