title: Down-regulation of mTOR leads to up-regulation of osteoprotegerin in bone marrow cells.
abstract: Osteoprotegerin (OPG)/osteoclastogenesis inhibitory factor regulates bone mass by inhibiting osteoclastic bone resorption. mTOR, which is the mammalian target of rapamycin, is a kinase and central regulator of cell growth, proliferation, and survival. By using Rapamycin, we studied whether mTOR pathway is associated with OPG protein production in the mouse bone marrow-derived stromal cell line ST2. Rapamycin markedly increased the level of soluble OPG in ST2 cells. This antibiotic treatment resulted in the suppression of phosphorylation of mTOR. Rapamycin had no effects on the proliferation, differentiation, or apoptosis of the cells. Treatment with bone morphogenetic protein-4, which can induce OPG protein in ST2 cells, also resulted in a decrease in the density of the phospho-mTOR-band, suggesting that the suppression of the phospho-mTOR pathway is necessary for OPG production in ST2 cells. Thus, suitable suppression of mTOR phosphorylation is a necessary requirement for OPG production in bone marrow stromal cells.
authors.affiliation: Department of Medicinal Biochemistry, School of Pharmacy, Aichi-Gakuin University, Nagoya, Aichi, Japan. makio@dpc.aichi-gakuin.ac.jp
authors.forename: Makio
authors.initials: M
authors.lastname: Mogi
authors.forename: Ayami
authors.initials: A
authors.lastname: Kondo
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D015536:Down-Regulation; D051379:Mice; D053244:Osteoprotegerin / Q000096:biosynthesis*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D015854:Up-Regulation
chemical_list: D002352:Carrier Proteins; D053244:Osteoprotegerin; C506031:Tnfrsf11b protein, mouse; D017853:Phosphotransferases (Alcohol Group Acceptor); C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus