title: 17β-estradiol activates mTOR in chondrocytes by AKT-dependent and AKT-independent signaling pathways.
abstract: To confirm whether 17β-estradiol (E2) activates mammalian target of rapamycin (mTOR) signaling pathway in chondrocytes and in what way activates mTOR. Human immortalized chondrocytes cell lines TC28a2 and C28/I2 were subjected to incubate with or without E2, LY294002 (the inhibitor of PI3K), rapamycin (the inhibitor of mTOR), or E2 in combination with LY294002 or rapamycin. Thereafter, protein levels of S6K1, p-S6K1, protein kinase B (AKT), and p-AKT were determined by Western blot analysis. Matrix metallopeptidase (MMP) 3 or MMP13 mRNA levels were evaluated by quantitative real-time PCR (qRT-PCR). Co-immunoprecipitation and Western blot analysis were performed to verify the interaction between ERα and mTOR. Both p-S6K1 and p-AKT protein levels in TC28a2 and C28/I2E2 cells were significantly increased by incubation with E2 (0.5 h and 1 h) (P < 0.05). Rapamycin did not affect the levels of p-AKT, but were significantly reduced by LY294002 or E2 in combination with LY294002. The levels of p-S6K1 were significantly decreased by incubation with LY294002, but the effect could be reversed by E2 in combination with LY294002. Rabbit anti-mTOR antibody was able to immunoprecipitate ERα after incubation with E2. Moreover, E2 inhibited the mRNA levels of MMP3 and MMP13 by mTOR pathway. E2 actives mTOR in chondrocytes through AKT-dependent and independent ways.
authors.affiliation: First Clinical Medical College, Shanxi Medical University Shanxi, China.
authors.forename: Yulei
authors.initials: Y
authors.lastname: Tao
authors.affiliation: Department of Orthopaedics, First Hospital of Shanxi Medical University Shanxi, China.
authors.forename: Haibiao
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Obstetrical, Yingshang County Peoples' Hospital North District, Anhui, China.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Sun
authors.affiliation: Guiyang Medical College Guizhou, China.
authors.forename: Xianxing
authors.initials: X
authors.lastname: Qiu
authors.affiliation: Department of Surgery, Center for Health Services and Technology Guizhou, China.
authors.forename: Changbo
authors.initials: C
authors.lastname: Xu
authors.affiliation: Luzhou Medical College Sichuan, China.
authors.forename: Changxiu
authors.initials: C
authors.lastname: Shi
authors.affiliation: Department of Thoracic Surgery, Linyi Peoples' Hospital Shandong, China.
authors.forename: Jiahui
authors.initials: J
authors.lastname: Du
mesh_terms: D002460:Cell Line; D019902:Chondrocytes / Q000187:drug effects* / Q000201:enzymology; D004789:Enzyme Activation; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000819:agonists / Q000378:metabolism; D006801:Humans; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D047428:Protein Kinase Inhibitors; D004958:Estradiol; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; C511768:MMP3 protein, human; D019278:Matrix Metalloproteinase 3
keywords: 17β-estradiol; AKT-dependent and AKT-independent pathways; chondrocytes; mTOR