Oscillatory flow-induced proliferation of osteoblast-like cells is mediated by alphavbeta3 and beta1 integrins through synergistic interactions of focal adhesion kinase and Shc with phosphatidylinositol 3-kinase and the Akt/mTOR/p70S6K pathway.
Interstitial flow in and around bone tissue is oscillatory in nature and affects the mechanical microenvironment for bone cell growth and formation. We investigated the role of oscillatory shear stress (OSS) in modulating the proliferation of human osteoblast-like MG63 cells and its underlying mechanisms. Application of OSS (0.5 +/- 4 dynes/cm(2)) to MG63 cells induced sustained activation of phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR/p70S6K (p70S6 kinase) signaling cascades and hence cell proliferation, which was accompanied by increased expression of cyclins A and D1, cyclin-dependent protein kinases-2, -4, and -6, and bone formation-related genes (c-fos, Egr-1, and Cox-2) and decreased expression of p21(CIP1) and p27(KIP1). OSS-induced activation of PI3K/Akt/mTOR/p70S6K and cell proliferation were inhibited by specific antibodies or small interference RNAs of alpha(v)beta(3) and beta(1) integrins and by dominant-negative mutants of Shc (Shc-SH2) and focal adhesion kinase (FAK) (FAK(F397Y)). Co-immunoprecipitation assay showed that OSS induces sustained increases in association of Shc and FAK with alpha(v)beta(3) and beta(1) integrins and PI3K subunit p85, which were abolished by transfecting the cells with FAK(F397Y) or Shc-SH2. OSS also induced sustained activation of ERK, which was inhibited by the specific PI3K inhibitor LY294002 and was required for OSS-induced activation of mTOR/p70S6K and proliferation in MG63 cells. Our findings provide insights into the mechanisms by which OSS induces osteoblast-like cell proliferation through activation of alpha(v)beta(3) and beta(1) integrins and synergistic interactions of FAK and Shc with PI3K, leading to the modulation of downstream ERK and Akt/mTOR/p70S6K pathways.
Lee
Ding-Yu
DY
Division of Medical Engineering Research, National Health Research Institutes, Miaoli 350, Taiwan.
Li
Yi-Shuan J
YS
Chang
Shun-Fu
SF
Zhou
Jing
J
Ho
Hui-Min
HM
Chiu
Jeng-Jiann
JJ
Chien
Shu
S
D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D019012:Integrin beta1 / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology* / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D012212:Rheology; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins / Q000378:metabolism*; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013314:Stress, Mechanical; D058570:TOR Serine-Threonine Kinases
D018797:Cell Cycle Proteins; D051546:Cyclooxygenase 2; D051766:Early Growth Response Protein 1; D048049:Extracellular Signal-Regulated MAP Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases; D039302:Integrin alphaVbeta3; D019012:Integrin beta1; D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D016760:Proto-Oncogene Proteins c-fos; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D058570:TOR Serine-Threonine Kinases; C497325:EGR1 protein, human; C528024:SHC1 protein, human; C496540:PTGS2 protein, human; C546842:MTOR protein, human