Quantitative proteomic analysis of dexamethasone-induced effects on osteoblast differentiation, proliferation, and apoptosis in MC3T3-E1 cells using SILAC.
CONCLUSIONS
The impairment of osteoblast differentiation is one cause of the glucocorticoid-induced osteoporosis (GCOP). The quantitative proteomic analysis of the dexamethasone (DEX)-induced effects of osteoblast differentiation, proliferation, and apoptosis using stable-isotope labeling by amino acids in cell culture (SILAC) demonstrated drastic changes of some key proteins in MC3T3-E1 cells.


BACKGROUND
The impairment of osteoblast differentiation is one of the main explanations of GCOP. SILAC enables accurate quantitative proteomic analysis of protein changes in cells to explore the underlying mechanism of GCOP.


METHODS
Osteoprogenitor MC3T3-E1 cells were treated with or without 10(−6) M DEX for 7 days, and the differentiation ability, proliferation, and apoptosis of the cells were measured. The protein level changes were analyzed using SILAC and liquid chromatography-coupled tandem mass spectrometry.


RESULTS
In this study, 10(−6) M DEX inhibited both osteoblast differentiation and proliferation but induced apoptosis in osteoprogenitor MC3T3-E1 cells on day 7. We found that 10(−6) M DEX increased the levels of tubulins (TUBA1A, TUBB2B, and TUBB5), IQGAP1, S100 proteins (S100A11, S100A6, S100A4, and S100A10), myosin proteins (MYH9 and MYH11), and apoptosis and stress proteins, while inhibited the protein levels of ATP synthases (ATP5O, ATP5H, ATP5A1, and ATP5F1), G3BP-1, and Ras-related proteins (Rab-1A, Rab-2A, and Rab-7) in MC3T3-E1 cells.


CONCLUSIONS
Several members of the ATP synthases, myosin proteins, small GTPase superfamily, and S100 proteins may participate in functional inhibition of osteoblast progenitor cells by GCs. Such protein expression changes may be of pathological significance in coping with GCOP.
Population Council, 1230 York Avenue, New York, NY 10065, USA.
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D017209:Apoptosis / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects*; D003907:Dexamethasone / Q000494:pharmacology*; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D007553:Isotope Labeling; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects*; D011506:Proteins / Q000378:metabolism; D040901:Proteomics; D009418:S100 Proteins / Q000378:metabolism; D013234:Stem Cells / Q000187:drug effects*; D000097795:ATPase Inhibitory Protein
D003907:Dexamethasone; D005938:Glucocorticoids; D020559:Monomeric GTP-Binding Proteins; D009218:Myosins; D011506:Proteins; D009418:S100 Proteins; D000097795:ATPase Inhibitory Protein