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The cell survival signal Akt is differentially activated by PDGF‐BB, EGF, and FGF‐2 in osteoblastic cells
Author(s) -
Chaudhary Lala R.,
Hruska Keith A.
Publication year - 2001
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/1097-4644(20010501)81:2<304::aid-jcb1045>3.0.co;2-u
Subject(s) - protein kinase b , wortmannin , platelet derived growth factor receptor , ly294002 , pi3k/akt/mtor pathway , microbiology and biotechnology , fibroblast growth factor , mapk/erk pathway , kinase , chemistry , growth factor , signal transduction , cancer research , biology , biochemistry , receptor
Stimulation of osteoblast survival signals may be an important mechanism of regulating bone anabolism. Protein kinase B (PKB/Akt), a serine‐threonine protein kinase, is a critical regulator of normal cell growth, cell cycle progression, and cell survival. In this study we have investigated the signaling pathways activated by growth factors PDGF‐BB, EGF, and FGF‐2 and determined whether PDGF‐BB, EGF, and FGF‐2 activated Akt in human or mouse osteoblastic cells. The results demonstrated that both ERK1 and ERK2 were activated by FGF‐2 and PDGF‐BB. Activation of ERK1 and ERK2 by PDGF‐BB and FGF‐2 was inhibited by PD 098059 (100 μM), a specific inhibitor of MEK. Wortmannin (500 nM), a specific inhibitor of phosphatidylinositol 3‐kinase ( PI 3‐K), inhibited the activation of ERK1 and ERK2 by PDGF‐BB but not by FGF‐2 suggesting that PI 3‐K mediated the activation of ERK MAPK pathway by PDGF‐BB but not by FGF‐2. Rapamycin, an inhibitor of p70 S6 protein kinase and a downstream target of ERK1/2 and PI 3‐K, did not affect the activation of ERK1 and ERK2 by the growth factors. Furthermore, our results demonstrated that Akt, a downstream target of PI 3‐K, was activated by PDGF‐BB but not by FGF‐2. Akt activation by PDGF‐BB was inhibited by PI 3‐kinase inhibitor LY294002. Rapamycin had no effect on Akt activation. Epidermal growth factor (EGF) also activated Akt in osteoblastic cells which was inhibited by LY294002 but not by rapamycin. Taken together, our data for the first time revealed that the activation of ERK1/2 by PDGF‐BB is mediated by PI 3‐K, and secondly, Akt is activated by PDGF‐BB and EGF but not by FGF‐2 in human and mouse osteoblastic cells. These results are of critical importance in understanding the role of these growth factors in apoptosis and cell survival. PDGF‐BB and EGF but not FGF‐2 may stimulate osteoblast cell survival. J. Cell. Biochem. 81:304–311, 2001. © 2001 Wiley‐Liss, Inc.