Yeh Lee-Chuan C, Ma Xiuye, Matheny Ronald W, Adamo Martin L, Lee John C
Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.
Growth Factors. 2010 Oct;28(5):318-28. doi: 10.3109/08977191003766874.
We previously showed that exogenous insulin-like growth factor-I (IGF-I) and bone morphogenetic protein-7 (BMP-7) synergistically stimulated osteoblast differentiation in fetal rat calvaria (FRC) cells. We have now shown that BMP-7 alone and the BMP-7 and IGF-I combination synergistically stimulated protein kinase D (PKD) phosphorylation at Ser744/748 and Ser916. Transfection of FRC cells with a constitutively active PKD stimulated marker expression, while transfection with a catalytically inactive PKD did not. Moreover, Gö6976, which inhibits protein kinase C (PKC) α and β1, blocked PKD phosphorylation and the synergistic action of the BMP-7 and IGF-I combination on osteoblast differentiation, whereas Gö6983, which inhibits PKCα, β, γ, δ, and ζ, did not. Our results suggest that the FRC cell differentiation induced by BMP-7 and the BMP-7 and IGF-I combination requires stimulation of PKD activity. Our results are consistent with a novel mechanism in which combined BMP-7 and IGF-I signaling activates upstream novel PKC(s), which then phosphorylates and activates PKD, leading to enhanced osteoblast differentiation.
我们之前发现，外源性胰岛素样生长因子-I（IGF-I）和骨形态发生蛋白-7（BMP-7）可协同刺激胎鼠颅骨（FRC）细胞的成骨细胞分化。我们现在发现，单独的BMP-7以及BMP-7与IGF-I的组合可协同刺激蛋白激酶D（PKD）在Ser744/748和Ser916位点的磷酸化。用组成型活性PKD转染FRC细胞可刺激标志物表达，而用催化失活的PKD转染则无此作用。此外，抑制蛋白激酶C（PKC）α和β1的Gö6976可阻断PKD磷酸化以及BMP-7与IGF-I组合对成骨细胞分化的协同作用，而抑制PKCα、β、β3、β4和β6的Gö6983则无此作用。我们的结果表明，BMP-7以及BMP-7与IGF-I组合诱导的FRC细胞分化需要刺激PKD活性。我们的结果与一种新机制一致，即BMP-7和IGF-I信号联合激活上游新的PKC，进而磷酸化并激活PKD，导致成骨细胞分化增强。
