Involvement of the Osteoinductive Factors, Tmem119 and BMP-2, and the ER Stress Response PERK–eIF2α–ATF4 Pathway in the Commitment of Myoblastic into Osteoblastic Cells
Involvement of the Osteoinductive Factors, Tmem119 and BMP-2, and the ER Stress Response PERK–eIF2α–ATF4 Pathway in the Commitment of Myoblastic into Osteoblastic Cells
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DOI：
10.1007/s00223-013-9828-1
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发表时间：
2013-12
影响因子：
4.2
通讯作者：
Ken-ichiro Tanaka;H. Kaji;Toru Yamaguchi;I. Kanazawa;L. Canaff;G. Hendy;T. Sugimoto
中科院分区：
文献类型：
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作者：
Ken-ichiro Tanaka;H. Kaji;Toru Yamaguchi;I. Kanazawa;L. Canaff;G. Hendy;T. Sugimoto
促进成肌细胞分化成骨细胞的骨诱导因子BMP-2和Tmem 119各自增加另一个的水平。然而，BMP-2和Tmem 119对成骨分化的相对贡献以及所涉及的机制尚不完全清楚。在本研究中，我们研究了BMP-2、Tmem 119和PERK-eIF 2 α-ATF 4内质网（ER）应激反应通路在C2 C12成肌细胞向成骨细胞分化中的关系。BMP-2和Tmem 119都诱导成骨细胞标志物Runx 2、Osterix、Col 1a 1、ALP和骨钙素的水平以及矿化。ER应激传感器PERK的BMP-2激活刺激eIF 2 α的磷酸化，并导致成骨细胞分化因子ATF 4的生物合成增加。当选择性抑制剂salubrinal阻断eIF 2 α的去磷酸化作用时，BMP-2和Tmem 119的成骨作用进一步增强。虽然BMP-2刺激P-eIF 2 α和ATF 4水平，但Tmem 119对P-eIF 2 α没有影响，而仅刺激ATF 4。通过siRNA降低内源性Tmem 119水平降低了ATF 4蛋白的基础水平和BMP-2刺激水平。总之，BMP-2通过PERK-eIF 2 α-ATF 4途径刺激成肌细胞分化为成骨细胞，但另外刺激Tmem 119，其本身增加ATF 4。因此，BMP-2刺激ATF 4既依赖于也不依赖于PERK-eIF 2 α ER应激反应途径。
The osteoinductive factors BMP-2 and Tmem119 that promote the differentiation of myoblasts into osteoblasts, each increase the levels of the other. However, the relative contributions of BMP-2 and Tmem119 to the osteogenic differentiation and the mechanisms involved are incompletely understood. In the present study, we examined the relationship among BMP-2, Tmem119, and the PERK–eIF2α–ATF4 endoplasmic reticulum (ER) stress response pathway in the differentiation of C2C12 myoblasts into osteoblastic cells. Both BMP-2 and Tmem119 induced levels of the osteoblast markers Runx2, Osterix, Col1a1, ALP, and osteocalcin, as well as mineralization. BMP-2 activation of the ER stress sensor PERK stimulated phosphorylation of eIF2α and led to increased biosynthesis of the osteoblast differentiation factor ATF4. When dephosphorylation of eIF2α was blocked by the selective inhibitor salubrinal, the osteogenic effects of BMP-2 and Tmem119 were enhanced further. Although BMP-2 stimulated both P-eIF2α and ATF4 levels, Tmem119 had no effect on P-eIF2α but stimulated ATF4 only. Reduction in endogenous Tmem119 levels by siRNA reduced both basal and BMP-2-stimulated levels of the ATF4 protein. In conclusion, BMP-2 stimulates differentiation of myoblasts into osteoblasts via the PERK–eIF2α–ATF4 pathway but in addition stimulates Tmem119, which itself increases ATF4. Hence, BMP-2 stimulates ATF4 both dependently and independently of the PERK–eIF2α ER stress response pathway.