TY - JOUR
T1 - Lactacystin, a proteasome inhibitor, enhances BMP-induced osteoblastic differentiation by increasing active Smads
AU - Ito, Yuki
AU - Fukushima, Hidefumi
AU - Katagiri, Takenobu
AU - Seo, Yoshinori
AU - Hirata, Shizu
AU - Zhang, Min
AU - Hosokawa, Ryuji
AU - Jimi, Eijiro
N1 - Funding Information:
This work was supported by a grant from the Suzuken Memorial Foundation (to E.J.); a grant-in-aid from the Takeda Science Foundation (to T.K.); the Ministry of Education, Culture, Sports, Science and Technology of Japan (to M.Z.: 22592042 ); and a grant-in-aid from Kyushu Dental College Internal Grants (to H.F. and E.J.).
PY - 2011/4/1
Y1 - 2011/4/1
N2 - Proteasome inhibitors enhance bone formation and osteoblastic differentiation in vivo and in vitro. In the present study, we examined whether the molecular mechanisms of lactacystin, one of many proteasome inhibitors, stimulated the osteoblastic differentiation of C2C12 cells that is induced by bone morphogenetic proteins (BMPs). Pretreatment with lactacystin enhanced the alkaline phosphatase (ALP) activity induced by BMP2, BMP4 or BMP7, but lactacystin did not induce ALP in the absence of BMPs. In addition, lactacystin-stimulated BMP2 induced mRNA expression of ALP, type I collagen, osteonectin, osteocalcin, Id1, Osterix, and Runx2. Lactacystin maintained BMP2-induced phosphorylation of Smad1/5/8 and increased the length of time that these Smads were bound to target DNA. Moreover, lactacystin prevented BMP receptor-induced Smad degradation. This enhancement of BMP2-induced ALP activity and Smad phosphorylation by lactacystin was also observed in primary osteoblasts. These findings suggest that pretreatment with lactacystin accelerates BMP-induced osteoblastic differentiation by increasing the levels of phosphorylated Smads, which are maintained because BMP receptor-induced degradation is inhibited. We propose that optimized stimulation by proteasome inhibitors in a clinical setting may facilitate autogenous or BMP-induced bone formation in areas of defective bone.
AB - Proteasome inhibitors enhance bone formation and osteoblastic differentiation in vivo and in vitro. In the present study, we examined whether the molecular mechanisms of lactacystin, one of many proteasome inhibitors, stimulated the osteoblastic differentiation of C2C12 cells that is induced by bone morphogenetic proteins (BMPs). Pretreatment with lactacystin enhanced the alkaline phosphatase (ALP) activity induced by BMP2, BMP4 or BMP7, but lactacystin did not induce ALP in the absence of BMPs. In addition, lactacystin-stimulated BMP2 induced mRNA expression of ALP, type I collagen, osteonectin, osteocalcin, Id1, Osterix, and Runx2. Lactacystin maintained BMP2-induced phosphorylation of Smad1/5/8 and increased the length of time that these Smads were bound to target DNA. Moreover, lactacystin prevented BMP receptor-induced Smad degradation. This enhancement of BMP2-induced ALP activity and Smad phosphorylation by lactacystin was also observed in primary osteoblasts. These findings suggest that pretreatment with lactacystin accelerates BMP-induced osteoblastic differentiation by increasing the levels of phosphorylated Smads, which are maintained because BMP receptor-induced degradation is inhibited. We propose that optimized stimulation by proteasome inhibitors in a clinical setting may facilitate autogenous or BMP-induced bone formation in areas of defective bone.
KW - BMP
KW - Lactacystin
KW - Osteoblast differentiation
KW - Proteasome inhibitor
KW - Smad1
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U2 - 10.1016/j.bbrc.2011.03.003
DO - 10.1016/j.bbrc.2011.03.003
M3 - Article
C2 - 21377449
AN - SCOPUS:79953163437
SN - 0006-291X
VL - 407
SP - 225
EP - 229
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
IS - 1
ER -