Truncated human LMP-1 triggers differentiation of C2C12 cells to an osteoblastic phenotype in vitro.
LIM mineralization protein-1 (LMP-1) is a novel intracellular osteoinductive protein that has been shown to induce bone formation both in vitro and in vivo. LMP-1 contains an N-terminal PDZ domain and three C-terminal LIM domains. In this study, we investigated whether a truncated form of human LMP-1 (hLMP-1[t]), lacking the three C-terminal LIM domains, triggers the differentiation of pluripotent myoblastic C(2)C(12) cells to the osteoblast lineage. C(2)C(12) cells were transiently transduced with Ad5-hLMP-1(t)-green fluorescent protein or viral vector control. The expression of hLMP-1(t) RNA and the truncated protein were examined. The results showed that hLMP-1(t) blocked myotube formation in C(2)C(12) cultures and significantly enhanced the alkaline phosphatase (ALP) activity. In addition, the expressions of ALP, osteocalcin, and bone morphogenetic protein (BMP)-2 and BMP-7 genes were also increased. The induction of these key osteogenic markers suggests that hLMP-1(t) can trigger the pluripotent myoblastic C2C12 cells to differentiate into osteoblastic lineage, thus extending our previous observation that LMP-1 and LMP-1(t) enhances the osteoblastic phenotype in cultures of cells already committed to the osteoblastic lineage. Therefore, C(2)C(12) cells are an appropriate model system for the examination of LMP-1 induction of the osteoblastic phenotype and the study of mechanisms of LMP-1 action.
Fei
Qinming
Q
Department of Orthopaedics, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
Boden
Scott D
SD
Sangadala
Sreedhara
S
Viggeswarapu
Manjula
M
Liu
Yunshan
Y
Titus
Louisa
L
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D019070:Cell Lineage / Q000235:genetics; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins; D018014:Gene Transfer Techniques; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D060588:LIM Domain Proteins; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000166:cytology*; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism; D051381:Rats; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism