M-Ras is activated by bone morphogenetic protein-2 and participates in osteoblastic determination, differentiation, and transdifferentiation.
The small GTPase M-Ras is highly expressed in the central nervous system and plays essential roles in neuronal differentiation. However, its other cellular and physiological functions remain to be elucidated. Here, we clarify the novel functions of M-Ras in osteogenesis. M-Ras was prominently expressed in developing mouse bones particularly in osteoblasts and hypertrophic chondrocytes. Its expression was elevated in C3H/10T1/2 (10T1/2) mesenchymal cells and in MC3T3-E1 preosteoblasts during differentiation into osteoblasts. Treatment of C2C12 skeletal muscle myoblasts with bone morphogenetic protein-2 (BMP-2) to bring about transdifferentiation into osteoblasts also induced M-Ras mRNA and protein expression. Moreover, the BMP-2 treatment activated the M-Ras protein. Stable expression of the constitutively active M-Ras(G22V) in 10T1/2 cells facilitated osteoblast differentiation. M-Ras(G22V) also induced transdifferentiation of C2C12 cells into osteoblasts. In contrast, knockdown of endogenous M-Ras by RNAi interfered with osteoblast differentiation in 10T1/2 and MC3T3-E1 cells. Osteoblast differentiation in M-Ras(G22V)-expressing C2C12 cells was inhibited by treatment with inhibitors of p38 MAP kinase (MAPK) and c-Jun N-terminal kinase (JNK) but not by inhibitors of MAPK and ERK kinase (MEK) or phosphatidylinositol 3-kinase. These results imply that M-Ras, induced and activated by BMP-2 signaling, participates in the osteoblastic determination, differentiation, and transdifferentiation under p38 MAPK and JNK regulation.
Watanabe-Takano
Haruko
H
Department of Biology, Graduate School of Science, Chiba University, Inageku, Chiba 263-8522, Japan.
Takano
Kazunori
K
Keduka
Etsuko
E
Endo
Takeshi
T
D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D054338:Cell Transdifferentiation / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D051379:Mice; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D018631:ras Proteins
D055396:Bone Morphogenetic Protein 2; D012333:RNA, Messenger; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C109418:Mras protein, mouse; D020559:Monomeric GTP-Binding Proteins; D018631:ras Proteins