TY - JOUR
T1 - Regulation of matrix Gla protein by parathyroid hormone in MC3T3-E1 osteoblast-like cells involves protein kinase A and extracellular signal-regulated kinase pathways
AU - Suttamanatwong, Supaporn
AU - Franceschi, Renny T.
AU - Carlson, Ann E.
AU - Gopalakrishnan, Rajaram
PY - 2007/10/1
Y1 - 2007/10/1
N2 - Inhibition of osteoblast-mediated mineralization is one of the major catabolic effects of parathyroid hormone (PTH) on bone. Previously, we showed that PTH induces matrix γ-carboxyglutamic acid (Gla) protein (MGP) expression and established that this induction is critical for PTH-mediated inhibition of osteoblast mineralization. In the present study, we focus on the mechanism through which PTH regulates MGP expression in osteoblastic MC3T3-E1 cells. Following transient transfection of these cells with a -748 bp murine MGP promoter-luciferase construct (pMGP-luc), PTH (10 -7 M) induced promoter activity in a time-dependent manner with a maximal four- to six fold induction seen 6 h after PTH treatment. Both H-89 (PKA inhibitor) and U0126 (MEK inhibitor), suppressed PTH induction of MGP promoter activity as well as the MGP mRNA level. In addition, forskolin (PKA activator) stimulated MGP promoter activity and mRNA levels confirming that PKA is one of the signaling molecules required for regulation of MGP by PTH. Co-transfection of MC3T3-E1 cells with pMGP-luc and MEK(SP), a plasmid encoding the constitutively active form of MEK, led to a dose-dependent increase in MGP promoter activity. Both MGP promoter activity and MGP mRNA level were not affected by the protein kinase C (PKC) inhibitor, GF109203X. However, phorbol 12-myristate 13-acetate (PMA), a selective PKC activator induced MGP mRNA expression through activation of extracellular signal-regulated kinase (ERK). Taken together, these results indicate that PTH regulates MGP via both PKA- and ERK-dependent pathways.
AB - Inhibition of osteoblast-mediated mineralization is one of the major catabolic effects of parathyroid hormone (PTH) on bone. Previously, we showed that PTH induces matrix γ-carboxyglutamic acid (Gla) protein (MGP) expression and established that this induction is critical for PTH-mediated inhibition of osteoblast mineralization. In the present study, we focus on the mechanism through which PTH regulates MGP expression in osteoblastic MC3T3-E1 cells. Following transient transfection of these cells with a -748 bp murine MGP promoter-luciferase construct (pMGP-luc), PTH (10 -7 M) induced promoter activity in a time-dependent manner with a maximal four- to six fold induction seen 6 h after PTH treatment. Both H-89 (PKA inhibitor) and U0126 (MEK inhibitor), suppressed PTH induction of MGP promoter activity as well as the MGP mRNA level. In addition, forskolin (PKA activator) stimulated MGP promoter activity and mRNA levels confirming that PKA is one of the signaling molecules required for regulation of MGP by PTH. Co-transfection of MC3T3-E1 cells with pMGP-luc and MEK(SP), a plasmid encoding the constitutively active form of MEK, led to a dose-dependent increase in MGP promoter activity. Both MGP promoter activity and MGP mRNA level were not affected by the protein kinase C (PKC) inhibitor, GF109203X. However, phorbol 12-myristate 13-acetate (PMA), a selective PKC activator induced MGP mRNA expression through activation of extracellular signal-regulated kinase (ERK). Taken together, these results indicate that PTH regulates MGP via both PKA- and ERK-dependent pathways.
KW - Extracellular signal-related kinase
KW - Matrix gla protein
KW - Osteoblast
KW - Parathyroid hormone
KW - Protein kinase A
KW - Protein kinase C
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U2 - 10.1002/jcb.21314
DO - 10.1002/jcb.21314
M3 - Article
C2 - 17407158
AN - SCOPUS:34948899776
SN - 0730-2312
VL - 102
SP - 496
EP - 505
JO - Journal of supramolecular structure and cellular biochemistry
JF - Journal of supramolecular structure and cellular biochemistry
IS - 2
ER -