title: Protein kinase D mediates the synergistic effects of BMP-7 and IGF-I on osteoblastic cell differentiation.
abstract: We previously showed that exogenous insulin-like growth factor-I (IGF-I) and bone morphogenetic protein-7 (BMP-7) synergistically stimulated osteoblast differentiation in fetal rat calvaria (FRC) cells. We have now shown that BMP-7 alone and the BMP-7 and IGF-I combination synergistically stimulated protein kinase D (PKD) phosphorylation at Ser744/748 and Ser916. Transfection of FRC cells with a constitutively active PKD stimulated marker expression, while transfection with a catalytically inactive PKD did not. Moreover, G&#x00F6;6976, which inhibits protein kinase C (PKC) &#x03B1; and &#x03B2;1, blocked PKD phosphorylation and the synergistic action of the BMP-7 and IGF-I combination on osteoblast differentiation, whereas G&#x00F6;6983, which inhibits PKC&#x03B1;, &#x03B2;, &#x03B3;, &#x03B4;, and &#x03B6;, did not. Our results suggest that the FRC cell differentiation induced by BMP-7 and the BMP-7 and IGF-I combination requires stimulation of PKD activity. Our results are consistent with a novel mechanism in which combined BMP-7 and IGF-I signaling activates upstream novel PKC(s), which then phosphorylates and activates PKD, leading to enhanced osteoblast differentiation.
authors.affiliation: Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA. yehl@uthscsa.edu
authors.forename: Lee-Chuan C
authors.initials: LC
authors.lastname: Yeh
authors.forename: Xiuye
authors.initials: X
authors.lastname: Ma
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Matheny
authors.forename: Martin L
authors.initials: ML
authors.lastname: Adamo
authors.forename: John C
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000818:Animals; D055419:Bone Morphogenetic Protein 7 / Q000494:pharmacology*; D002227:Carbazoles / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats
chemical_list: D055419:Bone Morphogenetic Protein 7; D002227:Carbazoles; D004791:Enzyme Inhibitors; C081021:Go 6976; D007334:Insulin-Like Growth Factor I; C089212:protein kinase D; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha