Mechanical stress activates Smad pathway through PKCδ to enhance interleukin-11 gene transcription in osteoblasts

• Published in: PloS one Vol. 5; no. 9; p. e13090
• Main Authors: Kido, Shinsuke, Kuriwaka-Kido, Rika, Umino-Miyatani, Yuka, Endo, Itsuro, Inoue, Daisuke, Taniguchi, Hisaaki, Inoue, Yasumichi, Imamura, Takeshi, Matsumoto, Toshio
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 29-09-2010; Public Library of Science (PLoS)
• Subjects: 21st century; Activator protein 1; Animals; Binding; Biochemistry; Biocompatibility; Bone marrow; Bone morphogenetic proteins; Bone Morphogenetic Proteins - genetics; Bone Morphogenetic Proteins - metabolism; Cancer; Cell Biology; Cell Biology/Cell Signaling; Cell Line; Cells, Cultured; Chemokines; Cytokines; Diabetes and Endocrinology/Bone and Mineral Metabolism; Differentiation; Enzymes; Experiments; Fibroblasts; Fluid flow; Gene expression; Humans; Interleukin; Interleukin 11; Interleukin-11 - genetics; Interleukin-11 - metabolism; Intracellular signalling; Kinases; Mechanical loading; Mechanical stimuli; Medical research; Medicine; Mice; Mutagenesis; Osteoblastogenesis; Osteoblasts; Osteoblasts - chemistry; Osteoblasts - enzymology; Osteoblasts - metabolism; Phosphorylation; Protein Binding; Protein kinase C; Protein Kinase C-delta - genetics; Protein Kinase C-delta - metabolism; Proteins; Shear stress; Shear stresses; Signal Transduction; siRNA; Site-directed mutagenesis; Smad protein; Smad Proteins - genetics; Smad Proteins - metabolism; Stress, Mechanical; Transcription; Transcription factors; Transcription, Genetic; Transfection; Transgenic animals; Japan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0013090

Mechanical stress rapidly induces ΔFosB expression in osteoblasts, which binds to interleukin (IL)-11 gene promoter to enhance IL-11 expression, and IL-11 enhances osteoblast differentiation. Because bone morphogenetic proteins (BMPs) also stimulate IL-11 expression in osteoblasts, there is a possibility that BMP-Smad signaling is involved in the enhancement of osteoblast differentiation by mechanical stress. The present study was undertaken to clarify whether mechanical stress affects BMP-Smad signaling, and if so, to elucidate the role of Smad signaling in mechanical stress-induced enhancement of IL-11 gene transcription.
Mechanical loading by fluid shear stress (FSS) induced phosphorylation of BMP-specific receptor-regulated Smads (BR-Smads), Smad1/5, in murine primary osteoblasts (mPOBs). FSS rapidly phosphorylated Y311 of protein kinase C (PKC)δ, and phosphorylated PKCδ interacted with BR-Smads to phosphorylate BR-Smads. Transfection of PKCδ siRNA or Y311F mutant PKCδ abrogated BR-Smads phosphorylation and suppressed IL-11 gene transcription enhanced by FSS. Activated BR-Smads bound to the Smad-binding element (SBE) of IL-11 gene promoter and formed complex with ΔFosB/JunD heterodimer via binding to the C-terminal region of JunD. Site-directed mutagenesis in the SBE and the AP-1 site revealed that both SBE and AP-1 sites were required for full activation of IL-11 gene promoter by FSS.
These results demonstrate that PKCδ-BR-Smads pathway plays an important role in the intracellular signaling in response to mechanical stress, and that a cross-talk between PKCδ-BR-Smads and ΔFosB/JunD pathways synergistically stimulates IL-11 gene transcription in response to mechanical stress.