Integrin αvβ3 mediates the synergetic regulation of core-binding factor α1 transcriptional activity by gravity and insulin-like growth factor-1 through phosphoinositide 3-kinase signaling

• Published in: Bone (New York, N.Y.) Vol. 69; pp. 126 - 132
• Main Authors: Dai, Zhongquan, Guo, Feima, Wu, Feng, Xu, Hongjie, Yang, Chao, Li, Jinqiao, Liang, Peilong, Zhang, Hongyu, Qu, Lina, Tan, Yingjun, Wan, Yumin, Li, Yinghui
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-12-2014; Elsevier
• Subjects: 3T3 Cells; Animals; Biological and medical sciences; Blotting, Western; Bone loss; Bone Remodeling - physiology; Cbfa1; Core Binding Factor Alpha 1 Subunit - metabolism; Diseases of the osteoarticular system; Fundamental and applied biological sciences. Psychology; Gravity; Gravity, Altered - adverse effects; IGF-1; Immunoprecipitation; Insulin-Like Growth Factor I - metabolism; Integrin alphaVbeta3 - metabolism; Integrin αvβ3; Medical sciences; Mice; Orthopedics; Osteoporosis. Osteomalacia. Paget disease; Phosphatidylinositol 3-Kinases - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Small Interfering; Signal Transduction - drug effects; Space Flight; Synergetic regulation; Transfection; Traumas. Diseases due to physical agents; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Weightlessness - adverse effects; hypergravity; IRS1; ALP; Synergetic regulation; co-immunoprecipitation; cell culture box; EGFP; co-IP; core-binding factor alpha 1; OSE2; PI3K; alkaline phosphatase; Bone loss; Gravity; CCB; Col1a1; Type I Collagen alpha 1 chain; Cbfa1; IGF-1; SMG; Osteoblast-Specific Element 2; Integrin αvβ3; insulin receptor substrate 1; enhanced green fluorescent protein; Insulin-like growth factor 1; simulated microgravity; phosphoinositide 3-kinase; HG; Enzyme; Transferases; Diseases of the osteoarticular system; Insulin like growth factor 1; Integrin; Kinase; Morphology; Orthopedics; Osteopenia
• ISSN: 8756-3282; 1873-2763
• DOI: 10.1016/j.bone.2014.09.018

Abstract Mechanical stimulation and biological factors coordinately regulate bone development and regeneration; however, the underlying mechanisms are poorly understood. Microgravity induces bone loss, which may be partly related to the development of resistance to local cytokines, including insulin-like growth factor 1 (IGF-1). Here, we report the involvement of integrin αvβ3 in microgravity-associated bone loss. An established OSE-3T3 cell model was stably transfected with a 6OSE2 (Osteoblast-Specific Element 2)-luciferase reporter and cultured under simulated microgravity (SMG) and hypergravity (HG) conditions in the presence or absence of IGF-1, the disintegrin echistatin, the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, or combinations of these agents. Activity of core-binding factor α1 (Cbfa1), an essential transcription factor for osteoblastic differentiation and osteogenesis, was reflected by luciferase activity. Different gravity conditions affected the induction of IGF-1 and subsequent effects on Cbfa1 transcription activity. SMG and HG influenced the expression and activity of integrin αvβ3 and phosphorylation level of p85. LY294002 inhibited the effects of HG or IGF-1 on Cbfa1 activity, indicating that HG and IGF-1 could increase Cbfa1 activity via PI3K signaling. Inhibition of integrin αvβ3 by echistatin attenuated the induction of IGF-1 and thus its effect on Cbfa1 activity under normal and HG conditions. Co-immunoprecipitation demonstrated that integrin β3 interacted with insulin receptor substrate 1, and that this interaction was decreased under SMG and increased under HG conditions. These results suggest that integrin αvβ3 mediates the synergetic regulation of Cbfa1 transcription activity by gravity and IGF-1 via PI3K signaling.