Glycosaminoglycan chains of biglycan promote bone morphogenetic protein-4-induced             osteoblast differentiation.
Biglycan (BGN) has been reported to promote bone morphogenetic protein-4 (BMP-4) stimulated osteoblastic differentiation. However, the underlying mechanism has yet to be fully elucidated. The glycosaminoglycan (GAG) chains of BGN have a variety of biological functions. In the present study, we explored the potential role of the GAG chains of BGN in promoting BMP-4-induced osteoblast differentiation. BGN knockout (KO) murine calvarial cells were transfected with adenovirus overexpressing wild-type BGN (Adv-BGN), adenovirus expressing GAG-mutant BGN (Adv-BGNm) and adenovirus without BGN (Adv-Emp). Transfected cells were treated with or without BMP-4. Subsequently, BMP-4 signaling and function were assessed by evaluating the expression of the osteoblast differentiation-related proteins, Smad1/5/8 phosphorylation and alkaline phosphatase (ALP) activity. Furthermore, the binding specificity of the transfected cells to BMP-4 was also investigated using immunofluorescence staining. Our study demonstrated that a mutant BGN lacking GAG chains decreased BGN-assisted BMP-4 signaling and osteoblast differentiation and that the expression of this mutant BGN in biglycan knockout (BGN‑KO) calvarial osteoblasts could not rescue its differentiation deficiency as efficiently as wild-type (WT) BGN. These results strongly suggest that the GAG chains of BGN promote BGN-assisted BMP-4 function.
Department of Orthopedics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, PR China.
Yaping
Y
Ye
Weihua
W
Hu
Fengjing
F
Guo
Weikai
W
Zhang
Jiang
J
Wang
Anmin
A
Chen
D000256:Adenoviridae / Q000235:genetics; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D058578:Biglycan / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D055415:Bone Morphogenetic Protein 4 / Q000378:metabolism / Q000502:physiology*; D002454:Cell Differentiation; D002478:Cells, Cultured; D015870:Gene Expression; D006025:Glycosaminoglycans / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D058574:Integrin-Binding Sialoprotein / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010006:Osteoblasts / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D015675:Osteocalcin / Q000378:metabolism; D053495:Osteopontin / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D012886:Skull / Q000166:cytology; D051785:Smad Proteins / Q000378:metabolism
D000943:Antigens, Differentiation; D058578:Biglycan; D055415:Bone Morphogenetic Protein 4; D006025:Glycosaminoglycans; C546872:Ibsp protein, mouse; D058574:Integrin-Binding Sialoprotein; D011994:Recombinant Proteins; D051785:Smad Proteins; D015675:Osteocalcin; D053495:Osteopontin; D000469:Alkaline Phosphatase