The Role of Pannexin 3 in Bone Biology.
Cell-cell and cell-matrix communications play important roles in both cell proliferation and differentiation. Gap junction proteins mediate signaling communication by exchanging small molecules and dramatically stimulating intracellular signaling pathways to determine cell fate. Vertebrates have 2 gap junction families: pannexins (Panxs) and connexins (Cxs). Unlike Cxs, the functions of Panxs are not fully understood. In skeletal formation, Panx3 and Cx43 are the most abundantly expressed gap junction proteins from each family. Panx3 is induced in the transient stage from the proliferation and differentiation of chondrocytes and osteoprogenitor cells. Panx3 regulates both chondrocyte and osteoblast differentiation via the activation of intracellular Ca2+signaling pathways through multiple channel activities: hemichannels, endoplasmic reticulum (ER) Ca2+channels, and gap junctions. Moreover, Panx3 also inhibits osteoprogenitor cell proliferation and promotes cell cycle exit through the inactivation of Wnt/β-catenin signaling and the activation of p21. Panx3-knockout (KO) mice have more severe skeletal abnormalities than those of Cx43-KO mice. A phenotypic analysis of Panx3-KO mice indicates that Panx3 regulates the terminal differentiation of chondrocytes by promoting vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP) 13. Based on the generation of Panx3-/-; Cx43-/-mice, Panx3 is upstream of Cx43 in osteogenesis. Panx3 promotes Cx43 expression by regulating Wnt/β-catenin signaling and osterix expression. Further, although Panx3 can function in 3 ways, Cx43 cannot function through the ER Ca2+channel, only via the hemichannels and gap junction routes. In this review, we discuss the current knowledge regarding the roles of Panx3 in skeletal formation and address the potential for new therapies in the treatment of diseases and pathologies associated with Panx3, such as osteoarthritis (OA).
1 Division of Operative Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan.|2 Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
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Ishikawa
2 Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
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Yamada
D000818:Animals; D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation / Q000502:physiology; D019902:Chondrocytes / Q000502:physiology; D017630:Connexins / Q000502:physiology*; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D051379:Mice; D010006:Osteoblasts / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology*; D010641:Phenotype; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D060449:Wnt Signaling Pathway
D017630:Connexins; D042461:Vascular Endothelial Growth Factor A; C528477:pannexin 3 protein, mouse; D053509:Matrix Metalloproteinase 13; C507081:Mmp13 protein, mouse
Panx3 ER Ca2+ channel signaling; Wnt/β-catenin; bone formation; endochondral ossification; gap junction proteins; osteoblast proliferation and differentiation