Abstract
Emdogain (enamel matrix derivative, EMD) is well recognized in periodontology. It is used in periodontal surgery to regenerate cementum, periodontal ligament, and alveolar bone. However, the precise molecular mechanisms underlying periodontal regeneration are still unclear. In this study, we investigated the proteins bound to amelogenin, which are suggested to play a pivotal role in promoting periodontal tissue regeneration. To identify new molecules that interact with amelogenin and are involved in osteoblast activation, we employed coupling affinity chromatography with proteomic analysis in fractionated SaOS-2 osteoblastic cell lysate. In SaOS-2 cells, many of the amelogenin-interacting proteins in the cytoplasm were mainly cytoskeletal proteins and several chaperone molecules of heat shock protein 70 (HSP70) family. On the other hand, the proteomic profiles of amelogenin-interacting proteins in the membrane fraction of the cell extracts were quite different from those of the cytosolic-fraction. They were mainly endoplasmic reticulum (ER)-associated proteins, with lesser quantities of mitochondrial proteins and nucleoprotein. Among the identified amelogenin-interacting proteins, we validated the biological interaction of amelogenin with glucose-regulated protein 78 (Grp78/Bip), which was identified in both cytosolic and membrane-enriched fractions. Confocal co-localization experiment strongly suggested that Grp78/Bip could be an amelogenin receptor candidate. Further biological evaluations were examined by Grp78/Bip knockdown analysis with and without amelogenin. Within the limits of the present study, the interaction of amelogenin with Grp78/Bip contributed to cell proliferation, rather than correlate with the osteogenic differentiation in SaOS-2 cells. Although the biological significance of other interactions are not yet explored, these findings suggest that the differential effects of amelogenin-derived osteoblast activation could be of potential clinical significance for understanding the cellular and molecular bases of amelogenin-induced periodontal tissue regeneration.
Highlights
IntroductionAmelogenins (enamel matrix proteins) are a group of lowmolecular-weight proteins found in developing tooth enamel [1]; it belongs to a family of extracellular matrix (ECM) proteins
Amelogenins are a group of lowmolecular-weight proteins found in developing tooth enamel [1]; it belongs to a family of extracellular matrix (ECM) proteins
As a precondition for establishing the physiological interaction between amelogenin and the cellular proteins, we firstly examined the pattern of cellular internalization of amelogenin
Summary
Amelogenins (enamel matrix proteins) are a group of lowmolecular-weight proteins found in developing tooth enamel [1]; it belongs to a family of extracellular matrix (ECM) proteins. Amelogenin genes are highly conserved in vertebrates [2], and this stability indicates the essential role in enamel formation. The role of amelogenins in periodontal ligament formation is supported by their presence during the development of cementum by directing the cells that form cementum to the root surface of teeth [5]. Amelogenins are secreted mainly by ameloblasts and partly by Hertwig's epithelial root sheet (HERS) cells [6]. Amelogenin is temporarily deposited onto the dentin root surface, and form an initial and essential step in cementogenesis [7]. Amelogenin plays an important role in enamel formation, and as a mediator of cementogenesis and in the attachment of periodontal ligament
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