Critical Role of Heparin Binding Domains of Ameloblastin for Dental Epithelium Cell Adhesion and Ameloblastoma Proliferation
Critical Role of Heparin Binding Domains of Ameloblastin for Dental Epithelium Cell Adhesion and Ameloblastoma Proliferation
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DOI：
10.1074/jbc.m109.033464
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发表时间：
2009-10-02
影响因子：
4.8
通讯作者：
Fukumoto, Satoshi
中科院分区：
文献类型：
--
作者：
Sonoda, Akira;Iwamoto, Tsutomu;Fukumoto, Satoshi
AMBN（成釉蛋白）是一种釉质基质蛋白，可调节成釉细胞的粘附、增殖和分化。在ambn缺陷小鼠中，成釉细胞从釉质基质中分离，继续增殖，形成多细胞层；通常，牙源性肿瘤会随着年龄的增长而在上颌骨发育。然而，AMBN在这些生物过程中的作用机制尚不清楚。通过使用重组AMBN蛋白，我们发现AMBN在c端一半具有肝素结合结构域，这些结构域对于AMBN与牙齿上皮细胞的结合至关重要。过表达全长AMBN蛋白可抑制人成釉细胞瘤AM-1细胞的增殖，而过表达肝素结合结构域缺陷的AMBN蛋白无抑制作用。在全长过表达ambn的AM-1细胞中，参与牙上皮祖细胞表型的Msx2表达降低，而细胞增殖抑制剂p21和p27表达升高。我们还发现，分化成釉细胞的标记物珐琅质的表达被诱导，这表明AMBN促进了牙源性肿瘤的分化。因此，我们的研究结果表明，AMBN通过肝素结合位点促进细胞结合，并通过Msx2、p21和p27抑制细胞增殖和维持分化表型，在预防牙源性肿瘤发展中发挥重要作用。
AMBN (ameloblastin) is an enamel matrix protein that regulates cell adhesion, proliferation, and differentiation of ameloblasts. In AMBN-deficient mice, ameloblasts are detached from the enamel matrix, continue to proliferate, and form a multiple cell layer; often, odontogenic tumors develop in the maxilla with age. However, the mechanism of AMBN functions in these biological processes remains unclear. By using recombinant AMBN proteins, we found that AMBN had heparin binding domains at the C-terminal half and that these domains were critical for AMBN binding to dental epithelial cells. Overexpression of full-length AMBN protein inhibited proliferation of human ameloblastoma AM-1 cells, but overexpression of heparin binding domain-deficient AMBN protein had no inhibitory effect. In full-length AMBN-overexpressing AM-1 cells, the expression of Msx2, which is involved in the dental epithelial progenitor phenotype, was decreased, whereas the expression of cell proliferation inhibitors p21 and p27 was increased. We also found that the expression of enamelin, a marker of differentiated ameloblasts, was induced, suggesting that AMBN promotes odontogenic tumor differentiation. Thus, our results suggest that AMBN promotes cell binding through the heparin binding sites and plays an important role in preventing odontogenic tumor development by suppressing cell proliferation and maintaining differentiation phenotype through Msx2, p21, and p27.