The role of annexin 2 in osteoblastic mineralization
The role of annexin 2 in osteoblastic mineralization
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DOI：
10.1242/jcs.00909
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发表时间：
2004-01-26
影响因子：
4
通讯作者：
Nielsen-Preiss, SM
中科院分区：
文献类型：
--
作者：
Gillette, JM;Nielsen-Preiss, SM
虽然细胞对骨分化和矿化的基本贡献已被广泛接受，但对这些过程在细胞内水平的调节仍知之甚少。我们的实验室最近鉴定出膜联蛋白 2 是一种参与成骨细胞矿化的蛋白质。膜联蛋白 2 作为与绿色荧光蛋白的融合蛋白在 SaOSLM2 成骨细胞中过表达两倍。膜联蛋白 2 的过度表达导致碱性磷酸酶活性增加以及矿化作用增加。我们的数据表明，碱性磷酸酶活性的增加并不是由于碱性磷酸酶转录物或蛋白质水平增加所致；而是由于碱性磷酸酶活性的增加。因此我们评估了作用机制。我们确定膜联蛋白 2 和碱性磷酸酶活性均定位于成骨细胞中称为脂筏的膜微域。膜联蛋白 2 过表达导致碱性磷酸酶活性增加，该活性以胆固醇依赖性方式与脂质微结构域相关。此外，用胆固醇螯合剂破坏脂筏或用特定反义寡核苷酸减少膜联蛋白2的表达都会导致矿化减少。因此，含有膜联蛋白 2 的完整脂筏似乎对碱性磷酸酶活性很重要，并且可能促进成骨细胞矿化过程。
While the basic cellular contributions to bone differentiation and mineralization are widely accepted, the regulation of these processes at the intracellular level remains inadequately understood. Our laboratory recently identified annexin 2 as a protein involved in osteoblastic mineralization. Annexin 2 was overexpressed twofold in SaOSLM2 osteoblastic cells as a fusion protein with green fluorescent protein. The overexpression of annexin 2 led to an increase in alkaline phosphatase activity as well as an increase in mineralization. Our data suggest that the increase in alkaline phosphatase activity does not result from increased alkaline phosphatase transcript or protein levels; therefore we evaluated mechanism of action. We determined that both annexin 2 and alkaline phosphatase activity were localized to membrane microdomains called lipid rafts in osteoblastic cells. Annexin 2 overexpression resulted in an increase in alkaline phosphatase activity that was associated with lipid microdomains in a cholesterol-dependent manner. Furthermore, disruption of lipid rafts with a cholesterol sequestering agent or reduction of annexin 2 expression by specific antisense oligonucleotides each resulted in diminished mineralization. Therefore, intact lipid rafts containing annexin 2 appear to be important for alkaline phosphatase activity and may facilitate the osteoblastic mineralization process.