Syndecan-1 regulates αvβ5 integrin activity in B82L fibroblasts
Syndecan-1 regulates αvβ5 integrin activity in B82L fibroblasts
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DOI：
10.1242/jcs.02970
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发表时间：
2006-06-15
影响因子：
4
通讯作者：
Rapraeger, Alan C.
中科院分区：
文献类型：
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作者：
McQuade, Kyle J.;Beauvais, DeannaLee M.;Rapraeger, Alan C.
B82 L小鼠成纤维细胞通过多配体蛋白聚糖-1介导的α（v）β（5）整联蛋白的活化对纤连蛋白或玻连蛋白作出反应。附着于syndecan-1特异性抗体的细胞仅显示丝状伪足延伸。然而，当抗体基质补充有血清或低浓度的吸附的玻连蛋白或纤连蛋白时，多配体锚定的细胞延伸板状伪足，所述血清或低浓度的吸附的玻连蛋白或纤连蛋白在单独铺板时不足以激活整联蛋白。通过用靶向α（v）整联蛋白的含（Arg-Gly-Asp）肽和功能阻断抗体处理以及通过siRNA介导的β（5）整联蛋白表达沉默来阻断整联蛋白活化。此外，通过与重组多配体蛋白聚糖-1胞外域核心蛋白的竞争以及通过小鼠特异性siRNA下调小鼠多配体蛋白聚糖-1表达，阻断了α（v）β（5）介导的细胞在高浓度玻连蛋白上的附着和扩散。利用siRNA的物种特异性，表达人多配体蛋白聚糖-1构建体的拯救实验将激活位点追踪到多配体蛋白聚糖-1胞外域。此外，全长小鼠和人syndecan-1都与β（5）整联蛋白亚基发生免疫共沉淀，但如果syndecan通过与可溶性重组syndecan-1胞外域竞争而被取代，则无法发生免疫共沉淀。这些结果表明多配体蛋白聚糖-1核心蛋白的胞外域含有与α（v）β（5）整联蛋白组装成复合物并调节α（v）β（5）整联蛋白活性的活性位点。
B82L mouse fibroblasts respond to fibronectin or vitronectin via a syndecan-1-mediated activation of the alpha(v)beta(5) integrin. Cells attached to syndecan-1-specific antibody display only filopodial extension. However, the syndecan-anchored cells extend lamellipodia when the antibody-substratum is supplemented with serum, or low concentrations of adsorbed vitronectin or fibronectin, that are not sufficient to activate the integrin when plated alone. Integrin activation is blocked by treatment with (Arg-Gly-Asp)-containing peptides and function-blocking antibodies that target alpha(v) integrins, as well as by siRNA-mediated silencing of beta(5) integrin expression. In addition, alpha(v)beta(5)-mediated cell attachment and spreading on high concentrations of vitronectin is blocked by competition with recombinant syndecan-1 ectodomain core protein and by downregulation of mouse syndecan-1 expression by mouse-specific siRNA. Taking advantage of the species-specificity of the siRNA, rescue experiments in which human syndecan-1 constructs are expressed trace the activation site to the syndecan-1 ectodomain. Moreover, both full-length mouse and human syndecan-1 coimmunoprecipitate with the beta(5) integrin subunit, but fail to do so if the syndecan is displaced by competition with soluble, recombinant syndecan-1 ectodomain. These results suggest that the ectodomain of the syndecan-1 core protein contains an active site that assembles into a complex with the alpha(v)beta(5) integrin and regulates alpha(v)beta(5) integrin activity.