CD44 and annexin A2 mediate the C5a chemotactic cofactor function of the vitamin D binding protein
CD44 and annexin A2 mediate the C5a chemotactic cofactor function of the vitamin D binding protein
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DOI：
10.4049/jimmunol.175.7.4754
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发表时间：
2005-10-01
影响因子：
4.4
通讯作者：
Kew, RR
中科院分区：
文献类型：
--
作者：
McVoy, LA;Kew, RR
维生素 D 结合蛋白 (DBP) 是一种血浆蛋白，可显着增强 C5a 和 C5a(desArg) 的趋化活性（共趋化活性）。本研究的目的是研究 DBP 如何使用中性粒细胞和转染 C5a 受体的 U937 细胞（U937-C5aR 细胞）介导这一过程，并比较 C 激活血清（DBP 依赖性）与纯化 C5a（DBP 独立）的趋化性。与细胞表面的结合对于该蛋白质发挥趋化辅助因子的作用至关重要，并且 DBP 与中性粒细胞质膜制剂上的硫酸软骨素蛋白聚糖 (CSPG) 结合。为了确定 CSPG 是否也具有介导趋化活性的功能，将 U937-C5aR 细胞在氯酸盐中生长以抑制 CSPG 硫酸化或用软骨素酶 AC 处理。任一治疗均仅显着抑制对 C 激活血清的趋化性。 CD44 是白细胞上的主要细胞表面 CSPG，具有促进趋化性的功能。用抗 CD44 处理细胞会阻断中性粒细胞和 U937-C5aR 细胞对 C 激活血清的趋化性，但不会阻断纯化的 C5a。共免疫沉淀、共聚焦显微镜和细胞结合研究证明，DBP 与细胞表面的 CD44 结合。膜联蛋白 A2 与脂筏中的 CD44 结合；因此，研究了其在介导共趋化活性中的潜在作用。结果表明，抗 A2 特异性抑制中性粒细胞和 U937-C5aR 对 C 激活血清的趋化性，阻断 DBP 与细胞的结合，并与抗 DBP 共定位于细胞表面。这些结果提供了明确的证据，表明 CD44 和膜联蛋白 A2 介导 DBP 的 C5a 趋化辅因子功能。
The vitamin D binding protein (DBP) is a plasma protein that significantly enhances the chemotactic activity of C5a and C5a(desArg) (cochemotactic activity). The objective of this study was to investigate how DBP mediates this process using neutrophils and U937 cells transfected with the C5a receptor (U937-C5aR cells) and comparing chemotaxis to C-activated serum (DBP dependent) vs purified C5a (DBP independent). Binding to the cell surface is essential for this protein to function as a chemotactic cofactor, and DBP binds to a chondroitin sulfate proteoglycan (CSPG) on neutrophil plasma membrane preparations. To determine whether a CSPG also functions to mediate cochemotactic activity, U937-C5aR cells were grown in chlorate to inhibit CSPG sulfation or treated with chondroitinase AC. Either treatment significantly inhibited chemotaxis only to C-activated serum. CD44 is a major cell surface CSPG on leukocytes, and functions to facilitate chemotaxis. Treatment of cells with anti-CD44 blocks chemotaxis of neutrophils and U937-C5aR cells to C-activated serum but not purified C5a. DBP binds to CD44 on the cell surface as evidenced by coimmunoprecipitation, confocal microscopy, and cell binding studies. Annexin A2 associates with CD44 in lipid rafts; therefore, its potential role in mediating cochemotactic activity was investigated. Results demonstrate that anti-A2 inhibits neutrophil and U937-C5aR chemotaxis specifically to C-activated serum, blocks DBP binding to cells, and colocalizes with anti-DBP on the cell surface. These results provide clear evidence that CD44 and annexin A2 mediate the C5a chemotactic cofactor function of DBP.