The novel complement inhibitor human CUB and Sushi multiple domains 1 (CSMD1) protein promotes factor I-mediated degradation of C4b and C3b and inhibits the membrane attack complex assembly
The novel complement inhibitor human CUB and Sushi multiple domains 1 (CSMD1) protein promotes factor I-mediated degradation of C4b and C3b and inhibits the membrane attack complex assembly
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DOI：
10.1096/fj.13-230706
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发表时间：
2013-12-01
期刊：
影响因子：
4.8
通讯作者：
Blom, Anna M.
中科院分区：
文献类型：
--
作者：
Escudero-Esparza, Astrid;Kalchishkova, Nikolina;Blom, Anna M.
CUB和Sushi多结构域1（CSMD 1）是一种跨膜蛋白，含有15个连续的补体控制蛋白（CCP）结构域，这些结构域是补体抑制剂的特征。我们表达了一个由15个C-末端CCP结构域组成的人CSMD 1的膜结合片段，并证明它在6%血清下通过经典途径抑制C3 b在中国仓鼠卵巢细胞表面的沉积70%，在1.25%血清下抑制C9（膜攻击复合物的组分）的沉积90%。此外，CSMD 1的该片段充当因子I介导的C3 b降解的辅因子。在进行的所有功能试验中，使用充分表征的补体抑制剂作为阳性对照，而科萨基腺病毒受体（一种对补体无影响的蛋白质）作为阴性对照。此外，与对照组相比，表达内源性CSMD 1的人T47乳腺癌细胞中表达的减弱在8%血清下使这些细胞上的C3 b沉积显著增加45%。此外，通过表达CSMD 1的可溶性17-21 CCP片段，我们发现CSMD 1通过促进I因子介导的C4 b/C3 b降解和在C7水平抑制MAC组装来抑制补体。我们的研究结果揭示了一种新的补体抑制剂的经典和凝集素途径。
CUB and Sushi multiple domains 1 (CSMD1) is a transmembrane protein containing 15 consecutive complement control protein (CCP) domains, which are characteristic for complement inhibitors. We expressed a membrane-bound fragment of human CSMD1 composed of the 15 C-terminal CCP domains and demonstrated that it inhibits deposition of C3b by the classical pathway on the surface of Chinese hamster ovary cells by 70% at 6% serum and of C9 (component of membrane attack complex) by 90% at 1.25% serum. Furthermore, this fragment of CSMD1 served as a cofactor to factor I-mediated degradation of C3b. In all functional assays performed, well-characterized complement inhibitors were used as positive controls, whereas Coxsackie adenovirus receptor, a protein with no effect on complement, was a negative control. Moreover, attenuation of expression in human T47 breast cancer cells that express endogenous CSMD1 significantly increased C3b deposition on these cells by 45% at 8% serum compared with that for the controls. Furthermore, by expressing a soluble 17-21 CCP fragment of CSMD1, we found that CSMD1 inhibits complement by promoting factor I-mediated C4b/C3b degradation and inhibition of MAC assembly at the level of C7. Our results revealed a novel complement inhibitor for the classical and lectin pathways.