Role of membrane cofactor protein (CD46) in regulation of C4b and C3b deposited on cells
Role of membrane cofactor protein (CD46) in regulation of C4b and C3b deposited on cells
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DOI：
10.4049/jimmunol.168.12.6298
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发表时间：
2002-06-15
影响因子：
4.4
通讯作者：
Atkinson, JP
中科院分区：
文献类型：
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作者：
Barilla-LaBarca, ML;Liszewski, MK;Atkinson, JP
沉积在宿主细胞上的C4 b和C3 b通过调节蛋白进行有限的蛋白水解裂解。膜辅因子蛋白（MCP; CD 46）、因子H和C4 b结合蛋白介导该反应，称为辅因子活性，也需要血浆丝氨酸蛋白酶因子I。为了探索流体相调节剂相对于在宿主细胞上表达的那些的作用，使用模型系统检查沉积在用人MCP转染的细胞上的补体片段，如通过FACS和Western印迹评估的。在MCP+细胞上与Ab和补体孵育后，C4 b在第一个小时内逐渐裂解为C4d和C4 c。在MCP-1细胞上没有检测到C4 b的裂解，表明MCP（而不是血清中的C4 BP）主要介导这种辅因子活性。MCP+细胞上的C3 b沉积未被阻断，因为经典途径活化发生在实质性C4 b裂解之前。然而，沉积的C3 b的裂解是快速的（
C4b and C3b deposited on host cells undergo limited proteolytic cleavage by regulatory proteins. Membrane cofactor protein (MCP; CD46), factor H, and C4b binding protein mediate this reaction, known as cofactor activity, that also requires the plasma serine protease factor I. To explore the roles of the fluid phase regulators vs those expressed on host cells, a model system was used examining complement fragments deposited on cells transfected with human MCP as assessed by FACS and Western blotting. Following incubation with Ab and complement on MCP+ cells, C4b was progressively cleaved over the first hour to C4d and C4c. There was no detectable cleavage of C4b on MCP- cells, indicating that MCP (and not C4BP in the serum) primarily mediates this cofactor activity. C3b deposition was not blocked on MCP+ cells because classical pathway activation occurred before substantial C4b cleavage. Cleavage, though, of deposited C3b was rapid (