Genetic, molecular and functional analyses of complement factor I deficiency
Genetic, molecular and functional analyses of complement factor I deficiency
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DOI：
10.1002/eji.200838702
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发表时间：
2009-01-01
影响因子：
5.4
通讯作者：
Blom, Anna M.
中科院分区：
文献类型：
--
作者：
Nilsson, Sara C.;Trouw, Leendert A.;Blom, Anna M.
补体抑制因子 I (FI) 完全缺乏会导致继发性补体缺乏，这是由于不受控制的自发替代途径激活导致对感染的易感性。目前对两名几乎完全缺乏 FI 的患者和三名未检测到血清 FI 的患者以及近亲家庭成员进行的基因检查显示，FI 的多个域存在纯合或复合杂合突变。这些突变被引入重组 FI 中，纯化所得蛋白质用于功能研究，同时使用瞬时转染来分析表达和分泌。 G170V突变导致蛋白质不表达，而突变Q232K、C237Y、S250L、I339M和H400L影响分泌。此外，C237Y和S250L突变体不能像WT那样有效地降解CO和C3b。截短的 Q336x 突变体可以在体外表达，但由于缺乏丝氨酸蛋白酶结构域而没有功能。此外，在患者血清中未检测到该截短的 FI。使用分子模型进行结构研究以预测突变对 FI 结构的潜在影响。这是第一项在功能水平上调查 FI 完全缺乏患者中发现的分子缺陷后果的研究。
Complete deficiency of complement inhibitor factor I (FI) results in secondary complement deficiency due to uncontrolled spontaneous alternative pathway activation leading to susceptibility to infections. Current genetic examination of two patients with near complete FI deficiency and three patients with no detectable serum FI and also close family members revealed homozygous or compound heterozygous mutations in several domains of FI. These mutations were introduced into recombinant FI and the resulting proteins were purified for functional studies, while transient transfection was used to analyze expression and secretion. The G170V mutation resulted in a protein that was not expressed, whereas the mutations Q232K, C237Y, S250L, I339M and H400L affected secretion. Furthermore, the C237Y and the S250L mutants did not degrade CO and C3b as efficiently as the WT. The truncated Q336x mutant could be expressed, in vitro, but was not functional because it lacks the serine protease domain. Furthermore, this truncated FI was not detected in serum of the patient. Structural investigations using molecular modeling were performed to predict the potential impact the mutations have on FI structure. This is the first study that investigates, at the functional level, the consequences of molecular defects identified in patients with full FI deficiency.