The role of homodimers in surfactant protein B function in vivo
The role of homodimers in surfactant protein B function in vivo
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DOI：
10.1074/jbc.275.5.3365
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发表时间：
2000-02-04
影响因子：
4.8
通讯作者：
Weaver, TE
中科院分区：
文献类型：
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作者：
Beck, DC;Ikegami, M;Weaver, TE
表面活性剂蛋白B （SP-B）在气道中被检测为依赖巯基的二聚体（M-r类似于16,000）。为了验证同型二聚体的形成对SP-B功能至关重要的假设，我们将报道的参与SP-B二聚体的半胱氨酸残基突变为丝氨酸（Cys(248) -> Ser），并将突变蛋白靶向转基因小鼠的远端呼吸上皮。在缺乏内源性SP-B二聚体（hSP-B-mon、mSP-B-/-）的情况下，将能够适当加工、分选和分泌人SP-B单体的转基因系与SP-B +/-小鼠杂交，实现对人SP-B单体的表达。在三个转基因系中的两个中，hSP-B-mon、mSP-B-/-小鼠肺结构正常，SP-C蛋白加工完整，板层体形成良好，寿命正常。肺功能研究显示，与野生型小鼠相比，hSP-B-mon、mSP-B-/-小鼠的滞回曲线发生了改变。从hSP-B-mon、mSP-B-/-小鼠中提取的大量表面活性剂组分比野生型小鼠提取的表面活性剂具有更高的体外最小表面张力。添加2% hSP-B单体的表面活性剂脂质比添加2% hSP-B二聚体的表面活性剂脂质吸附更慢，表面张力更高。综上所述，这些数据表明SP-B二聚体在降低泡内表面张力方面的作用。
Surfactant protein B (SP-B) is detected in the airways as a sulfhydryl-dependent dimer (M-r similar to 16,000). To test the hypothesis that formation of homodimers is critical for SP-B function, the cysteine residue reported to be involved in SP-B dimerization was mutated to serine (Cys(248) --> Ser) and the mutated protein was targeted to the distal respiratory epithelium of transgenic mice. Transgenic lines which demonstrated appropriate processing, sorting, and secretion of human SP-B monomer were crossed with SP-B +/- mice to achieve expression of human monomer in the absence of endogenous SP B dimer (hSP-B-mon, mSP-B-/-). In two of three transgenic lines, hSP-B-mon, mSP-B-/- mice had normal lung structure, complete processing of SP-C proprotein, well formed lamellar bodies, and normal longevity. Pulmonary function studies revealed an altered hysteresis curve for hSP-B-mon, mSP-B-/- mice relative to wild type mice. Large aggregate surfactant fractions from hSP-B-mon, mSP-B-/- mice resulted in higher minimum surface tension in vitro compared with surfactant from wild type mice. Surfactant lipids supplemented with 2% hSP-B monomer resulted in slower adsorption and higher surface tension than surfactant with 2% hSP-B dimer, Taken together, these data indicate a role for SP-B dimer in surface tension reduction in the alveolus.