Delineation of the amino acid residues involved in transcytosis and catabolism of mouse IgG1.
Delineation of the amino acid residues involved in transcytosis and catabolism of mouse IgG1.
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DOI：
10.4049/jimmunol.158.5.2211
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发表时间：
1997-03
影响因子：
4.4
通讯作者：
C. Medesan;D. Matesoi;C. Radu;V. Ghetie;E. Ward
中科院分区：
文献类型：
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作者：
C. Medesan;D. Matesoi;C. Radu;V. Ghetie;E. Ward
MHC I类相关受体FcRn参与血清γ-球蛋白（IgG）的转胞吞作用并调节其血清持久性。已使用定点诱变和X射线晶体学分析将啮齿动物IgG的Fc区上的FcRn相互作用位点映射到CH 2-CH 3结构域界面处的残基。在当前研究中，使用源自小鼠IgG 1的重组突变Fc铰链片段研究了该界面处单个残基（H310、H433和N434）在介导Fc-FcRn相互作用中的作用。此外，两个高度保守的Fc组氨酸（H435和H436）已突变为丙氨酸，并在小鼠中的转胞吞作用和药代动力学研究以及使用重组可溶性FcRn的竞争结合测定中分析所得突变的Fc铰链片段。分析表明，H310、H435和在较小程度上H436突变为丙氨酸导致Fc铰链片段在体内和体外测定中的活性降低。因此，除了先前定义的1253在FcRn-IgG相互作用中的作用外，这些组氨酸在介导该Fc受体进行的功能中发挥关键作用。还分析了这些突变对Fc铰链片段与葡萄球菌蛋白A结合的影响，并证明了小鼠IgG 1上FcRn和葡萄球菌蛋白A相互作用位点的部分重叠，但不完全重叠。
The MHC class I-related receptor, FcRn, is involved in both the transcytosis of serum gamma-globulins (IgGs) and in regulating their serum persistence. The interaction site of FcRn on the Fc region of rodent IgG has been mapped to residues at the CH2-CH3 domain interface using site-directed mutagenesis and x-ray crystallographic analyses. In the current study, the role of individual residues (H310, H433, and N434) at this interface in mediating the Fc-FcRn interaction has been investigated using recombinant, mutated Fc hinge fragments derived from mouse IgG1. In addition, two highly conserved Fc histidines (H435 and H436) have been mutated to alanine, and the resulting mutated Fc hinge fragments were analyzed in both transcytosis and pharmacokinetic studies in mice and in competition binding assays using recombinant, soluble FcRn. The analyses indicate that mutation of H310, H435, and, to a lesser extent, H436 to alanine results in reduced activity of the Fc hinge fragments in both in vivo and in vitro assays. Thus, in addition to the previously defined role of 1253 in the FcRn-IgG interaction, these histidines play a key role in mediating the functions conducted by this Fc receptor. The effects of these mutations on binding of Fc hinge fragments to staphylococcal protein A have also been analyzed and demonstrate a partial, but not complete, overlap of the FcRn and staphylococcal protein A interaction sites on mouse IgG1.