Identification of potential C1-binding sites in the immunoglobulin CL domains.

IF 4.8 4区 医学 Q2 IMMUNOLOGY
Saeko Yanaka, Atsuji Kodama, Shigetaka Nishiguchi, Rina Fujita, Jiana Shen, Pornthip Boonsri, Duckyong Sung, Yukiko Isono, Hirokazu Yagi, Yohei Miyanoiri, Takayuki Uchihashi, Koichi Kato
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引用次数: 0

Abstract

Immunoglobulin G (IgG) molecules that bind antigens on the membrane of target cells spontaneously form hexameric rings, thus recruiting C1 to initiate the complement pathway. However, our previous report indicated that a mouse IgG mutant lacking the Cγ1 domain activates the pathway independently of antigen presence through its monomeric interaction with C1q via the CL domain, as well as Fc. In this study, we investigated the potential interaction between C1q and human CL isoforms. Quantitative single-molecule observations using high-speed atomic force microscopy revealed that human Cκ exhibited comparable C1q binding capabilities with its mouse counterpart, surpassing the Cλ types, which have a higher isoelectric point than the Cκ domains. Nuclear magnetic resonance and mutation experiments indicated that the human and mouse Cκ domains share a common primary binding site for C1q, centred on Glu194, a residue conserved in the Cκ domains but absent in the Cλ domains. Additionally, the Cγ1 domain, with its high isoelectric point, can cause electrostatic repulsion to the C1q head and impede the C1q-interaction adjustability of the Cκ domain in Fab. The removal of the Cγ1 domain is considered to eliminate these factors and thus promote Cκ interaction with C1q with the potential risk of uncontrolled activation of the complement pathway in vivo in the absence of antigen. However, this research underscores the presence of potential subsites in Fab for C1q binding, offering promising targets for antibody engineering to refine therapeutic antibody design.

鉴定免疫球蛋白 CL 结构域中潜在的 C1 结合位点。
与靶细胞膜上抗原结合的 IgG 分子会自发形成六聚体环,从而招募 C1 启动补体途径。然而,我们之前的报告表明,缺乏 Cγ1 结构域的小鼠 IgG 突变体通过 CL 结构域与 C1q 以及 Fc 的单体相互作用激活补体途径,而不受抗原存在的影响。在这项研究中,我们研究了 C1q 与人类 CL 异构体之间的潜在相互作用。使用高速原子力显微镜进行的定量单分子观察显示,人Cκ与小鼠对应物的C1q结合能力相当,超过了等电点高于Cκ结构域的Cλ类型。核磁共振和突变实验表明,人和小鼠的 Cκ 结构域有一个共同的 C1q 主要结合位点,其中心是 Glu194,这个残基在 Cκ 结构域中是保守的,但在 Cλ 结构域中却不存在。此外,Cγ1 结构域的等电点较高,会对 C1q 头产生静电排斥,阻碍 Fab 中 Cκ 结构域的 C1q 相互作用可调节性。去除 Cγ1 结构域被认为能消除这些因素,从而促进 Cκ 与 C1q 的相互作用,但在体内没有抗原的情况下,可能会有不受控制地激活补体途径的风险。不过,这项研究强调了 Fab 中存在与 C1q 结合的潜在亚位点,为抗体工程提供了有希望的目标,以完善治疗性抗体的设计。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
International immunology
International immunology 医学-免疫学
CiteScore
9.30
自引率
2.30%
发文量
51
审稿时长
6-12 weeks
期刊介绍: International Immunology is an online only (from Jan 2018) journal that publishes basic research and clinical studies from all areas of immunology and includes research conducted in laboratories throughout the world.
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