Choi Juho, Jeon Yerin, Roh Youngin, Jang Jeongyun, Lee Eunbin, Villamante Luigie, Kim Minjae, Kwon Myung-Hee
Department of Biomedical Sciences, Graduate School, Ajou University, Suwon, Republic of Korea.
Department of Microbiology, Ajou University School of Medicine, Suwon, Republic of Korea.
Front Mol Biosci. 2024 May 2;11:1346259. doi: 10.3389/fmolb.2024.1346259. eCollection 2024.
The C domain of IgG antibodies controls assembly and secretion, mediated by the molecular chaperone BiP via the endoplasmic reticulum protein quality control (ERQC) mechanism. However, it is not clear whether the variable domains are necessary for this process. Here, we generated IgG1 antibodies in which the V domain (V and/or V) was either removed or replaced, and then assessed expression, assembly, and secretion in HEK293 cells. All Ig variants formed a covalent linkage between the C and C, were successfully secreted in an assembled form. Replacement of the cognate V with a non-secretory pseudo V (V) hindered secretion of individual or assembled secretion of neither heavy chains (HCs) nor light chains (LCs). The LC (V-C) exhibited a less folded structure compared to the wild type (wt) LC, as evidenced by enhanced stable binding to the molecular chaperone BiP and susceptibility to proteolytic degradation. Molecular dynamics simulation demonstrated dramatic alterations in overall structure of Fab (Fd-LC) from wt Fab. These findings suggest that V domains do not initiate HC:LC assembly and secretion; instead, the critical factor governing IgG assembly and secretion is the C-C pairing. Additionally, the structural integrity of the V domain is crucial for IgG secretion. These data offer valuable insight into the design of bioactive molecules based on an IgG backbone.
IgG抗体的C结构域通过内质网蛋白质质量控制(ERQC)机制,由分子伴侣BiP介导来控制组装和分泌。然而,尚不清楚可变结构域对于该过程是否必要。在此,我们生成了去除或替换V结构域(V和/或V)的IgG1抗体,然后评估其在HEK293细胞中的表达、组装和分泌情况。所有Ig变体在C和C之间形成了共价连接,并以组装形式成功分泌。用非分泌性假V(V)替换同源V既不阻碍重链(HCs)也不阻碍轻链(LCs)的个体分泌或组装分泌。与野生型(wt)轻链相比,轻链(V-C)呈现出折叠程度较低的结构,这通过与分子伴侣BiP的稳定结合增强以及对蛋白水解降解的敏感性得以证明。分子动力学模拟表明,与野生型Fab相比,Fab(Fd-LC)的整体结构发生了显著变化。这些发现表明,V结构域不会启动HC:LC的组装和分泌;相反,控制IgG组装和分泌的关键因素是C-C配对。此外,V结构域的结构完整性对于IgG分泌至关重要。这些数据为基于IgG骨架的生物活性分子设计提供了有价值的见解。