A critical role for UBXN3B in IgG homeostasis and maternal transfer

UBXN3B 在 IgG 稳态和母体转移中的关键作用

基本信息

批准号：
10302314
负责人：
PENGHUA WANG
金额：
$ 24.6万
依托单位：
UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-11-13 至 2022-10-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10302314
关键词：
ATP phosphohydrolase Albumins Antibodies Antigens Back Biological Assay Blood Circulation Breast Feeding Cell Cycle Cell physiology Cells DNA DNA Viruses Data Dendritic Cells Double Stranded DNA Virus Fc Receptor Fetus Foundations Future Genetic Genotype Half-Life Herpesvirus 1 Homeostasis Human Immune Immunoglobulin A Immunoglobulin G Immunoglobulin M Immunoglobulins In Vitro Infection Innate Immune Response Knock-out Knockout Mice Lysosomes Mediating Microscopy Mitochondria Mothers Mus Newborn Infant Optics Pathogenicity Pathway interactions Periodicity Persons Phenotype Physiologic pulse Physiological Pinocytosis Play Proteins Publishing RNA Virus Infections Receptor Cell Recycling Regulation Research Resolution Role Serum Serum Proteins Signal Pathway Signal Transduction Solid Stimulator of Interferon Genes Sting Injury Therapeutic Monoclonal Antibodies Time Vascular Endothelial Cell Vesicle Viral Virus Virus Diseases Wild Type Mouse Work adaptive immune response cofactor ds-DNA experimental study gene function improved in vivo intestinal epithelium macrophage microbial neonatal Fc receptor overexpression pathogen protein degradation receptor reconstruction response therapeutic target transcytosis ubiquitin-protein ligase viral RNA

项目摘要

Immunoglobulin G (IgG) is the most abundant Ig and has a long half-life (~21 days in humans, ~7 days in mice) relative to other Ig and serum proteins. People with IgG deficiencies are vulnerable to microbial infections; however, the underlying causes are unknown. The serum IgG and albumin are continuously internalized by vascular endothelial cells, macrophages and dendritic cells through pinocytosis, then sorted partly to the lysosomes for degradation and partly recycled by the neonatal Fc receptor (FcRn) back to the blood circulation. Thus, FcRn is crucial for maintaining a normal serum IgG level by extending its half-life. It is also essential for maternal IgG transfer to fetuses, providing a crucial adaptive immune protection to fetuses. Herein we propose an important role for a UBX domain-containing protein (UBXN) in regulating the serum IgG recycling. Our preliminary studies demonstrated that the serum levels of antigen- specific and total IgG were reduced in Ubxn3b knockout mice when compared to their wild-type littermates; while the IgM levels were the same. Mechanistically, in vivo pulse-and-chase experiments showed that IgG was degraded much faster in the knockout mice than their littermates. In line with this, in vitro pulse-and- chase experiments showed that IgG was unable to be recycled in knockout cells. We thus hypothesize that UBXN3B is crucial for maintaining IgG homeostasis and it regulates FcRn-mediated IgG recycling and transcytosis. First, we will determine if the half-life of IgG subclasses is reduced, if maternal IgG transfer from the mother to fetus and across the intestinal epithelia is blocked in the knockout mice. Second, we will determine if IgG recycling and transcytosis is deficient in knockout cells, if FcRn-mediated IgG recycling/transcytosis is reliant on UBXN3B and if the cellular fate/ localization of IgG/ FcRn is altered in knockout cells. We hope to prove a critical role for UBXN3B in IgG recycling and maternal transfer and would establish a functional relationship between FcRn and UBXN3B. Our results from the mouse work could be also applicable to humans because the UBXN3B protein is highly conserved across species, and could provide an alternative therapeutic target for improving the serum half-life of therapeutic monoclonal antibodies or reducing the half-life of pathogenic antibodies. We hope that the results from this R21 will lay a solid foundation for more in-depth mechanistic and functional studies.

免疫球蛋白 G (IgG) 是最丰富的 Ig，半衰期很长（在人类中约为 21 天，在人类中约为 7 天）小鼠）相对于其他 Ig 和血清蛋白。 IgG 缺乏的人容易受到微生物的侵害感染；然而，根本原因尚不清楚。血清IgG和白蛋白持续检测通过胞饮作用被血管内皮细胞、巨噬细胞和树突状细胞内化，然后部分分选至溶酶体进行降解，部分由新生儿 Fc 受体 (FcRn) 回收回到血液循环。因此，FcRn 对于通过延长血清 IgG 水平来维持正常的血清 IgG 水平至关重要。它的半衰期。它对于母体 IgG 向胎儿的转移也至关重要，提供重要的适应性免疫对胎儿的保护。在此，我们提出了含有 UBX 结构域的蛋白 (UBXN) 在调节血清 IgG 循环。我们的初步研究表明，抗原的血清水平与野生型同窝小鼠相比，Ubxn3b 敲除小鼠的特异性和总 IgG 降低；而 IgM 水平相同。从机制上讲，体内脉冲和追踪实验表明 IgG 基因敲除小鼠中的降解速度比同窝小鼠要快得多。与此相符，体外脉冲- Chase 实验表明 IgG 无法在基因敲除细胞中回收。因此我们假设 UBXN3B 对于维持 IgG 稳态至关重要，它调节 FcRn 介导的 IgG 回收和转胞吞作用。首先，我们将确定 IgG 亚类的半衰期是否缩短，如果母体 IgG 在基因敲除小鼠中，从母体到胎儿以及穿过肠上皮的转移被阻断。第二，我们将确定敲除细胞中 IgG 回收和转胞吞作用是否存在缺陷，如果 FcRn 介导的 IgG 回收/转胞吞作用依赖于 UBXN3B，并且如果 IgG/FcRn 的细胞命运/定位发生改变敲除细胞。我们希望证明 UBXN3B 在 IgG 回收和母体移植中的关键作用将在 FcRn 和 UBXN3B 之间建立功能关系。我们的小鼠实验结果也可能适用于人类，因为 UBXN3B 蛋白在物种间高度保守，并且可以为改善治疗性单克隆抗体的血清半衰期提供替代治疗靶点抗体或减少致病抗体的半衰期。我们希望这次 R21 的结果能够奠定为更深入的机械和功能研究奠定了坚实的基础。