CD5L 通过 J 链与 IgM 结合。

CD5L associates with IgM via the J chain.

机构信息

State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, P.R. China.

Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, P.R. China.

出版信息

Nat Commun. 2024 Sep 27;15(1):8397. doi: 10.1038/s41467-024-52175-y.

DOI:10.1038/s41467-024-52175-y

PMID:39333069

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC11437284/

Abstract

CD5 antigen-like (CD5L), also known as Spα or AIM (Apoptosis inhibitor of macrophage), emerges as an integral component of serum immunoglobulin M (IgM). However, the molecular mechanism underlying the interaction between IgM and CD5L has remained elusive. In this study, we present a cryo-electron microscopy structure of the human IgM pentamer core in complex with CD5L. Our findings reveal that CD5L binds to the joining chain (J chain) in a Ca-dependent manner and further links to IgM via a disulfide bond. We further corroborate recently published data that CD5L reduces IgM binding to the mucosal transport receptor pIgR, but does not impact the binding of the IgM-specific receptor FcμR. Additionally, CD5L does not interfere with IgM-mediated complement activation. These results offer a more comprehensive understanding of IgM and shed light on the function of the J chain in the immune system.

摘要

CD5 抗原样（CD5L），也称为 Spα 或 AIM（巨噬细胞凋亡抑制剂），是血清免疫球蛋白 M（IgM）的一个组成部分。然而，IgM 和 CD5L 之间相互作用的分子机制仍未被揭示。在这项研究中，我们呈现了人 IgM 五聚体核心与 CD5L 复合物的低温电子显微镜结构。我们的发现表明，CD5L 以 Ca 依赖性的方式与连接链（J 链）结合，并通过二硫键进一步与 IgM 连接。我们进一步证实了最近发表的数据，即 CD5L 降低了 IgM 与黏膜转运受体 pIgR 的结合，但不影响 IgM 特异性受体 FcμR 的结合。此外，CD5L 不干扰 IgM 介导的补体激活。这些结果提供了对 IgM 的更全面理解，并阐明了 J 链在免疫系统中的功能。