| Autor: |
Oskam, Nienke, den Boer, Maurits A., Lukassen, Marie V., Heer, Pleuni Ooijevaar-de, Veth, Tim S., van Mierlo, Gerard, Lai, Szu-Hsueh, Derksen, Ninotska I. L., Yin, Victor, Streutker, Marij, Franc, Vojtech, Šiborová, Marta, Damen, Mirjam J. A., Kos, Dorien, Barendregt, Arjan, Bondt, Albert, van Goudoever, Johannes B., de Haas, Carla J. C., Aerts, Piet C., Muts, Remy M. |
| Předmět: |
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| Zdroj: |
Proceedings of the National Academy of Sciences of the United States of America; 12/12/2023, Vol. 120 Issue 50, p1-15, 22p |
| Abstrakt: |
Immunoglobulin M (IgM) is an evolutionary conserved key component of humoral immunity, and the first antibody isotype to emerge during an immune response. IgM is a large (1 MDa), multimeric protein, for which both hexameric and pentameric structures have been described, the latter additionally containing a joining (J) chain. Using a combination of single-particle mass spectrometry and mass photometry, proteomics, and immunochemical assays, we here demonstrate that circulatory (serum) IgM exclusively exists as a complex of J-chain-containing pentamers covalently bound to the small (36 kDa) protein CD5 antigen-like (CD5L, also called apoptosis inhibitor of macrophage). In sharp contrast, secretory IgM in saliva and milk is principally devoid of CD5L. Unlike IgM itself, CD5L is not produced by B cells, implying that it associates with IgM in the extracellular space. We demonstrate that CD5L integration has functional implications, i.e., it diminishes IgM binding to two of its receptors, the FcaµR and the polymeric Immunoglobulin receptor. On the other hand, binding to FcµR as well as complement activation via C1q seem unaffected by CD5L integration. Taken together, we redefine the composition of circulatory IgM as a J-chain containing pentamer, always in complex with CD5L. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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