Structural and functional characterization of human and murine C5a anaphylatoxins
- Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus (Denmark)
- Aarhus University, Bartholin Building, Wilhelm Meyers Allé 4, DK-8000 Aarhus (Denmark)
- Medical School Hannover, Hannover (Germany)
The structure of the human C5aR antagonist, C5a-A8, reveals a three-helix bundle conformation similar to that observed for human C5a-desArg, whereas murine C5a and C5a-desArg both form the canonical four-helix bundle. These conformational differences are discussed in light of the differential C5aR activation properties observed for the human and murine complement anaphylatoxins across species. Complement is an ancient part of the innate immune system that plays a pivotal role in protection against invading pathogens and helps to clear apoptotic and necrotic cells. Upon complement activation, a cascade of proteolytic events generates the complement effectors, including the anaphylatoxins C3a and C5a. Signalling through their cognate G-protein coupled receptors, C3aR and C5aR, leads to a wide range of biological events promoting inflammation at the site of complement activation. The function of anaphylatoxins is regulated by circulating carboxypeptidases that remove their C-terminal arginine residue, yielding C3a-desArg and C5a-desArg. Whereas human C3a and C3a-desArg adopt a canonical four-helix bundle fold, the conformation of human C5a-desArg has recently been described as a three-helix bundle. Here, the crystal structures of an antagonist version of human C5a, A8{sup Δ71–73}, and of murine C5a and C5a-desArg are reported. Whereas A8{sup Δ71–73} adopts a three-helix bundle conformation similar to human C5a-desArg, the two murine proteins form a four-helix bundle. A cell-based functional assay reveals that murine C5a-desArg, in contrast to its human counterpart, exerts the same level of activition as murine C5a on its cognate receptor. The role of the different C5a conformations is discussed in relation to the differential activation of C5a receptors across species.
- OSTI ID:
- 22347767
- Journal Information:
- Acta Crystallographica. Section D: Biological Crystallography, Vol. 70, Issue Pt 6; Other Information: PMCID: PMC4051506; PMID: 24914981; PUBLISHER-ID: dw5099; OAI: oai:pubmedcentral.nih.gov:4051506; Copyright (c) Schatz-Jakobsen et al. 2014; This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0907-4449
- Country of Publication:
- Denmark
- Language:
- English
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