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Kallikrein Cleaves C3 and Activates Complement

Kallikrein Cleaves C3 and Activates Complement

Sarah Irmscher, Nadia Döring, Luke D Halder, Emeraldo A H Jo, Isabell Kopka, Christine Dunker, Ilse D Jacobsen, Shanshan Luo, Hortense Slevogt, Stefan Lorkowski, Niklas Beyersdorf, Peter F Zipfel, Christine Skerka

J Innate Immun. 2018;10(2):94-105.

PMID: 29237166

Abstract:

The human plasma contact system is an immune surveillance system activated by the negatively charged surfaces of bacteria and fungi and includes the kallikrein-kinin, the coagulation, and the fibrinolytic systems. Previous work shows that the contact system also activates complement, and that plasma enzymes like kallikrein, plasmin, thrombin, and FXII are involved in the activation process. Here, we show for the first time that kallikrein cleaves the central complement component C3 directly to yield active components C3b and C3a. The cleavage site within C3 is identical to that recognized by the C3 convertase. Also, kallikrein-generated C3b forms C3 convertases, which trigger the C3 amplification loop. Since kallikrein also cleaves factor B to yield Bb and Ba, kallikrein alone can trigger complement activation. Kallikrein-generated C3 convertases are inhibited by factor H; thus, the kallikrein activation pathway merges with the amplification loop of the alternative pathway. Taken together, these data suggest that activation of the contact system locally enhances complement activation on cell surfaces. The human pathogenic microbe Candida albicans activates the contact system in normal human serum. However, C. albicans immediately recruits factor H to the surface, thereby evading the alternative and likely kallikrein-mediated complement pathways.

Chemicals Related in the Paper:

Catalog Number	Product Name	CAS Number	Price
AP37213562	Complement factor D from human plasma	37213-56-2	Price
AP9001018	Kallikrein from human plasma	9001-01-8	Price
AP9001905	Plasmin from human plasma	9001-90-5	Price

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