Thromb Haemost 2022; 122(08): 1265-1278
DOI: 10.1055/a-1719-5584
Review Article

The Story of the Fibrin(ogen) αC-Domains: Evolution of Our View on Their Structure and Interactions

Leonid Medved
1   Center for Vascular and Inflammatory Diseases and the Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States
,
John W. Weisel
2   Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States
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Funding This work was supported by National Institutes of Health grants HL056051 to L.M., and HL030954, HL148227, and P01-HL40387 to J.W.W.
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Abstract

Although much has been established concerning the overall structure and function of fibrinogen, much less has been known about its two αC regions, each consisting of an αC-connector and an αC-domain, but new information has been accumulating. This review summarizes the state of our current knowledge of the structure and interactions of fibrinogen's αC regions. A series of studies with isolated αC regions and their fragments demonstrated that the αC-domain forms compact ordered structures consisting of N- and C-terminal subdomains including β sheets and suggested that the αC-connector has a poly(L-proline) type II structure. Functionally, the αC-domains interact intramolecularly with each other and with the central region of the molecule, first demonstrated by electron microscopy and then quantified by optical trap force spectroscopy. Upon conversion of fibrinogen into fibrin, the αC-domains switch from intra- to intermolecular interactions to form ordered αC polymers. The formation of αC polymers occurs mainly through the homophilic interaction between the N-terminal subdomains; interaction between the C-terminal subdomains and the αC-connectors also contributes to this process. Considerable evidence supports the idea that the αC-regions accelerate fibrin polymerization and affect the final structure of fibrin clots. The interactions between αC-regions are important for the mechanical properties of clots, increasing their stiffness and extensibility. Conversion of fibrinogen into fibrin results in exposure of multiple binding sites in its αC regions, providing interaction of fibrin with different proteins and cell types during hemostasis and wound healing. This heretofore mysterious part of the fibrinogen molecule is finally giving up its secrets.



Publikationsverlauf

Eingereicht: 16. September 2021

Angenommen: 09. Dezember 2021

Accepted Manuscript online:
13. Dezember 2021

Artikel online veröffentlicht:
08. Februar 2022

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