FGB

The protein encoded by this gene is the beta component of fibrinogen, a blood-borne glycoprotein comprised of three pairs of nonidentical polypeptide chains. Following vascular injury, fibrinogen is cleaved by thrombin to form fibrin which is the most abundant component of blood clots. In addition, various cleavage products of fibrinogen and fibrin regulate cell adhesion and spreading, display vasoconstrictor and chemotactic activities, and are mitogens for several cell types. Mutations in this gene lead to several disorders, including afibrinogenemia, dysfibrinogenemia, hypodysfibrinogenemia and thrombotic tendency. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jun 2014]

Fibrinogen Beta Chain

Cleaved by the protease thrombin to yield monomers which, together with fibrinogen alpha (FGA) and fibrinogen gamma (FGG), polymerize to form an insoluble fibrin matrix. Fibrin has a major function in hemostasis as one of the primary components of blood clots. In addition, functions during the early stages of wound repair to stabilize the lesion and guide cell migration during re-epithelialization. Was originally thought to be essential for platelet aggregation, based on in vitro studies using anticoagulated blood. However subsequent studies have shown that it is not absolutely required for thrombus formation in vivo. Enhances expression of SELP in activated platelets. Maternal fibrinogen is essential for successful pregnancy. Fibrin deposition is also associated with infection, where it protects against IFNG-mediated hemorrhage. May also facilitate the antibacterial immune response via both innate and T-cell mediated pathways.

Adaptive immune response Source: UniProtKB-KW
Blood coagulation, fibrin clot formation Source: UniProtKB
Cell adhesion Source: GO_Central
Cell-matrix adhesion Source: BHF-UCL
Cellular protein-containing complex assembly Source: BHF-UCL
Cellular response to interleukin-1 Source: Ensembl
Cellular response to leptin stimulus Source: Ensembl
Fibrinolysis Source: UniProtKB
Induction of bacterial agglutination Source: CACAO
Innate immune response Source: UniProtKB-KW
Negative regulation of endothelial cell apoptotic process Source: BHF-UCL
Negative regulation of extrinsic apoptotic signaling pathway via death domain receptors Source: BHF-UCL
Plasminogen activation Source: UniProtKB
Platelet aggregation Source: BHF-UCL
Positive regulation of ERK1 and ERK2 cascade Source: BHF-UCL
Positive regulation of exocytosis Source: BHF-UCL
Positive regulation of heterotypic cell-cell adhesion Source: BHF-UCL
Positive regulation of peptide hormone secretion Source: BHF-UCL
Positive regulation of protein secretion Source: BHF-UCL
Positive regulation of substrate adhesion-dependent cell spreading Source: BHF-UCL
Positive regulation of vasoconstriction Source: BHF-UCL
Protein polymerization Source: BHF-UCL
Response to calcium ion Source: BHF-UCL

Secreted

Congenital afibrinogenemia (CAFBN):
The disease is caused by variants affecting the gene represented in this entry. Patients with congenital fibrinogen abnormalities can manifest different clinical pictures. Some cases are clinically silent, some show a tendency toward bleeding and some show a predisposition for thrombosis with or without bleeding. Rare autosomal recessive disorder is characterized by bleeding that varies from mild to severe and by complete absence or extremely low levels of plasma and platelet fibrinogen.
Dysfibrinogenemia, congenital (DYSFIBRIN):
A disorder characterized by qualitative abnormalities (dysfibrinogenemia) of the circulating fibrinogen. Affected individuals are frequently asymptomatic, but some patients have bleeding diathesis, thromboembolic complications, or both. In some cases, dysfibrinogenemia is associated with low circulating fibrinogen levels (hypodysfibrinogenemia).

Conversion of fibrinogen to fibrin is triggered by thrombin, which cleaves fibrinopeptides A and B from alpha and beta chains, and thus exposes the N-terminal polymerization sites responsible for the formation of the soft clot. The soft clot is converted into the hard clot by factor XIIIA which catalyzes the epsilon-(gamma-glutamyl)lysine cross-linking between gamma chains (stronger) and between alpha chains (weaker) of different monomers.