CFB siRNA (Human)

This gene encodes complement factor B, a component of the alternative pathway of complement activation. Factor B circulates in the blood as a single chain polypeptide. Upon activation of the alternative pathway, it is cleaved by complement factor D yielding the noncatalytic chain Ba and the catalytic subunit Bb. The active subunit Bb is a serine protease which associates with C3b to form the alternative pathway C3 convertase. Bb is involved in the proliferation of preactivated B lymphocytes, while Ba inhibits their proliferation. This gene localizes to the major histocompatibility complex (MHC) class III region on chromosome 6. This cluster includes several genes involved in regulation of the immune reaction. Polymorphisms in this gene are associated with a reduced risk of age-related macular degeneration. The polyadenylation site of this gene is 421 bp from the 5' end of the gene for complement component 2. [provided by RefSeq, Jul 2008]

CFB: Factor B which is part of the alternate pathway of the complement system is cleaved by factor D into 2 fragments: Ba and Bb. Bb, a serine protease, then combines with complement factor 3b to generate the C3 or C5 convertase. It has also been implicated in proliferation and differentiation of preactivated B- lymphocytes, rapid spreading of peripheral blood monocytes, stimulation of lymphocyte blastogenesis and lysis of erythrocytes. Ba inhibits the proliferation of preactivated B-lymphocytes. Defects in CFB are a cause of susceptibility to hemolytic uremic syndrome atypical type 4 (AHUS4). An atypical form of hemolytic uremic syndrome. It is a complex genetic disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, renal failure and absence of episodes of enterocolitis and diarrhea. In contrast to typical hemolytic uremic syndrome, atypical forms have a poorer prognosis, with higher death rates and frequent progression to end-stage renal disease. Susceptibility to the development of atypical hemolytic uremic syndrome can be conferred by mutations in various components of or regulatory factors in the complement cascade system. Other genes may play a role in modifying the phenotype. Belongs to the peptidase S1 family. 2 isoforms of the human protein are produced by alternative splicing.

Protein type: EC 3.4.21.47; Protease; Secreted, signal peptide; Secreted

Chromosomal Location of Human Ortholog: 6p21.3

Cellular Component: extracellular space; plasma membrane; extracellular region

Molecular Function: complement binding; serine-type endopeptidase activity

Biological Process: complement activation, alternative pathway; regulation of complement activation; innate immune response; proteolysis; complement activation

Disease: Macular Degeneration, Age-related, 14; Complement Factor B Deficiency; Hemolytic Uremic Syndrome, Atypical, Susceptibility To, 4