Complement component 3 (C3). C3, a protein coding gene, is part of a system of proteins that fight against the disease. Mutations in C3 can cause C3 glomerulopathy, build up of parts of C3. [R].

C3G is ultra-rare [R]. C3 is integral in the complement system, a group of proteins that are responsible for fighting against viruses and bacteria [R].

C3 plays a central role in the activation of complement system. Its activation is required for both classical and alternative complement activation pathways. People with C3 deficiency are susceptible to bacterial infection.

C3 has been linked to kidney failure due to C3 overreactivity and attacking kidney cells. [R] Hereditary deficiency in one of the complement proteins will usually lead to a high frequency of recurrent microbial infections.

Decreased complement levels also are associated with an increased risk of developing an autoimmune disease. Both C3 and C4 levels are typically depressed in SLE while C3 alone is low in septicemia and infections caused by fungi or parasites such as malaria. Increased complement activity may be seen in:

• Cancer
• Ulcerative colitis

Decreased complement activity may be seen in:

• Bacterial infections (especially Neisseria)
• Cirrhosis
• Glomerulonephritis
• Hepatitis
• Hereditary angioedema
• Kidney transplant rejection
• Lupus nephritis
• Malnutrition
• Systemic lupus erythematosus

Complement 3 (C3) generates C3a . C3a converts to ASP or acylation-stimulating-protein due to its stimulating action on triglyceride synthesis in human fat and skin cells (fibroblasts) (R).

ASP inhibits the action of hormone-sensitive lipase, which is linked to the pathogenesis of obesity, having been demonstrated to be present at increased levels in patients with obesity, diabetes type 2 and coronary artery disease (R).

     age-related macular degeneration Genetics Home Reference provides information about age-related macular degeneration. atypical hemolytic-uremic syndrome Genetics Home Reference provides information about atypical hemolytic-uremic syndrome. C3 glomerulopathy At least one mutation in the C3 gene has been found to cause a rare form of kidney disease called C3 glomerulopathy. This disorder damages the kidneys and can lead to end-stage renal disease (ESRD), a life-threatening condition that prevents the kidneys from filtering fluids and waste products from the body effectively. The identified C3 gene mutation deletes two amino acids from the C3 protein. This genetic change is described as a "gain-of-function" mutation because it leads to an altered version of the protein that overactivates the complement system. The overactive system damages structures in the kidneys called glomeruli, which are clusters of tiny blood vessels that help filter waste products from the blood. Damage to glomeruli prevents the kidneys from filtering waste products normally and can lead to ESRD. Several other changes in the C3 gene do not cause C3 glomerulopathy directly but appear to increase the likelihood of developing the disorder. In particular, the C3F allotype is seen more frequently in people with this condition than in the general population. Researchers are working to determine how the C3F allotype may influence disease risk. other disorders At least 17 mutations in the C3 gene have been found to cause C3 deficiency, a rare condition characterized by recurrent bacterial infections beginning in childhood. The genetic changes that cause C3 deficiency lead to an altered version of the C3 protein or prevent cells from producing any of this protein. These mutations are described as "loss-of-function" because the abnormal or missing C3 protein prevents normal activation of the complement system. As a result, the immune system is less able to protect the body against foreign invaders (such as bacteria).

     The C3 gene provides instructions for making a protein called complement component 3 (or C3). This protein plays a key role in a part of the body's immune response known as the complement system. The complement system is a group of proteins that work together to destroy foreign invaders (such as bacteria and viruses), trigger inflammation, and remove debris from cells and tissues. The C3 protein is essential for turning on (activating) the complement system. The presence of foreign invaders triggers the C3 protein to be cut (cleaved) into two smaller pieces. One of these pieces, called C3b, interacts with several other proteins on the surface of cells to trigger the complement system's response. This process must be carefully regulated so the complement system targets only unwanted materials and does not damage the body's healthy cells. Researchers have identified two major forms (allotypes) of the C3 protein, which are known as C3S and C3F. In the general population, C3S is more common than C3F. The two allotypes differ by a single protein building block (amino acid), although it is unclear whether they function differently.

The following transcription factors affect gene expression:

• GR-alpha
• GR-beta
• AP-1
• AhR
• Max
• c-Jun
• USF1
• USF-1

Tissue specificity:

Plasma. The acylation stimulating protein (ASP) is expressed in adipocytes and released into the plasma during both the fasting and postprandial periods.

Caution:

According to PubMed:21527715, the interaction surface between C3 and CR2 reported in PubMed:11387479 is artifactual and can be ascribed to the presence of zinc acetate in the buffer.

Molecular Function:

• C5l2 Anaphylatoxin Chemotactic Receptor Binding
• Endopeptidase Inhibitor Activity
• Receptor Binding
• Serine-Type Endopeptidase Activity
• Cofactor Binding
• Lipid Binding

Biological Processes:

• Complement Activation
• Complement Activation, Alternative Pathway
• Complement Activation, Classical Pathway
• Fatty Acid Metabolic Process
• G-Protein Coupled Receptor Signaling Pathway
• Immune Response
• Inflammatory Response
• Positive Regulation Of Activation Of Membrane Attack Complex
• Positive Regulation Of Angiogenesis
• Positive Regulation Of Apoptotic Cell Clearance
• Positive Regulation Of Glucose Transport
• Positive Regulation Of G-Protein Coupled Receptor Protein Signaling Pathway
• Positive Regulation Of Lipid Storage
• Positive Regulation Of Protein Phosphorylation
• Positive Regulation Of Type Iia Hypersensitivity
• Positive Regulation Of Vascular Endothelial Growth Factor Production
• Regulation Of Complement Activation
• Regulation Of Immune Response
• Regulation Of Triglyceride Biosynthetic Process
• Signal Transduction
• Blood Coagulation
• Positive Regulation Of Developmental Growth
• Positive Regulation Of Erk1 And Erk2 Cascade
• Response To Estradiol
• Response To Estrogen
• Response To Glucocorticoid
• Response To Magnesium Ion
• Response To Progesterone
• Tolerance Induction

Drug Bank:

• Intravenous Immunoglobulin