Complement component 5a
complement component 5 | |||||||
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Chr. 9 q34.1 | |||||||
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C5a is a protein fragment released from cleavage of
Structure
Human polypeptide C5a contains 74 amino acids and has 11kDa. NMR spectroscopy proved that the molecule is composed of four helices and connected by peptide loops with three disulphide bonds between helix IV and II, III. There is a short 1.5 turn helix on N-terminus but all agonist activity take place in the C-terminus. C5a is rapidly metabolised by a serum enzyme carboxypeptidase B to a 72 amino acid form C5a des-Arg without C terminal arginine.[2][3]
Functions
C5a is an
Binding process
C5a interact with
C5a binding to the receptor is a two-stage process: an interaction between basic residues in the helical core of C5a and acidic residues in the extracellular N-terminal domain allows the C-terminus of C5a to bind to residues in the receptor transmembrane domains. The latter interaction leads to receptor activation, and the transduction of the ligand binding signal across the cell
Sensitivity of C5aR1 to C5a stimulation is enhanced by lipopolysaccharides exposure. C5a, acting via C5aR1, is shown to differentially modulate lipopolysaccharides-induced inflammatory responses in primary human monocytes versus macrophages,[7] yet this is not due to C5aR1 upregulation.[8] C5L2 is another C5a receptor that is thought to regulate the C5a-C5aR1 effects. There is apparently contradictory evidence showing decoy receptor activity conferring anti-inflammatory properties and also signalling activity conferring pro-inflammatory properties.[9][1]
Diseases
C5a is a powerful inflammatory mediator, and seems to be a key factor in the development of pathology of many inflammatory diseases involving the complement system such as sepsis, rheumatoid arthritis, inflammatory bowel disease, systemic lupus erythemotosis, psoriasis. The inhibitor of C5a that can block its effects would be helpful in medical applications. Another candidate is PMX53 or PMX205 that is highly specific for CD88 and effectively reduces inflammatory response.
References
- ^ PMID 19464229.
- PMID 23383423.
- S2CID 22630287.
- PMID 27094554.
- S2CID 4338594.
- ^ Fujita T (14 October 1999). Boulay F (ed.). "PROW and IWHLDA present the GUIDE on: CD88". Protein Reviews on the Web. Archived from the original on 2008-07-24.
- S2CID 207429042.
- PMID 21630250.
- PMID 23383423.
- S2CID 9206660.
- PMID 22924972.
- PMID 12218141.
- PMID 19324972.
- PMID 21292772.
- PMID 29915941.
- PMID 23756248.
- PMID 23479227.
- PMID 32634128.
- PMID 23982144.
- S2CID 245556050.
External links
- Complement+C5a at the U.S. National Library of Medicine Medical Subject Headings (MeSH)