Serum amyloid P component

APCS
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 4AYU, 1GYK, 1LGN, 1SAC, 2A3W, 2A3X, 2A3Y, 2W08, 3D5O, 3KQR, 4AVS, 4AVT, 4AVV
Identifiers
Aliases	APCS, HEL-S-92n, PTX2, SAP, amyloid P component, serum
External IDs	OMIM: 104770; MGI: 98229; HomoloGene: 123932; GeneCards: APCS; OMA:APCS - orthologs
Gene location (Human) Chr. Chromosome 1 (human)[1] Band 1q23.2 Start 159,587,826 bp[1] End 159,588,865 bp[1]
Gene location (Mouse) Chr. Chromosome 1 (mouse)[2] Band 1 H3|1 80.33 cM Start 172,721,528 bp[2] End 172,722,608 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right lobe of liver gallbladder islet of Langerhans pancreatic ductal cell body of pancreas kidney cervix placenta right coronary artery duodenum Top expressed in left lobe of liver sexually immature organism ureter thoracic diaphragm abdominal wall atrioventricular valve kidney semi-lunar valve islet of Langerhans stomach More reference expression data BioGPS More reference expression data
Gene ontology Molecular function calcium ion binding unfolded protein binding metal ion binding virion binding complement component C1q complex binding carbohydrate binding identical protein binding low-density lipoprotein particle binding Cellular component blood microparticle extracellular matrix extracellular exosome nucleus extracellular space extracellular region collagen-containing extracellular matrix Biological process negative regulation of monocyte differentiation negative regulation of acute inflammatory response negative regulation of viral entry into host cell chaperone-mediated protein complex assembly negative regulation of viral process negative regulation of glycoprotein metabolic process protein folding acute-phase response negative regulation of exo-alpha-sialidase activity negative regulation of wound healing innate immune response complement activation, classical pathway Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 325 20219 Ensembl ENSG00000132703 ENSMUSG00000026542 UniProt P02743 P12246 RefSeq (mRNA) NM_001639 NM_011318 RefSeq (protein) NP_001630 NP_035448 Location (UCSC) Chr 1: 159.59 – 159.59 Mb Chr 1: 172.72 – 172.72 Mb PubMed search [3] [4]
Wikidata
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The serum amyloid P component (SAP) is the identical serum form of the amyloid P component (AP), a 25 kDa pentameric protein first identified as the pentagonal constituent of in vivo pathological deposits called "amyloid".^[5] APCS is its human gene.^[6]

In amyloidosis

SAP makes up 14% of the dry mass of amyloid deposits^[7] and is thought to be an important contributor to the pathogenesis of a related group of diseases called the Amyloidoses.^[8] These conditions are characterised by the ordered aggregation of normal globular proteins and peptides into insoluble fibres, which disrupt tissue architecture and are associated with cell death. SAP is thought to decorate and stabilise aggregates by preventing proteolytic cleavage and hence inhibiting fibril removal via the normal protein scavenging mechanisms.^[9] This association is utilised in the routine clinical diagnostic technique of SAP scintigraphy whereby radio-labelled protein is injected into patients to locate areas of amyloid deposition.^[10] The SAP-amyloid association has also been identified as a possible drug target for anti-amyloid therapy, with the recent development and first stage clinical trials of a compound called CPHPC (R-1-[6-[R-2-carboxy-pyrrolidin-1-yl]-6-oxohexanoyl] pyrrolidine-2-carboxylic acid), a small molecule able to strip AP from deposits by reducing levels of circulating SAP.^[11]

Structure

SAP is a member of the pentraxins family, characterised by calcium-dependent ligand binding and a distinctive flattened β-jellyroll structure similar to that of the legume lectins.^[12] The name "pentraxin" is derived from the Greek words for five (penta) and berries (ragos), relating to the radial symmetry of five monomers forming a ring approximately 95 across and 35 deep. Human SAP has 51% sequence homology with C-reactive protein (CRP), a classical acute phase response plasma protein, and is a more distant relative to the "long" pentraxins such as PTX3 (a cytokine-modulated molecule) and several neuronal pentraxins. Both SAP and CRP are evolutionary conserved in all vertebrates and are also found in distant invertebrates such as the horseshoe crab (Limulus polyphemus).^[13]

References