Human serum amyloid P component has been used as a standard in a study to characterize it as a plasma marker for Parkinson′s disease by a proteomic approach.
Biochem/physiol Actions
Serum amyloid P component (SAP) is named for its universal presence in amyloid deposits (senile plaque and neurofibrillary tangles) in Alzheimer patients although it is exclusively synthesized in the periphery. SAP levels in CSF can be useful for assessing cognitive impairment in AD patients. However, SAP appeared not to be required for A beta deposition since no endogenous SAP immunoreactivity was detectable in transgenic mouse overexpressing beta-protein precursor. SAP belongs to the pentraxins family of oligomeric serum proteins which is highly conserved through evolution. Its presence has been found in Limulus polyphemus haemolymph. A recent report demonstrated that, in the presence of calcium, SAP can bind to free DNA and chromatin released through apoptosis or necrosis, displacing histone H1 and causing its solubilization and degradation. SAP knock out mice developed antinuclear autoimmunity and glomerulonephritis. However, the protective role of SAP in human SLE is still controversial. In addition, SAP neutralizes LPS and is potentially useful in defense against serious gram-negative sepsis in humans.
