Phosphorylation of human serum amyloid A protein by protein kinase C.
Monokine-induced hepatic secretion of serum amyloid A protein (apo-SAA), an acute-phase reactant, is followed by rapid association with high-density lipoprotein (HDL) in plasma. Plasma clearance of apo-SAA is more rapid than any of the other HDL apolipoproteins. It has been shown that, of the acute-phase HDL3 apolipoproteins, apo-SAA preferentially associates with neutrophil membranes. HDL apolipoproteins have been shown to activate protein kinase C in endothelial cells. We therefore investigated potential phosphorylation of HDL3 apolipoproteins by protein kinase C. Apo-SAA was the only apolipoprotein phosphorylated (Km = 12 mM). Phosphorylation of the apo-SAA-containing HDL3 particle was selective for the more basic isoforms of apo-SAA (pI 7.0, 7.4, 7.5 and 8.0), with more acidic isoforms being phosphorylated when delipidated acute-phase apolipoproteins were used as substrate. However, phosphorylation was not in itself responsible for the establishment of the apo-SAA isoforms.
Nel
A E
AE
Department of Internal Medicine, University of Stellenbosch Medical School, Tygerberg, South Africa.
De Beer
M C
MC
Shephard
E G
EG
Strachan
A F
AF
Vandenplas
M L
ML
De Beer
F C
FC
D000596:Amino Acids / Q000032:analysis; D001053:Apolipoproteins / Q000378:metabolism; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007525:Isoelectric Focusing; D010449:Peptide Mapping; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D000685:Serum Amyloid A Protein / Q000378:metabolism*
D000596:Amino Acids; D001053:Apolipoproteins; D000685:Serum Amyloid A Protein; C035165:apolipoprotein SAA; D011493:Protein Kinase C