Expression and function of serum amyloid A, a major acute-phase protein, in normal and disease states

Serum amyloid A (SAA), the precursor protein in inflammation-associated rea ctive amyloidosis (AA-type), is an acute phase reactant whose level in the blood increases in response to various insults, it is expressed in the live r, but its physiological role is not well understood. Recently, a broader v iew of SAA expression and function has been emerging. Expression studies sh ow local production of SAA proteins in histologically normal, atherosclerot ic, Alzheimer, inflammatory, and tumor tissues. Binding sites in the SAA pr otein for high density lipoproteins, calcium, laminin, and heparin/heparan- sulfate were described. Adhesion motifs were identified and new functions, affecting cell adhesion, migration, proliferation and aggregation have been described. These findings emphasize the importance of SAA in various physi ological and pathological processes, including inflammation, atherosclerosi s, thrombosis, AA-amyloidosis, rheumatoid arthritis, and neoplasia. In addi tion, recent experiments suggest that SAA may play a "housekeeping" role in normal human tissues. (C) 2000 Lippincott Williams & Wilkins, Inc.