Serum amyloid A-4 protein (SAA4)

Serum amyloid A-4 protein (SAA4) is the major constitutively expressed member of the SAA family, distinct from acute-phase reactants SAA1 and SAA2. SAA4 is a small (~12–14 kDa) secreted, amphipathic α-helical protein produced predominantly by hepatocytes, but also found in other tissues. It binds high-density lipoproteins (HDL) via specific helical domains and participates in cholesterol transport. Its expression is independent of inflammatory cytokines but notably increased in chronic inflammation, atherosclerotic disease, and several cancers. SAA4 functions as an extracellular hub protein, mediating interactions between lipoproteins, cell surface receptors (such as LOX-1 and CD36), and proteoglycans, thereby modulating cholesterol homeostasis and immune processes. Elevated SAA4 protein levels serve as diagnostic biomarkers for inflammatory and degenerative diseases. Its structure features disordered regions that confer binding flexibility, facilitating its diverse biological functions[1][2][4][6].

Other names

Serum amyloid A4Constitutive serum amyloid A proteinCSAAC-SAASAA-4serum amyloid A-4 protein

Not directly targeted by marketed drugs; participates as circulating biomarker and possible mediator of cell signaling by binding HDL and cell surface receptors such as LOX-1 and CD36[1]. Potential future immunomodulatory interventions plausible.