MOUSE SERUM AMYLOID-A PROTEIN (SAA(5)) STRUCTURE AND EXPRESSION

作者：DEBEER MC; KINDY MS; LANE WS; DEBEER FC

来源：Journal of Biological Chemistry, 1994, 269(6): 4661-4667.

A novel member of the mouse serum amyloid A protein family, SAA(5), has been identified as a normal apolipoprotein component of non-acute-phase high density lipoprotein (HDL). The structure of SAA(5) was derived from a clone isolated from a normal Balb/c liver cDNA library. The clone predicts a pre-SAA(5) molecule of 130 residues from which an 18-residue leader peptide is cleaved. The mature molecule has an octapeptide insert spanning from position 70 to 77. Similar inserts are found in human C-SAA and, paradoxically, in acute-phase SAA molecules of a number of other species. There is 48% amino acid identity between apo-SAA(5) and the other mouse SAA proteins and 57% identity between the human C-SAA and apo-SAA(5). The SAA, mRNA is three times larger than previously identified SAA mRNAs. Although SAA(5) is constitutively expressed in the liver, it has a rapid albeit muted response to inflammatory stimuli. The increase of SAA(5) mRNA is due to increased transcription rather than mRNA stabilization. Plasma SAA(5) levels during the acute phase are biphasic, either because of translational control or displacement from HDL and rapid clearance. We propose that constitutive SAAs (SAA(5)) on normal HDL contribute to its normal physiological role, whereas the dramatically inducible family members (SAA(1), SAA(2), SAA(3)) equip this particle for an altered functional role during inflammation.

• 出版日期1994-2-11