Abstract
Serum amyloid A4 (SAA4) is a constitutive apolipoprotein of high-density lipoprotein. It exhibits N-linked glycosylation in its second half. There are both glycosylated and nonglycosylated forms in plasma and the ratio of these two forms varies among individuals. This study was conducted to examine the influence of genetic polymorphism of SAA4 on its glycosylation status. In 55 healthy subjects, SAA4 polymorphism was analyzed by PCR combined direct sequencing and its glycosylation status was analyzed by immunoblotting. The results showed that the percentage of glycosylation in subjects with amino acid substitutions at positions 71 and/or 84 was significantly (P < 0.05) higher than that in subjects with the wild type. The polymorphism had no influence on the plasma concentration of SAA4. These findings suggest that the changes in protein structures alter the efficiency of glycosylation in the SAA4 molecule. The functional implication of this should be of interest.
Highlights
Serum amyloid A (SAA) is a polymorphic protein [1,2,3,4]
Since we noted that the ratio of G : NG varies among individuals and might be constant within individuals, this study aimed to examine whether the glycosylation of Serum amyloid A4 (SAA4) is genetically regulated
This study revealed that polymorphism of SAA4 influenced glycosylation efficiency
Summary
Serum amyloid A (SAA) is a polymorphic protein [1,2,3,4]. The synthesis of SAA1 and SAA2 (acute phase SAA; A-SAA) is increased in inflammatory disorders They may play roles in the immune system, lipoprotein metabolism, and tissue repair during or subsequent to inflammation [2, 3]. They are serum precursors of AA proteins, the chief constituents of reactive amyloid deposits [4]. SAA4 has 112 amino acids, with an insertion of eight amino acids at the position corresponding to residue 70 of A-SAA [5] Since we noted that the ratio of G : NG varies among individuals and might be constant within individuals, this study aimed to examine whether the glycosylation of SAA4 is genetically regulated
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