Increased sialylation and defucosylation of plasma proteins are early events in the acute phase response.
Within hours of turpentine injection to stimulate the acute phase (AP) response in rats, the N-acetylneuraminic acid content of plasma proteins increases and that of fucose decreases, each by about 60%. The two changes are inversely related (r = -0.97). The NeuAc/Gal ratio increases from the normal 0.75 to 1.0 on day 2 of the AP. Whereas 50% of the isolated oligosaccharides of normal plasma proteins are retarded on immobilized Ricinus communis agglutinin, those from day 2 AP plasma fail to do so. This indicates that NeuAc caps the normally Gal-terminated chains. alpha1-Acid glycoprotein (a positive AP protein), alpha1-macroglobulin (a non-AP protein), and alpha1-inhibitor3 (a negative AP protein) also show similar alterations in NeuAc/Gal ratio and decreases in Fuc. alpha2-Macroglobulin, which arises only during the AP, does not contain significant amounts of Fuc. Sambucus nigra agglutinin (alpha2,6-linked NeuAc-specific) binds a majority of plasma proteins, and binding is increased during the AP response. Maackia amurensis lectin (alpha2,3-linked NeuAc-specific) binds only three proteins in normal plasma and three additional proteins in AP plasma. The Fuc-specific Aleuria aurantia agglutinin and Lens culinaris agglutinin each detect five proteins in normal plasma. Their binding decreases during the AP response. These results show that: (1) sialylation and defucosylation of preexisting plasma proteins occur rapidly in the AP response; (2) sialylation caps the preexisting Gal-terminating oligosaccharides; and (3) the oligosaccharides of even the non-AP and negative AP proteins are modified. These changes are distinct from the elevation in the levels of protein-bound monosaccharides and the altered concanavalin A-binding profile the oligosaccharides of AP proteins acquire in diseases.
Chavan
Manasi M
MM
Biochemistry and Cell Biology, ACTREC, Navi Mumbai 410 208, India. mchavan@notes.cc.sunysb.edu
Kawle
Poonam D
PD
Mehta
Narendra G
NG
D000210:Acute-Phase Reaction / Q000097:blood* / Q000139:chemically induced; D000818:Animals; D001798:Blood Proteins / Q000032:analysis*; D005643:Fucose / Q000097:blood* / Q000737:chemistry; D006023:Glycoproteins / Q000097:blood* / Q000737:chemistry; D006031:Glycosylation; D019158:N-Acetylneuraminic Acid / Q000097:blood* / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D051381:Rats; D017208:Rats, Wistar
D001798:Blood Proteins; D006023:Glycoproteins; D005643:Fucose; D019158:N-Acetylneuraminic Acid