IgA1 is the premier serum glycoprotein recognized by human galectin-1 since T antigen (Galbeta1-->3GalNAc-) is far superior to non-repeating N-acetyl lactosamine as ligand.
Human heart galectin-1 (HHL) was separated by high pressure liquid chromatography from endogenous glycoproteins co-purified with it during affinity chromatography. These glycoproteins offered excellent ligands for HHL binding and were rich in T antigen (Galbeta1-->3 GalNAc-) of O-linked oligosaccharides. In enzyme linked lectin assay and hemagglutination inhibition assay, human IgA1, bovine fetuin and other O-glycosylated T antigen-bearing glycoproteins bound to the lectin efficiently in contrast to single N-acetyl lactosamine (LacNAc)-bearing N-linked oligosaccharides released from them and to IgG which is not O-glycosylated. HHL binding to IgA1 and fetuin was unaffected by removal of their N-linked oligosaccharides by alpha-mannosidase. When immobilized, O-glycosylated serum proteins but not IgG could capture HHL from its solutions. Desialylated or polymeric IgA1 was better inhibitor than monomeric IgA1. The findings suggest a possible role for galectin-1 in anchoring of microbial and cancer cells known to be rich in T antigen, in high serum IgA1 turn over and in tissue sequestering of IgA1 immune complexes especially after their microbial desialylation in IgA nephropathy and other immune complex-mediated disorders.
Sangeetha
S R
SR
Division of Biochemistry, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram 695011, India.
Appukuttan
P S
PS
D000116:Acetylgalactosamine / Q000031:analogs & derivatives / Q000378:metabolism; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000276:immunology / Q000378:metabolism*; D001212:Asialoglycoproteins / Q000378:metabolism; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D037483:Galectin 1 / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology / Q000378:metabolism*; D008024:Ligands; D009439:Neuraminidase / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D037121:Plant Lectins / Q000378:metabolism; D043323:alpha-Mannosidase / Q000378:metabolism
D015295:Antigens, Tumor-Associated, Carbohydrate; D001212:Asialoglycoproteins; D037483:Galectin 1; D007070:Immunoglobulin A; D008024:Ligands; D009844:Oligosaccharides; D037121:Plant Lectins; C103104:asialo-galactosyl-acetylgalactosamine; C043696:jacalin; C016467:Thomsen-Friedenreich antigen; D009439:Neuraminidase; D043323:alpha-Mannosidase; D000116:Acetylgalactosamine