Characterisation of insulin-like growth factor receptors and insulin receptors in the human placenta using lectin affinity methods.
Insulin and insulin-like growth factor receptors (IR, IGF-IR, IGF-IIR) from human placental cell membranes were solubilised and their glycoprotein properties were studied in terms of their interaction with five lectins: wheat germ agglutinin (WGA), banana lectin (BanLec), phytohaemagglutinin (PHA), concanavalin A (Con A), and Sambucus nigra agglutinin (SNA). The pattern of binding to the immobilised lectins indicated that the glycosylation of the IGF-IR, IGF-IIR and IR differed. We found several populations of receptors in placental cell membranes, differing with respect to their oligosaccharide moieties. IGF-IIR populations bore highly branched complex type N-glycans with a very high content of oligosaccharides terminating with Sia, high-mannose type N-glycans and hybrid type N-glycans. All these glycans seemed to be attached to the same IGF-II receptor molecules. Two major glycoforms of IR were detected, one having multiple highly branched N-glycans with a low content of terminal Sia and the other, having high-mannose type glycans attached to multiple N-glycosylation sites. As for the IGF-IR, multiple glycoforms were detected, bearing complex type N-glycans with various content of Sia-terminating branches, hybrid type N-glycans or high-mannose type N-glycans. The specific binding of (125)I-IGF-II to its receptor increased in the presence of immobilised WGA and SNA, which might imply the existence of a mammalian lectin counterpart whose potential physiological significance may lie in different targeting to various membrane compartments, thereby potentially modifying their cell signalling pathways.
Masnikosa
Romana
R
INEP-Institute for the Application of Nuclear Energy, Belgrade, Serbia and Montenegro. romana@inep.co.yu
Baricević
Ivona
I
Jones
David R
DR
Nedić
Olgica
O
D001667:Binding, Competitive; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D005260:Female; D006023:Glycoproteins / Q000737:chemistry*; D006031:Glycosylation; D006801:Humans; D037102:Lectins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D010920:Placenta / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000737:chemistry* / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000737:chemistry* / Q000378:metabolism; D011972:Receptor, Insulin / Q000737:chemistry* / Q000378:metabolism
D006023:Glycoproteins; D037102:Lectins; D008024:Ligands; D017527:Receptor, IGF Type 2; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin