Affinity modulation of human placental insulin and insulin-like growth factor receptors by lectins.
The ability of plant lectins to modify the interactions of the insulin receptor (IR) and insulin-like growth factor (IGF) receptors (IGFRs) with their ligands was investigated. The lectins profoundly affected the competition-binding curves for (125)I-labelled IGF-I and insulin, causing an increase in the affinity of placental IGF1R and IR towards their ligands. This increment was of such a magnitude that it could affect the receptors' specificity towards these ligands. The lower the ligand concentration, the greater was the lectin-induced affinity shift, which suggests potential physiological significance of the effect. The affinity modulation occurred in a lectin-specific and dose-dependent manner. In contrast to IGF1R and IR, the binding of (125)I-labelled IGF-II to its receptors resisted lectin modulation. Here we provide evidence of the possibility of external modulation of the affinity of placental IGF1R and IR via interactions of the receptors' carbohydrate moieties with lectins. The existence of modulators that would selectively inhibit or enhance the binding of IGFs or insulin to their corresponding receptors may have important implications for placental cell responses to these molecules.
Masnikosa
Romana
R
INEP-Institute for the Application of Nuclear Energy, University of Belgrade, Banatska 31 b, 11080 Belgrade, 381 Serbia. masnikosa_romana@yahoo.co.uk
Nikolić
Anna
A
Nedić
Olgica
O
D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007457:Iodine Radioisotopes; D037102:Lectins / Q000494:pharmacology*; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011869:Radioligand Assay; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*
D007328:Insulin; D007457:Iodine Radioisotopes; D037102:Lectins; D017527:Receptor, IGF Type 2; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin