Relationship between alpha subunit ligand occupancy and beta subunit autophosphorylation in insulin/insulin-like growth factor-1 hybrid receptors
| Autor: | Jeffrey E. Pessin, Anne L. Frattali |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
biology
medicine.medical_treatment Interleukin 5 receptor alpha subunit Autophosphorylation Gi alpha subunit Cell Biology Biochemistry Molecular biology Interleukin 10 receptor alpha subunit Insulin receptor Insulin-like growth factor Insulin receptor substrate biology.protein medicine Molecular Biology G alpha subunit |
| Zdroj: | Journal of Biological Chemistry. 268:7393-7400 |
| ISSN: | 0021-9258 |
| DOI: | 10.1016/s0021-9258(18)53187-2 |
| Popis: | Insulin receptor beta subunit autophosphorylation occurs in an intramolecular trans-reaction in which one beta subunit phosphorylates the adjacent beta subunit within an alpha 2 beta 2 holoreceptor complex (Frattali, A. L., Treadway, J. L., and Pessin, J. E. (1992) J. Biol. Chem. 267, 19521-19528). To determine the spatial relationship between alpha subunit occupancy and beta subunit autophosphorylation, the vaccinia virus/bacteriophage T7 transient expression system was used to generate insulin/insulin-like growth factor (IGF)-1 hybrid receptors. The extent of hybrid receptor formation was proportional to the molar ratio of the insulin and IGF-1 receptor expression plasmids used for transfection of cultured fibroblasts. Insulin/IGF-1 hybrid receptors displayed high affinity binding for insulin and IGF-1 similar to that observed for homotypic insulin and IGF-1 receptors, respectively. As expected, insulin poorly competed for 125I-IGF-1 binding to the insulin/IGF-1 hybrid receptors compared with IGF-1. IGF-1, however, competed more efficiently than insulin for 125I-insulin binding, indicating interactions between the alpha subunit binding sites. Furthermore, insulin or IGF-1 stimulated the autophosphorylation of both beta subunits within wild type insulin/IGF-1 hybrid receptors. Ligand-stimulated autophosphorylation of two different mutant/wild type insulin/IGF-1 hybrid receptors also resulted in the labeling of each beta subunit independent of which alpha subunit was occupied with ligand. These data demonstrate that insulin/IGF-1 hybrid receptors bind both ligands with high affinity and that occupancy of either alpha subunit results in a series of intramolecular trans-autophosphorylation reactions between beta subunits. |
| Databáze: | OpenAIRE |
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