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Differences in antibody recognition of the triiodothyronine nuclear receptor and c-erbA products
H C Freake1, A Santos, Y Goldberg
1Department of Medicine, University of Minnesota, Minneapolis 55455.
Abstract:
The in vitro translated products of several c-erbA cDNAs have recently been shown to bind thyroid hormones with high affinity and have been termed thyroid hormone receptors. We have used a panel of five erbA-related antibodies to probe the relationship between c-erbA translated products and thyroid hormone receptors, as conventionally measured by 125I-T3 labeling of nuclear extracts. All five antibodies immunoprecipitated the chick c-erbA translated products, but only one of them recognized chick liver and brain T3 receptor, as judged by acceleration of sedimentation through sucrose gradients. None of the antibodies reacted with rat liver and brain or human liver T3 receptors, although one antibody did immunoprecipitate a human c-erbA translated product. We conclude that the T3 receptor, as conventionally measured from these sources, is related but not identical to recently cloned c-erbA sequences.
Insights
Thyroid hormone receptors (T3 receptors) are related but not identical to cloned c-erbA sequences. Antibodies identified differences between c-erbA products and T3 receptors in chick, rat, and human tissues.
Area of Science:
- Molecular Endocrinology
- Genetics
- Biochemistry
Background:
- In vitro translated products of c-erbA cDNAs bind thyroid hormones, termed thyroid hormone receptors.
- Conventional measurement of thyroid hormone receptors involves 125I-T3 labeling of nuclear extracts.
Purpose of the Study:
- To investigate the relationship between c-erbA translated products and conventionally measured thyroid hormone receptors.
- To differentiate c-erbA sequences from actual thyroid hormone receptors using antibody probes.
Main Methods:
- Utilized five erbA-related antibodies for immunoprecipitation assays.
- Assessed antibody recognition of chick, rat, and human thyroid hormone receptors via sucrose gradient sedimentation.
- Compared immunoprecipitated c-erbA products with T3 receptor binding activity.
Main Results:
- All five antibodies immunoprecipitated chick c-erbA translated products.
- Only one antibody recognized chick liver and brain T3 receptor.
- No antibodies reacted with rat or human T3 receptors, though one recognized a human c-erbA product.
Conclusions:
- Thyroid hormone receptors, as conventionally measured, are related to, but distinct from, recently cloned c-erbA sequences.
- Antibody-based analysis reveals molecular differences between c-erbA gene products and functional thyroid hormone receptors across species.