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Biochemical analysis of the epithelin receptor
J M Culouscou1, G W Carlton, M Shoyab
1Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121.
The Journal of Biological Chemistry
|May 15, 1993
Summary
Epithelins 1, 2, and 3 bind to the same receptor on human breast carcinoma cells. Researchers identified two classes of binding sites and a 140-145 kDa epithelin-binding protein complex.
Area of Science:
- Cell Biology
- Molecular Endocrinology
- Cancer Research
Background:
- Epithelins are cysteine-rich proteins modulating epithelial cell growth.
- Understanding epithelin-receptor interactions is crucial for cancer research.
Purpose of the Study:
- To characterize epithelin receptors on MDA-MB-468 human breast carcinoma cells.
- To investigate the binding kinetics and identify the molecular nature of epithelin receptors.
Main Methods:
- Equilibrium binding studies using iodinated epithelin 1.
- Competition binding assays with unlabeled epithelins.
- Chemical cross-linking to identify binding proteins.
Main Results:
- Two classes of epithelin binding sites were identified: high affinity (Kd ≈ 2 x 10(-10) M, 290 receptors/cell) and low affinity (Kd ≈ 10(-8) M, 32,000 receptors/cell).
- Epithelins 1, 2, and 3 competed for the same binding sites.
- A 140-145 kDa protein complex formed upon epithelin 1 binding was detected via cross-linking.
Conclusions:
- MDA-MB-468 cells express distinct high and low affinity epithelin binding sites.
- All three epithelins likely interact with the same receptor protein.
- A 140-145 kDa protein is identified as a potential epithelin receptor or part of the receptor complex.