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Multiple growth hormone-binding proteins are expressed on insulin-producing cells
A Møldrup1, N Billestrup, N A Thorn
1Hagedorn Research Laboratory, Gentofte, Denmark.
Molecular Endocrinology (Baltimore, Md.)
|August 1, 1989
Summary
Rat islet tumor cells (RIN-5AH) possess multiple growth hormone (GH) binding proteins on their plasma membrane. These proteins are involved in GH-stimulated proliferation and insulin production, indicating their crucial role in endocrine function.
Area of Science:
- Endocrinology
- Cell Biology
- Molecular Biology
Background:
- The rat insulinoma cell line RIN-5AH expresses growth hormone (GH) binding sites.
- RIN-5AH cells exhibit increased proliferation and insulin production in response to GH.
Purpose of the Study:
- To characterize the GH-binding proteins in RIN-5AH cells.
- To investigate the role of these proteins in GH-mediated cellular responses.
Main Methods:
- Affinity cross-linking studies to identify GH-binding subunits.
- Cellular fractionation to determine the localization of GH-binding activity.
- Triton X-100 solubilization and GH-affinity chromatography for protein purification.
Main Results:
- RIN-5AH cells possess major GH-binding subunits (110K) forming disulfide-linked multimers (300K) and a minor 180K GH-binding protein.
- 86% of GH-binding activity is localized to the plasma membrane, with soluble binding characteristics in Triton X-100.
- Purified fractions revealed multiple GH-binding proteins, including 180K, 94K, 86K, 64K, and 54K species.
Conclusions:
- RIN-5AH cells express multiple GH-binding proteins, primarily on the plasma membrane.
- These proteins likely mediate GH signaling for cell proliferation and insulin production.