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Åke Lernmark

Principal investigator

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Multiple growth hormone-binding proteins are expressed on insulin-producing cells

Author

  • Annette Møldrup
  • Nils Billestrup
  • Niels A. Thorn
  • Åke Lernmark
  • Jens Høiriis Nielsen

Summary, in English

The insulin-producing rat islet tumor cell line, RIN-5AH, expresses somatogen binding sites and responds to GH by increased proliferation and insulin production. Affinity cross-linking shows that RIN-5AH cells contain two major GH-binding subunits of Mr 100-130K (110K), which appear to exist as disulfide-linked multimers of Mr 270-350K (300K). In addition, a minor Mr 180K GH-binding protein is identified which does not appear to be associated with other proteins by disulfide bridges. A plasma membrane-enriched fraction accounts for 86% of the RIN-cell GH-binding activity while cytosol and intracellular organelles are low in GH-binding activity. The plasma membrane-bound activity is soluble in Triton X-100 with intact hormone binding characteristics. The apparent KD in detergent solution is estimated to 18 ng/ml (8 x 10-10 m).125l-hGH-affinity cross-linking to intact and detergent-solubilized membranes as well as hGH-affinity purified protein reveals labeled proteins of Mr 180K and Mr 285-350K. In contrast to the cross-linked Mr 300K complexes of intact cells those of disintegrated cellular material are resistant to reduction with dithiothreitol, and it is speculated that this is due to intersubunit cross-linking of the disulfide-linked Mr 110K GH-binding subunits. The GH-binding proteins are purified approximately 100-fold by one cycle of hGH-affinity chromatography and five major proteins of Mr 180K, 94K, 86K, 64K, and 54K are identified by silver staining in the purified fraction. It is concluded that the RIN-5AH cells have multiple GH-binding proteins which may mediate signals for either proliferation and/or insulin production.

Publishing year

1989-01-01

Language

English

Pages

1173-1182

Publication/Series

Molecular Endocrinology

Volume

3

Issue

8

Document type

Journal article

Publisher

The Endocrine Society

Status

Published

ISBN/ISSN/Other

  • ISSN: 0888-8809