Skip to main content
NCBI home page
Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1983 Nov;80(21):6538–6541. doi: 10.1073/pnas.80.21.6538

Somatocrinin receptor coupled with cAMP-dependent protein kinase on anterior pituitary granules.

M J Lewin, F Reyl-Desmars, N Ling
PMCID: PMC390388  PMID: 6314330

Abstract

The molecular mechanism of growth hormone release by synthetic somatocrinin was investigated on purified hog anterior pituitary secretory granules; the granules were found to contain a cAMP-dependent protein kinase that catalyzed [gamma-32P]-ATP histone phosphorylation with maximal rates ranging from 1 to 5 nmol of Pi incorporated per mg of protein per 20 min. The activity of this enzyme was further stimulated by somatocrinin. Stimulation was observed at concentrations as low as 0.3 pM, and the half-maximal effect was obtained with 35 +/- 8 pM (n = 4). Michaelis-Menten analysis of phosphorylation kinetics suggested that the peptide did not change significantly the reaction's Vmax, but produced a dramatic increase in enzyme affinity for cAMP: the apparent Km for the nucleotide decreased from 400 X 10(-9) M under unstimulated conditions to 15 X 10(-9) M in the presence of 100 pM somatocrinin. Furthermore, a Hill plot of concentration-dependence curve indicated the existence of negative cooperativity. At the concentration of 35 pM, the less potent analogs of somatocrinin [designated hpGRF-44 to indicate source (human pancreas, hp), activity (growth hormone-releasing factor, GRF), and amino acid composition], hpGRF-(1-37) and [Phe1]hpGRF-(1-40) had 20% and 7%, respectively, of the effect of somatocrinin. The biologically inactive analog hpGRF-(2-40) had no evident effect at concentrations up to 0.1 microM. Therefore, we suggest that somatocrinin stimulation of growth hormone release involves activation of exocytosis through a phosphorylation mechanism mediated by a granular receptor coupled with a cAMP-dependent protein kinase.

Full text

PDF
6538

Images in this article

6539Image
on p.6539

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Benoit R., Böhlen P., Ling N., Briskin A., Esch F., Brazeau P., Ying S. Y., Guillemin R. Presence of somatostatin-28-(1-12) in hypothalamus and pancreas. Proc Natl Acad Sci U S A. 1982 Feb;79(3):917–921. doi: 10.1073/pnas.79.3.917. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Brazeau P., Ling N., Böhlen P., Esch F., Ying S. Y., Guillemin R. Growth hormone releasing factor, somatocrinin, releases pituitary growth hormone in vitro. Proc Natl Acad Sci U S A. 1982 Dec;79(24):7909–7913. doi: 10.1073/pnas.79.24.7909. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Brazeau P., Ling N., Esch F., Böhlen P., Mougin C., Guillemin R. Somatocrinin (growth hormone releasing factor) in vitro bioactivity; Ca++ involvement, cAMP mediated action and additivity of effect with PGE2. Biochem Biophys Res Commun. 1982 Nov 30;109(2):588–594. doi: 10.1016/0006-291x(82)91762-4. [DOI] [PubMed] [Google Scholar]
  4. Brazeau P., Vale W., Burgus R., Ling N., Butcher M., Rivier J., Guillemin R. Hypothalamic polypeptide that inhibits the secretion of immunoreactive pituitary growth hormone. Science. 1973 Jan 5;179(4068):77–79. doi: 10.1126/science.179.4068.77. [DOI] [PubMed] [Google Scholar]
  5. Dahlquist F. W. The meaning of Scatchard and Hill plots. Methods Enzymol. 1978;48:270–299. doi: 10.1016/s0076-6879(78)48015-2. [DOI] [PubMed] [Google Scholar]
  6. Esch F. S., Böhlen P., Ling N. C., Brazeau P. E., Wehrenberg W. B., Guillemin R. Primary structures of three human pancreas peptides with growth hormone-releasing activity. J Biol Chem. 1983 Feb 10;258(3):1806–1812. [PubMed] [Google Scholar]
  7. Guillemin R., Brazeau P., Böhlen P., Esch F., Ling N., Wehrenberg W. B. Growth hormone-releasing factor from a human pancreatic tumor that caused acromegaly. Science. 1982 Nov 5;218(4572):585–587. doi: 10.1126/science.6812220. [DOI] [PubMed] [Google Scholar]
  8. LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
  9. Labrie F., Lemaire S., Poirier G., Pelletier G., Boucher R. Adenohypophyseal secretory granules. I. Their phosphorylation and association with protein kinase. J Biol Chem. 1971 Dec 10;246(23):7311–7317. [PubMed] [Google Scholar]
  10. Mangeat P., Marchis-Mouren G., Cheret A. M., Lewin M. J. Specific activation of cyclic AMP-dependent protein kinase(s) by H2-histamine agonists in isolated gastric mucosal cells from guinea-pig. Biochim Biophys Acta. 1980 May 22;629(3):604–608. doi: 10.1016/0304-4165(80)90165-8. [DOI] [PubMed] [Google Scholar]
  11. René E., Willoughby J., Brazeau P. Differentiation between the somatostatin inhibition and the post-somatostatin rebound observed on growth hormone secretion in vitro. Regul Pept. 1982 Nov;4(6):325–331. doi: 10.1016/0167-0115(82)90143-4. [DOI] [PubMed] [Google Scholar]
  12. Reyl F. J., Lewin M. J. Intracellular receptor for somatostatin in gastric mucosal cells: decomposition and reconstitution of somatostatin-stimulated phosphoprotein phosphatases. Proc Natl Acad Sci U S A. 1982 Feb;79(4):978–982. doi: 10.1073/pnas.79.4.978. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Walsh D. A., Ashby C. D., Gonzalez C., Calkins D., Fischer E. H. Krebs EG: Purification and characterization of a protein inhibitor of adenosine 3',5'-monophosphate-dependent protein kinases. J Biol Chem. 1971 Apr 10;246(7):1977–1985. [PubMed] [Google Scholar]
  14. Wehrenberg W. B., Ling N., Brazeau P., Esch F., Böhlen P., Baird A., Ying S., Guillemin R. Somatocrinin, growth hormone releasing factor, stimulates secretion of growth hormone in anesthetized rats. Biochem Biophys Res Commun. 1982 Nov 30;109(2):382–387. doi: 10.1016/0006-291x(82)91732-6. [DOI] [PubMed] [Google Scholar]
  15. Wehrenberg W. B., Ling N., Böhlen P., Esch F., Brazeau P., Guillemin R. Physiological roles of somatocrinin and somatostatin in the regulation of growth hormone secretion. Biochem Biophys Res Commun. 1982 Nov 30;109(2):562–567. doi: 10.1016/0006-291x(82)91758-2. [DOI] [PubMed] [Google Scholar]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences

RESOURCES