Molecular Endocrinology, Vol 8, 1083-1090, Copyright © 1994 by Endocrine Society

ARTICLES

Inhibition of rat prolactin (PRL) storage by coexpression of human PRL

JM Arrandale and PS Dannies
Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510.

GH4C1 cells increase storage of rat PRL and accumulation of dense core secretory granules when they are treated with 300 nM insulin, 1 nM estradiol, and 10 nM epidermal growth factor. In the experiments reported here, intracellular rat PRL increased from 4% of the total amount produced in 24 h in control cultures to 15% in treated cultures. When GH4C1 cells were transfected with DNA sequences so that they coexpressed human PRL, the storage of rat PRL was no longer induced by hormone treatment; transfected clones contained less than 5% of the total produced in 24 h in both control and treated cultures. The sum of rat and human PRL produced by these clones was not more than rat PRL produced by the untransfected cells, so the storage capacity of the cells was not exceeded. The transfected clones made between 1 to 40 times more rat than human PRL. Release of human and rat PRL was stimulated by depolarizing the cells, indicating both still were in a regulated pathway, even though storage could not be induced. Mutations of human PRL with threonine substituted for asn31 or alanine substituted for ser34 did not block induction of rat PRL storage when coexpressed in GH4C1 clones. We conclude the ability to increase rat PRL storage is a process with marked specificity because it is inhibited by relatively low amounts of human PRL and inhibition requires asn31 and ser34 in human PRL. Such specificity is consistent with a receptor-mediated mechanism that concentrates PRL into dense cores of secretory granules.

This article has been cited by other articles:

				P. S. Dannies Protein Hormone Storage in Secretory Granules: Mechanisms for Concentration and Sorting Endocr. Rev., February 1, 1999; 20(1): 3 - 21. [Abstract] [Full Text]

				W. Han, D. Li, A. K. Stout, K. Takimoto, and E. S. Levitan Ca2+-Induced Deprotonation of Peptide Hormones Inside Secretory Vesicles in Preparation for Release J. Neurosci., February 1, 1999; 19(3): 900 - 905. [Abstract] [Full Text] [PDF]

				M. S. Lee, R. Dirkx Jr., M. Solimena, and P. S. Dannies Stabilization of the Receptor Protein Tyrosine Phosphatase-Like Protein ICA512 in GH4C1 Cells upon Treatment with Estradiol, Insulin, and Epidermal Growth Factor Endocrinology, June 1, 1998; 139(6): 2727 - 2733. [Abstract] [Full Text] [PDF]

				Z. Sun, M. S. Lee, H. K. Rhee, J. M. Arrandale, and P. S. Dannies Inefficient Secretion of Human H27A-Prolactin, a Mutant That Does Not Bind Zn2+ Mol. Endocrinol., September 1, 1997; 11(10): 1544 - 1551. [Abstract] [Full Text]

				V. Brechler, W. N. Chu, J. D. Baxter, G. Thibault, and T. L. Reudelhuber A Protease Processing Site Is Essential for Prorenin Sorting to the Regulated Secretory Pathway J. Biol. Chem., August 23, 1996; 271(34): 20636 - 20640. [Abstract] [Full Text] [PDF]

				S.-U. Gorr and S. U. Gorr Differential Storage of Prolactin, Granins (Chromogranin B and Secretogranin II), and Constitutive Secretory Markers in Rat Pituitary GH(4)C(1) Cells J. Biol. Chem., February 16, 1996; 271(7): 3575 - 3580. [Abstract] [Full Text] [PDF]

				L. Stahl, R. Wright, J. Castle, and A. Castle The unique proline-rich domain of parotid proline-rich proteins functions in secretory sorting J. Cell Sci., January 6, 1996; 109(6): 1637 - 1645. [Abstract] [PDF]

				A. Castle, J. Schwarzbauer, R. Wright, and J. Castle Differential targeting of recombinant fibronectins in AtT-20 cells based on their efficiency of aggregation J. Cell Sci., January 12, 1995; 108(12): 3827 - 3837. [Abstract] [PDF]