Characterization and regulation of prolactin receptors in MA-10 Leydig cells.

Abstract

The aim of this study is to further characterize the prolactin receptors (PRL-R) previously reported in the murine Leydig tumor MA-10 cell line, as well as to study their homologous and heterologous regulation. Two forms of PRL-R, a high and a low molecular weight form, were revealed by studies of covalent crosslinking of 125I-human GH to cultured MA-10 cells or cell membranes and immunoprecipitation of the solubilized PRL-R complexes with polyclonal anti PRL-R antibody, followed by SDS-PAGE and autoradiography. The long form had a molecular weight of 101 kDa and was predominant when the study was performed in the presence of protease inhibitors. The short form, with a molecular weight of 39 kDa, appeared, at least in part, to be a proteolytic product of the longer form. The same size forms of PRL-R were detected by crosslinking studies in the parental C57BL/6 mouse testicular Leydig cells, indicating the physiological relevance of the MA-10 cell model to the study of Leydig cell PRL-R. Homologous down-regulation of PRL-R was demonstrated in cultured MA-10 cells exposed for 24 h to increasing concentrations of PRL. In contrast, heterologous, 3 5-fold up-regulation of PRL-R was induced by various cAMP-elevating agents, including 8-bromo-cAMP (10(-4) -10(-3) M), dibutyryl cAMP (3 x 10(-3) M) and cholera toxin (1-10 ng/ml), although not by hCG (up to 100 ng/ml). This up-regulatory effect was apparently the result of a change in affinity, since cholera toxin caused a 2.4-fold increase in PRL-R affinity, with no change in the number of binding sites. In summary, these studies provide further evidence that MA-10 Leydig cells can serve as a physiologically relevant model for the study of PRL and PRL-R interactions, both at the functional level, as shown in our previous study, and at the structural and regulatory levels as shown in the current study.

• Authors: E Weiss-Messer, R Ber, T Amit, R J Barkey
• Journal: Molecular and cellular endocrinology (Mol Cell Endocrinol) Vol. 143 Issue 1-2 Pg. 53-64 (Aug 25 1998) ISSN: 0303-7207 [Print] Ireland
• PMID: 9806350 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Receptors, Prolactin
• 8-Bromo Cyclic Adenosine Monophosphate
• Bucladesine
• Prolactin
• Cholera Toxin
• Cyclic AMP

Topics

• 8-Bromo Cyclic Adenosine Monophosphate (pharmacology)
• Animals
• Bucladesine (pharmacology)
• Cholera Toxin (pharmacology)
• Cyclic AMP (agonists)
• Leydig Cells (metabolism)
• Male
• Mice
• Prolactin (metabolism, pharmacology)
• Receptors, Prolactin (agonists, chemistry, metabolism)
• Tumor Cells, Cultured
• Up-Regulation