Abstract
Prolactin (PRL) is essential for progesterone biosynthesis and luteal cell hypertrophy of the rat corpus luteum during pregnancy. Both the long and short form of the PRL receptor have been identified in the corpus luteum of pregnant rat. The long form has been shown to transduce PRL signal in other cells, whereas no information is available on the role of the short form, especially in the corpus luteum. In the present study, we have cloned a rat ovarian-specific phosphoprotein, PRAP (PRL Receptor Associated Protein), which has no significant homology to other known proteins. We have demonstrated that this protein is immunoprecipitated by anti-PRL receptor and anti-phosphotyrosine antibodies. To determine whether PRAP associates with either the long or the short form of the PRL receptor, fusion proteins with glutathione S-transferase containing the cytoplasmic domain of the long or short form of the PRL receptor were produced, purified, and incubated with luteal proteins. Our results indicate that PRAP preferentially binds to the short form of the PRL receptor. Thus, the long form and short forms of the PRL receptor may signal through distinct pathways. These data provide evidence for the involvement of a novel protein in PRL signal transduction and suggest that PRAP may contribute to the luteotropic effects of PRL on the corpus luteum during pregnancy.
Highlights
To explore the possibility that the PRL-inducible 32-kDa luteal phosphoprotein may be involved in the PRL signal transduction pathway, we first examined if this protein associates with the PRL receptor in the corpus luteum
Since this result demonstrates that the 32-kDa protein is associated with the PRL receptor in luteal cell extracts, we refer to this protein as PRL receptor associated protein, or PRAP
Parallel incubations of the luteal cell extracts with anti-phosphotyrosine antibody resulted in the immunoprecipitation of PRAP (Fig. 1), consistent with PRAP being a substrate for PRL receptor-associated protein tyrosine kinases
Summary
To explore the possibility that the PRL-inducible 32-kDa luteal phosphoprotein may be involved in the PRL signal transduction pathway, we first examined if this protein associates with the PRL receptor in the corpus luteum. Luteal cell extracts were immunoprecipitated with the U6 monoclonal antibody against the rat PRL receptor and immunoblotted with the PRAP antiserum. The 32-kDa protein was efficiently precipitated by the U6 antibody, but not by a control IgG. Since this result demonstrates that the 32-kDa protein is associated with the PRL receptor in luteal cell extracts, we refer to this protein as PRL receptor associated protein, or PRAP. Parallel incubations of the luteal cell extracts with anti-phosphotyrosine antibody resulted in the immunoprecipitation of PRAP (Fig. 1), consistent with PRAP being a substrate for PRL receptor-associated protein tyrosine kinases. To determine if the association of PRAP with the PRL receptor is dependent upon PRL binding, corpora lutea obtained
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
