This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Yan, G.-z. Articles by Bancroft, C. Search for Related Content PubMed PubMed Citation Articles by Yan, G.-z. Articles by Bancroft, C.

Mediation by Calcium of Thyrotropin-Releasing Hormone Action on the Prolactin Promoter via Transcription Factor Pit-1

Department of Physiology and Biophysics, Mount Sinai School of Medicine, City University of New York New York, New York 10029

Address requests for reprints to: Dr. Carter Bancroft, Box 1218, Mount Sinai School of Medicine.One Gustave L. Levy Place, New York, New York 10029.

Abstract

Mediation by Ca²⁺ of TRH action on the PRL promoter was investigated by both additivity and pharmacological studies and by techniques that probe more gene-proximal events. TRH required the presence of Ca²⁺ in the medium for stimulation of transient expression in GH₃ cells of a PRL-chloramphenicol acetyltransferase (PRL-CAT) construct containing proximal PRL promoter sequences [(-187)PRL-CAT]. Chronic 12-O-tetradecanoyl phorbol-13-acetate downregulation of cellular protein kinase C did not block induction of expression of (-187)PRL-CAT by either Ca²⁺ or TRH. In studies with Ca²⁺ blockers, the Ca²⁺ flux inhibitors cobalt ion and nimodipine blocked induction of (-187)PRL-CAT expression by either Ca²⁺ or TRH. On the other hand, the Ca²⁺ immobilizers 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'- tetraacetic acid acetoxymethyltetraester and 8-(N,N- diethylamino)octyl 3,4,5-trimethoxybenzoate blocked induction of expression of this construct by Ca²⁺ but not by TRH, suggesting that TRH regulation of the PRL promoter may be dependent on Ca²⁺ fluxes but insensitive to Ca²⁺ immobilization. We have shown previously that the PRL promoter pit-1 binding site 1P is a TRH response element. In the present studies, Ca²⁺ regulation studies with 5'-deletion mutants of (-204)PRL-CAT showed that (-75)PRL-CAT, containing the single pit-1 binding site 1P, also contains a Ca²⁺ response element. The observation that two copies of a site 1P oligomer transferred a Ca²⁺ response to either of the two minimal constructs (-39)PRL-CAT or (-39)mouse metallothionein-CAT showed that site 1P is an independent Ca²⁺ response element. Analysis of site 1P mutants yielded a strong correlation between the ability to bind pit-1 and to transfer a Ca²⁺ response. In addition, coexpression of a mutant pit-1 possessing reduced trans-activational activity strongly inhibited TRH regulation of (-187)PRL-CAT and partially blocked Ca²⁺ regulation of this construct. We conclude that Ca²⁺ mediates TRH action on the PRL promoter, and that pit-1 represents a gene-proximal mediator in this signaling pathway.

FOOTNOTES

This work was supported by NIH Grant GM-36847, ACS Grant BC-665, and an Irma T. Hirschl Career Scientist Award (to C.B.)

Received for publication July 16, 1991. Revision received August 5, 1991. Accepted for publication August 5, 1991.

This article has been cited by other articles:

				J. Hayakawa, M. Ohmichi, K. Tasaka, Y. Kanda, K. Adachi, Y. Nishio, K. Hisamoto, S. Mabuchi, S. Hinuma, and Y. Murata Regulation of the PRL Promoter by Akt through cAMP Response Element Binding Protein Endocrinology, January 1, 2002; 143(1): 13 - 22. [Abstract] [Full Text] [PDF]

				B. Andersen and M. G. Rosenfeld POU Domain Factors in the Neuroendocrine System: Lessons from Developmental Biology Provide Insights into Human Disease Endocr. Rev., February 1, 2001; 22(1): 2 - 35. [Abstract] [Full Text]

				A. Kimura, M. Ohmichi, K. Tasaka, Y. Kanda, H. Ikegami, J. Hayakawa, K. Hisamoto, K.-i. Morishige, S. Hinuma, H. Kurachi, et al. Prolactin-releasing Peptide Activation of the Prolactin Promoter Is Differentially Mediated by Extracellular Signal-regulated Protein Kinase and c-Jun N-terminal Protein Kinase J. Biol. Chem., February 4, 2000; 275(5): 3667 - 3674. [Abstract] [Full Text] [PDF]

				Y.-H. Wang and R. A. Maurer A Role for the Mitogen-Activated Protein Kinase in Mediating the Ability of Thyrotropin-Releasing Hormone to Stimulate the Prolactin Promoter Mol. Endocrinol., July 1, 1999; 13(7): 1094 - 1104. [Abstract] [Full Text]

				M. S. Fliss, P. M. Hinkle, and C. Bancroft Expression Cloning and Characterization of PREB (Prolactin Regulatory Element Binding), a Novel WD Motif DNA-Binding Protein with a Capacity to Regulate Prolactin Promoter Activity Mol. Endocrinol., April 1, 1999; 13(4): 644 - 657. [Abstract] [Full Text]

				I. M. Colin and J. L. Jameson Estradiol Sensitization of Rat Pituitary Cells to Gonadotropin-Releasing Hormone: Involvement of Protein Kinase C- and Calcium-Dependent Signaling Pathways Endocrinology, September 1, 1998; 139(9): 3796 - 3802. [Abstract] [Full Text] [PDF]

				P. W. Howard and R. A. Maurer A Composite Ets/Pit-1 Binding Site in the Prolactin Gene Can Mediate Transcriptional Responses to Multiple Signal Transduction Pathways J. Biol. Chem., September 8, 1995; 270(36): 20930 - 20936. [Abstract] [Full Text] [PDF]

				A. M. Lew and H. P. Elsholtz A Dopamine-responsive Domain in the N-terminal Sequence of Pit-1 J. Biol. Chem., March 31, 1995; 270(13): 7156 - 7160. [Abstract] [Full Text] [PDF]

				P Sun, H Enslen, P S Myung, and R A Maurer Differential activation of CREB by Ca2+/calmodulin-dependent protein kinases type II and type IV involves phosphorylation of a site that negatively regulates activity. Genes & Dev., November 1, 1994; 8(21): 2527 - 2539. [Abstract] [PDF]

				S. Radovick, M. Nations, Y. Du, L. A. Berg, B. D. Weintraub, and F. E. Wondisford A Mutation in the POU-Homeodomain of Pit-1 Responsible for Combined Pituitary Hormone Deficiency Science, August 21, 1992; 257(5073): 1115 - 1118. [Abstract] [PDF]