This Article Full Text 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 Coss, D. Articles by Walker, A. M. Search for Related Content PubMed PubMed Citation Articles by Coss, D. Articles by Walker, A. M. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB (L)-ASPARTIC ACID Medline Plus Health Information Dietary Proteins

Dissociation of Janus Kinase 2 and Signal Transducer and Activator of Transcription 5 Activation after Treatment of Nb2 Cells with a Molecular Mimic of Phosphorylated Prolactin¹

Division of Biomedical Sciences (D.C., C.B.K., L.Y., R.L., A.M.W.), University of California, Riverside, California 92521; and Division of Biochemical and Musculoskeletal Medicine (P.I.), Human Metabolism and Clinical Biochemistry, University of Sheffield Medical School, Sheffield S10 2RX, United Kingdom

Address all correspondence to: Ameae M. Walker, Division of Biomedical Sciences, University of California, Riverside, California 92521.

We have previously demonstrated that phosphorylated PRL acts as an antagonist to the Nb2 proliferative activities of unmodified PRL. A molecular mimic of phosphorylated PRL, which substitutes an aspartate residue for the normally phosphorylated serine (serine 179), has the same properties. Because it takes less than one fourth the amount of phosphorylated hormone, or the aspartate mutant, to block the proliferative activity of unmodified hormone, we have investigated whether the high potency of the aspartate mutant is achieved by the production of an alternate and interfering intracellular signal cascade. Nb2 cells were exposed to 5 or 500 ng/ml human NIDDK PRL, wild-type recombinant PRL (unmodified PRL), or aspartate mutant PRL (pseudophosphorylated PRL) for 1, 5, or 10 min at 37 C. At 5 ng/ml and 10 min, wild-type recombinant PRL showed greater activation of Janus kinase 2 (JAK 2) than the NIDDK preparation. This is consistent with a previous report of higher proliferative activity for the wild-type hormone and is primarily a reflection of the presence of some phosphorylated hormone in the NIDDK preparation. At 500 ng/ml and 10 min, saturation eliminated any differences between responses to the two preparations. JAK 2 activation was not seen in response to the aspartate mutant at either concentration. Signal transducer and activator of transcription 5 (STAT 5) activation was, however, just as robust for the aspartate-treated cells as for the other two groups. Time course experiments eliminated the possibility that STAT 5 phosphorylation in response to the aspartate mutant was the result of JAK 2 activation at earlier time points. Experiments in the present study also interestingly showed preassociation of JAK 2 and STAT 5 in the absence of PRL and the absence of detectable phosphorylation of either JAK 2 or STAT 5. Like JAK 2, receptor phosphorylation was absent with the aspartate mutant. A comparison between STAT 5a and STAT 5b activation showed a marked reduction in STAT 5b phosphorylation in response to the aspartate mutant, with concomitant reduction in STAT 5a-STAT 5b heterodimers. STAT 5a activation, however, was indistinguishable between the wild-type and aspartate mutant. We conclude that the nonproliferative aspartate mutant signals and activates STAT 5 without, or with minimal, use of JAK 2 or receptor phosphorylation. The wild-type proliferative PRL, on the other hand, uses receptor phosphorylation and JAK 2 activation.

This article has been cited by other articles:

				V. L. Williams, A. DeGuzman, H. Dang, M. Kawaminami, T. W. C. Ho, D. G. Carter, and A. M. Walker Common and specific effects of the two major forms of prolactin in the rat testis Am J Physiol Endocrinol Metab, December 1, 2007; 293(6): E1795 - E1803. [Abstract] [Full Text] [PDF]

				E. Ueda, U. Ozerdem, Y.-H. Chen, M. Yao, K. T. Huang, H. Sun, M. Martins-Green, P. Bartolini, and A. M Walker A molecular mimic demonstrates that phosphorylated human prolactin is a potent anti-angiogenic hormone. Endocr. Relat. Cancer, March 1, 2006; 13(1): 95 - 111. [Abstract] [Full Text] [PDF]

				V. Goffin, S. Bernichtein, P. Touraine, and P. A. Kelly Development and Potential Clinical Uses of Human Prolactin Receptor Antagonists Endocr. Rev., May 1, 2005; 26(3): 400 - 422. [Abstract] [Full Text] [PDF]

				M. D. Schroeder, J. L. Brockman, A. M. Walker, and L. A. Schuler Inhibition of Prolactin (PRL)-Induced Proliferative Signals in Breast Cancer Cells by a Molecular Mimic of Phosphorylated PRL, S179D-PRL Endocrinology, December 1, 2003; 144(12): 5300 - 5307. [Abstract] [Full Text] [PDF]

				T. M. Badger, M. J. J. Ronis, S. J. Frank, Y. Chen, and L. He Effects of Chronic Ethanol on Hepatic and Renal CYP2C11 in the Male Rat: Interactions with the Janus-Kinase 2-Signal Transducer and Activators of Transcription Proteins 5b Pathway Endocrinology, September 1, 2003; 144(9): 3969 - 3976. [Abstract] [Full Text] [PDF]

				I. Y. H. Mak, J. J. Brosens, M. Christian, F. A. Hills, L. Chamley, L. Regan, and J. O. White Regulated Expression of Signal Transducer and Activator of Transcription, Stat5, and its Enhancement of PRL Expression in Human Endometrial Stromal Cells in Vitro J. Clin. Endocrinol. Metab., June 1, 2002; 87(6): 2581 - 2588. [Abstract] [Full Text] [PDF]

				A M Walker Unmodified and phosphorylated prolactin and gamma delta T cell development and function Lupus, October 1, 2001; 10(10): 735 - 741. [Abstract] [PDF]

				S. Bernichtein, S. Kinet, S. Jeay, M. Llovera, D. Madern, J. A. Martial, P. A. Kelly, and V. Goffin S179D-Human PRL, a Pseudophosphorylated Human PRL Analog, Is an Agonist and Not an Antagonist Endocrinology, September 1, 2001; 142(9): 3950 - 3963. [Abstract] [Full Text] [PDF]

				A. Glasow, L.-C. Horn, S. E. Taymans, C. A. Stratakis, P. A. Kelly, U. Kohler, J. Gillespie, B. K. Vonderhaar, and S. R. Bornstein Mutational Analysis of the PRL Receptor Gene in Human Breast Tumors with Differential PRL Receptor Protein Expression J. Clin. Endocrinol. Metab., August 1, 2001; 86(8): 3826 - 3832. [Abstract] [Full Text] [PDF]

				X. Xu, E. Kreye, C. B. Kuo, and A. M. Walker A Molecular Mimic of Phosphorylated Prolactin Markedly Reduced Tumor Incidence and Size When DU145 Human Prostate Cancer Cells Were Grown in Nude Mice Cancer Res., August 1, 2001; 61(16): 6098 - 6104. [Abstract] [Full Text] [PDF]

				R. S. Bridges, B. A. Rigero, E. M. Byrnes, L. Yang, and A. M. Walker Central Infusions of the Recombinant Human Prolactin Receptor Antagonist, S179D-PRL, Delay the Onset of Maternal Behavior in Steroid-Primed, Nulliparous Female Rats Endocrinology, February 1, 2001; 142(2): 730 - 739. [Abstract] [Full Text] [PDF]

				D. Coss, L. Yang, C. B. Kuo, X. Xu, R. A. Luben, and A. M. Walker Effects of prolactin on osteoblast alkaline phosphatase and bone formation in the developing rat Am J Physiol Endocrinol Metab, December 1, 2000; 279(6): E1216 - E1225. [Abstract] [Full Text] [PDF]

				M. E. Freeman, B. Kanyicska, A. Lerant, and G. Nagy Prolactin: Structure, Function, and Regulation of Secretion Physiol Rev, October 1, 2000; 80(4): 1523 - 1631. [Abstract] [Full Text] [PDF]