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 Jinsi-Parimoo, A. Articles by Gershengorn, M. C. Search for Related Content PubMed PubMed Citation Articles by Jinsi-Parimoo, A. Articles by Gershengorn, M. C.

Constitutive Activity of Native Thyrotropin-Releasing Hormone Receptors Revealed Using a Protein Kinase C-Responsive Reporter Gene

Division of Molecular Medicine, Department of Medicine, Cornell University Medical College and The New York Hospital, New York, New York 10021

Address all correspondence and requests for reprints to: Marvin C. Gershengorn, Cornell University Medical College, 1300 York Avenue, New York, New York 10021. E-mail: mcgersh{at}mail.med.cornell.edu

The native TRH receptor (TRH-R), which is a G protein-coupled receptor that signals via the phosphoinositide transduction pathway, has been assumed to be inactive in the absence of agonist. In contrast, a mutant mouse TRH-R (C335Stop TRH-R) was shown previously to exhibit constitutive (or agonist-independent) signaling activity. In this report, we measured signaling activity of TRH-Rs using a protein kinase C-responsive reporter gene instead of formation of inositol phosphate second messenger molecules. Using this more sensitive system, we show that native mouse TRH-Rs exhibit agonist-independent signaling activity that is directly proportional to the number of receptors expressed in COS-1 cells and is inhibited by negative antagonist benzodiazepine drugs. As expected, the basal signaling activity of native TRH-Rs is lower than C335Stop TRH-Rs. Constitutive activity of native TRH-Rs is not peculiar to COS-1 cells in which receptor density is markedly elevated, because it can also be demonstrated in Madin Darby canine kidney cells stably expressing mouse TRH-Rs and GH₄C₁ cells endogenously expressing rat TRH-Rs. These findings support the thesis that native TRH-Rs oscillate between active and inactive states. We suggest that demonstration of constitutive activity of native receptors may depend on the sensitivity of the signaling assay employed.

This article has been cited by other articles:

				R. Parmentier, S. Kolbaev, B. P. Klyuch, D. Vandael, J.-S. Lin, O. Selbach, H. L. Haas, and O. A. Sergeeva Excitation of Histaminergic Tuberomamillary Neurons by Thyrotropin-Releasing Hormone J. Neurosci., April 8, 2009; 29(14): 4471 - 4483. [Abstract] [Full Text] [PDF]

				B. W. Jones, G. J. Song, E. K. Greuber, and P. M. Hinkle Phosphorylation of the Endogenous Thyrotropin-releasing Hormone Receptor in Pituitary GH3 Cells and Pituitary Tissue Revealed by Phosphosite-specific Antibodies J. Biol. Chem., April 27, 2007; 282(17): 12893 - 12906. [Abstract] [Full Text] [PDF]

				S. Engel, S. Neumann, N. Kaur, V. Monga, R. Jain, J. Northup, and M. C. Gershengorn Low Affinity Analogs of Thyrotropin-releasing Hormone Are Super-agonists J. Biol. Chem., May 12, 2006; 281(19): 13103 - 13109. [Abstract] [Full Text] [PDF]

				S.-J. Han, F. F. Hamdan, S.-K. Kim, K. A. Jacobson, L. M. Bloodworth, B. Li, and J. Wess Identification of an Agonist-induced Conformational Change Occurring Adjacent to the Ligand-binding Pocket of the M3 Muscarinic Acetylcholine Receptor J. Biol. Chem., October 14, 2005; 280(41): 34849 - 34858. [Abstract] [Full Text] [PDF]

				T. C. Kent, K. S. J. Thompson, and L. H. Naylor Development of a Generic Dual-Reporter Gene Assay for Screening G-Protein-Coupled Receptors J Biomol Screen, August 1, 2005; 10(5): 437 - 446. [Abstract] [PDF]

				X. Lu, W. Huang, S. Worthington, P. Drabik, R. Osman, and M. C. Gershengorn A Model of Inverse Agonist Action at Thyrotropin-Releasing Hormone Receptor Type 1: Role of a Conserved Tryptophan in Helix 6 Mol. Pharmacol., November 1, 2004; 66(5): 1192 - 1200. [Abstract] [Full Text] [PDF]

				Y. Sun and M. C. Gershengorn Correlation between Basal Signaling and Internalization of Thyrotropin-Releasing Hormone Receptors: Evidence for Involvement of Similar Receptor Conformations Endocrinology, August 1, 2002; 143(8): 2886 - 2892. [Abstract] [Full Text] [PDF]

				K. Prufer and J. Barsony Retinoid X Receptor Dominates the Nuclear Import and Export of the Unliganded Vitamin D Receptor Mol. Endocrinol., August 1, 2002; 16(8): 1738 - 1751. [Abstract] [Full Text] [PDF]

				L. Q. Nguyen, O. K. Arseven, H. Gerber, B. S. Stein, J. L. Jameson, and P. Kopp Cloning of the Cat TSH Receptor and Evidence Against an Autoimmune Etiology of Feline Hyperthyroidism Endocrinology, February 1, 2002; 143(2): 395 - 402. [Abstract] [Full Text] [PDF]

				H. Shinozaki, F. Fanelli, X. Liu, J. Jaquette, K. Nakamura, and D. L. Segaloff Pleiotropic Effects of Substitutions of a Highly Conserved Leucine in Transmembrane Helix III of the Human Lutropin/Choriogonadotropin Receptor with Respect to Constitutive Activation and Hormone Responsiveness Mol. Endocrinol., June 1, 2001; 15(6): 972 - 984. [Abstract] [Full Text] [PDF]

				S. Harder, X. Lu, W. Wang, F. Buck, M. C. Gershengorn, and T. O. Bruhn Regulator of G Protein Signaling 4 Suppresses Basal and Thyrotropin Releasing-Hormone (TRH)-Stimulated Signaling by Two Mouse TRH Receptors, TRH-R1 and TRH-R2 Endocrinology, March 1, 2001; 142(3): 1188 - 1194. [Abstract] [Full Text] [PDF]

				A.-O. Colson, J. H. Perlman, A. Jinsi-Parimoo, D. R. Nussenzveig, R. Osman, and M. C. Gershengorn A Hydrophobic Cluster between Transmembrane Helices 5 and 6 Constrains the Thyrotropin-Releasing Hormone Receptor in an Inactive Conformation Mol. Pharmacol., December 1, 1998; 54(6): 968 - 978. [Abstract] [Full Text]

				E. Geras-Raaka, L. Arvanitakis, C. Bais, E. Cesarman, E. A. Mesri, and M. C. Gershengorn Inhibition of Constitutive Signaling of Kaposi's Sarcoma-associated Herpesvirus G Protein-Coupled Receptor by Protein Kinases in Mammalian Cells in Culture J. Exp. Med., March 2, 1998; 187(5): 801 - 806. [Abstract] [Full Text] [PDF]

				A. M. Thomson, J. T. Rogers, and P. J. Leedman Thyrotropin-releasing Hormone and Epidermal Growth Factor Regulate Iron-regulatory Protein Binding in Pituitary Cells via Protein Kinase C-dependent and -independent Signaling Pathways J. Biol. Chem., October 6, 2000; 275(41): 31609 - 31615. [Abstract] [Full Text] [PDF]

				K. M. Kroeger, A. C. Hanyaloglu, R. M. Seeber, L. E. C. Miles, and K. A. Eidne Constitutive and Agonist-dependent Homo-oligomerization of the Thyrotropin-releasing Hormone Receptor. DETECTION IN LIVING CELLS USING BIOLUMINESCENCE RESONANCE ENERGY TRANSFER J. Biol. Chem., April 13, 2001; 276(16): 12736 - 12743. [Abstract] [Full Text] [PDF]