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 Chazenbalk, G. D. Articles by Rapoport, B. Search for Related Content PubMed PubMed Citation Articles by Chazenbalk, G. D. Articles by Rapoport, B.

On the Functional Importance of Thyrotropin Receptor Intramolecular Cleavage¹

Autoimmune Disease Unit, Cedars-Sinai Research Institute, and University of California School of Medicine, Los Angeles, California 90048

Address all correspondence and requests for reprints to: Basil Rapoport, M.B., Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Suite B-131, Los Angeles, California 90048.

We examined the relationship between TSH receptor (TSHR) cleavage into two subunits and ligand-independent, constitutive activity characteristic of this receptor. Because of homology to the thrombin receptor-tethered ligand, we focused initially on a region in the vicinity of the second, downstream cleavage site of the TSHR ectodomain. We introduced into the wild-type TSHR three mutations. One mutation, TSHR(GQE_367–369NET) prevents cleavage at site 2. The other two mutations, ELK_369–371T-Y (TSHR-E1a2) and NPQE_372–375SAIF (TSHR-E1b), introduce major changes into the potential tethered ligand. Basal, steady state intracellular cAMP levels in cloned, stably transfected Chinese hamster ovary cells were expressed as a function of the number of receptors (cAMP/receptor). None of these three mutations decreased ligand-independent constitutive activity, thereby excluding the tethered ligand hypothesis as well as a requirement for cleavage at site 2 in this process. Turning to the more upstream site 1 in the TSHR ectodomain, we examined a receptor (TSHR-50AA) with deletion of a unique 50-amino acid insertion (residues 317–366) that appears to be involved in cleavage at this site. Constitutive cAMP production was similar to that of the wild-type TSHR. Finally, we studied a TSHR mutant that cleaves at neither site 1 (deletion of residues 317–366) nor site 2 (GQE_367–369NET substitution) and, therefore, does not cleave into A and B subunits. Again, the basal, constitutive level of cAMP production was similar to that of the wild-type TSHR.

In summary, contrary to the prevailing hypothesis based on several lines of evidence, TSHR cleavage into subunits is not associated with constitutive, ligand-independent activity.

This article has been cited by other articles:

				M. Freamat and S. A Sower A sea lamprey glycoprotein hormone receptor similar with gnathostome thyrotropin hormone receptor J. Mol. Endocrinol., October 1, 2008; 41(4): 219 - 228. [Abstract] [Full Text] [PDF]

				Y. Mizutori, C.-R. Chen, S. M. McLachlan, and B. Rapoport The Thyrotropin Receptor Hinge Region Is Not Simply a Scaffold for the Leucine-Rich Domain but Contributes to Ligand Binding and Signal Transduction Mol. Endocrinol., May 1, 2008; 22(5): 1171 - 1182. [Abstract] [Full Text] [PDF]

				T. Ando, R. Latif, and T. F Davies Antibody-induced modulation of TSH receptor post-translational processing J. Endocrinol., October 1, 2007; 195(1): 179 - 186. [Abstract] [Full Text] [PDF]

				C.-R. Chen, G. D. Chazenbalk, K. A. Wawrowsky, S. M. McLachlan, and B. Rapoport Evidence that Human Thyroid Cells Express Uncleaved, Single-Chain Thyrotropin Receptors on Their Surface Endocrinology, June 1, 2006; 147(6): 3107 - 3113. [Abstract] [Full Text] [PDF]

				R. Latif, T. Ando, and T. F. Davies Monomerization as a Prerequisite for Intramolecular Cleavage and Shedding of the Thyrotropin Receptor Endocrinology, December 1, 2004; 145(12): 5580 - 5588. [Abstract] [Full Text] [PDF]

				W. R. Moyle, Y. Xing, W. Lin, D. Cao, R. V. Myers, J. E. Kerrigan, and M. P. Bernard Model of Glycoprotein Hormone Receptor Ligand Binding and Signaling J. Biol. Chem., October 22, 2004; 279(43): 44442 - 44459. [Abstract] [Full Text] [PDF]

				G. D. Chazenbalk, C.-R. Chen, S. M. McLachlan, and B. Rapoport Does Thyrotropin Cleave Its Cognate Receptor? Endocrinology, January 1, 2004; 145(1): 4 - 10. [Abstract] [Full Text] [PDF]

				I. Ciullo, R. Latif, P. Graves, and T. F. Davies Functional Assessment of the Thyrotropin Receptor-{beta} Subunit Endocrinology, July 1, 2003; 144(7): 3176 - 3181. [Abstract] [Full Text] [PDF]

				C.-R. Chen, G. D. Chazenbalk, S. M. McLachlan, and B. Rapoport Targeted Restoration of Cleavage in a Noncleaving Thyrotropin Receptor Demonstrates that Cleavage Is Insufficient to Enhance Ligand-Independent Activity Endocrinology, April 1, 2003; 144(4): 1324 - 1330. [Abstract] [Full Text] [PDF]

				N. Ghinea, C. Baratti-Elbaz, A. De Jesus-Lucas, and E. Milgrom TSH Receptor Interaction with the Extracellular Matrix: Role on Constitutive Activity and Sensitivity to Hormonal Stimulation Mol. Endocrinol., May 1, 2002; 16(5): 912 - 923. [Abstract] [Full Text] [PDF]

				H. Nikkila, D. R. McMillan, B. S. Nunez, L. Pascoe, K. M. Curnow, and P. C. White Sequence Similarities between a Novel Putative G Protein-Coupled Receptor and Na+/Ca2+ Exchangers Define a Cation Binding Domain Mol. Endocrinol., September 1, 2000; 14(9): 1351 - 1364. [Abstract] [Full Text]