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Endocrinology. 2009 Jan;150(1):519-29. doi: 10.1210/en.2008-0878. Epub 2008 Aug 21.

Characterization of thyrotropin receptor antibody-induced signaling cascades.

Author information

1
Thyroid Research Unit, Mount Sinai School of Medicine, James J. Peters Veterans Affairs Medical Center, New York, New York 10468, USA. syed.morshed@mssm.edu

Abstract

The TSH receptor (TSHR) is constitutively active and is further enhanced by TSH ligand binding or by stimulating TSHR antibodies (TSHR-Abs) as seen in Graves' disease. TSH is known to activate the thyroid epithelial cell via both Galphas-cAMP/protein kinase A/ERK and Galphaq-Akt/protein kinase C coupled signaling networks. The recent development of monoclonal antibodies to the TSHR has enabled us to investigate the hypothesis that different TSHR-Abs may have unique signaling imprints that differ from TSH ligand itself. We have, therefore, performed sequential studies, using rat thyrocytes (FRTL-5, passages 5-20) as targets, to examine the signaling pathways activated by a series of monoclonal TSHR-Abs in comparison with TSH itself. Activation of key signaling molecules was estimated by specific immunoblots and/or enzyme immunoassays. Continuing constitutive TSHR activity in thyroid cells, deprived of TSH and serum for 48 h, was demonstrated by pathway-specific chemical inhibition. Under our experimental conditions, TSH ligand and TSHR-stimulating antibodies activated both Galphas and Galphaq effectors. Importantly, some TSHR-blocking and TSHR-neutral antibodies were also able to generate signals, influencing primarily the Galphaq effectors and induced cell proliferation. Most strikingly, antibodies that used the Galphaq cascades used c-Raf-ERK-p90RSK as a unique signaling cascade not activated by TSH. Our study demonstrated that individual TSHR-Abs had unique molecular signatures which resulted in sequential preferences. Because downstream thyroid cell signaling by the TSHR is both ligand dependent and independent, this may explain why TSHR-Abs are able to have variable influences on thyroid cell biology.

PMID:
18719020
PMCID:
PMC2630889
DOI:
10.1210/en.2008-0878
[Indexed for MEDLINE]
Free PMC Article

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