The Amino-Terminal Half of the Cytoplasmic Tail of the Thyrotropin Receptor Is Essential for Full Activities of Receptor Function

Abstract

We investigated the role of the cytoplasmic tail of the thyrotropin receptor (TSHR) in signal transduction using mutants with truncation at the cytoplasmic tail. Mutant without residues 700-764 completely lost inositol phosphate response to agonists and showed decreased basal cAMP level. Mutant without residues 710-764 showed full cAMP responses but blunted inositol phosphate responses. However, mutant without residues 722-764 retained all signal transduction activities. These findings suggest that the amino-terminal half of the cytoplasmic tail (up to residue 721) is essential for full expression of functional activities.