The interaction of benzodiazepines with thyrotropin‐releasing hormone receptors on clonal pituitary cells

Joels, Lesley A.; Drummond, Alan H.

doi:10.1111/j.1476-5381.1989.tb11837.x

Cited by 7 publications

(1 citation statement)

References 19 publications

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“…TRH-R1 evokes large responses in oocytes when TRH binds. Because TRH-R1 exhibits low basal signaling activity, it is not desensitized in oocytes and activation of TRH-R1 is inhibited by pretreatment with the inverse agonist CDE, acting as an antagonist (Joels and Drummond, 1989). It is difficult to measure constitutive signaling by 7TMRs in oocytes directly because constitutively active receptors are desensitized.…”

Section: Resultsmentioning

confidence: 99%

Carboxyl Tail Cysteine Mutants of the Thyrotropin-Releasing Hormone Receptor Type 1 Exhibit Constitutive Signaling: Role of Palmitoylation

Du¹,

Raaka²,

Grimberg³

et al. 2005

Mol Pharmacol

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We studied the role of carboxyl tail cysteine residues and their palmitoylation in constitutive signaling by the thyrotropin-releasing hormone (TRH) receptor type 1 (TRH-R1) in transfected mammalian cells and in Xenopus laevis oocytes. To study palmitoylation, we inserted a factor Xa cleavage site within the third extracellular loop of TRH-R1, added a carboxyl-terminal C9 immunotag and expressed the mutant receptor in Chinese hamster ovary cells. We identified TRH-R1-specific palmitoylation in the transmembrane helix-7/carboxyl-tail receptor fragment mainly at Cys-335 and Cys-337. In contrast to a mutant truncated at Cys-335 that was reported previously to be constitutively active, a receptor truncated at Lys-338 (K338Stop), which preserves Cys-335 and Cys-337, and C337Stop and N336Stop, which preserve Cys-335, did not exhibit increased constitutive signaling. TRH-R1 mutants substituted singly by Gly or Ser at Cys-335 or Cys-337 did not exhibit constitutive signaling. By contrast, substitution of both cysteines (C335G/ C337G or C335S/C337S) yielded TRH-R1 mutants that exhibited marked constitutive signaling in mammalian cells. In the oocyte, constitutive signaling by C335G/C337G resulted in homologous (of C335G/C337G) and heterologous (of M1 muscarinic receptor) desensitization. Because both Cys-335 and Cys-337 have to be substituted or deleted for constitutive signaling, we propose that a single palmitoylation site in the proximal carboxyl tail is sufficient to constrain TRH-R1 in an inactive conformation.

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Section: Resultsmentioning

confidence: 99%