The C-Terminus of the Prostaglandin-E-Receptor EP₃ Subtype is Essential for Activation of GTP-Binding Protein

Authors: Irie, Atsushi¹; Sugimoto, Yukihiko¹; Namba, Tsunehisa²; Asano, Tomiko³; Ichikawa, Atsushi¹; Negishi, Manabu¹

Source: FEBS Journal, Volume 224, Number 1, August (II) 1994 , pp. 161-166(6)

Publisher: Wiley-Blackwell

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Abstract:

Three isoforms of the mouse prostaglandin-E-receptor EP₃ subtype (EP₃), EP_3α, EP_3β, and EP_3γ, with different C-termini, which are produced through alternative splicing, showed different efficiencies with respect to heterotrimeric GTP-binding protein activation and adenylate cyclase inhibition [Sugimoto, Y., Negishi, M., Hayashi, Y., Namba, T., Honda, A., Watabe, A., Hirata, M., Narumiya, S. & Ichikawa, A. (1993) J. Biol. Chem. 268, 2712-2718; Irie, A., Sugimoto, Y., Namba, T., Harazono, A., Honda, A., Watabe, A., Negishi, M., Narumiya, S. & Ichikawa, A. (1993) Eur. J. Biochem. 217, 313-318]. To assess the role of the C-terminus in GTP-binding protein coupling, we truncated the C-terminus of EP₃ at an alternative splicing site and expressed the mutant receptor. The truncated receptor retained the ability to physically associate with G_i2, forming an agonist/receptor/G_i2 ternary complex, and to undergo the characteristic conversion of its agonist-binding affinity, mediated by a guanine nucleotide from a low-affinity state to a high-affinity state. However, sulprostone, an EP₃ agonist, failed not only to inhibit the forskolin-induced CAMP accumulation in the mutant receptor-expressing cells but also to stimulate the GTPase activity in the mutant receptor-expressing cell membrane. These results indicated that the C-terminus of EP₃ is essential for the activation of GTP-binding protein.

Document Type: Research article

Affiliations: 1: Department of Physiological Chemistry, Kyoto University, Japan 2: Department of Pharmacology, Kyoto University, Japan 3: Department of Biochemistry, Institute for Developmental Research, Aichi Prefectural Colony, Japan

Publication date: 1994-08-01