An aromatic amino acid within intracellular loop 2 of the prostaglandin EP2 receptor is a prerequisite for selective association and activation of Gαs.
We previously demonstrated that the aromatic moiety of Tyr143within the intracellular loop 2 (ICL2) region of the prostaglandin EP2 receptor plays a crucial role in Gs coupling. Here we investigated whether the ICL2 of the EP2 receptor directly binds to Gαs and whether an aromatic moiety affects this interaction. In Chinese hamster ovary cells, mutations of Tyr143reduced the ability of the EP2 receptor to interact with G proteins as demonstrated by GTPγS sensitivity, as well as the ability of agonist-induced cAMP formation, with the rank order of Phe>Tyr (wild-type)=Trp>Leu>Ala (=0). We found that the wild-type ICL2 peptide (i2Y) and its mutant with Phe at Tyr143(i2F) inhibited receptor-G protein complex formation of wild-type EP2 in membranes, whereas the Ala-substituted mutant (i2A) did not. Specific interactions between these peptides and the Gαs protein were detected by surface plasmon resonance, but Gαs showed different association rates, with a rank order of i2F>i2Y≫i2A, with similar dissociation rates. Moreover, i2F and i2Y, but not i2A activated membrane adenylyl cyclase. These results indicate that the ICL2 region of the EP2 receptor is its potential interaction site with Gαs, and that the aromatic side chain moiety at position 143 is a determinant for the accessibility of the ICL2 to the Gαs protein.
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
Akiko
A
Yano
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
Yuko
Y
Takahashi
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
Hiromi
H
Moriguchi
Department of Pharmaceutical Biochemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan; AMED-CREST, Tokyo 100-0004, Japan.
Tomoaki
T
Inazumi
Priority Organization for Innovation and Excellence, Kumamoto University, Kumamoto, Japan.
Tomoaki
T
Koga
Department of Bioorganic Synthetic Chemistry, Graduate School of Pharmaceutical Sciences, Tokushima University, Tokushima, Japan.
Akira
A
Otaka
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan; Department of Pharmaceutical Biochemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan; AMED-CREST, Tokyo 100-0004, Japan. Electronic address: ysugi@kumamoto-u.ac.jp.
Yukihiko
Y
Sugimoto
D019943:Amino Acid Substitution; D000818:Animals; D002864:Chromogranins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020125:Mutation, Missense; D000072417:Protein Domains; D017433:Protein Structure, Secondary; D058307:Receptors, Prostaglandin E, EP2 Subtype / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D002864:Chromogranins; C545644:PTGER2 protein, human; D058307:Receptors, Prostaglandin E, EP2 Subtype; C406732:GNAS protein, human; D019205:GTP-Binding Protein alpha Subunits, Gs
Eicosanoid; G protein-coupled receptor; Heterotrimeric G protein; Prostaglandin; Prostanoid receptor; Receptor structure-function