Institute of Biochemistry, Universität Leipzig, Brüderstraße 34, 04103 Leipzig, Germany.
J Med Chem. 2012 Sep 13;55(17):7437-49. doi: 10.1021/jm300414b. Epub 2012 Sep 5.
The ghrelin receptor displays a high constitutive activity suggested to be involved in the regulation of appetite and food intake. Here, we have created peptides with small changes in the core binding motif -wFw- of the hexapeptide KwFwLL-NH(2) that can swap the peptide behavior from inverse agonism to agonism, indicating the importance of this sequence. Introduction of β-(3-benzothienyl)-d-alanine (d-Bth), 3,3-diphenyl-d-alanine (d-Dip) and 1-naphthyl-d-alanine (d-1-Nal) at position 2 resulted in highly potent and efficient inverse agonists, whereas the substitution of d-tryptophane at position 4 with 1-naphthyl-d-alanine (d-1-Nal) and 2-naphthyl-d-alanine (d-2-Nal) induces agonism in functional assays. Competitive binding studies showed a high affinity of the inverse agonist K-(d-1-Nal)-FwLL-NH(2) at the ghrelin receptor. Moreover, mutagenesis studies of the receptor revealed key positions for the switch between inverse agonist and agonist response. Hence, only minor changes in the peptide sequence can decide between agonism and inverse agonism and have a major impact on the biological activity.
胃饥饿素受体显示出较高的固有活性，被认为参与了食欲和食物摄入的调节。在这里，我们在六肽 KwFwLL-NH（2）的核心结合基序 -wFw- 中进行了微小的改变，创造了一些肽，这些肽可以将肽的行为从反向激动剂转变为激动剂，表明该序列的重要性。在 2 位引入 β-(3-苯并噻吩基)-d-丙氨酸（d-Bth）、3,3-二苯基-d-丙氨酸（d-Dip）和 1-萘基-d-丙氨酸（d-1-Nal），导致高效能的反向激动剂，而在 4 位用 1-萘基-d-丙氨酸（d-1-Nal）和 2-萘基-d-丙氨酸（d-2-Nal）替代 d-色氨酸，则在功能测定中诱导激动作用。竞争性结合研究表明，反向激动剂 K-(d-1-Nal)-FwLL-NH（2）在胃饥饿素受体上具有高亲和力。此外，受体的突变研究揭示了反向激动剂和激动剂反应之间转换的关键位置。因此，肽序列的微小变化可以决定激动剂和反向激动剂之间的选择，并对生物活性产生重大影响。
