Tyr1 and Ile7 of glucose-dependent insulinotropic polypeptide (GIP) confer differential ligand selectivity toward GIP and glucagon-like peptide-1 receptors.
Glucagon like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones released in response to food intake and potentiate insulin secretion from pancreatic beta cells through their distinct yet related G protein-coupled receptors, GLP1R and GIPR. While GLP-1 and GIP exhibit similarity in their N-terminal sequence and overall alpha-helical structure, GLP-1 does not bind to GIPR and vice versa. To determine which amino acid residues of these peptide ligands are responsible for specific interaction with their respective receptors, we generated mutant GIP in which several GLP-1-specific amino acid residues were substituted for the original amino acids. The potency of the mutant ligands was examined using HEK293 cells transfected with GLP1R or GIPR expression plasmids together with a cAMP-responsive element-driven luciferase (CRE-luc) reporter plasmid. A mutated GIP peptide in which Tyr(1), Ile(7), Asp(15), and His(18) were replaced by His, Thr, Glu, and Ala, respectively, was able to activate both GLP1R and GIPR with moderate potency. Replacing the original Tyr(1) and/or Ile(7) in the N-terminal moiety of this mutant peptide allowed full activation of GIPR but not of GLP1R. However, reintroducing Asp(15) and/or His(18) in the central alpha-helical region did not significantly alter the ligand potency. These results suggest that Tyr/His(1) and Ile/Thr(7) of GIP/GLP-1 peptides confer differential ligand selectivity toward GIPR and GLP1R.
Moon
Mi Jin
MJ
Graduate School of Medicine, Korea University, Seoul 136-705, Korea.
Kim
Hee Young
HY
Kim
Sin Gon
SG
Park
Juri
J
Choi
Dong Seop
DS
Hwang
Jong-Ik
JI
Seong
Jae Young
JY
D000595:Amino Acid Sequence; D000818:Animals; D000077270:Exenatide; D005749:Gastric Inhibitory Polypeptide / Q000737:chemistry* / Q000378:metabolism*; D000067757:Glucagon-Like Peptide-1 Receptor; D006801:Humans; D007532:Isoleucine / Q000378:metabolism*; D008024:Ligands; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D051381:Rats; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism*; D018027:Receptors, Glucagon / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000378:metabolism*; D014688:Venoms / Q000737:chemistry
C000593833:GLP1R protein, human; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D008024:Ligands; D010455:Peptides; D011964:Receptors, Gastrointestinal Hormone; D018027:Receptors, Glucagon; D011994:Recombinant Proteins; D014688:Venoms; D007532:Isoleucine; D014443:Tyrosine; D005749:Gastric Inhibitory Polypeptide; D000077270:Exenatide; C041086:gastric inhibitory polypeptide receptor