Structural motifs of pituitary adenylate cyclase-activating polypeptide (PACAP) defining PAC1-receptor selectivity

• Published in: Regulatory peptides 1999-02, Vol.79 (2-3), p.83-92
• Main Authors: SCHÄFER, H, JIE ZHENG, MORYS-WORTMANN, C, FÖLSCH, U. R, SCHMIDT, W. E
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Amino Acid Sequence; Binding Sites; Biological and medical sciences; Cell Line; Cell receptors; Cell structures and functions; Cyclic AMP - biosynthesis; Fundamental and applied biological sciences. Psychology; Molecular and cellular biology; Molecular Sequence Data; Neuropeptide receptors; Neuropeptides - chemistry; Neuropeptides - metabolism; Pancreas - cytology; Peptide Fragments - metabolism; Pituitary Adenylate Cyclase-Activating Polypeptide; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; Receptors, Pituitary Hormone - genetics; Receptors, Pituitary Hormone - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Vasoactive Intestinal Peptide - analogs & derivatives; Vasoactive Intestinal Peptide - metabolism
• ISSN: 0167-0115; 1873-1686
• DOI: 10.1016/S0167-0115(98)00147-5

Pituitary adenylate cyclase-activating polypeptide (PACAP) interacts with three types of PACAP/VIP-receptors. The PAC1-receptor accepts PACAP as a high affinity ligand but not vasoactive intestinal peptide (VIP) similarly binding to VPAC1- and VPAC2-receptors. To identify those amino acids not present in VIP defining PAC1-receptor selectivity of PACAP, radio receptor binding assays on AR4-2J cells were performed. It could be shown that PACAP(1-27) exhibited a distinct and much higher susceptibility to VIP-amino acid substitutions, compared to PACAP(1-38). Positions 4 and 5 seem to be most important for receptor binding of PACAP(1-27), whereas position 13 was identified to be crucial for maximal affinity of PACAP(1-38). PACAP(29-38) extension analogues of VIP revealed a stabilizing effect of the C-terminus of PACAP(1-38) on the optimal peptide conformation. The substitution analogues were also checked for their capacity to stimulate IP3 and cAMP formation in AR4-2J cells. Compared to PACAP(1-27) and PACAP(1-38), most analogues revealed potencies reduced congruously to their lower binding affinities. However, one of the analogues, PACAP(1-27) substituted in position 5, may represent a weak antagonist since this peptide was less potent in inducing second messengers than in label displacement. Our findings indicate that PACAP(1-27) and PACAP(1-38) differ in terms of their requirement of the amino acids in positions 4, 5, 9, 11 and 13 for maximal interaction with the PAC1-receptor.