Structural motifs of pituitary adenylate cyclase-activating polypeptide (PACAP) defining PAC1-receptor selectivity.
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.
Schäfer
H
H
Laboratory of Molecular Gastroenterology and Hepatology, 1st Department of Internal Medicine, Christian-Albrechts-University of Kiel, Germany.
Zheng
J
J
Morys-Wortmann
C
C
Fölsch
U R
UR
Schmidt
W E
WE
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D000242:Cyclic AMP / Q000096:biosynthesis; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism*; D010179:Pancreas / Q000166:cytology; D010446:Peptide Fragments / Q000378:metabolism; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014660:Vasoactive Intestinal Peptide / Q000031:analogs & derivatives / Q000378:metabolism
D009479:Neuropeptides; D010446:Peptide Fragments; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone; C108046:pituitary adenylate cyclase-activating-peptide (1-38), pig; D014660:Vasoactive Intestinal Peptide; D000242:Cyclic AMP