Receptor occupancy and adenylate cyclase activation in AR 4-2J rat pancreatic acinar cell membranes by analogs of pituitary adenylate cyclase-activating peptides amino-terminally shortened or modified at position 1, 2, 3, 20, or 21.
In AR 4-2J rat pancreatic acinar cell membranes, receptors for the two pituitary adenylate cyclase-activating peptides (PACAP) PACAP-27 (the short version of PACAP) and PACAP-38 [the long version, with a carboxyl-terminal (residues 28-38) extension] can be subdivided into (a) type A receptors, with high affinity (Kd, 0.3-0.5 nM) for both PACAP-27 and PACAP-38, and (b) type B receptors, with high affinity for PACAP-38 (Kd, 0.3 nM) but low affinity for PACAP-27 (Kd, 20 nM). Determinants of agonist/antagonist activity in 47 PACAP-27 and PACAP-38 analogs (mono- or disubstituted in positions 1, 2, 3, 20, and 21) or amino-terminally shortened were tested by (a) the occupancy of PACAP-A receptors, preferentially labeled with [125I-N-acetyl-His1]PACAP-27, and that of PACAP-A and -B receptors, both labeled with 125I-PACAP-38, and (b) the resulting activation or inhibition of adenylate cyclase. For PACAP-A receptor recognition, deprotonated His1 was a major determinant for PACAP-27 but not PACAP-38; the Kd of 125I-PACAP-27 decreased 2.4-fold at 37 degrees between pH 6.0 and 7.5 and 3.6-fold at 15 degrees, whereas the IC50 of [N-acetyl-His1]PACAP-27 was less affected and that of PACAP(2-27), PACAP(2-38), and PACAP(1-38) was pH independent. In addition, PACAP-A receptors coupled to adenylate cyclase were much more sensitive to PACAP-38 derivatives than to PACAP-27 derivatives; for instance, [D-Phe2]PACAP-38 was a more potent antagonist (Ki, 5 nM) than [D-Phe2]PACAP-27 (Ki, 350 nM), and PACAP(6-38) was a more potent antagonist (Ki, 7 nM) than PACAP(6-27) (Ki, 300 nM). PACAP-B receptors, apart from showing high affinity for PACAP-38, displayed relatively high affinity for amino-terminally shortened PACAP-38 fragments and poor affinity for PACAP-27 and PACAP-27 fragments.
Robberecht
P
P
Department of Biochemistry and Nutrition, Medical School, Université Libre de Bruxelles, Belgium.
Gourlet
P
P
De Neef
P
P
Woussen-Colle
M C
MC
Vandermeers-Piret
M C
MC
Vandermeers
A
A
Christophe
J
J
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000187:drug effects / Q000378:metabolism*; D000409:Alanine / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes; D007700:Kinetics; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology*; D010179:Pancreas / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D010446:Peptide Fragments / Q000494:pharmacology*; D010649:Phenylalanine / Q000378:metabolism; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011487:Protein Conformation; D051381:Rats; D011956:Receptors, Cell Surface / Q000145:classification / Q000378:metabolism*; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone; D012689:Sequence Homology, Nucleic Acid; D012694:Serine / Q000378:metabolism
C495403:Adcyap1 protein, rat; D000067956:Adenylyl Cyclase Inhibitors; D007457:Iodine Radioisotopes; D009479:Neuropeptides; D010446:Peptide Fragments; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011956:Receptors, Cell Surface; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone; D012694:Serine; D010649:Phenylalanine; D001120:Arginine; D000262:Adenylyl Cyclases; D000409:Alanine