Structural Requirements for the Occupancy of Pituitary Adenylate-Cyclase-Activating-Peptide (PACAP) Receptors and Adenylate Cyclase Activation in Human Neuroblastoma NB-OK-1 Cell Membranes. Discovery of PACAP(6-38) as a Potent Antagonist

Eur J Biochem. 1992 Jul 1;207(1):239-46. doi: 10.1111/j.1432-1033.1992.tb17043.x.

Abstract

In these structure activity studies, the 46 analogs of the 27-amino-acid form of the pituitary-adenylate-cyclase-activating peptide, PACAP(1-27), and the 38-amino-acid form, PACAP(1-38), were either monosubstituted or bisubstituted at positions 1-3, 20 and 21 or N-terminally shortened. All analogs were compared on human neuroblastoma NB-OK-1 cell membranes for their ability to occupy 125I-[AcHis1]PACAP(1-27)-labelled receptors (AcHis, N alpha-acetylhistidine) and to activate adenylate cyclase (in terms of potency and intrinsic activity). The monophasic slope of dose/effect curves on both parameters suggested interaction with one class of PACAP receptor. Residues 28-38 in the C-terminally extended peptide, PACAP(1-38), played a favorable role in recognition, in that receptors coupled to adenylate cyclase were, in general, more sensitive to PACAP(1-38) analogs than to the corresponding PACAP(1-27) analogs. At variance with PACAP(6-27), PACAP(6-38) was well recognized and acted as a potent competitive antagonist (Ki 1.5 nM). Residues 1-3 were all important in enzyme activation: modification of the beta-turn potential gave full agonists (the LAla2 and DAla2 derivatives) or partial agonists (LPhe2 and DPhe2; LArg2 and DArg2; Glu3 and Asn3). Finally, a proper alpha-helix was also important: the combined substitution of Lys21/Lys22 by Gly21/Gly22 decreased the binding affinity sharply.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenylyl Cyclases / metabolism*
  • Amino Acid Sequence
  • Binding, Competitive
  • Cell Membrane / metabolism*
  • Enzyme Activation
  • Humans
  • Kinetics
  • Molecular Sequence Data
  • Neuroblastoma
  • Neuropeptides / pharmacology*
  • Peptide Fragments / pharmacology*
  • Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Cell Surface / antagonists & inhibitors
  • Receptors, Cell Surface / drug effects
  • Receptors, Cell Surface / metabolism*
  • Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Pituitary Hormone*
  • Sequence Homology, Nucleic Acid
  • Signal Transduction / drug effects
  • Structure-Activity Relationship
  • Tumor Cells, Cultured

Substances

  • Neuropeptides
  • Peptide Fragments
  • Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Cell Surface
  • Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
  • Receptors, Pituitary Hormone
  • pituitary adenylate-cyclase-activating-peptide (6-38)
  • Adenylyl Cyclases

Associated data

  • GENBANK/UNKNOWN