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P De Neef

Publications and source records attributed to P De Neef.

13 recordsLinked to original sources
PubMed1992

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.

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.

Adenylyl Cyclases↗
PubMed1992

Stimulation of rat pancreatic tumoral AR4-2J cell proliferation by pituitary adenylate cyclase-activating peptide.

In the present work the effects of the novel neuropeptide Pituitary Adenylate Cyclase Activating Peptide (PACAP) on both AR4-2J cell growth and the modulation of ornithine decarboxylase activity were investigated. Both PACAP38 and the amidated form PACAP27 caused a concentration-dependent stimulation of AR4-2J cell growth; the maximal increase was seen at 1 nmol/L (30% above control, P less than 0.01) with a half-maximal effect at 0.01 nmol/L. Ornithine decarboxylase activity was also increased by PACAP in a dose-dependent manner, reaching half-maximal stimulation at 0.5 nmol/L. The addition of 1 nmol/L of somatostatin analog SMS 201-995 totally suppressed PACAP-stimulated AR4-2J cell growth. Vasoactive intestinal polypeptide (3 mumol/L) and 8-bromo-cyclic adenosine monophosphate (1 mmol/L) had no effect on cell proliferation. Treatment of cells by pertussis toxin (25 ng.mL-1.day-1) suppressed PACAP-stimulated AR4-2J cell growth but enhanced PACAP-induced stimulation of adenylate cyclase activity. It was concluded that PACAP stimulates AR4-2J cell proliferation by a mechanism that seems independent of cyclic adenosine monophosphate production. The mitogenic effect of PACAP depends on a pertussis toxin-sensitive G protein and is associated with an increase of ornithine decarboxylase activity.

Adenylate Cyclase Toxin↗
PubMed1992

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.

Adenylyl Cyclase Inhibitors↗
PubMed1978

The interaction of caerulein with the rat pancreas. 2. Specific binding of [3H]caerulein on dispersed acinar cells.

1. [3H]Caerulein was bound to dispersed acinar cells from rat pancreas in a rapid, reversible, specific, saturable, and temperature-dependent manner. Binding decreased above pH 6.5. Treatment of intact cells with 2, 4-dinitrophenol and oligomycin, p-choloromercuribenzoate, diisopropylfluoro-phosphate and glutaraldehyde impaired [3H]caerulein binding whereas the addition of EGTA inhibited binding. The C-terminal octapeptide of pancreozymin, desulfated caerulein and pentagastrin inhibited binding of [3H]caerulein whereas vasoactive intestinal polypeptide, secretin, bombesin or carbamoylcholine were wothout effect. The good resistance of [3H]caerulein to inactivation by acinar cells at 37 degrees C was reflected in the high proportion of tracer remaining capable of binding to fresh acinar cells. 2. Scatchard plots of [3H]caerulein binding were curvilinear with an upward concavity. The addition of an excess of unlabeled caerulein resulted in the release of as much as 65% of bound [3H]caerulein within 1 min at 37 degrees C. The dissociation of remainder followed much slower kinetics. 3. The results suggested that intact rat pancreatic acinar cells have one class of caerulein binding sites existing in two states: one with high affinity and another with low affinity, the proportion of sites in each state depending on the degree of site occupancy (negative cooperativity), and on the intracellular concentration of nucleotides.

Animals↗
PubMed1976

In vitro action of bombesin and bombesin-like peptides on amylase secretion, calcium efflux, and adenylate cyclase activity in the rat pancreas: a comparison with other secretagogues.

Bombesin (a tetradecapeptide), the C-terminal nonapeptide of bombesin (bombesin-NP), and litorin (a parent nonapeptide), each stimulated amylase secretion from rat pancreatic fragments. These responses were not affected by atropine. The concentrations that produced half-maximal stumulation of secretion were 0.25 nM for bombesin, 0.30 nM for bombesin-NP, and 0.07 nM for litorin, as compared to 0.12 nM for caerulein and 0.80 muM for the cholinergic agent carbamylcholine. When used at maximal concentrations, bombesin, bombesin-NP, and litorin showed no action on cyclic AMP levels in the presence of 5 mM theophylline. By contrast, caerulein and secretin increased cyclic AMP levels by 27 and 208%, respectively. Bombesin, bombesin-NP, and litorin did not activate adenylate cyclase in a purified pancreatic plasma membrane preparation, whereas caerulein and secretin increased this activity 20 and 16-times, respectively...

Adenylyl Cyclases↗
PubMed1975

Pancreatic secretion of total protein and of three hydrolases collected in healthy subjects via duodenoscopic cannulation. Effects of secretin, pancreozymin, and caerulein.

Pancreatic secretion of total protein and of three types of hydrolases (amylase, lipase, and thymotrypsinogen(s) was determined in human subjects free of gastrointestinal disease. Pure pancreatic juice was collected by canulation of Wirsung's duct under duodenoscopy. Rapid intravenous injection of pancreozymin (1 Crick-Harper-Raper U per kg) stimulated secretion of total protein and hydrolases within 1 min. This stimulation was of short duration and had a half-life of 70 to 100 sec. Rapid intravenous injection of caerulein (20) ng per kg) induced a similar response. Parallel variations in total protein, amylase, lipase, and chymotrypsinogen(s) were observed in the three experiments where complete enzyme analyses were performed.

Adult↗
PubMed1975

In vitro interactions of gastrointestinal hormones on cyclic adenosine 3':5'-monophosphate levels and amylase output in the rat pancreas.

Four-fold increases in cyclic AMP levels were observed 5 to 10 min after rat pancreatic fragments were incubated with 10-7 M secretin or 10-6 M vasoactive intestinal polypeptide (VIP), in addition to 10 mM theophylline. From dose-response curves it appears that, on a molar basis, the potency of secretin was 20 times higher than that of VIP. It is concluded that cyclic AMP is probably the intracellular messenger of both secretin and VIP in centroacinar cells. Pancreozymin, caerulein, and the C-terminal octapeptide of pancreozymin inhibited the production of cyclic AMP observed with secretin of VIP, suggesting that the first three peptides were acting at a binding site different from the agonists, but coupled with the same adenylate cyclase. In acinar cells, secretin was able to exert slight ecbolic effects, and was also able to potentiate the effect of maximal concentrations of pancreozymin, caerulein, or the C-terminal octapeptide of pancreozymin. There was no simple correlation between amylase output and cyclic AMP levels, and copious amylase secretion was elicited even at control levels of cyclic AMP. Glucagon was neither an agonist nor an antagonist of any of the other polypeptides tested.

Amylases↗