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

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, Nα‐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 β‐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 α‐helix was also important: the combined substitution of Lys21/Lys22 by Gly21/Gly22 decreased the binding affinity sharply.

Role of transglutaminase 2 in PAC1 receptor mediated protection against hypoxia-induced cell death and neurite outgrowth in differentiating N2a neuroblastoma cells

“…The EC50 values for PACAP-27 mediated transglutaminase-catalysed amine incorporation (0.08 nM) and protein cross-linking activity (0.4 nM) are in-line with the affinity of PACAP-27 for the PAC1 receptor (Dickson et al, 2006;Dickson and Finlayson, 2009;Harmar et al, 2012). Furthermore, PACAP-27-induced TG2 activity was blocked by the PAC1 receptor antagonist PACAP 6-38 (Robberecht et al, 1992). Overall these data suggest that activation of TG2 by PACAP-27 is mediated via the PAC1 receptor.…”

Dipeptidyl‐peptidase IV hydrolyses gastric inhibitory polypeptide, glucagon‐like peptide‐1(7–36)amide, peptide histidine methionine and is responsible for their degradation in human serum

“…Gallwitz et al (1990) have shown that the C-terminal fragment of the peptide is important for receptor binding of the hormone, but is not sufficient to transduce a biological action as does the intact peptide (raise in cyclic AMP levels in rat insulinoma RINm5F cells). It appears that as in the case of glucagon (Unson et al, 1989), of GIP (Schmidt et al, 1986(Schmidt et al, , 1987 and of other members of the VIP/glucagon peptide family (Christophe et al, 1989;Robberecht et al, 1992) also for GLP-1(7-36)amide an intact N-terminus is needed for signal transduction and biological action. Provided this, action of DPP IV inactivates GLPl(7-36)amide.…”

Pituitary adenylate cyclase‐activating polypeptide inhibits cutaneous immune function

“…PACAP 38, PACAP 6-38 [51], and neuropeptide Y were purchased from Peninsula Laboratories (San Carlos, CA).…”