Pituitary adenylate cyclase-activating polypeptide (PACAP) stimulates cyclic AMP formation as well as peptide output of cultured pituitary melanotrophs and AtT-20 corticotrophs

Molecular cloning and functional expression of the pituitary adenylate cyclase-activating polypeptide type I receptor.

“…VIP and secretin did not inhibit binding of 1251-PACAP-27 at doses of up to 1 ,uM. These results are in close agreement with the pharmacological profile of type PACAP receptors reported for an adrenal pheochromocytoma cell line, PC12H (9), and hypothalamic and anterior pituitary membranes (30,40,41). In addition, the cloned receptor can be subclassified as a type IA, having nearly equal affinity for PACAP-27 and PACAP-38, similar to the type IA described in AR4-2J cell membranes (42).…”

“…Already three types of receptors for PACAP have been identified, of which one has high affimity and specificity (type I) and may be subdivided into subtypes with various abilities to activate adenylate cyclase and the phosphatidylinositol/Ca2+ cascade (40)(41)(42). Despite these rapid advances, little is known about the physiologic actions of PACAP and its receptors.…”

Pituitary Adenyl Cyclase-Activating Peptide: A Hypophysiotropic Factor That Stimulates Proopiomelanocortin Gene Transcription, and Proopio-melanocortin-Derived Peptide Secretion in Corticotropic Cells

“…Although only activation of adenylate cyclase by PACAP has as yet been evidenced in AtT20 cells [19], we sought to determine whether this pathway is the main mechanism for POMC gene regulation. To this end, we used a genetic approach to selectively inactivate PKA with a dominant inhibitory mutant of this enzyme [22], Indeed, we have previously shown that expression by gene transfer of a regulatory subunit lacking cAMP binding sites selectively blocks cAMP-mediated transcription in AtT20 cells [23].…”

“…While some studies based on static incubation of cultured pituitary cells favor a stimulatory effect on the secretion of GH, ACTH and LH [13,14] or even an inhibitory effect on that of PRL [15] , others show a lack of influence on the output of ACTH and GH and rather suggest a potentiation by PACAP of LHRH-stimulated secretion of gonatropins [16] , PACAP also elevates intracellular free calcium con centrations in somatotropes and gonatotropes, as well as in folliculo-stellatecells [8,17], In fact, cytochemical stud ies with biotinylated PACAP identified pituitary follicu lo-stellate, GH and PRL cells as the major targets for PACAP, whereas a lesser number of corticotropes and very few gonadotropes were found to combine the ligand [18]. In view of this apparent confusing picture related to the heterogeneous nature of pituitary cell population, we and others switched to the proopiomelanocortin (POMC) cell line AtT20 and GH3 cell model systems and showed the cells to bear PACAP receptors functionally coupled to cAMP production and peptide secretion [19,20], In recent years, the regulation of POMC gene expres sion by CRH has received much attention [21], The molecular mechanism by which CRH-stimulated POMC gene transcription has been extensively studied and, using AtT20 corticotrophs, we were able to recently show that the stimulatory action of CRH is closely related to PKA activation and involves multiple cAMP-responsive regu latory sequences located in the 5' regulatory promoter region of the POMC gene [Boutillier et al, submitted]. In addition, to enhance cAMP formation in AtT20 cortico trophs [19], PACAP has been shown to activate other sec ond-messenger-dependent regulatory pathways in other cell types [5,6].…”

“…In view of this apparent confusing picture related to the heterogeneous nature of pituitary cell population, we and others switched to the proopiomelanocortin (POMC) cell line AtT20 and GH3 cell model systems and showed the cells to bear PACAP receptors functionally coupled to cAMP production and peptide secretion [19,20], In recent years, the regulation of POMC gene expres sion by CRH has received much attention [21], The molecular mechanism by which CRH-stimulated POMC gene transcription has been extensively studied and, using AtT20 corticotrophs, we were able to recently show that the stimulatory action of CRH is closely related to PKA activation and involves multiple cAMP-responsive regu latory sequences located in the 5' regulatory promoter region of the POMC gene [Boutillier et al, submitted]. In addition, to enhance cAMP formation in AtT20 cortico trophs [19], PACAP has been shown to activate other sec ond-messenger-dependent regulatory pathways in other cell types [5,6]. Thus, we investigated whether PKA represents the central intracellular relay by which the neu ropeptides regulate the POMC gene.…”