Youssef Anouar

A Cloned Frog Vasoactive Intestinal Polypeptide/ Pituitary Adenylate Cyclase-Activating Polypeptide Receptor Exhibits Pharmacological and Tissue Distribution Characteristics of Both VPAC1 and VPAC2 Receptors in Mammals

Three receptor subtypes for the neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) have been identified in mammals: the PAC1 receptor (PAC1-R) which is selectively activated by PACAP, and two VPAC receptors (VPAC1-R and VPAC2-R), which are equally stimulated by PACAP and VIP. The structures of PACAP and VIP have been well conserved during evolution, but little is known about VIP/PACAP receptors in nonmammalian species. An amphibian VIP/PACAP receptor complementary DNA (cDNA) has been cloned and characterized from a frog (Rana ridibunda) pituitary cDNA library. The predicted protein contains seven putative transmembrane domains and exhibits the highest sequence identity (65%) with the human VPAC1-R. The cloned cDNA was transiently expressed in LLC-PK1 cells, and its pharmacological profile was determined in comparison with the human VPAC1-R. Both PACAP and VIP stimulated cAMP accumulation through the cloned receptor with an EC50 of about 30 nm. ...

Regulatory Effects of Estrogens on the Pituitary Content of Secretogranin II and Chromogranin A

Modulation of pituitary content of secretogranin II and chromogranin A has been compared to that of luteinizing hormone (LH) in adult female rats following gonadectomy and subsequent estradiol therapy. Both proteins were quantified using two specific antisera, BS 487 and anti‐CAP‐14, respectively. Ovariectomy promoted an increase in the concentration of secretogranin II and chromogranin A, though to a lesser degree than that of LH. Moreover, intracellular processing of secretogranin II was significantly enhanced. Daily estradiol injection further increased pituitary secretogranin II and LH contents while that of chromogranin A was reduced to sham‐operated control values. These data 1) demonstrate that both granins are differentially regulated through ovarian factors, and 2) confirm that regulation of secretogranin II production may be closely related to that of LH.

Chromogranins/Secretogranins and Derived Peptides: Insights from the Amphibian Model

ABSTRACT Chromogranins/secretogranins (Cg/Sg) are a class of acidic, secretory proteins that occur in endocrine, neuroendocrine, and neuronal cells. Cloning and characterization of chromogranin A, chromogranin B, and secretogranin II revealed that selective sequences within these proteins, bounded by potential processing sites, have been remarkably conserved between amphibian and mammalian species. Two peptides, named secretoneurin and vasostatin, which occur in these regions, have been shown to exert various biological activities. Cg/Sg may also be involved in the formation of secretory granules in amphibians as in mammals. Recent results obtained on the function of Cg/Sg as propeptide precursors and as granulogenic factors in different vertebrate species are discussed.