The pituitary adenylate cyclase activating polypeptide (PACAP I) and VIP (PACAP II VIP1) receptors stimulate inositol phosphate synthesis in transfected CHO cells through interaction with different G proteins.
The PACAP receptor (PACAP I receptor, selective for PACAP) and the PACAP II VIP1 receptor (recognizing PACAP and VIP with the same high affinity) were stably expressed in Chinese Hamster Ovary (CHO) cells. Cell lines expressing different receptor densities, as measured by binding saturation curves, were selected. Inositol phosphate production was stimulated dose dependently in all the cell lines by PACAP and VIP, and the order of potency of the agonists was identical to that of high affinity receptor occupancy. The stimulatory effect of a saturating peptide concentration was proportional to the total receptor density. At similar receptor densities, however, the PACAP receptor mediated stimulation was higher than the VIP receptor-mediated stimulation. Pretreatment of the cells with pertussis toxin for 8 h had no effect on receptor densities, did not alter the PACAP stimulated inositol phosphate synthesis by the cells expressing the PACAP I receptor but markedly inhibited the response of the cells expressing the PACAP II VIP1 receptor. Thus, the present results indicate that the two G(s)-coupled PACAP I and PACAP II VIP1 receptors may stimulate IP production. The maximal stimulation depended on the number of receptor expressed; the PACAP I and PACAP II VIP1 receptors probably activated the phospholipase C through G proteins of the G(q), and of the G(i)/G(o) families, respectively.
Van Rampelbergh
J
J
Department of Biochemistry and Nutrition, School of Medicine, Université Libre de Bruxelles, Brussels, Belgium.
Poloczek
P
P
Françoys
I
I
Delporte
C
C
Winand
J
J
Robberecht
P
P
Waelbroeck
M
M
D037361:Adenylate Cyclase Toxin; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D019204:GTP-Binding Proteins / Q000502:physiology*; D015870:Gene Expression; D007295:Inositol Phosphates / Q000378:metabolism; D009479:Neuropeptides / Q000494:pharmacology; D037342:Pertussis Toxin; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D010957:Plasmids; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone / Q000235:genetics / Q000502:physiology*; D018005:Receptors, Vasoactive Intestinal Peptide / Q000235:genetics / Q000502:physiology*; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D014162:Transfection; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D007295:Inositol Phosphates; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D010566:Virulence Factors, Bordetella; D014660:Vasoactive Intestinal Peptide; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins