Molecular and functional characterization of pituitary adenylate cyclase-activating polypeptide (PACAP-38)/vasoactive intestinal polypeptide receptors in pancreatic beta-cells and effects of PACAP-38 on components of the insulin secretory system.
It has been previously demonstrated that pituitary adenylate cyclase-activating polypeptide (PACAP) regulates insulin secretion. PACAP exerts its biological action by binding to at least three different receptor subtypes coupled to different signal transduction mechanisms. The signaling pathways underlying the insulinotropic effect of PACAP involve mainly the activation of adenylate cyclase to form cAMP, which directly and indirectly, through increased intracellular Ca2+, stimulates insulin exocytosis. In the present study we have characterized the functional and molecular expression of PACAP/vasoactive intestinal polypeptide receptors isoforms and subtypes and its isoforms in a beta-cell line and in isolated rat pancreatic islets. Although insulinoma cells express the messenger RNA encoding PAC1 (-R and -hop variants), VPAC1 and VPAC2, binding experiments indicate the preponderance of PAC1 over VPAC 1-2 receptors. We have also shown that the main signaling pathway of PACAP in beta-cells is mediated by adenylate cyclase, whereas the inositol 1,4,5-trisphosphate pathway is almost inactive. Furthermore, we have demonstrated that PACAP exerts long-term effects on beta-cells, such as transcriptional regulation of the insulin gene and genes of the glucose-sensing system (GLUT1 and hexokinase 1).
Borboni
P
P
Department of Internal Medicine, University of Rome Tor Vergata, Italy. borboni@uniroma2.it
Porzio
O
O
Pierucci
D
D
Cicconi
S
S
Magnaterra
R
R
Federici
M
M
Sesti
G
G
Lauro
D
D
D'Agata
V
V
Cavallaro
S
S
Marlier
L N
LN
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D051272:Glucose Transporter Type 1; D006593:Hexokinase / Q000235:genetics; D007328:Insulin / Q000032:analysis / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma; D007515:Islets of Langerhans / Q000737:chemistry / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009479:Neuropeptides / Q000235:genetics* / Q000502:physiology*; D010190:Pancreatic Neoplasms; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D018005:Receptors, Vasoactive Intestinal Peptide / Q000235:genetics* / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
C495403:Adcyap1 protein, rat; D051272:Glucose Transporter Type 1; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D018005:Receptors, Vasoactive Intestinal Peptide; C495679:Slc2a1 protein, rat; D006593:Hexokinase; D000262:Adenylyl Cyclases