Islet neogenesis-associated protein signaling in neonatal pancreatic rat islets: involvement of the cholinergic pathway.
Islet neogenesis associated protein (INGAP) increases islet mass and insulin secretion in neonatal and adult rat islets. In the present study, we measured the short- and long-term effects of INGAP-PP (a pentadecapeptide having the 104-118 amino acid sequence of INGAP) upon islet protein expression and phosphorylation of components of the PI3K, MAPK and cholinergic pathways, and on insulin secretion. Short-term exposure of neonatal islets to INGAP-PP (90 s, 5, 15, and 30 min) significantly increased Akt1(-Ser473) and MAPK3/1(-Thr202/Tyr204) phosphorylation and INGAP-PP also acutely increased insulin secretion from islets perifused with 2 and 20 mM glucose. Islets cultured for 4 days in the presence of INGAP-PP showed an increased expression of Akt1, Frap1, and Mapk1 mRNAs as well as of the muscarinic M3 receptor subtype, and phospholipase C (PLC)-beta2 proteins. These islets also showed increased Akt1 and MAPK3/1 protein phosphorylation. Brief exposure of INGAP-PP-treated islets to carbachol (Cch) significantly increased P70S6K(-Thr389) and MAPK3/1 phosphorylation and these islets released more insulin when challenged with Cch that was prevented by the M3 receptor antagonist 4-DAMP, in a concentration-dependent manner. In conclusion, these data indicate that short- and long-term exposure to INGAP-PP significantly affects the expression and the phosphorylation of proteins involved in islet PI3K and MAPK signaling pathways. The observations of INGAPP-PP-stimulated up-regulation of cholinergic M3 receptors and PLC-beta2 proteins, enhanced P70S6K and MAPK3/1 phosphorylation and Cch-induced insulin secretion suggest a participation of the cholinergic pathway in INGAP-PP-mediated effects.
Barbosa
Helena C
HC
Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, 13083-970 Campinas-SP, São Paulo-SP, Brazil.
Bordin
Silvana
S
Anhê
Gabriel
G
Persaud
Shanta J
SJ
Bowe
James
J
Borelli
Maria I
MI
Gagliardino
Juan J
JJ
Boschero
Antonio C
AC
D000818:Animals; D000831:Animals, Newborn; D000951:Antigens, Neoplasm / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics; D015151:Immunoblotting; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D037181:Lectins, C-Type; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D000073718:Pancreatitis-Associated Proteins; D010766:Phosphorylation / Q000187:drug effects; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics; D010880:Piperidines / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D002352:Carrier Proteins; D007328:Insulin; D037181:Lectins, C-Type; D000073718:Pancreatitis-Associated Proteins; D010880:Piperidines; C000612141:REG3A protein, human; C000612144:Reg3b protein, rat; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D002217:Carbachol; D017853:Phosphotransferases (Alcohol Group Acceptor); C546845:mTOR protein, rat; C494920:Akt1 protein, rat; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3