Protein kinase A translocation and insulin secretion in pancreatic beta-cells: studies with adenylate cyclase toxin from Bordetella pertussis.
Activation of protein kinase A (cAMP-dependent protein kinase; PKA) triggers insulin secretion in the beta-cell. Adenylate cyclase toxin (ACT), a bacterial exotoxin with adenylate cyclase activity, and forskolin, an activator of adenylate cyclase, both dose-dependently increased insulin secretion in the presence, but not the absence, of glucose in insulin-secreting betaTC3 cells. The stimulation of cAMP release by either agent was dose-dependent but glucose-independent. Omission of extracellular Ca(2+) totally abolished the effects of ACT on insulin secretion and cytosolic cAMP accumulation. ACT and forskolin caused rapid and dramatic increases in cytosolic Ca(2+), which were blocked by nifedipine and the omission of extracellular Ca(2+). Omission of glucose completely blocked the effects of forskolin and partially blocked the effects of ACT on cytosolic Ca(2+). PKA alpha, beta and gamma catalytic subunits (Calpha, Cbeta and Cgamma respectively) were identified in betaTC6 cells by confocal microscopy. Glucose and glucagon-like polypeptide-1 (GLP-1) caused translocation of Calpha to the nucleus and of Cbeta to the plasma membrane and the nucleus, but did not affect the distribution of Cgamma. In conclusion, glucose and GLP-1 amplify insulin secretion via cAMP production and PKAbeta activation.
Gao
Zhiyong
Z
Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine, 5135 Main Building, 34th Street and Civic Center Blvd, Philadelphia, PA 19104-4399, U.S.A.
Young
Robert A
RA
Trucco
Matteo M
MM
Greene
Scott R
SR
Hewlett
Erik L
EL
Matschinsky
Franz M
FM
Wolf
Bryan A
BA
D037361:Adenylate Cyclase Toxin / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020134:Catalytic Domain; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D020033:Protein Isoforms; D021381:Protein Transport / Q000187:drug effects
D037361:Adenylate Cyclase Toxin; D007328:Insulin; D007527:Isoenzymes; D020033:Protein Isoforms; D000242:Cyclic AMP; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases; C463959:protein kinase A Calpha; D002118:Calcium