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.
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.
Zhiyong
Z
Gao
Robert A
RA
Young
Matteo M
MM
Trucco
Scott R
SR
Greene
Erik L
EL
Hewlett
Franz M
FM
Matschinsky
Bryan A
BA
Wolf
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