Oscillations of cyclic AMP in hormone-stimulated insulin-secreting beta-cells.
Cyclic AMP is a ubiquitous second messenger that transduces signals from a variety of cell surface receptors to regulate diverse cellular functions, including secretion, metabolism and gene transcription. In pancreatic beta-cells, cAMP potentiates Ca2+-dependent exocytosis and mediates the stimulation of insulin release exerted by the hormones glucagon and glucagon-like peptide-1 (GLP-1) (refs 4, 5-6). Whereas Ca2+ signals have been extensively characterized and shown to involve oscillations important for the temporal control of insulin secretion, the kinetics of receptor-triggered cAMP signals is unknown. Here we introduce a new ratiometric evanescent-wave-microscopy approach to measure cAMP concentration beneath the plasma membrane, and show that insulin-secreting beta-cells respond to glucagon and GLP-1 with marked cAMP oscillations. Simultaneous measurements of intracellular Ca2+ concentration revealed that the two messengers are interlinked and reinforce each other. Moreover, cAMP oscillations are capable of inducing rapid on-off Ca2+ responses, but only sustained elevation of cAMP concentration induces nuclear translocation of the catalytic subunit of the cAMP-dependent protein kinase. Our results establish a new signalling mode for cAMP and indicate that temporal encoding of cAMP signals might constitute a basis for differential regulation of downstream cellular targets.
Dyachok
Oleg
O
Department of Medical Cell Biology, Uppsala University, BMC, Box 571, SE-751 23 Uppsala, Sweden.
Isakov
Yegor
Y
Sågetorp
Jenny
J
Tengholm
Anders
A
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D005934:Glucagon / Q000494:pharmacology*; D052216:Glucagon-Like Peptide 1 / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D051381:Rats
D007328:Insulin; D021122:Protein Subunits; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium