cAMP-regulated guanine nucleotide exchange factor II (Epac2) mediates Ca2+-induced Ca2+ release in INS-1 pancreatic beta-cells

J Physiol. 2001 Oct 15;536(Pt 2):375-85. doi: 10.1111/j.1469-7793.2001.0375c.xd.


1. The signal transduction pathway responsible for cAMP-dependent Ca2+-induced Ca2+ release (CICR) from endoplasmic reticulum Ca2+ stores was assessed in the insulin-secreting cell line INS-1. 2. CICR was triggered by the GLP-1 receptor agonist exendin-4, an effect mimicked by caffeine, Sp-cAMPS or forskolin. CICR required influx of Ca2+ through L-type voltage-dependent Ca2+ channels, and was blocked by treatment with nimodipine, thapsigargin, or ryanodine, but not by the IP3 receptor antagonist xestospongin C. 3. Treatment with the cAMP antagonist 8-Br-Rp-cAMPS blocked CICR in response to exendin-4, whereas the PKA inhibitor H-89 was ineffective when tested at a concentration demonstrated to inhibit PKA-dependent gene expression. 4. RT-PCR of INS-1 cells demonstrated expression of mRNA coding for the type-II isoform of cAMP-regulated guanine nucleotide exchange factor (cAMP-GEF-II, Epac2). 5. CICR in response to forskolin was blocked by transient transfection and expression of a dominant negative mutant isoform of cAMP-GEF-II in which inactivating mutations were introduced into the exchange factor's two cAMP-binding domains. 6. It is concluded that CICR in INS-1 cells results from GLP-1 receptor-mediated sensitization of the intracellular Ca2+ release mechanism, a signal transduction pathway independent of PKA, but which requires cAMP-GEF-II.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Caffeine / pharmacology
  • Calcium / metabolism*
  • Colforsin / pharmacology
  • Cyclic AMP / metabolism*
  • Cyclic AMP-Dependent Protein Kinase Type II
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Down-Regulation / physiology
  • Exenatide
  • Gene Expression / physiology
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Insulinoma
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology
  • Islets of Langerhans / metabolism*
  • Pancreatic Neoplasms
  • Peptides / pharmacology
  • Phosphodiesterase Inhibitors / pharmacology
  • Rats
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Transfection
  • Tumor Cells, Cultured
  • Venoms*


  • Guanine Nucleotide Exchange Factors
  • Peptides
  • Phosphodiesterase Inhibitors
  • Ryanodine Receptor Calcium Release Channel
  • Venoms
  • Colforsin
  • Caffeine
  • Exenatide
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinase Type II
  • Cyclic AMP-Dependent Protein Kinases
  • Calcium