Epac-selective cAMP Analog 8-pCPT-2'-O-Me-cAMP as a Stimulus for Ca2+-induced Ca2+ Release and Exocytosis in Pancreatic Beta-Cells

J Biol Chem. 2003 Mar 7;278(10):8279-85. doi: 10.1074/jbc.M211682200. Epub 2002 Dec 20.

Abstract

The second messenger cAMP exerts powerful stimulatory effects on Ca(2+) signaling and insulin secretion in pancreatic beta-cells. Previous studies of beta-cells focused on protein kinase A (PKA) as a downstream effector of cAMP action. However, it is now apparent that cAMP also exerts its effects by binding to cAMP-regulated guanine nucleotide exchange factors (Epac). Although one effector of Epac is the Ras-related G protein Rap1, it is not fully understood what the functional consequences of Epac-mediated signal transduction are at the cellular level. 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate (8-pCPT-2'-O-Me-cAMP) is a newly described cAMP analog, and it activates Epac but not PKA. Here we demonstrate that 8-pCPT-2'-O-Me-cAMP acts in human pancreatic beta-cells and INS-1 insulin-secreting cells to mobilize Ca(2+) from intracellular Ca(2+) stores via Epac-mediated Ca(2+)-induced Ca(2+) release (CICR). The cAMP-dependent increase of [Ca(2+)](i) that accompanies CICR is shown to be coupled to exocytosis. We propose that the interaction of cAMP and Epac to trigger CICR explains, at least in part, the blood glucose-lowering properties of an insulinotropic hormone (glucagon-like peptide-1, also known as GLP-1) now under investigation for use in the treatment of type-2 diabetes mellitus.

Publication types

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

MeSH terms

  • Bacterial Proteins / metabolism
  • Calcium / metabolism*
  • Cells, Cultured
  • Cyclic AMP / analogs & derivatives
  • Cyclic AMP / pharmacology*
  • Electrochemistry
  • Exocytosis / drug effects*
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Humans
  • Immunohistochemistry
  • Islets of Langerhans / cytology
  • Islets of Langerhans / drug effects*
  • Islets of Langerhans / metabolism
  • Luminescent Proteins / metabolism

Substances

  • 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate
  • Bacterial Proteins
  • Guanine Nucleotide Exchange Factors
  • Luminescent Proteins
  • RAPGEF3 protein, human
  • yellow fluorescent protein, Bacteria
  • Cyclic AMP
  • Calcium