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cAMP‐regulated guanine nucleotide exchange factor II (Epac2) mediates Ca 2+ ‐induced Ca 2+ release in INS‐1 pancreatic β‐cells
Author(s) -
Kang Guoxin,
Chepurny Oleg G.,
Holz George G.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0375c.xd
Subject(s) - guanine nucleotide exchange factor , forskolin , thapsigargin , signal transduction , endoplasmic reticulum , ryanodine receptor , inositol trisphosphate receptor , chemistry , biology , endocrinology , receptor , microbiology and biotechnology , inositol , medicine , biochemistry
1 The signal transduction pathway responsible for cAMP‐dependent Ca 2+ ‐induced Ca 2+ release (CICR) from endoplasmic reticulum Ca 2+ 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 Ca 2+ through L‐type voltage‐dependent Ca 2+ channels, and was blocked by treatment with nimodipine, thapsigargin, or ryanodine, but not by the IP 3 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 Ca 2+ release mechanism, a signal transduction pathway independent of PKA, but which requires cAMP‐GEF‐II.