OBJECTIVE: Glucagon-like peptide-1 (GLP-1) increases intracellular Ca(2+) concentrations ([Ca(2+)](i)), resulting in insulin secretion from pancreatic beta-cells. The molecular mechanism(s) of the GLP-1-mediated regulation of [Ca(2+)](i) was investigated. RESEARCH DESIGN AND METHODS: GLP-1-induced changes in [Ca(2+)](i) were measured in beta-cells isolated from Cd38(+/+) and Cd38(-/-) mice. Calcium-mobilizing second messengers were identified by measuring levels of nicotinic acid adenine dinucleotide phosphate (NAADP) and cyclic ADP-ribose (ADPR), using a cyclic enzymatic assay. To locate NAADP- and cyclic ADPR-producing enzyme(s), cellular organelles were separated using the sucrose gradient method. RESULTS: A GLP-1-induced [Ca(2+)](i) increase showed a cooperative Ca(2+) signal, i.e., an initial [Ca(2+)](i) rise mediated by the action of NAADP that was produced in acidic organelles and a subsequent long-lasting increase of [Ca(2+)](i) by the action of cyclic ADPR that was produced in plasma membranes and secretory granules. GLP-1 sequentially stimulated production of NAADP and cyclic ADPR in the organelles through protein kinase A and cAMP-regulated guanine nucleotide exchange factor II. Furthermore, the results showed that NAADP production from acidic organelles governed overall Ca(2+) signals, including insulin secretion by GLP-1, and that in addition to CD38, enzymes capable of synthesizing NAADP and/or cyclic ADPR were present in beta-cells. These observations were supported by the study with Cd38(-/-) beta-cells, demonstrating production of NAADP, cyclic ADPR, and Ca(2+) signal with normal insulin secretion stimulated by GLP-1. CONCLUSIONS: Our findings demonstrate that the GLP-1-mediated Ca(2+) signal for insulin secretion in pancreatic beta-cells is a cooperative action of NAADP and cyclic ADPR spatiotemporally formed by multiple enzymes.
OBJECTIVE:Glucagon-like peptide-1 (GLP-1) increases intracellular Ca(2+) concentrations ([Ca(2+)](i)), resulting in insulin secretion from pancreatic beta-cells. The molecular mechanism(s) of the GLP-1-mediated regulation of [Ca(2+)](i) was investigated. RESEARCH DESIGN AND METHODS: GLP-1-induced changes in [Ca(2+)](i) were measured in beta-cells isolated from Cd38(+/+) and Cd38(-/-) mice. Calcium-mobilizing second messengers were identified by measuring levels of nicotinic acid adenine dinucleotide phosphate (NAADP) and cyclic ADP-ribose (ADPR), using a cyclic enzymatic assay. To locate NAADP- and cyclic ADPR-producing enzyme(s), cellular organelles were separated using the sucrose gradient method. RESULTS: A GLP-1-induced [Ca(2+)](i) increase showed a cooperative Ca(2+) signal, i.e., an initial [Ca(2+)](i) rise mediated by the action of NAADP that was produced in acidic organelles and a subsequent long-lasting increase of [Ca(2+)](i) by the action of cyclic ADPR that was produced in plasma membranes and secretory granules. GLP-1 sequentially stimulated production of NAADP and cyclic ADPR in the organelles through protein kinase A and cAMP-regulated guanine nucleotide exchange factor II. Furthermore, the results showed that NAADP production from acidic organelles governed overall Ca(2+) signals, including insulin secretion by GLP-1, and that in addition to CD38, enzymes capable of synthesizing NAADP and/or cyclic ADPR were present in beta-cells. These observations were supported by the study with Cd38(-/-) beta-cells, demonstrating production of NAADP, cyclic ADPR, and Ca(2+) signal with normal insulin secretion stimulated by GLP-1. CONCLUSIONS: Our findings demonstrate that the GLP-1-mediated Ca(2+) signal for insulin secretion in pancreatic beta-cells is a cooperative action of NAADP and cyclic ADPR spatiotemporally formed by multiple enzymes.
Authors: Abdelilah Arredouani; A Mark Evans; Jianjie Ma; John Parrington; Michael X Zhu; Antony Galione Journal: Islets Date: 2010-09-01 Impact factor: 2.694
Authors: Igor Dzhura; Oleg G Chepurny; Grant G Kelley; Colin A Leech; Michael W Roe; Elvira Dzhura; Parisa Afshari; Sundeep Malik; Michael J Rindler; Xin Xu; Youming Lu; Alan V Smrcka; George G Holz Journal: J Physiol Date: 2010-11-01 Impact factor: 5.182
Authors: Oleg G Chepurny; Grant G Kelley; Igor Dzhura; Colin A Leech; Michael W Roe; Elvira Dzhura; Xiangquan Li; Frank Schwede; Hans-G Genieser; George G Holz Journal: Am J Physiol Endocrinol Metab Date: 2009-12-15 Impact factor: 4.310