Kim BJ, Park KH, Yim CY, Takasawa S, Okamoto H, Im MJ, Kim UH. Generation of nicotinic acid adenine dinucleotide phosphate and cyclic ADP-ribose by glucagon-like peptide-1 evokes Ca2+ signal that is essential for insulin secretion in mouse pancreatic islets.
Diabetes 2008;
57:868-78. [PMID:
18184929 DOI:
10.2337/db07-0443]
[Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
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.
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