Glucose Regulates Free Cytosolic Zn2+ Concentration, Slc39 (ZiP), and Metallothionein Gene Expression in Primary Pancreatic Islet beta-Cells
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Published version
Author(s)
Bellomo, EA
Meur, G
Rutter, GA
Type
Journal Article
Abstract
Zn2+ is an important cofactor for insulin biosynthesis and storage in pancreatic β-cells. Correspondingly, polymorphisms in the SLC30A8 gene, encoding the secretory granule Zn2+ transporter ZnT8, are associated with type 2 diabetes risk. Using a genetically engineered (FRET)-based sensor (eCALWY-4), we show here that elevated glucose time-dependently increases free cytosolic Zn2+ ([Zn2+]cyt) in mouse pancreatic β-cells. These changes become highly significant (853 ± 96 pM versus 452 ± 42 pM, p < 0.001) after 24 h and are associated with increased expression of the Zn2+ importer family members Slc39a6, Slc39a7, and Slc39a8, and decreased expression of metallothionein 1 and 2. Arguing that altered expression of the above genes is not due to altered [Zn2+]cyt, elevation of extracellular (and intracellular) [Zn2+] failed to mimic the effects of high glucose. By contrast, increases in intracellular cAMP prompted by 3-isobutyl-1-methylxanthine and forskolin partially mimicked the effects of glucose on metallothionein, although not ZiP, gene expression. Modulation of intracellular Ca2+ and insulin secretion with pharmacological agents (tolbutamide and diazoxide) suggested a possible role for changes in these parameters in the regulation of Slc39a6 and Slc39a7 but not Slc39a8, nor metallothionein expression. In summary, 1) glucose induces increases in [Zn2+]cyt, which are then likely to facilitate the processing and/or the storage of insulin and its cocrystallization with Zn2+, and 2) these increases are associated with elevated expression of zinc importers. Conversely, a chronic increase in [Zn2+]cyt following sustained hyperglycemia may contribute to β-cell dysfunction and death in some forms of diabetes.
Date Issued
2011-07-22
Date Acceptance
2011-05-13
Citation
Journal of Biological Chemistry, 2011, 286 (29), pp.25778-25789
ISSN
1083-351X
Publisher
American Society for Biochemistry and Molecular Biology
Start Page
25778
End Page
25789
Journal / Book Title
Journal of Biological Chemistry
Volume
286
Issue
29
Copyright Statement
© 2011 by The American Society for Biochemistry and Molecular Biology, Inc.. Free via Creative Commons: CC-BY license
License URL
Subjects
Science & Technology
Life Sciences & Biomedicine
Biochemistry & Molecular Biology
BIOCHEMISTRY & MOLECULAR BIOLOGY
GENOME-WIDE ASSOCIATION
ZINC TRANSPORTER ZNT8
INSULIN-SECRETION
INTRACELLULAR ZINC
BUFFERING CAPACITY
ENDOCRINE PANCREAS
DIABETIC-RATS
CELLULAR ZINC
ALPHA-CELLS
RISK LOCI
Publication Status
Published