title: Glucose regulates free cytosolic Zn²⁺ concentration, Slc39 (ZiP), and metallothionein gene expression in primary pancreatic islet β-cells.
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.
authors: Section of Cell Biology, Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, London SW7 2AZ, UK.
authors: Elisa A
authors: EA
authors: Bellomo
authors: Gargi
authors: G
authors: Meur
authors: Guy A
authors: GA
authors: Rutter
references: Biochem Soc Trans. 1990 Feb;18(1):122-4
references: 2185075
references: Biochim Biophys Acta. 2000 May 1;1465(1-2):190-8
references: 10748254
references: Cell Metab. 2008 Jul;8(1):26-37
references: 18590690
references: J Clin Invest. 1975 Oct;56(4):1066-70
references: 1099118
references: J Biol Chem. 2000 Nov 17;275(46):36269-77
references: 10967119
references: J Nutr. 1987 May;117(5):886-93
references: 3585542
references: Exp Mol Pathol. 1984 Dec;41(3):377-83
references: 6391954
references: Science. 2007 Jun 1;316(5829):1336-41
references: 17463249
references: Diabetes Obes Metab. 2009 Nov;11 Suppl 4:202-14
references: 19817803
references: Biol Trace Elem Res. 1994 Sep;42(3):209-16
references: 7826814
references: Proc Natl Acad Sci U S A. 1988 Dec;85(23):8943-7
references: 3057496
references: J Biol Chem. 2009 Jun 12;284(24):16289-16297
references: 19363034
references: J Anat. 1995 Jun;186 ( Pt 3):629-37
references: 7559135
references: Nat Cell Biol. 2004 Mar;6(3):207-14
references: 15039777
references: Annu Rev Nutr. 2004;24:151-72
references: 15189117
references: Diabetologia. 2010 Aug;53(8):1656-68
references: 20424817
references: Exp Biol Med (Maywood). 2001 Jan;226(1):43-51
references: 11368237
references: EMBO J. 1993 Apr;12(4):1355-62
references: 8467794
references: J Biol Chem. 2003 Mar 14;278(11):9796-801
references: 12514170
references: J Clin Invest. 1938 Nov;17(6):725-8
references: 16694619
references: Biochem J. 2003 Oct 1;375(Pt 1):51-9
references: 12839489
references: Proc Natl Acad Sci U S A. 2009 Sep 1;106(35):14872-7
references: 19706465
references: Nat Methods. 2009 Oct;6(10):737-40
references: 19718032
references: J Am Chem Soc. 2004 Jan 28;126(3):712-3
references: 14733534
references: Science. 2007 Jun 1;316(5829):1341-5
references: 17463248
references: Br J Nutr. 1988 Nov;60(3):499-507
references: 3219321
references: Biometals. 2005 Aug;18(4):313-7
references: 16158222
references: J Biol Chem. 2002 May 24;277(21):19049-55
references: 11904301
references: Nat Immunol. 2006 Sep;7(9):971-7
references: 16892068
references: Diabetes. 2005 Jun;54(6):1789-97
references: 15919801
references: Exp Biol Med (Maywood). 2010 Jun;235(6):741-50
references: 20511678
references: PLoS One. 2009 May 25;4(5):e5684
references: 19492079
references: Biophys J. 1993 Feb;64(2):525-32
references: 8457676
references: Diabetes. 2007 Apr;56(4):1095-106
references: 17229937
references: Biochem J. 2004 Jan 1;377(Pt 1):149-58
references: 14563207
references: J Biol Chem. 1999 Jul 30;274(31):21645-50
references: 10419473
references: Biochemistry. 1991 Jan 29;30(4):917-24
references: 1671209
references: J Histochem Cytochem. 1994 Jul;42(7):877-84
references: 8014471
references: APMIS. 2003 Dec;111(12):1147-54
references: 14678025
references: Diabetes. 2009 Sep;58(9):2070-83
references: 19542200
references: Diabetes. 2006 Mar;55(3):600-7
references: 16505221
references: Biochem J. 2009 Jul 15;421(3):371-6
references: 19450229
references: Curr Opin Cell Biol. 1997 Aug;9(4):553-9
references: 9261054
references: Nat Protoc. 2007;2(5):1236-47
references: 17546019
references: Diabetes. 2001 Sep;50(9):2040-6
references: 11522669
references: Diabetes. 2000 Mar;49(3):367-72
references: 10868957
references: Pflugers Arch. 2004 Feb;447(5):744-51
references: 12748859
references: Proc Natl Acad Sci U S A. 2008 Jul 22;105(29):10161-6
references: 18626018
references: Diabetes. 1981 Apr;30(4):341-5
references: 7009279
references: Diabetologia. 2009 Mar;52(3):463-76
references: 19165461
references: Exp Cell Res. 2009 Aug 15;315(14):2463-70
references: 19467229
references: J Biol Chem. 2005 Apr 15;280(15):15456-63
references: 15705588
references: J Cell Biochem. 1994;55 Suppl:54-65
references: 7929618
references: Brain Res. 2008 Mar 14;1199:10-9
references: 18272141
references: Science. 2005 Jan 21;307(5708):384-7
references: 15662004
references: Am J Physiol Lung Cell Mol Physiol. 2008 Jun;294(6):L1127-36
references: 18390834
references: Horm Metab Res. 2000 Nov-Dec;32(11-12):542-7
references: 11246822
references: Science. 1973 Feb 9;179(4073):569-71
references: 4346825
references: Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9307-12
references: 9689076
references: Br J Pharmacol. 2010 Feb 1;159(3):669-77
references: 20128805
references: Diabetologia. 2000 Aug;43(8):1020-30
references: 10990080
references: Diabetologia. 1988 May;31(5):329-33
references: 3294070
references: J Leukoc Biol. 2009 Aug;86(2):337-48
references: 19401385
references: Diabetes Res. 1993;22(2):67-75
references: 8205739
references: Nature. 2007 Feb 22;445(7130):881-5
references: 17293876
references: Int J Clin Pract Suppl. 2001 Sep;(123):13-8
references: 11594291
references: J Biol Inorg Chem. 2006 Nov;11(8):1049-62
references: 16924557
references: FEBS Lett. 1973 Jul 15;33(3):311-4
references: 4353994
references: Mol Med. 2007 Jul-Aug;13(7-8):371-5
references: 17622324
references: Endocrinology. 2002 Sep;143(9):3695-8
references: 12193586
references: Cell Calcium. 2003 Sep;34(3):281-4
references: 12887975
references: J Biol Chem. 2011 Apr 15;286(15):13647-56
references: 21335550
references: Diabetologia. 1980 Sep;19(3):174-82
references: 6997118
references: Glia. 2006 Aug 1;54(2):125-34
references: 16718685
references: J Biol Chem. 2006 Apr 7;281(14):9361-72
references: 16407176