SLC30A3 responds to glucose- and zinc variations in beta-cells and is critical for insulin production and in vivo glucose-metabolism during beta-cell stress.
BACKGROUND
Ion transporters of the Slc30A- (ZnT-) family regulate zinc fluxes into sub-cellular compartments. beta-cells depend on zinc for both insulin crystallization and regulation of cell mass.


RESULTS
This study examined: the effect of glucose and zinc chelation on ZnT gene and protein levels and apoptosis in beta-cells and pancreatic islets, the effects of ZnT-3 knock-down on insulin secretion in a beta-cell line and ZnT-3 knock-out on glucose metabolism in mice during streptozotocin-induced beta-cell stress. In INS-1E cells 2 mM glucose down-regulated ZnT-3 and up-regulated ZnT-5 expression relative to 5 mM. 16 mM glucose increased ZnT-3 and decreased ZnT-8 expression. Zinc chelation by DEDTC lowered INS-1E insulin content and insulin expression. Furthermore, zinc depletion increased ZnT-3- and decreased ZnT-8 gene expression whereas the amount of ZnT-3 protein in the cells was decreased. Zinc depletion and high glucose induced apoptosis and necrosis in INS-1E cells. The most responsive zinc transporter, ZnT-3, was investigated further; by immunohistochemistry and western blotting ZnT-3 was demonstrated in INS-1E cells. 44% knock-down of ZnT-3 by siRNA transfection in INS-1E cells decreased insulin expression and secretion. Streptozotocin-treated mice had higher glucose levels after ZnT-3 knock-out, particularly in overt diabetic animals.


CONCLUSIONS
Zinc transporting proteins in beta-cells respond to variations in glucose and zinc levels. ZnT-3, which is pivotal in the development of cellular changes as also seen in type 2 diabetes (e.g. amyloidosis in Alzheimer's disease) but not previously described in beta-cells, is present in this cell type, up-regulated by glucose in a concentration dependent manner and up-regulated by zinc depletion which by contrast decreased ZnT-3 protein levels. Knock-down of the ZnT-3 gene lowers insulin secretion in vitro and affects in vivo glucose metabolism after streptozotocin treatment.
Smidt
Kamille
K
Department of Pharmacology, University of Aarhus, Arhus, Denmark.
Jessen
Niels
N
Petersen
Andreas Brønden
AB
Larsen
Agnete
A
Magnusson
Nils
N
Jeppesen
Johanne Bruun
JB
Stoltenberg
Meredin
M
Culvenor
Janetta G
JG
Tsatsanis
Andrew
A
Brock
Birgitte
B
Schmitz
Ole
O
Wogensen
Lise
L
Bush
Ashley I
AI
Rungby
Jørgen
J
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005215:Fasting / Q000097:blood; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D006943:Hyperglycemia / Q000378:metabolism; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D051379:Mice; D018345:Mice, Knockout; D051381:Rats; D013311:Streptozocin; D013312:Stress, Physiological / Q000187:drug effects*; D015032:Zinc / Q000494:pharmacology*; D000075703:Zinc Transporter 8
D001786:Blood Glucose; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D002614:Chelating Agents; D007328:Insulin; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C491177:Slc30a3 protein, mouse; C516348:Slc30a8 protein, mouse; D000075703:Zinc Transporter 8; D013311:Streptozocin; D005947:Glucose; D015032:Zinc