The KATP channel is critical for calcium sequestration into non-ER compartments in mouse pancreatic beta cells.
K(ATP) channel activity influences beta cell Ca(2+) homeostasis by regulating Ca(2+) influx through L-type Ca(2+) channels. The present paper demonstrates that loss of K(ATP) channel activity due to pharmacologic or genetic ablation affects Ca(2+) storage in intracellular organelles. ATP depletion, by the mitochondrial inhibitor FCCP, led to Ca(2+) release from the endoplasmic reticulum (ER) of wildtype beta cells. Blockade of ER Ca(2+) ATPases by cyclopiazonic acid abolished the FCCP-induced Ca(2+) transient. In beta cells treated with K(ATP) channel inhibitors FCCP elicited a significantly larger Ca(2+) transient. Cyclopiazonic acid did not abolish this Ca(2+) transient suggesting that non-ER compartments are recruited as additional Ca(2+) stores in beta cells lacking K(ATP) channel activity. Genetic ablation of K(ATP) channels in SUR1KO mice produced identical results. In INS-1 cells transfected with a mitochondrial-targeted Ca(2+)-sensitive fluorescence dye (ratiometric pericam) the increase in mitochondrial Ca(2+) evoked by tolbutamide was 5-fold larger compared to 15 mM glucose. These data show that genetic or pharmacologic ablation of K(ATP) channel activity conveys Ca(2+) release from a non-ER store. Based on the sensitivity to FCCP and the property of tolbutamide to increase mitochondrial Ca(2+) it is suggested that mitochondria are the recruited store. The change in Ca(2+) sequestration in beta cells treated with insulinotropic antidiabetics may have implications for beta cell survival and the therapeutic use of these drugs.
Dufer
Martina
M
Institute of Pharmacy, Department of Pharmacology, University of Tubingen, Tubingen, Germany.
Haspel
Dirk
D
Krippeit-Drews
Peter
P
Kelm
Mandy
M
Ranta
Felicia
F
Nitschke
Roland
R
Ullrich
Susanne
S
Aguilar-Bryan
Lydia
L
Bryan
Joseph
J
Drews
Gisela
G
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002451:Cell Compartmentation; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D015221:Potassium Channels / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D011955:Receptors, Drug / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D064233:Sulfonylurea Receptors; D014044:Tolbutamide / Q000494:pharmacology
D018528:ATP-Binding Cassette Transporters; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D014044:Tolbutamide; D005947:Glucose; D002118:Calcium