TY - JOUR
T1 - Calbindin-D(28k) controls [Ca2+](i) and insulin release. Evidence obtained from calbindin-D(28k) knockout mice and β cell lines
AU - Sooy, Karen
AU - Schermerhorn, Thomas
AU - Noda, Mitsuhiko
AU - Surana, Manju
AU - Rhoten, William B.
AU - Meyer, Michael
AU - Fleischer, Norman
AU - Sharp, Geoffrey W.G.
AU - Christakos, Sylvia
PY - 1999/11/26
Y1 - 1999/11/26
N2 - The role of the calcium-binding protein, calbindin-D(28k) in potassium/depolarization-stimulated increases in the cytosolic free Ca2+ concentration ([Ca2+](i)) and insulin release was investigated in pancreatic islets from calbindin-D(28k) nullmutant mice (knockouts; KO) or wild type mice and β cell lines stably transfected and overexpressing calbindin. Using single islets from KO mice and stimulation with 45 mM KCl, the peak of [Ca2+](i) was 3.5-fold greater in islets from KO mice compared with wild type islets (p<0.01) and [Ca2+](i) remained higher during the plateau phase. In addition to the increase in [Ca2+](i) in response to KCl there was also a significant increase in insulin release in islets isolated from KO mice. Evidence for modulation by calbindin of [Ca2+](i) and insulin release was also noted using β cell lines. Rat calbindin was stably expressed in βTC-3 and βHC-13 cells. In response to depolarizing concentrations of K+, insulin release was decreased by 45-47% in calbindin expressing βTC cells and was decreased by 7080% in calbindin expressing βHC cells compared with insulin release from vector transfected βTC or βHC cells (p < 0.01). In addition, the K+-stimulated intracellular calcium peak was markedly inhibited in calbindin expressing βHC cells compared with vector transfected cells (225 nM versus 1,100 nM, respectively). Buffering of the depolarization-induced rise in [Ca2+](i) was also observed in calbindin expressing βTC cells. In summary, our findings, using both isolated islets from calbindin-D(28k) KO mice and β cell lines, establish a role for calbindin in the modulation of depolarization-stimulated insulin release and suggest that calbindin can control the rate of insulin release via regulation of [Ca2+](i).
AB - The role of the calcium-binding protein, calbindin-D(28k) in potassium/depolarization-stimulated increases in the cytosolic free Ca2+ concentration ([Ca2+](i)) and insulin release was investigated in pancreatic islets from calbindin-D(28k) nullmutant mice (knockouts; KO) or wild type mice and β cell lines stably transfected and overexpressing calbindin. Using single islets from KO mice and stimulation with 45 mM KCl, the peak of [Ca2+](i) was 3.5-fold greater in islets from KO mice compared with wild type islets (p<0.01) and [Ca2+](i) remained higher during the plateau phase. In addition to the increase in [Ca2+](i) in response to KCl there was also a significant increase in insulin release in islets isolated from KO mice. Evidence for modulation by calbindin of [Ca2+](i) and insulin release was also noted using β cell lines. Rat calbindin was stably expressed in βTC-3 and βHC-13 cells. In response to depolarizing concentrations of K+, insulin release was decreased by 45-47% in calbindin expressing βTC cells and was decreased by 7080% in calbindin expressing βHC cells compared with insulin release from vector transfected βTC or βHC cells (p < 0.01). In addition, the K+-stimulated intracellular calcium peak was markedly inhibited in calbindin expressing βHC cells compared with vector transfected cells (225 nM versus 1,100 nM, respectively). Buffering of the depolarization-induced rise in [Ca2+](i) was also observed in calbindin expressing βTC cells. In summary, our findings, using both isolated islets from calbindin-D(28k) KO mice and β cell lines, establish a role for calbindin in the modulation of depolarization-stimulated insulin release and suggest that calbindin can control the rate of insulin release via regulation of [Ca2+](i).
UR - http://www.scopus.com/inward/record.url?scp=0033607686&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033607686&partnerID=8YFLogxK
U2 - 10.1074/jbc.274.48.34343
DO - 10.1074/jbc.274.48.34343
M3 - Article
C2 - 10567411
AN - SCOPUS:0033607686
SN - 0021-9258
VL - 274
SP - 34343
EP - 34349
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 48
ER -