Plasma membrane Ca2+-ATPase overexpression depletes both mitochondrial and endoplasmic reticulum Ca2+ stores and triggers apoptosis in insulin-secreting BRIN-BD11 cells.
Ca(2+) may trigger apoptosis in β-cells. Hence, the control of intracellular Ca(2+) may represent a potential approach to prevent β-cell apoptosis in diabetes. Our objective was to investigate the effect and mechanism of action of plasma membrane Ca(2+)-ATPase (PMCA) overexpression on Ca(2+)-regulated apoptosis in clonal β-cells. Clonal β-cells (BRIN-BD11) were examined for the effect of PMCA overexpression on cytosolic and mitochondrial [Ca(2+)] using a combination of aequorins with different Ca(2+) affinities and on the ER and mitochondrial pathways of apoptosis. β-cell stimulation generated microdomains of high [Ca(2+)] in the cytosol and subcellular heterogeneities in [Ca(2+)] among mitochondria. Overexpression of PMCA decreased [Ca(2+)] in the cytosol, the ER, and the mitochondria and activated the IRE1α-XBP1s but inhibited the PRKR-like ER kinase-eIF2α and the ATF6-BiP pathways of the ER-unfolded protein response. Increased Bax/Bcl-2 expression ratio was observed in PMCA overexpressing β-cells. This was followed by Bax translocation to the mitochondria with subsequent cytochrome c release, opening of the permeability transition pore, and apoptosis. In conclusion, clonal β-cell stimulation generates microdomains of high [Ca(2+)] in the cytosol and subcellular heterogeneities in [Ca(2+)] among mitochondria. PMCA overexpression depletes intracellular [Ca(2+)] stores and, despite a decrease in mitochondrial [Ca(2+)], induces apoptosis through the mitochondrial pathway. These data open the way to new strategies to control cellular Ca(2+) homeostasis that could decrease β-cell apoptosis in diabetes.
Jiang
Lin
L
Laboratoire de Pharmacodynamie et de Thérapeutique, Université Libre de Bruxelles, Faculté deMédecine, Bâtiment GE, 808 route de Lennik, B-1070 Brussels, Belgium.
Allagnat
Florent
F
Nguidjoe
Evrard
E
Kamagate
Adama
A
Pachera
Nathalie
N
Vanderwinden
Jean-Marie
JM
Brini
Marisa
M
Carafoli
Ernesto
E
Eizirik
Décio L
DL
Cardozo
Alessandra K
AK
Herchuelz
André
A
D051702:Activating Transcription Factor 6 / Q000235:genetics / Q000378:metabolism; D000331:Aequorin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D003920:Diabetes Mellitus / Q000201:enzymology / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000201:enzymology*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D010539:Permeability; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D056811:Unfolded Protein Response / Q000235:genetics; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP
D051702:Activating Transcription Factor 6; D000331:Aequorin; D002118:Calcium; D045304:Cytochromes c; D006360:Heat-Shock Proteins; D053499:Plasma Membrane Calcium-Transporting ATPases; D051028:bcl-2-Associated X Protein; C497113:Atf6 protein, rat; C494828:Bax protein, rat; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP