Bcl-2 functionally interacts with inositol 1,4,5-trisphosphate receptors to regulate calcium release from the ER in response to inositol 1,4,5-trisphosphate.
Inositol 1,4,5-trisphosphate (InsP3) receptors (InsP3Rs) are channels responsible for calcium release from the endoplasmic reticulum (ER). We show that the anti-apoptotic protein Bcl-2 (either wild type or selectively localized to the ER) significantly inhibited InsP3-mediated calcium release and elevation of cytosolic calcium in WEHI7.2 T cells. This inhibition was due to an effect of Bcl-2 at the level of InsP3Rs because responses to both anti-CD3 antibody and a cell-permeant InsP3 ester were decreased. Bcl-2 inhibited the extent of calcium release from the ER of permeabilized WEHI7.2 cells, even at saturating concentrations of InsP3, without decreasing luminal calcium concentration. Furthermore, Bcl-2 reduced the open probability of purified InsP3Rs reconstituted into lipid bilayers. Bcl-2 and InsP3Rs were detected together in macromolecular complexes by coimmunoprecipitation and blue native gel electrophoresis. We suggest that this functional interaction of Bcl-2 with InsP3Rs inhibits InsP3R activation and thereby regulates InsP3-induced calcium release from the ER.
Chen
Rui
R
Department of Medicine, Comprehensive Cancer Center, Case Western Reserve University and University Hospitals of Cleveland, OH 44106, USA.
Valencia
Ignacio
I
Zhong
Fei
F
McColl
Karen S
KS
Roderick
H Llewelyn
HL
Bootman
Martin D
MD
Berridge
Michael J
MJ
Conway
Stuart J
SJ
Holmes
Andrew B
AB
Mignery
Gregory A
GA
Velez
Patricio
P
Distelhorst
Clark W
CW
D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D046911:Macromolecular Substances; D011485:Protein Binding; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
D017252:CD3 Complex; D015220:Calcium Channels; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D046911:Macromolecular Substances; D019253:Proto-Oncogene Proteins c-bcl-2; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium