Role of inositol 1,4,5-trisphosphate receptors in apoptosis in DT40 lymphocytes.
The role of inositol 1,4,5-trisphosphate receptors (IP(3)R) in caspase-3 activation and cell death was investigated in DT40 chicken B-lymphocytes stably expressing various IP(3)R constructs. Both full-length type-I IP(3)R and a truncated construct corresponding to the caspase-3 cleaved "channel-only" fragment were able to support staurosporine (STS)-induced caspase-3 activation and cell death even when the IP(3)R construct harbored a mutation that inactivates the pore of the Ca(2+) channel (D2550A). However, a full-length wild-type IP(3)R did not promote caspase-3 activation when the 159-amino acid cytosol-exposed C-terminal tail was deleted. STS caused an increase in cytosolic free Ca(2+) in DT40 cells expressing wild-type or pore-dead IP(3)R mutants. However, in the latter case all the Ca(2+) increase originated from Ca(2+) entry across the plasma membrane. Caspase-3 activation of pore-dead DT40 cells was also more sensitive to extracellular Ca(2+) chelation when compared with wild-type cells. STS-mediated release of cytochrome c into the cytosol and mitochondrial membrane potential depolarization could also be observed in DT40 cells lacking IP(3)Rs or containing the pore-dead mutant. We conclude that nonfunctional IP(3)Rs can sustain apoptosis in DT40 lymphocytes, because they facilitate Ca(2+) entry mechanisms across the plasma membrane. Although the intrinsic ion-channel function of IP(3)Rs is dispensable for apoptosis induced by STS, the C-terminal tail of IP(3)Rs appears to be essential, possibly reflecting key protein-protein interactions with this domain.
Khan
M Tariq
MT
Department of Pathology and Cell Biology, Thomas Jefferson University School of Medicine, 1020 Locust Street, Philadelphia, PA 19107, USA.
Bhanumathy
Cunnigaiper D
CD
Schug
Zachary T
ZT
Joseph
Suresh K
SK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002645:Chickens; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism*; D008214:Lymphocytes / Q000166:cytology* / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial; D009154:Mutation / Q000235:genetics; D019311:Staurosporine / Q000494:pharmacology
D053496:Inositol 1,4,5-Trisphosphate Receptors; D045304:Cytochromes c; D053148:Caspase 3; D019311:Staurosporine; D002118:Calcium