Ca2+ signaling modulates cytolytic T lymphocyte effector functions.
Cytolytic T cells use two mechanisms to kill virally infected cells, tumor cells, or other potentially autoreactive T cells in short-term in vitro assays. The perforin/granule exocytosis mechanism uses preformed cytolytic granules that are delivered to the target cell to induce apoptosis and eventual lysis. FasL/Fas (CD95 ligand/CD95)-mediated cytolysis requires de novo protein synthesis of FasL by the CTL and the presence of the death receptor Fas on the target cell to induce apoptosis. Using a CD8(+) CTL clone that kills via both the perforin/granule exocytosis and FasL/Fas mechanisms, and a clone that kills via the FasL/Fas mechanism only, we have examined the requirement of intra- and extracellular Ca2+ in TCR-triggered cytolytic effector function. These two clones, a panel of Ca2+ antagonists, and agonists were used to determine that a large biphasic increase in intracellular calcium concentration, characterized by release of Ca2+ from intracellular stores followed by a sustained influx of extracellular Ca2+, is required for perforin/granule exocytosis. Only the sustained influx of extracellular Ca2+ is required for FasL induction and killing. Thapsigargin, at low concentrations, induces this small but sustained increase in [Ca2+]i and selectively induces FasL/Fas-mediated cytolysis but not granule exocytosis. These results further define the role of Ca2+ in perforin and FasL/Fas killing and demonstrate that differential Ca2+ signaling can modulate T cell effector functions.
Esser
M T
MT
Department of Microbiology, University of Virginia, Health Sciences Center, Charlottesville, Virginia 22908, USA.
Haverstick
D M
DM
Fuller
C L
CL
Gullo
C A
CA
Braciale
V L
VL
D015703:Antigens, CD / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002999:Clone Cells / Q000378:metabolism; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D005089:Exocytosis / Q000502:physiology; D053222:Fas Ligand Protein; D053804:Granzymes; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism* / Q000502:physiology; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D012697:Serine Endopeptidases; D015398:Signal Transduction / Q000502:physiology; D013602:T-Lymphocytes, Cytotoxic / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D019014:fas Receptor / Q000276:immunology
D015703:Antigens, CD; D053222:Fas Ligand Protein; D007476:Ionophores; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D019014:fas Receptor; D054353:Perforin; D015759:Ionomycin; D019284:Thapsigargin; D053804:Granzymes; D012697:Serine Endopeptidases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium