Association of serine protease with the rise of intracellular calcium in cytotoxic T lymphocytes.
The precise role of the granular enzyme A (granzyme A), a serine protease, in the lytic process of cytotoxic T lymphocytes (CTL) is not clear. We have recently constructed a CTL line transfected with the antisense gene of granzyme A (a-GrA). These a-GrA CTL had lower GrA activity as well as decreased lytic activities, as measured by 51Cr and by DNA degradation assays. Furthermore, at low effector:target ratio (1:8) in prolonged lytic assays, they could not lyse targets as rapidly as the control CTL. When we examined their ability to exocytose BLT (CBZ-L-lys-thiobenzyl)-esterase in the presence of anti-CD3 antibody, the a-GrA CTL exocytosed poorly compared to the parental CTL or control transfectant with a CAT gene. Most strikingly, a-GrA cells could not release intracellular stores of Ca2+ in response to anti-CD3 induction, although the Ca2+ flux was normal when they were stimulated with ionomycin. When the parental CTL was treated with a specific benzyllactam inhibitor of BLT-esterase or N-tosyl-L-phenylalanylchloromethyl ketone, the Ca2+ flux induced by anti-CD3 was also suppressed. We propose that granzyme A is involved in the signal transduction pathway that causes the rise of the intracellular calcium.
Koo
G C
GC
Department of Immunology Research, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
Luk
Y
Y
Talento
A
A
Wu
J
J
Sirotina
A
A
Fischer
P A
PA
Blake
J T
JT
Nguyen
M P
MP
Parsons
W
W
Poe
M
M
D001552:Benzazepines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003602:Cytotoxicity, Immunologic; D053804:Granzymes; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000378:metabolism
D001552:Benzazepines; C102811:L 157227; D015842:Serine Proteinase Inhibitors; D053804:Granzymes; D012697:Serine Endopeptidases; D002118:Calcium