Granzyme A initiates an alternative pathway for granule-mediated apoptosis.
Granzyme (gzm) B-deficient cytotoxic lymphocytes (CTL) have a severe defect in the rapid induction of target cell apoptosis that is almost completely corrected by prolonged incubation of the CTL effectors and their targets. We show in this report that perforin-dependent, gzmB-independent cytotoxicity is caused by gzmA (or tightly linked genes). CTL deficient for gzmA and gzmB retain normal perforin function, but these CTL have a cytotoxic defect in vivo that is as severe as perforin-deficient CTL. Collectively, these results suggest that perforin provides target cell access and/or trafficking signals for the gzms, and that the gzms themselves deliver the lethal hits. The gzmA pathway appears to function independently from gzmB and may therefore provide a critical "back-up" system when gzmB is inhibited in the target cell.
Shresta
S
S
Department of Internal Medicine and Genetics, Washington University Medical School, St. Louis, Missouri 63110, USA.
Graubert
T A
TA
Thomas
D A
DA
Raptis
S Z
SZ
Ley
T J
TJ
D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002455:Cell Division; D003170:Complement Pathway, Alternative / Q000187:drug effects*; D053938:DNA Fragmentation; D004195:Disease Models, Animal; D006086:Graft vs Host Disease / Q000473:pathology; D053804:Granzymes; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D008817:Mice, Mutant Strains; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011994:Recombinant Proteins / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000494:pharmacology* / Q000502:physiology; D015842:Serine Proteinase Inhibitors; D013602:T-Lymphocytes, Cytotoxic / Q000737:chemistry / Q000166:cytology / Q000276:immunology
D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D054353:Perforin; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases