Synergistic action of protein kinase C theta and calcineurin is sufficient for Fas ligand expression and induction of a crmA-sensitive apoptosis pathway in Jurkat T cells.
Deletion of activated peripheral T cell clones by apoptosis requires the regulated expression of Fas ligand (FasL) and sensitization of these cells to CD95-mediated signaling. To investigate the signaling pathways responsible for FasL expression in T cells, we tested-besides subfamily-selective protein kinase C (PKC) inhibitors - the effect of constitutively active mutants of representatives of all PKC subfamilies, i.e. PKCalpha,epsilon,theta,iota, on FasL luciferase promoter reporter constructs. In synergy with a constitutively active form of protein phosphatase 2B calcineurin (CaN), only PKCtheta, but not PKCalpha,epsilon,iota, preferentially induced FasL promoter reporter activity and, consequently, FasL protein expression in Jurkat T cells. Activation of an inducible PKCtheta AE-estrogen receptor fusion mutant led to a CaN-dependent and rapid FasL reporter activity detected as early as 4 h after addition of 4-hydroxytamoxifen, incidating a direct effect of PKCtheta action on FasL expression. Consistently, in Jurkat T cells, expression of PKCtheta AE / CaN significantly enhanced FasL protein expression and apoptosis in a CD95-dependent manner since cell death was not observed in T cells co-expressing the caspase-8 inhibitor crmA. Taken together, our results support the notion that PKCtheta and CaN are sufficient to regulate apoptosis through FasL expression.
Villunger
A
A
Department of Medical Chemistry, University of Innsbruck, Medical School, Innsbruck, Austria.
Ghaffari-Tabrizi
N
N
Tinhofer
I
I
Krumböck
N
N
Bauer
B
B
Schneider
T
T
Kasibhatla
S
S
Greil
R
R
Baier-Bitterlich
G
G
Uberall
F
F
Green
D R
DR
Baier
G
G
D000952:Antigens, Polyomavirus Transforming / Q000235:genetics; D017209:Apoptosis; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D053222:Fas Ligand Protein; D015870:Gene Expression; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D019169:Jurkat Cells; D008024:Ligands; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics*; D008934:Mitogens / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D017346:Protein Serine-Threonine Kinases; D015843:Serpins / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014764:Viral Proteins
D000952:Antigens, Polyomavirus Transforming; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D007527:Isoenzymes; D008024:Ligands; D008562:Membrane Glycoproteins; D008934:Mitogens; D016328:NF-kappa B; D015843:Serpins; D018808:Transcription Factor AP-1; D014764:Viral Proteins; D015759:Ionomycin; C074641:interleukin-1beta-converting enzyme inhibitor; D017346:Protein Serine-Threonine Kinases; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; C482576:MAP3K1 protein, human; D019703:Calcineurin; D013755:Tetradecanoylphorbol Acetate