Potentiation of CD3-induced expression of the linker for activation of T cells (LAT) by the calcineurin inhibitors cyclosporin A and FK506.
The activation of blood cells, including T cells, triggers intracellular signals that control the expression of critical molecules, including cytokines and cytokine receptors. We show that T-cell receptor (TCR) ligation increases the cellular level of the protein linker for activation of T cells (LAT), a molecule critical for T-cell development and function. T-cell activation increased LAT messenger RNA, as determined by reverse transcription-polymerase chain reaction and by Northern blotting. The TCR-induced increase in LAT expression involved the activation of the serine/threonine kinases PKC and MEK, because inhibitors of these kinases blocked the increase in LAT. Accordingly, the PKC activator phorbol myristate acetate up-regulated LAT expression. Strikingly, the calcineurin inhibitors cyclosporin A (CsA) and FK506 strongly potentiated TCR-induced LAT expression, suggesting that the activation of calcineurin following TCR ligation negatively regulates LAT expression. Accordingly, Ca(++ )ionophores, which can activate calcineurin by increasing intracellular Ca(++), blocked the TCR-induced increase in cellular LAT. CsA and FK506 blocked the Ca(++ )ionophores' inhibitory effect on LAT expression. Notably, CsA and FK506 preferentially up-regulated TCR-induced LAT expression; under the same conditions, these compounds did not increase the expression of 14 other molecules that previously had been implicated in T-cell activation. These data show that TCR-induced LAT expression involves the activation of the PKC-Erk pathway and is negatively regulated by the activation of calcineurin. Furthermore, the potentiation of TCR-induced LAT expression by CsA and FK506 suggests that the action of these agents involves up-regulating the cellular level of critical signaling molecules. These findings may have important therapeutic implications. (Blood. 2000;95:2733-2741)
Peters
D
D
Department of Surgery, Division of Transplantation, University of Wisconsin, Madison, WI, USA.
Tsuchida
M
M
Manthei
E R
ER
Alam
T
T
Cho
C S
CS
Knechtle
S J
SJ
Hamawy
M M
MM
D048868:Adaptor Proteins, Signal Transducing; D018106:CD28 Antigens / Q000502:physiology*; D017252:CD3 Complex / Q000502:physiology*; D000001:Calcimycin / Q000494:pharmacology; D065095:Calcineurin Inhibitors; D002352:Carrier Proteins / Q000235:genetics*; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008565:Membrane Proteins; D010750:Phosphoproteins / Q000235:genetics*; D011493:Protein Kinase C / Q000378:metabolism; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology*; D016559:Tacrolimus / Q000494:pharmacology*; D014158:Transcription, Genetic
D048868:Adaptor Proteins, Signal Transducing; D018106:CD28 Antigens; D017252:CD3 Complex; D065095:Calcineurin Inhibitors; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007211:Indoles; C110810:LAT protein, human; D008565:Membrane Proteins; D010750:Phosphoproteins; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D000001:Calcimycin; D016572:Cyclosporine; D011493:Protein Kinase C; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C064758:Ro 31-8220; D016559:Tacrolimus