NF-kappa B activation induced by T cell receptor/CD28 costimulation is mediated by protein kinase C-theta.
Protein kinase C-theta (PKCtheta) is a Ca(2+)-independent member of the PKC family that is selectively expressed in skeletal muscle and T lymphocytes and plays an important role in T cell activation. However, the molecular basis for the important functions of PKCtheta in T cells and the manner in which it becomes coupled to the T cell receptor-signaling machinery are unknown. We addressed the functional relationship between PKCtheta and CD28 costimulation, which plays an essential role in T cell receptor-mediated IL-2 production. Here, we provide evidence that PKCtheta is functionally coupled to CD28 costimulation by virtue of its selective ability to activate the CD28RE/activator protein-1 (AP-1) element in the IL-2 gene promoter. First, CD28 costimulation enhanced the membrane translocation and catalytic activation of PKCtheta. Second, among several PKC isoforms, PKCtheta was the only one capable of activating NF-kappaB or CD28RE/AP-1 reporters in T cells (but not in 293T cells). Third, wild-type PKCtheta synergized with CD28/CD3 signals to activate CD28RE/AP-1. In addition, PKCtheta selectively synergized with Tat to activate a CD28RE/AP-1 reporter. Fourth, CD3/CD28-induced CD28RE/AP-1 activation and NF-kappaB nuclear translocation were blocked by a selective PKCtheta inhibitor. Last, PKCtheta-mediated activation of the same reporter was inhibited by the proteasome inhibitor MG132 (which blocks IkappaB degradation) and was found to involve IkappaB-kinase beta. These findings identify a unique PKCtheta-mediated pathway for the costimulatory action of CD28, which involves activation of the IkappaB-kinase beta/IkappaB/NF-kappaB-signaling cascade.
Coudronniere
N
N
Division of Cell Biology, La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, CA 92121, USA.
Villalba
M
M
Englund
N
N
Altman
A
A
D001692:Biological Transport; D018106:CD28 Antigens / Q000378:metabolism*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051550:I-kappa B Kinase; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction
D018106:CD28 Antigens; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D016328:NF-kappa B; D011948:Receptors, Antigen, T-Cell; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta