L. Tuosto et al., Mitogen-activated kinase kinase kinase 1 regulates T cell receptor- and CD28-mediated signaling events which lead to NF-kappa B activation, EUR J IMMUN, 30(9), 2000, pp. 2445-2454
Optimal activation of Rel/NF-kappa B transcription factors in T lymphocytes
requires a CD28-delivered co-stimulatory signal in addition to TCR engagem
ent. Although, Rel/NF-kappa B transcription factors are critical regulators
of many T cell functions, the mechanisms and molecules, which link the sur
face receptors to their activation, are poorly characterized. Using Jurkat
T cells stimulated with superantigen presented on B7-positive APC, we showe
d that CD28- and TCR-stimulated NF-KB-dependent transcription is associated
to the activation of IRE kinase beta (IKK beta) and, to a lesser extent, o
f I kappa B kinase alpha (IKK alpha). A dominant negative mutant of the MAP
3 kinase MEKK1, a kinase known to regulate the JNK pathway and to activate
NF-kappa B-dependent transcription in many cell types, strongly inhibits CD
28- and TCR-induced IKK activity, whereas the dominant negative mutants of
the NF-kappa B-inducing kinase (NIK) did not exert any significant effects.
In addition, TCR/CD28 stimulation results in the recruitment and autophosp
horylation of endogenous MEKK1, whereas endogenous NIK was not detectably a
ctivated. Our data identify MEKK1 as a critical step in coupling signals in
itiated by TCR and CD28 to the downstream pathways which lead to both AP-1
and NF-kappa B activation in T lymphocytes.