Regulation of IkB alpha phosphorylation by PKC- and Ca(2+)-dependent signal transduction pathways.
The Ca(2+)-dependent phosphatase calcineurin, a target of FK506 and CsA, synergizes with PKC-induced activation of nuclear factor (NF)-kappa B in T cell lines. We have investigated whether this synergy is present in other cell types and the mechanism(s) by which these two pathways lead to NF-kappa B activation. While this synergy is present in other cell types, in the monocytic cell line U937 calcineurin is also sufficient to activate NF-kappa B. Having previously shown that Ca(2+)- and PKC-dependent pathways synergize by accelerating the degradation of IkB alpha, we focused on the regulation of IkB alpha phosphorylation. While PKC-dependent pathways sequentially result in the phosphorylation and in an incomplete degradation of IkB alpha in T cell lines, co-activation of Ca(2+)-dependent pathways accelerates the rate of IkB alpha phosphorylation and results in its complete degradation. Activation of Ca(2+)-dependent pathways alone do not result in the phosphorylation and/or degradation of IkB alpha in Jurkat T or in U937 cells. Treatment of T cells with the selective PKC inhibitor GF109203X abrogates the PMA-induced IkB alpha phosphorylation/degradation irrespective of activation of Ca(2+)-dependent pathways, but not the phosphorylation and degradation of IkB alpha induced by TNF-alpha, a PKC-independent stimulus. Contrary to the interaction with PKC, Ca(2+)-dependent pathways synergize with TNF-alpha not at the level of IkB alpha phosphorylation, but at the level of its degradation. These results indicate that Ca(2+)-dependent pathways, including the phosphatase calcineurin, participate in the regulation of NF-kappa B in a cell specific fashion and synergize with PKC-dependent and -independent pathways at the level of IkB alpha phosphorylation and degradation.
Steffan
N M
NM
Department of Immunology, Mayo Clinic, Rochester, MN 55905, USA.
Bren
G D
GD
Frantz
B
B
Tocci
M J
MJ
O'Neill
E A
EA
Paya
C V
CV
D000818:Animals; D019703:Calcineurin; D002118:Calcium / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D020672:I-kappa B Proteins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*
D002148:Calmodulin-Binding Proteins; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha; D011493:Protein Kinase C; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D002118:Calcium