Primary human CD4+ T cells contain heterogeneous I kappa B kinase complexes: role in activation of the IL-2 promoter.
NF-kappa B transcription factors play an important role in the activation of the IL-2 gene in response to TCR ligation. The release of NF-kappa B factors to the nucleus requires phosphorylation and degradation of the inhibitory kappa-B proteins (I kappa Bs). I kappa B alpha and I kappa B beta phosphorylation is dependent on dual signaling by the TCR and the CD28 accessory receptor. This pathway involves a multisubunit I kappa B kinase (IKK) complex, which includes the IKK alpha (IKK-1) and IKK beta (IKK-2) kinases. We demonstrate that stimulation of primary human CD4+ T cells by CD3/CD28 activates two distinct endogenous IKK complexes, a heterodimeric IKK alpha/beta and a homodimeric IKK beta complex. IKK beta overexpression in a Jurkat cell line resulted in the formation of a constitutively active IKK complex, which was CD3/CD28 inducible. In contrast, ectopic expression of IKK alpha assembled into a complex with negligible I kappa B kinase activity. Moreover, IKK beta, but not IKK alpha, overexpression enhanced transcriptional activation of the CD28 response element in the IL-2 promoter. Conversely, only kinase-inactive IKK beta interfered in the activation of the IL-2 promoter. Sodium salicylate, an inhibitor of IKK beta, but not IKK alpha, activity, inhibited IL-2 promoter activation as well as IL-2 secretion and interfered in activation of both the heterodimeric as well as the homodimeric IKK complexes in primary CD4+ T cells. Taken together, these data demonstrate the presence of an IKK beta-mediated signaling pathway that is activated by TCR and CD28 coligation and regulates IL-2 promoter activity.
Khoshnan
A
A
Division of Clinical Immunology and Allergy, Department of Medicine, Center for Health Sciences, Los Angeles, CA 90095, USA.
Kempiak
S J
SJ
Bennett
B L
BL
Bae
D
D
Xu
W
W
Manning
A M
AM
June
C H
CH
Nel
A E
AE
D000911:Antibodies, Monoclonal / Q000378:metabolism; D018106:CD28 Antigens / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017252:CD3 Complex / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000201:enzymology*; D002478:Cells, Cultured; D019281:Dimerization; D004789:Enzyme Activation / Q000235:genetics / Q000276:immunology; D006801:Humans; D051550:I-kappa B Kinase; D007376:Interleukin-2 / Q000235:genetics* / Q000378:metabolism; D007527:Isoenzymes / Q000096:biosynthesis / Q000502:physiology; D019169:Jurkat Cells / Q000201:enzymology; D011401:Promoter Regions, Genetic / Q000276:immunology*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000502:physiology*; D020218:Response Elements / Q000276:immunology; D015533:Transcriptional Activation / Q000276:immunology*
D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D017252:CD3 Complex; D007376:Interleukin-2; D007527:Isoenzymes; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human